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Pancreatic Cancer: Genetics, Genomics and Immunotherapy

Posted in Bio Instrumentation in Experimental Life Sciences Research, Biological Networks, Gene Regulation and Evolution, Biomarkers & Medical Diagnostics, BioSimilars, CANCER BIOLOGY & Innovations in Cancer Therapy, Cancer Prevention: Research & Programs, Cell Biology, Signaling & Cell Circuits, Disease Biology, Small Molecules in Development of Therapeutic Drugs, Drug Delivery Platform Technology, Genome Biology, Genomic Testing: Methodology for Diagnosis, Human Immune System in Health and in Disease, Medical and Population Genetics, Molecular Genetics & Pharmaceutical, Nutrition, Personalized and Precision Medicine & Genomic Research, Regulated Clinical Trials: Design, Methods, Components and IRB related issues, tagged adenocarcinoma, Cancer - General, Clinical Trials, Immunotherapy, pancreatic biology, Pancreatic cancer, pancreatic genetics, Ronald A. DePinho, Tilda Barliya, Weill Medical College of Cornell University on April 11, 2013| 9 Comments »

Author: Tilda Barliya PhD

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Word Cloud By Danielle Smolyar

Pancreatic cancer has been previously addressed here in our blog (I-IX) but a recent diagnosis of a colleague urged me to go back to the basics and search for more answers and updates hoping it would offer some peace.

Pancreatic cancer is the 4th leading cause of death in the united states with only 3% rate for 5-year survival rate (1). Due to lack of symptoms and limitation in diagnostic methods, patients are mostly diagnosed at mush advanced stages. When reach these stages, patients start to show symptoms of weight loss, abdominal pain, jaundice, by than, the cancer has already spread.

Several treatment options are available in which surgical resection (for the 15%-20% that are eligible for it) increase the 5-year survival rate by up to 20% , and that’s mainly because the cancer comes back about 85 percent of the time (1,2). These statistics are very hard to comprehend, especially with the progress been made in other types of cancer.

So Why pancreatic cancer is so deadly?

Pancreatic cancer biology and genetics. Nabeel Bardeesy & Ronald A. DePinho. Nature Reviews Cancer 2002: 2, 897-909

The pancreas is a highly vascularized 6 inch dual-function gland that plays a major role in the body. It secretes digestive enzymes and hormones (i.e; insulin, glucagon, somatostatin and pancreatic polypeptide) which assist in the digestion of fats and the absorption of nutrients. These enzymes help further digest carbohydrates, proteins and lipids in the chyme.

It is postulated that a tumor starts to overcome the functionally of the pancreas; causing reduction of important hormones (insulin) and enzymes (digestive enzymes) production thus impacting the overall ability of the body to absorb nutrients and get energy coins thus affecting the overall performance of the body. Several studies were conducted to evaluate the connection between dietary factors and induction of pancreatic cancer, however no direct correlation was observed (11, 12)

More so, the pancreas is located at the junction of several organs; liver, gall bladder and intestines, thus enabling metastatic cells to harbor multiple vital organ. Most patients die for liver failure due to liver metastases.

These factors; late- diagnosis, reduction in overall body function and failure of vital organs (such as the liver due to metastasis), cause the aggressive and fast death of these panvreatic patients.

A growing number of studies have identified common mutational profiles in simultaneous lesions, providing supportive evidence of the relationship between pancreatic intraepithelial neoplasia (PanINs) and the pathogenesis of pancreatic adenocarcinoma. Nabeel Bardeesy and Ronald A. DePinho summarized this data in Figure and table inserted herein. Intriguingly, there seems to be an ordered series of mutational events in association with specific neoplastic stages (1,4).

Pancreatic cancer biology and genetics. Nabeel Bardeesy & Ronald A. DePinho. Nature Reviews Cancer 2002, 2: 897-909.

The combination of these multiple mutations render pancreatic cancer cells resistant to current chemo and radiotherapy. More so, known pancreatic cancer antigens have generated relatively weak immune responses due to these combined mutagenesis (5, 16). These crucial somatic genetic mutations can generate pancreatic cancer proteins that are essentially altered self proteins

Therefore, in order to design a good immunotherapeutic approach one must incorporate at least one agent against a pancreatic cancer target as well as one or more agents that will modify both local and systemic mechanisms of pancreatic-cancer-induced.

Another important element that needs to be taken into consideration are the immunological checkpoints. These checkpoints serve two purposes:

To help generate and maintain self-tolerance, by eliminating T cells that are specific for self-antigens.
To restrain the amplitude of normal T-cell responses so that they do not ‘overshoot’ in their natural response to foreign pathogens

The prototypical immunological checkpoint is mediated by the cytotoxic-T-lymphocyte-associated protein 4 (CTLA4) counter regulatory receptor that is expressed by T cells when they become activated (6). CTLA4 binds two B7 FAMILY members on the surface APCs — B7.1 (also known as CD80) and B7.2 (also known as CD86): with roughly 20-fold higher affinity than the T-cell surface protein CD28 binds these molecules. CD28 is a co-stimulatory receptor that is constitutively expressed on naive T cells. Because of its higher affinity, CTLA4 out-competes CD28 for B7.1/B7.2 binding, resulting in the downmodulation of T-cell responses (7). Monoclonal antibodies that downregulate B7-H1 and B7-H4 are currently in clinical development. This is just one example of the potential use of targeted therapy for use in clinical trials.

Dan Laheru* and Elizabeth M. Jaffee have summarized the immunotherapy clinical trials back in 2005:

Herein you can read about the latest summary of the NCI portfolio on Pancreatic cancer and research highlights : http://www.cancer.gov/researchandfunding/reports/pancreatic-research-progress.pdf

Here’s their recommendation for future plans for clinical trials:

Perform well-designed Phase II studies to help define strategies likely to succeed in a Phase III setting.
Adopt consistent entry and evaluation criteria for Phase II trials.
Conduct high-priority Phase III trials as intergroup trials and include scientifically appropriate biorepositories.
Conduct trials on rational combinations of targeted agents and develop predictive biomarkers to assist in patient selection.
Explore use of immune therapies, particularly among those with earlier stage disease.
Share trial outcomes, including those of trials with negative results.

According to the NCI clinical trial results from two phase III clinical trials, the targeted therapies sunitinib (Sutent®) and everolimus (Afinitor®) increased the length of time patients with pancreatic neuroendocrine tumors (panNET) survived without the disease progressing. And, in the sunitinib trial, patients who received the drug also had better overall survival. The findings were published February 9, 2011, in the New England Journal of Medicine (NEJM). Although neuroadenoma is rare and presents only 2% of all pancreatic cancer, no effective treatment was available, now these results may offer some hope (9).

More so, a four-drug chemotherapy regimen has produced the longest improvement in survival ever seen in a phase III clinical trial of patients with metastatic pancreatic cancer, one of the deadliest types of cancer (10). Patients who received the regimen, called FOLFIRINOX, lived approximately 4 months longer than patients treated with the current standard of care, gemcitabine (11.1 months compared with 6.8 months).

In summary:

Remarkable progress has been made in understanding the genetics and development biology pancreatic cancer have offered new potential targets for therapy. ” The availability of powerful new technologies and continued contributions of investigators in many related disciplines provides a measure of optimism towards future progress in treating this disease (1)”. Latest results of clinical trials may also shade some hope for patients suffering from this horrible disease.

On a personal note, I hope these new opportunities and clinical trials will offer another avenue to my colleague……

REFERENCES

1. Nabeel Bardeesy and Ronald A.DePinho. Pancreatic cancer biology and genetics. Nature Cancer reviews 2002, 2: 897-909. http://www.nature.com/nrc/journal/v2/n12/full/nrc949.html

2. Melinda Wenner. What makes pancreatic cancer so deadly. Scientific American 2008. http://www.scientificamerican.com/article.cfm?id=experts-pancreatic-cancer-gene-upshaw

3. Pancreas. Wikipedia. http://en.wikipedia.org/wiki/Pancreas

4. Jaffee, E. M., Hruban, R. H., Canto, M. & Kern, S.E. Focus on pancreas cancer. Cancer Cell 2, 25–28 (2002). http://www.sciencedirect.com/science/article/pii/S1535610802000934

5. Dan Laheru* and Elizabeth M. Jaffee. Immunotherapy for pancreatic cancer – science driving clinical progress. Nature Reviews: Cancer. 2005. 5: 459-467. http://www.nature.com/nrc/journal/v5/n6/full/nrc1630.html

6. Coyle, A. J. & Gutierrez-Ramos, J. C. The expanding B7 superfamily: increasing complexity in co-stimulatory signals regulating T cell function. Nature Immunol 2001. 2, 203–209. http://www.nature.com/ni/journal/v2/n3/full/ni0301_203.html

7. Walunas, T. L., Bakker, C. Y. & Bluestone, J. A. CTLA-4 ligation blocks CD28-dependent T cell activation. J. Exp. Med 1996. 183, 2541–2550. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2192609/

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2192609/pdf/je18362541.pdf

8. Pancreatic Cancer: A summary of NCI’s portfolio and highlights of recent research progress 2010. http://www.cancer.gov/researchandfunding/reports/pancreatic-research-progress.pdf

9. NCI bulletin: Targeted Therapies May Be Effective Against Rare Pancreatic Cancer. http://www.cancer.gov/clinicaltrials/results/summary/2011/panNET-Therapy0411

10. NCI bulletin: Chemotherapy Regimen Extends Survival in Advanced Pancreatic Cancer Patients http://www.cancer.gov/clinicaltrials/results/summary/2011/pancreatic-chemo0611

11. Nilsen TI, Vatten LJ. A prospective study of lifestyle factors and the risk of pancreatic cancer in NordTrondelag, Norway. Cancer Causes Control 2000;11:645-52. http://www.ncbi.nlm.nih.gov/pubmed/10977109

12. Marshall JR, Freudenheim J. Alcohol. In: Schottenfeld D, Fraumeni JF Jr., eds. Cancer Epidemiology and Prevention, 3rd ed. New York: Oxford University Press, 2006. P. 243-58. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780195149616.001.0001/acprof-9780195149616

13. Alison P. Klein. Identifying people at a high risk of developing pancreatic cancer. Nature Reviews Cancer 2012, 13: 66-74. http://www.nature.com/nrc/journal/v13/n1/full/nrc3420.html

14. John P. Morris, Sam C. Wang & Matthias Hebrok. KRAS, Hedgehog, Wnt and the twisted developmental biology of pancreatic ductal adenocarcinoma.Nature Reviews Cancer 2012. 10:683-695. http://www.nature.com/nrc/journal/v10/n10/full/nrc2899.html

15. Patrick Goymer. Imaging: Early detection for pancreatic cancer. Nature Reviews Cancer 2008, 8: 408-409. http://www.nature.com/nrc/journal/v8/n6/full/nrc2407.html

16. Koido S, Homma S, Takahara A, Namiki Y, Tsukinaga S, Mitobe J, Odahara S, Yukawa T, Matsudaira H, Nagatsuma K, Uchiyama K, Satoh K, Ito M, Komita H, Arakawa H, Ohkusa T, Gong J, Tajiri H. Current Immunotherapeutic Approaches in Pancreatic Cancer, Clin Dev Immunol. 2011;2011:267539. http://www.hindawi.com/journals/cdi/2011/267539/

Acute Lymphoblastic Leukemia and Bone Marrow Transplantation

Posted in Biomarkers & Medical Diagnostics, BioSimilars, CANCER BIOLOGY & Innovations in Cancer Therapy, Disease Biology, Small Molecules in Development of Therapeutic Drugs, Personalized and Precision Medicine & Genomic Research, Population Health Management, Genetics & Pharmaceutical, Regulated Clinical Trials: Design, Methods, Components and IRB related issues, Stem Cells for Regenerative Medicine, tagged Acute Lymphoblastic Leukemia (ALL), Allogeneic stem cell transplant, Autologous stem cell transplant, Chemotherapy, Clinical Trials, donors, Graft-versus-host disease (GVHD), haploidentical transplants, Hematopoietic stem cell transplantation, Radiation therapy, Targeted therapy on March 27, 2013| 5 Comments »

Acute Lymphoblastic Leukemia and Bone Marrow Transplantation

Author, Editor: Tilda Barliya PhD

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Word Cloud By Danielle Smolyar

Acute lymphoblastic leukemia (ALL) is a malignant disorder of lymphoid progenitor cells was previously discussed for the genetic origin and the prognostic factors used in clinical trials (1). We will now focus on the treatment options with emphasis on the bone marrow transplantation (2).

According to the National Cancer Institute (NCI), the treatment of childhood ALL usually has 3 phases (3a):

Induction Therapy: The goal is to kill leukemia cells in both the blood and the bone marrow and induce a remission.
Consolidation/Intensification Therapy: It begins once the leukemia is in remission. The goal is to kill any remaining leukemia cells that may not be active but may regrow and cause relapse.
Maintenance Therapy: The goal is to kill any remaining leukemia cells that may regrow and cause relapse. In this phase the different cancer treatments are usually been given at lower doses than those in the previous phases.

Four types of cancer treatment are used:

Chemotherapy – The way the chemotherapy is given depends on the child’s risk group. Children with high-risk ALL receive more anticancer drugs, higher doses of anticancer drugs, and receive treatment for a longer time than children with standard-risk ALL.. The full list of approved drug (3b)
Radiation Therapy– is a cancer treatment that uses high-energy x-rays or other types of radiation to kill cancer cells or keep them from growing. There are two types of radiation therapy. External radiation therapy uses a machine outside the body to send radiation toward the cancer. Internal radiation therapy uses a radioactive substance sealed in needles, seeds, wires, or catheters that are placed directly into or near the cancer. External radiation therapy may be used to treat childhood ALL that has spread, or may spread, to the brain and spinal cord.
Chemotherapy with stem cell transplantation – A method inwhich stem cells (immature blood cells) are removed from the blood or bone marrow of a donor. After the patient receives treatment, the donor’s stem cells are given to the patient through an infusion. These reinfused stem cells grow into (and restore) the patient’s blood cells. Stem cell transplant is rarely used as initial treatment for children and teenagers with ALL. It is used more often as part of treatment for ALL that relapses
Targeted Therapy – Tyrosine Kinase Inhibitors (TKIs) are targeted therapy drugs that block the enzyme, tyrosine kinase, which causes stem cells to become more white blood cells or blasts than the body needs. For example, imatinib mesylate (Gleevec) is a TKI used in the treatment of children with Philadelphia chromosome-positive ALL. However, because patients can develop resistance to these drugs, new tyrosine kinase inhibitors are being investigated. For example, nilotinib (AMN-107) is being studied for patients with Philadelphia chromosome positive ALL who are resistant to imatinib

Bone Marrow or Peripheral Blood Stem cell Transplant for ALL

Stem cell transplants (SCT) offer a way for doctors to use high doses of chemo. Although the drugs destroy the patient’s bone marrow, transplanted stem cells can restore the bone marrow’s ability to make blood. Stem cells for a transplant come from either the blood or from the bone marrow. Bone marrow transplants were more common in the past, but they have largely been replaced by peripheral blood stem cell transplant (PBSCT).

Types of Transplants (4).

The stem cells can come from either the patient (an autologous transplant) or from a matched donor (an allogeneic transplant).

Allogeneic stem cell transplant: In an allogeneic transplant, the stem cells come from someone else – usually a donor whose tissue type is a very close match to the patient’s. The donor may be a brother or sister if they are a good match. Less often, an unrelated donor may be found. An allogeneic transplant is the preferred type of transplant for ALL when it is available.
“Mini-transplant”: “mini-transplant” (also called a non-myeloablative transplant or reduced-intensity transplant), where they get lower doses of chemo and radiation that do not destroy all the cells in their bone marrow. They then are given the donor stem cells. These cells enter the body and form a new immune system, which sees the leukemia cells as foreign and attacks them (a graft-versus-leukemia effect). This is not a standard treatment for ALL, and is being studied to find out how useful it may be.
Autologous stem cell transplant: In an autologous transplant, a patient’s own stem cells are removed from his or her bone marrow or blood. They are frozen and stored while the person gets treatment (high-dose chemo and/or radiation). The stem cells are then given back to the patient after treatment.

One problem with autologous transplants is that it is hard to separate normal stem cells from leukemia cells in the bone marrow or blood samples. Even after treating the stem cells in the lab to try to kill or remove any leukemia cells, there is the risk of returning some leukemia cells with the stem cell transplant

Stem cell transplants and side effects (4):

Early side effects: Early side effects are much the same as those caused by any other type of high-dose chemo, such as nausea, vomiting, loss of appetite, mouth sores, and hair loss. Because of the high doses of chemo used, these can sometimes be severe.

Infection resulting from a weakened immune system is the most common side effect. Because the stem cell procedure is done more swiftly, the risk period is shorter than with bone marrow transplantation. The risk for infection is most critical during the first 6 weeks following the transplant, but it takes 6 – 12 months post-transplant for a patient’s immune system to fully recover. Immune systems of patients with graft-versus-host disease can take even longer to function normally. Low red cell count and platelet counts are also early-side effects that when happens are treated with blood transfusion.

A rare but serious side effect of stem cell transplant is called veno-occlusive disease of the liver (VOD). In this disease, the high doses of chemo given for the transplant damage the liver. Symptoms include weight gain (from fluid collecting), liver swelling, and yellowing of the skin and eyes (jaundice). When severe, it can lead to liver failure, kidney failure, and even death.

Long-term side effects: Some side effects can last for a long time, or may not happen until years after the transplant. These long-term side effects can include the following:

Acute/Chronic Graft-versus-host disease (GVHD), which occurs only in a donor transplant
Organ damage: lungs ( shortness of breath), ovaries (infertility and loss of menstrual period), thyroid, eyes (cataract), bone etc.
Developing another type of leukemia or other cancer several years later.

ALL (and AML), Bone Marrow transplant and Clinical Trials

Back in the early 80’s, chemotherapy was shown to cure a substantial portions of patients with ALL. Yet some patients had high risk of relapse when treated using conventional regimens, due to patient- and disease-related variables. Bone marrow transplantation (BMT) was found to have encouraging results depending on the circumstances, yet the relative role between chemo and BMT to high-risk patients was controversial.

It was believed that the factors which predict poor outcome with chemo do not adversely affect the transplant outcome, yet this assumption was not based on comparing similar predicting factors . More so, the prognostic factors for outcome after BMT were not well-defined and the optimal regimen for transplant was not agreed upon. Thus, researches aimed to identify the characteristics and factors affecting good outcome after transplantation for ALL in first and second remission.

For this, 690 patients with HLA-identical sibling receiving allogeneic BMT either after first or second complete remission (CR). Numerous factors were accounted for including; age, sex, donor-recipient sex match, chemo regimen and presence of GVHD.

Of the many factors evaluated, several were highly significant in BMT outcome:

GVHD – It may have both favorable and unfavorable effect on the outcome. On one hand it may reduce leukemia relapse but on the other hand it may increase transplant-related mortality.
Conditioning chemo regimens – most chemo regimens had negative effects of the BTM outcome. By, since the study group included only a small number of patients and these studies were conducted before the new chemo types/regimes using high-does etoposide, this factor may need to be reevaluated.
Donor-recipient sex match – This factor was found to be highly significant in female receiving donors from male-matched donors. These patients had higher risk of relapse and treatment failure. This was probably due to host sensitization to the H-Y antigens. This data is also needed to be handled with cautious due to the small number of patients.
Immune phenotype – Blood cell type and leukocyte levels at the beginning of the treatment is a another crucial factor. Higher leukocyte levels and non-T cell phenotype resulted in adverse outcome which led to remission.
Patient age – Age did not play a role when comparing the outcome after first relapse, but was found to be more favorable for younger ages (<16) when comparing the outcome after second relapse.
First relapse – a failure of first therapy override any other variable. The medical situation ( on/off chemo) at the time of a first relapse is highly important. If relapse occurred while OFF chemo, patients had better prognosis.

A recent study conducted by Wing Leung, M.D., Ph.D from St. Jude Children Hospital shows that that transplantation offers real hope of survival to patients with high-risk leukemia that is not curable with intensive chemotherapy. Bone marrow transplant survival more than doubled in recent years for young, high-risk leukemia patients who lacked genetically matched donors (5).

Five years after transplantation, survival was 65 percent for the 37 St. Jude patients with high-risk ALL treated at the hospital between 2000 and 2007, compared to 28 percent for the 57 St. Jude ALL patients who underwent treatment between 1991 and 1999. For AML patients, success rates grew from 34 % to 74%.

Dr. Leung explains that historically, transplant patients fared best and suffered fewer complications when the donors were relatives who carried the same six proteins on their white blood cells. Known as HLA proteins, they serve as markers to help the immune system distinguish between an individual’s healthy tissue and diseased cells that should be eliminated.

However, St. Jude investigators pioneered the use of haploidentical transplants (=partially genetically matched donors such as parents), demonstrating that careful matching of patients and donors and proper processing of the hematopoietic donor cells enhances the anti-cancer effect of transplantation without significantly increasing side effects.

The process involves careful testing and HLA screening of potential donors to identify the one whose immune system is likely to mount the most aggressive attack against remaining leukemia cells using specialized immune cells known as natural killer cells (5).

Dr. Leung further explains that the odds of finding a good haploidentical donor are 70 to 80 percent, compared to about a 25 percent chance of having a matched sibling donor, Leung said. The likelihood of finding a genetically identical, unrelated donor ranges from about 60 to 90 percent depending on the patient’s race or ethnicity.

Summary

Previous study have identified several factors that may affect the outcome of BMT in high-risk patients and included GVHD, blood count, chemo regimen prior to the transplantation, donor-sex matched and others. In a more recent study, however, the results indicated that all patients with very high-risk leukemia should be considered as candidates for HCT (Allogeneic hematopoietic cell transplantation) early in the course of diagnosis or relapse treatment, regardless of the availability of a matched donor or the intensity of prior chemotherapy. HLA typing, donor search, and transplant center referral should be performed as soon as possible. Patients with persistent minimal residual disease (MRD) or hematologic relapse while on therapy are also considered candidates for HCT in current protocols. There are several major differences between previous years study-analyses and this current one that needs to be taken into consideration before including or excluding each of them. [A]; 24% of the allogeneic HCTs in patients younger than 20 years worldwide were performed using cord blood grafts vs the previous bone marrow transplant procedure, [B] differences chemo-regimens between the previous and current years, [C] different transplant approaches evolved simultaneously, and therefore it is difficult to conduct retrospective analyses and [D] matching in HLA-C was not required for unrelated donor HCTs before 2008 in several institutes and therefore outcomes after contemporary 8 of 8 loci-matched transplantations may even be better than those favorable rates reported.

The data reported within is highly important and may increase patients survival rates and increased quality of lives. It is therefore necessary that different clinical-trial centers will re-evaluate current protocols and consider this new approach.

REFERENCES:

1. Acute Lymphoblastic Leukemia (ALL) and Nanotechnology. Author Tilda Barliya PhD

http://pharmaceuticalintelligence.com/2013/03/21/acute-lymphoblastic-leukemia-all-and-nanotechnology/

2. In Focus: Identity of Cancer Stem Cells. Author Ritu Saxena

http://pharmaceuticalintelligence.com/2013/03/22/in-focus-identity-of-cancer-stem-cells/

3a. NCI: Childhood Acute Lymphoblastic Leukemia Treatment (PDQ®).

http://www.cancer.gov/cancertopics/pdq/treatment/childALL/Patient/page4

3b. Drugs Approved for Acute Lymphoblastic Leukemia (ALL)

http://www.cancer.gov/cancertopics/druginfo/leukemia#dal1

4. American Cancer Society: Leukemia–Acute Lymphocytic Overview

http://www.cancer.org/cancer/leukemia-acutelymphocyticallinadults/overviewguide/leukemia-all-overview-treating-bone-marrow-stem-cell.

5. W. Leung, D. Campana, J. Yang, D. Pei, E. Coustan-Smith, K. Gan, J. E. Rubnitz, J. T. Sandlund, R. C. Ribeiro, A. Srinivasan, C. Hartford, B. M. Triplett, M. Dallas, A. Pillai, R. Handgretinger, J. H. Laver, C.-H. Pui. High success of hematopoietic cell transplantation regardless of donor source in children with very high-risk leukemia. Blood, 2011; DOI: 10.1182/blood-2011-01-333070

http://bloodjournal.hematologylibrary.org/content/118/2/223.full

6. AJ Barrett, MM Horowitz, RP Gale, JC Biggs, BM Camitta, KA Dicke, E Gluckman, RA Good, RH Herzig, and MB Lee. Marrow transplantation for acute lymphoblastic leukemia: factors affecting relapse and survival. Blood August 1, 1989vol. 74 no. 2 862-871

http://bloodjournal.hematologylibrary.org/content/74/2/862.full.pdf+html

7. Fujii H, Tradeau JD., Teachey DT., Fish JD., Grupp SA., Schlts KR and Reid GS. In vivo control of acute lymphoblastic leukemia by immunostimulatory CpG oligonucleotides. Blood 2007, 109: 2008-2013.

http://bloodjournal.hematologylibrary.org/content/109/5/2008.full.pdf+html

8. Schrauder A, Reiter A, Gadner H, Niethammer D, Klingebiel T, Kremens B, Wolfram Ebell P, Zimmermann M, Niggli F, Wolf-Dieter Ludwig, Riehm H, Welte K, and Schrappe M. Superiority of Allogeneic Hematopoietic Stem-Cell Transplantation Compared With Chemotherapy Alone in High-Risk Childhood T-Cell Acute Lymphoblastic Leukemia: Results From ALL-BFM 90 and 95. J Clin Oncol 2006 24:5742-5749.

http://jco.ascopubs.org/content/24/36/5742.full.pdf+html

9. O. Ringde´n, M. Labopin, A. Bacigalupo, W. Arcese, U.W. Schaefer, R. Willem. Transplantation of Peripheral Blood Stem Cells as Compared With Bone Marrow From HLA-Identical Siblings in Adult Patients With Acute Myeloid Leukemia and Acute Lymphoblastic Leukemia. Journal of Clinical Oncology 2002, Vol 20, No 24 (December 15),: pp 4655-4664.

http://jco.ascopubs.org/content/20/24/4655.full.pdf+html

10. Bunin N, Carston M, Wall D, Adams R, Casper J, Kamani N, King R, and the National Marrow Donor Program Working Group. Unrelated marrow transplantation for children with acute lymphoblastic leukemia in second remission. Blood 2002, May 1, vol 99: 3151-3157. http://bloodjournal.hematologylibrary.org/content/99/9/3151.full.pdf+html

11. Mehmet Uzunel, Jonas Mattsson, Marie Jaksch, Mats Remberger, and Olle Ringde´n. The signiﬁcance of graft-versus-host disease and pretransplantation minimal residual disease status to outcome after allogeneic stem cell transplantation in patients with acute lymphoblastic leukemia. Blood 2001 98: 1982-1985. http://bloodjournal.hematologylibrary.org/content/98/6/1982.full.pdf+html

12. Marina Cetkovic-Cvrlje, Bertram A. Roers, Barbara Waurzyniak, Xing-Ping Liu, and Fatih M. Uckun. Targeting Janus kinase 3 to attenuate the severity of acute graft-versus-host disease across the major histocompatibility barrier in mice. Blood 2001 98: 1607-1613. http://bloodjournal.hematologylibrary.org/content/98/5/1607.full.pdf+html

13. Kate A. Wheeler, Susan M. Richards, Clifford C. Bailey, Brenda Gibson, Ian M. Hann, Frank G. H. Hill, and Judith M. Chessells for the Medical Research Council Working Party on Childhood Leukaemia. Bone marrow transplantation versus chemotherapy in the treatment of very high–risk childhood acute lymphoblastic leukemia in ﬁrst remission: results from Medical Research Council UKALL X and XI. Blood 2000 96: 2412-2418. http://bloodjournal.hematologylibrary.org/content/96/7/2412.full.pdf+html

14. O. Ringde´n, M. Remberger, T. Ruutu, J. Nikoskelainen, L. Volin, L. Vindeløv, T. Parkkali, S. Lenhoff, B. Sallerfors, L. Mellander, P. Ljungman, and N. Jacobsen, for the Nordic Bone Marrow Transplantation Group. Increased Risk of Chronic Graft-Versus-Host Disease, Obstructive Bronchiolitis, and Alopecia With Busulfan Versus Total Body Irradiation: Long-Term Results of a Randomized Trial in Allogeneic Marrow Recipients With Leukemia. 1999 93: 2196-2201. http://bloodjournal.hematologylibrary.org/content/93/7/2196.full.pdf+html

15. Christopher J.C. Knechtli, Nicholas J. Goulden, Jeremy P. Hancock, Victoria L.G. Grandage, Emma L. Harris, Russell J. Garland, Claire G. Jones, Anthony W. Rowbottom, Linda P. Hunt, Ann F. Green, Emer Clarke, Alan W. Lankester, Jacqueline M. Cornish, Derwood H. Pamphilon, Colin G. Steward, and Anthony Oakhill. Minimal Residual Disease Status Before Allogeneic Bone Marrow Transplantation Is an Important Determinant of Successful Outcome for Children and Adolescents With Acute Lymphoblastic Leukemia. Blood 1998 92: 4072-4079. http://bloodjournal.hematologylibrary.org/content/92/11/4072.full.pdf+html

16. Daniel J. Weisdorf, Amy L. Billett, Peter Hannan, Jerome Ritz, Stephen E. Sallan, Michael Steinbuch, and Norma K.C. Ramsay. Autologous Versus Unrelated Donor Allogeneic Marrow Transplantation for Acute Lymphoblastic Leukemia. Blood 1997 90: 2962-2968. http://bloodjournal.hematologylibrary.org/content/90/8/2962.full.pdf+html

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In focus: Melanoma therapeutics

Posted in CANCER BIOLOGY & Innovations in Cancer Therapy, Cell Biology, Signaling & Cell Circuits, Chemical Biology and its relations to Metabolic Disease, Disease Biology, Small Molecules in Development of Therapeutic Drugs, FDA Regulatory Affairs, Human Immune System in Health and in Disease, Molecular Genetics & Pharmaceutical, Pharmaceutical Analytics, Regulated Clinical Trials: Design, Methods, Components and IRB related issues, tagged Aldesleukin, American Cancer Society, angiogenesis, biochemotherapy, BRAF, Chemotherapy, Clinical Trials, Dacarbazine, Eastern Cooperative Oncology Group, ECOG, FDA, gp100, IFN-gamma, IFN-α-2b, IL-2, Immunotherapy, Interferon gamma, Interleukin-2, Ipilimumab, Jak3, MAPK, Melanoma, metastatic, OS, overall survival, PFS, progression-free survival, Proleukin, response rate, RR, Temozolomide, Therapy, vaccine, VEGFR, Vemurafenib, Yervoy on March 8, 2013| 5 Comments »

In focus: Melanoma therapeutics

Author and Curator: Ritu Saxena, Ph.D.

In the last post of Melanoma titled “In focus: Melanoma Genetics”, I discussed the clinical characteristics and the genetics involved in Melanoma. This post would discuss melanoma therapeutics, both current and novel.

According to the American Cancer Society, more than 76,000 new cases and more than 9100 deaths from melanoma were reported in the United States in 2012[1] Melanoma develops from the malignant transformation of melanocytes, the pigment-producing cells that reside in the basal epidermal layer in human skin. Although most melanomas arise in the skin, they may also arise from mucosal surfaces or at other sites to which neural crest cells migrate.

Melanoma therapeutics

Surgical treatment of cutaneous melanoma employs specific surgical margins depending on the depth of invasion of the tumor and there are specific surgical treatment guidelines of primary, nodal, and metastatic melanoma that surgeons adhere to while treatment. Melanoma researchers have been focusing on developing adjuvant therapies for that would increase the survival post-surgery.

Chemotherapy

Among traditional chemotherapeutic agents, only dacarbazine is FDA approved for the treatment of advanced melanoma (Eggermont AM and Kirkwood JM, Eur J Cancer, Aug 2004;40(12):1825-36). Dacarbazine is a triazene derivative and alkylates and cross-links DNA during all phases of the cell cycle, resulting in disruption of DNA function, cell cycle arrest, and apoptosis. Currently, 17 clinical trials are underway to test the efficacy and effectiveness of dacarbazine against melanoma as either a single agent or in combination chemotherapy regimens with other anti-cancer chemotherapeutic agents such as cisplatin, paclitaxel. Temozolomide is a triazene analog of dacarbazine and is approved for the treatment of malignant gliomas. At physiologic pH, it is converted to a short-lived active cytotoxic compound, monomethyl triazeno imidazole carboxamide (MTIC). MTIC methylates DNA at the O6 and N7 positions of guanine, resulting in inhibition of DNA replication. Unlike dacarbazine, which is metabolized to MITC only in the liver, temozolomide is metabolized to MITC at all sites. Temozolomide is administered orally and penetrates well into the central nervous system. Temozolomide is being tested in many combination regimens for patients with melanoma metastatic to the brain (Douglas JG and Margolin K, Semin Oncol, Oct 2002;29(5):518-24).

Immunotherapy

Melanoma and the immune system are closely related. Hence, immunotherapy has been explored in the treatment of the disease. The two most widely investigated immunotherapy drugs for melanoma are Interferon (IFN)-alpha and Interleukin-2 (IL-2).

The role of IFNalpha-2b in the adjuvant therapy of patients with localized melanoma at high risk for relapse was established by the results of three large randomized trials conducted by the US Intergroup; all three trials demonstrated an improvement in relapse-free survival and two in overall survival. One of these trials, a large randomized multicenter trial performed by the Eastern Cooperative Oncology Group (ECOG), in high-risk melanoma patients showed significant improvements in relapse-free and overall survival with adjuvant IFN-α-2b therapy, compared with standard observation (ECOG 1684). The results of the study led to FDA approval of IFN-α-2b for treatment of melanoma. This study was performed on patients with deep primary tumors without lymph node involvement and node-positive melanomas. In other studies, little antitumor activity has been demonstrated in IFN-α-2b–treated metastatic stage IV melanoma.

Recombinant IL-2 showed an overall response rate of 15-20% in metastatic melanoma and was capable of producing complete and durable remissions in about 6% of patients treated. Based upon these data, the US FDA has approved the use of high-dose IL-2 for the therapy of patients with metastatic melanoma. Aldesleukin (Brand name: Proleukin) is a recombinant analog of the endogenous cytokine interleukin-2 (IL-2). It binds to and activates the IL-2 receptor (IL-2R), followed by heterodimerization of the IL-2R beta and gamma(c) cytoplasmic chains; activation of Jak3; and phosphorylation of tyrosine residues on the IL-2R beta chain, resulting in an activated receptor complex (NCI). The activated complex recruits several signaling molecules that act as substrates for regulatory enzymes associated with the complex. It is administered intravenously and stimulates lymphokine-activating killer (LAK) cells, natural killer (NK) cells and the production of cytokines such as gamma interferon (nm|OK). Several clinical trials are currently underway using Aldesleukin to determine the efficacy of combination treatment in melanoma patients.

Another anti-cancer immunotherapeuty-based mechanism involved inhibition of inhibitory signal of cytotoxic T lymphocyte-associated antigen 4 (CTLA-4), a molecule on T-cells that plays a critical role in regulating natural immune responses. Ipilimumab (Brand name: Yervoy) was by FDA for melanoma treatment. It is a human monoclonal antibody (MAb) T-cell potentiator that specifically blocks CTLA-4. It is approved for inoperable advanced (Stage III) or metastatic (Stage IV) melanoma in newly diagnosed or previously treated patients (nm|OK). The approval, March 25, 2011, was based on a randomized (3:1:1) double-blind double-dummy clinical trial (MDX010-20) in patients with unresectable or metastatic melanoma who had received at least one prior systemic treatment for melanoma. Patients were randomly assigned to receive either ipilimumab, 3 mg/kg intravenously, in combination with the tumor vaccine (n=403); ipilimumab plus vaccine placebo (n=137); or tumor vaccine with placebo (n=136). Patients treated with ipilimumab alone had a median overall survival (OS) of 10 months while those treated with tumor vaccine had a median OS of 6 months. The trial also demonstrated a statistically significant improvement in OS for patients treated with the combination of ipilimumab plus tumor vaccine compared with patients treated with tumor vaccine alone. For more information on the trial, check the clinical trials website, www.clinicaltrials.gov

Signaling pathway inhibitors

Approximately 90% of BRAF gene mutations involve valine (V) to glutamic acid (E) mutation at number 600 residue (V600E). The resulting oncogene product, BRAF (V600E) kinase is highly active and exhibits elevated MAPK pathway. The BRAF(V600E) gene mutation occurs in approximately 60% of melanomas indicating that it could be therapeutically relevant. Vemurafenib (Brand name: Zelboraf) is a novel small-molecule inhibitor of BRAF (V600E) kinase. It selectively binds to the ATP-binding site and inhibits the activity of BRAF (V600E) kinase. Vemurafebib inhibits over active MAPK pathway by inhibiting the mutated BRAF kinase, thereby reducing tumor cell proliferation (NCI). Encouraging results of phase III randomized, open-label, multicenter trial were reported recently at the 2011 ASCO meeting (Chapman PB, et al, ASCO 2011, Abstract LBA4). The trial compared the novel BRAF inhibitor vemurafenib with dacarbazine in patients with BRAF-mutated melanoma. Previously untreated, unresectable stage IIIC or stage IV melanoma that tested positive for BRAF mutation were randomized (1:1) to vemurafenib or dacarbazine. The response rate (RR) was significantly high (48.4%) in vemurafenib treated patients as compared to 5.5% in dacarbazine among the 65% of patients evaluable for RR to date. In addition, vemurafenib was associated with significantly improved OS and PFS compared to dacarbazine in patients with previously untreated BRAF (V600E) mutation bearing patients with metastatic melanoma.

Biochemotherapy

Biochemothreapy combine traditional chemotherapy with immunotherapies, such as IL-2 and IFN-α-2b. These combination therapies seemed promising in phase II trials, however, seven large studies failed to show statistically significant increased overall survival rates for various biochemotherapy regimens in patients with stage IV metastasis (Margolin KA, et al, Cancer, 1 Aug 2004;101(3):435-8). Owing to inconsistent results of the available studies with regard to benefit including RR, OS and progression time, and consistently high toxicity rates, clinical practice guideline do not recommend biochemotherapy for the treatment of metastatic melanoma (Verma S, et al, Curr Oncol, April 2008; 15(2): 85–89).

Vaccines

The use of therapeutic vaccines is an ongoing area of research, and clinical trials of several types of vaccines (whole cell, carbohydrate, peptide) are being conducted in patients with intermediate and late-stage melanoma. Vaccines are also being tested in patients with metastatic melanoma to determine their immune effects and to define their activity in combination with other immunotherapeutic agents such as IL-2 or IFNalpha (Agarwala S, Am J Clin Dermatol, 2003;4(5):333-46). In fact, recently investigators at the Indiana University Health Goshen Center for Cancer Care (Goshen, IN) conducted a randomized, multicenter phase III trial involving 185 patients with stage IV or locally advanced stage III cutaneous melanoma. The patients were assigned into treatment groups with IL-2 alone or with vaccine (gp100) followed by IL-2. The vaccine-IL-2 group had a significantly improved OR as compared to the IL-2-only group (16% Vs. 6%) and longer progression free survival (2.2 months Vs. 1.6 months). The median overall survival was also longer in the vaccine-interleukin-2 group than in the interleukin-2-only group (17.8 months Vs. 11.1 months). Thus, a combination of vaccine and immunotherapy showed a better response rate and longer progression-free survival than with interleukin-2 alone in patients with advanced melanoma (Schwartzentruber DJ, et al, N Engl J Med, 2 Jun 2011;364(22):2119-27).

Which Treatment When?

Earlier, there were essentially two main options for patients suffering from advanced melanoma, dacarbazine and IL-2. Dacarbazine, a chemotherapeutic agent produces modest improvements in survival or symptomatic benefits in most patients. Interleukin-2 -based drugs, on the other hand, induce long-term remissions in a small group of patients but are highly toxic. Recently, FDA approved ipilimumab and vemurafenib for patients with metastatic melanoma. Apart from these, therapies are also aiming at starving the tumor by inhibiting angiogenesis or depleting nutrients essential for cancer growth. Of the antiangiogenic compounds, VEGFR inhibitors SU5416 and AG-013736 demonstrated broad-spectrum antitumor activity in mice bearing xenografts of human cancer cell lines originating from various tissues, including melanoma. In addition, several trials are currently underway to test the efficacy of the drugs in combination. In the future, personalized medicine-based recommendations of novel and existing drugs for melanoma patients might be the way to go.

Reference:

Related articles on Melanoma on this Open Access Online Scientific Journal:

In focus: Melanoma Genetics Curator- Ritu Saxena, Ph.D.
Thymosin alpha1 and melanoma Author/Editor- Tilda Barliya, Ph.D.
A New Therapy for Melanoma Reporter- Larry H Bernstein, M.D.
Melanoma: Molecule in Immune System Could Help Treat Dangerous Skin Cancer Reporter: Prabodh Kandala, Ph.D.
Why Braf inhibitors fail to treat melanoma. Reporter: Prabodh Kandala, Ph.D.

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“Thymosin alpha1 and melanoma”

Posted in Bio Instrumentation in Experimental Life Sciences Research, Biomarkers & Medical Diagnostics, BioSimilars, CANCER BIOLOGY & Innovations in Cancer Therapy, Disease Biology, Small Molecules in Development of Therapeutic Drugs, Drug Delivery Platform Technology, Health Economics and Outcomes Research, Human Immune System in Health and in Disease, Population Health Management, Genetics & Pharmaceutical, Regulated Clinical Trials: Design, Methods, Components and IRB related issues, tagged Clark's multi-step model, Clinical Trials, Dacarbazine, immunomodulatory, immunosurveillance, Immunotherapy, Melanoma, risk factors, Thymosin, Thymosin a1, Thymosine and melanoma on February 15, 2013| 2 Comments »

Author, Editor: Tilda Barliya, PhD

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Word Cloud By Danielle Smolyar

Although melanoma accounts for only 4 percent of all dermatologic cancers, it is responsible for 80 percent of deaths from skin cancer; only 14 percent of patients with metastatic melanoma survive for five years (1). The incidence of melanoma is increasing worldwide, with a growing fraction of patients with advanced disease for which prognosis remains poor despite advances in the field (2). Treatment options are limited despite advances in immunotherapy and targeted therapy. For patients with surgically resected, thick (≥2 mm) primary melanoma with or without regional lymph node metastases, the only effective adjuvant therapy is interferon-α (IFN-α). However, because of the limited benefit upon disease-free survival and the smaller potential improvement of overall survival, the indication for IFN-α treatment remains controversial (2). A better understanding of melanoma immunosurveillance is therefore essential to enable the design of better, targeted melanoma therapies (4).

Risk factors (2):

Family history of melanoma, multiple benign or atypical nevi, and a previous melanoma
Immunosuppression
Sun sensitivity
Exposure to ultraviolet radiation

Each of these risk factors corresponds to a genetic predisposition or an environmental stressor that contributes to the genesis of melanoma and each factor is understood to various degrees at a molecular level. The Clark model of the progression of melanoma emphasizes the stepwise transformation of melanocytes to melanoma. The model depicts the proliferation of melanocytes in the process of forming nevi and the subsequent development of dysplasia, hyperplasia, invasion, and metastasis.

This Clark’s multi-step model, and predict that the acquisition of a BRAF mutation can be a founder event in melanocytic neoplasia. While mutations of the BRAF gene are frequent in melanomas on non-chronic sun damaged skin which are prevalent in Caucasians, acral and mucosal melanomas harbor mutations of the KIT gene as well as the amplifications of cyclin D1 or cyclin-dependent kinase 4 gene.

The choice of target antigens is key to the success of tumour vaccination or tumour immunotherapy. Melanoma candidate antigens include: (A) mutated or aberrantly expressed molecules (e.g. CDK4, MUM-1, beta-catenin) (B) cancer/testis antigens (e.g. MAGE, BAGE and GAGE) and (C) melanoma- associated antigens (MAA).

MAAs are self-antigens normally expressed during the differentiation of melanocytes and play a role in different enzymatic steps of melanogenesis. However, in transformed melanocytes (melanoma cells), MAAs are often overexpressed (4).

The main MAAs are tyrosinase, an enzyme that catalyses the production of melanin from tyrosine by oxidation, the tyrosinase-related proteins (TRP-1) and 2 (TRP-2), the glycoprotein (gp)100 (silver-gene) and MelanA/MART. It is thought that the specialized cell biology of melanin synthesis may favour the loading of MAA peptides into the antigen presentation pathway. 50% of melanoma patients have tumour-infiltrating lymphocytes (TILs) recognising tyrosinase and Melan A, indicating that these antigens are important in the natural melanoma immunosurveillance. Moreover, MAAs are well characterized in mice and humans, allowing the development of tetramers to detect antigen-specific immune responses.

Tα1 Mechanism of action

Tα1, a 28 amino acid peptide of ∼3.1 kDa, is endogenously produced by the thymus gland by the cleavage of its precursor pro-Ta1. Although the fine immunologic mechanism(s) of action of T1 have not fully been elucidated, experimental evidence points to its strong immunomodulatory properties. In particular, it was reported that Ta1 enhances T cell–mediated immune responses by several mechanisms, including increased T cell production (i.e., CD4+, CD8+, and CD3+ cells), stimulation of T cell differentiation and/or maturation, reduction of T cell apoptosis, and restoration of T cell–mediated antibody production (5).

Furthermore, it was demonstrated that T1 acts on the immune system by modulating the release of proinflammatory cytokines (i.e., interleukin-2 (IL-2), interferon-gamma (IFN-)),12–14 and through the activation of natural killer and dendritic cells.12 In addition, T1 was also demonstrated to have direct effects on cancer cells by increasing the levels of expression of different tumor antigens and of components of the major histocompatibility complex class I, as well as by reducing cancer cell growth.

Together, these experimental findings bear relevance for cancer immunotherapy and suggest that T1 can activate innate and adaptive immune responses and modulate the immunophenotype of cancer cells, improving their immunogenicity and their recognition by the immune system.

Danielli R and colleagues have very nicely outlined the use of the Thymosin a1 in the clinical setting for treating melanoma (5) titled :”Thymosin a1 in melanoma: from the clinical trial setting to the daily practice and beyond”. A large body of available preclinical in vitro and in vivo evidence points to thymosin alpha 1 (Ta1) as a useful immunomodulatory peptide,with significant therapeutic potential in metastatic melanoma in the absence of clinically meaningful toxicity. The results emerging frominitial trials provide support of the ability of T1 to improve the clinical outcome of advanced melanoma patients through the activation of the immune system.

Ta1 and Clinical Trials in Melanoma

A large scale, randomized, phase II study was conducted at 64 European centers between 2002 and 2006 to investigate the efficacy of Ta1 administered in combination with DTIC (Dacarbazine) or with DTIC + IFNa, versus only DTIC + IFNa, in 488 previously untreated patients with cutaneous metastatic melanoma. The study was designed to evaluate the ability of Ta1 to potentiate the therapeutic efficacy of DTIC.

Patients were randomly assigned to five treatment groups: DTIC + IFNa and 1.6 mg of Ta1; DTIC + IFNa and 3.2 mg of T1; DTIC + IFN-a and 6.4 mg of Ta1; DTIC + 3.2 mg of Ta1; and DTIC + IFNa

Results:

The clinical rate (CBR), defined as the proportion of patients with a complete response, partial response, or stable disease, was significantly higher in patients who received Ta1 + DTIC than in those who received control therapy. Results in patients who received T1 (all groups combined) compared with those who received the control treatment

Improved progression-free survival (hazard ratio (HR): 0.80;
95%confidence interval (CI): 0.63–1.01; P = 0.06) and
OS (median: 9.4 vs. 6.6 months)

These outcomes suggested to addition of Thymosin a1 to the treatment resulted in the reduction in the risk of mortality and disease progression in patients with metastatic malignant melanoma, and pointed to a poor effect of IFN- in the combination. More so, the poor results of the IFN group is not surprising due to the limited therapeutic activity of IFN observed in phase III clinical trials.

This study however have some limitations as standard assessment criteria, such as RECIST and WHO indications, conventionally applied to cytotoxic agents, do not adequately capture some patterns of response observed in the course of immunotherapy; stemming from these considerations, immune-related response criteria (irRC) were developed to measure primary and secondary endpoints in immunotherapy clinical trials.

Therefore the above study might underestimate the therapeutic efficacy of Thymosin a1 since irRC criteria were not used.

In Summary:

A large scale phase III clinical trial should be designed to further explore the therapeutic activity of Thymosine a1 in melanoma patients with defined endpoints and irRC criteria. Moreover, combination studies should explore the activity of T1 in association with other approved agents, such as ipilimumab and vemurafenib or as maintenance therapy in melanoma patients who experience clinical benefit after treatment with these agents.

Also, because of the pleiotropic immunemechanism(s) of action of T1, including the upregulation of T cell–driven immune responses against specific tumor antigens, priming of immune responses and potentiation of antitumor T cell–mediated immune responses through the activation of Toll-like receptor 9 on dendritic cells, coupling Ta1 to cancer vaccines should be an additional useful therapeutic strategy to pursue. T1 could, in fact, prove helpful in overcoming the limited immunogenicity and the short-lived persistency of adequate immunologic antitumor responses frequently reported as potential causes of failure of therapeutic vaccines.

Ref:

1. Arlo J. Miller, M.D.,., and Martin C. Mihm, Jr. Mechanisms of disease: Melanoma. N Engl J Med 2006 (6); 355:51-65.

http://www.nejm.org.rproxy.tau.ac.il/doi/pdf/10.1056/NEJMra052166

http://www.nejm.org/doi/full/10.1056/NEJMra052166

2. Garbe C., Eigentler TK., Keilholz U., Hauschild A and Kirkwood JM. Systematic review of medical treatment in melanoma: current status and future prospects. Oncologist 2011;16(1):5-24.

http://theoncologist.alphamedpress.org/content/16/1/5.long

3. http://flipper.diff.org/app/items/info/1983

4. Träger U, Sierro S, Djordjevic G, Bouzo B, Khandwala S, et al. (2012) The Immune Response to Melanoma Is Limited by Thymic Selection of Self-Antigens. PLoS ONE 7(4): e35005. doi:10.1371/journal.pone.0035005.

http://www.plosone.org/article/info:doi/10.1371/journal.pone.0035005

5. Riccardo Danielli, Ester Fonsatti, Luana Calabr` o, Anna Maria Di Giacomo, and Michele Maio. Thymosin 1 in melanoma: from the clinical trial setting to the daily practice and beyond. Ann. N.Y. Acad. Sci. 1270 (2012) 8–12.

http://www.ncbi.nlm.nih.gov/pubmed/16822996

http://onlinelibrary.wiley.com/doi/10.1111/j.1749-6632.2012.06757.x/abstract

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Prostate Cancer and Nanotechnology

Author, Curator: Tilda Barliya, PhD

Prostate cancer is common and a frequent cause of cancer death. In the United States, prostate cancer is the most commonly diagnosed visceral cancer. In 2012, there were expected to be about 242,000 new prostate cancer diagnoses and about 28,000 prostate cancer deaths. Prostate cancer is second only to nonmelanoma skin cancer and lung cancer as the leading cause of cancer and cancer death, respectively, in US men. Worldwide, in 2008 there were estimated to be 903,000 new cases of prostate cancer and 258,000 prostate cancer deaths making it the second most commonly diagnosed cancer in men and the sixth leading cause of male cancer death (1).

Prostate cancer survival is related to many factors, especially the extent of tumor at the time of diagnosis. The five-year relative survival among men with cancer confined to the prostate (localized) or with just regional spread is 100 percent compared with 31.9 percent among those diagnosed with distant metastases . While men with advanced stage disease may benefit from palliative treatment, their tumors are generally not curable

Prostate-specific antigen (PSA) testing revolutionized prostate cancer screening. Although PSA was originally introduced as a tumor marker to detect cancer recurrence or disease progression following treatment, it became widely adopted for cancer screening by the early 1990s. Subsequently, professional societies issued guidelines supporting prostate cancer screening with PSA. PSA testing led to a dramatic increase in the incidence of prostate cancer, the majority of these newly-diagnosed cancers were clinically localized which led to an increase in radical prostatectomy and radiation therapy, aggressive treatments intended to cure these early-stage cancers (2). However, PSA is also elevated in a number of benign conditions, particularly benign prostatic hyperplasia (BPH) and prostatitis

So what is PSA?

PROSTATE SPECIFIC ANTIGEN (PSA) — PSA is a glycoprotein produced by prostate epithelial cells. PSA levels may be elevated in men with prostate cancer because PSA production is increased and because tissue barriers between the prostate gland lumen and the capillary are disrupted, releasing more PSA into the serum.

A research team led by Prof. Langer and Prof. Farokhzad from MIT and and Brigham and Women’s Hospital in Boston have developed a nanotechnology strategies adopted for the management of prostate cancer. In particular, the combination of targeted and controlled-release polymer nanotechnologies has recently resulted in the clinical development of BIND-14, a promising targeted Docetaxel-loaded nanoprototype, which can be validated for use in the prostate cancer therapy and entered clinical trials in January 2011

The BIND-014 nanoparticles have three components: one that carries the drug (docetaxel), one that targets PSMA, and one that helps evade macrophages and other immune-system cells.

Clinical results

The Phase I clinical trial involved 17 patients with advanced or metastatic tumors who had already gone through traditional chemotherapy. In Phase I trials, researchers evaluate a potential drug’s safety and study its effects in the body. To determine safe dosages, patients were given escalating doses of the nanoparticles. So far, doses of BIND-014 have reached the amount of docetaxel usually given without nanoparticles, with no new side effects. The known side effects of docetaxel have also been milder.

In the 48 hours after treatment, the researchers found that docetaxel concentration in the patients’ blood was 100 times higher with the nanoparticles as compared to docetaxel administered in its conventional form. Higher blood concentration of BIND-014 facilitated tumor targeting resulting in tumor shrinkage in patients, in some cases with doses of BIND-014 that correspond to as low as 20 percent of the amount of docetaxel normally given. The nanoparticles were also effective in cancers in which docetaxel usually has little activity, including cervical cancer and cancer of the bile ducts.

Summary:

Early detection of prostate cancer increased dramatically the five-year survival of patients. “This study demonstrates for the first time that it is possible to generate medicines with both targeted and programmable properties that can concentrate the therapeutic effect directly at the site of disease, potentially revolutionizing how complex diseases such as cancer are treated”. The Phase I clinical trial is still ongoing and continued dose escalation is underway; BIND Biosciences is now planning Phase II trials, which will further investigate the treatment’s effectiveness in a larger number of patients.

REFERENCES

1. Richard M Hoffman. Screening for prostate cancer. http://www.uptodate.com/contents/screening-for-prostate-cancer

2. http://web.mit.edu/newsoffice/2012/cancer-particle-0404.html

3. http://www.bindbio.com/content/pages/news/news_detail.jsp/q/news-id/70

4. State of the art in oncologic imaging of Prostate

http://pharmaceuticalintelligence.com/2013/01/28/state-of-the-art-in-oncologic-imaging-of-prostate/

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Personalized medicine gearing up to tackle cancer

Posted in CANCER BIOLOGY & Innovations in Cancer Therapy, Interviews with Scientific Leaders, Personalized and Precision Medicine & Genomic Research, Regulated Clinical Trials: Design, Methods, Components and IRB related issues, tagged ASCO, CAT-scan, Clinical Trials, Gleevac, MD Anderson Cancer center, molecular aberrations, Personalized medicine, phase I on January 7, 2013| 15 Comments »

Personalized medicine gearing up to tackle cancer

Reporter: Ritu Saxena, Ph.D.

Article ID #10: Personalized medicine gearing up to tackle cancer. Published on 1/7/2013

WordCloud Image Produced by Adam Tubman

Article-7.1.3. Personalized medicine gearing up to tackle cancer

Views of leading cancer researcher, Dr. Apostolia M. Tsimberidou

Since the inception of personalized medicine, it has been visualized that a patient walking into a doctor’s office would be recommended a treatment tailored around his/her genetic and molecular profile. Although this idea of personalized medicine still seems far-fetched, it is currently being implemented in a few clinics, including that of Apostolia M. Tsimberidou, MD, PhD.

Dr. Tsimberidou is an associate professor in the Department of Investigational Cancer Therapeutics at The University of Texas MD Anderson Cancer Center and a member of the American Society of Clinical Oncology (ASCO) Educational Committee. She is also the brains behind a large study of personalized medicine-based cancer treatment. The findings of her successful phase I clinical trial in late-stage cancer patients has attracted a lot of attention. I recently had a chance to interview her and find out her views on the current status, challenges and future of personalized medicine.

Dr. Tsimberidou explains the basis of her study, “We analyze tumors from patients with cancer to identify molecular aberrations, which are then used to select optimal treatment.” On the basis of the molecular aberrations determined, the patients were recommended for treatment with matched anti-cancer therapeutic drugs. The results obtained in terms of clinical outcomes of patients were intriguing. Among patients harboring one molecular aberration, there was a significant improvement in the median survival duration of patients who underwent matched therapy (13.4 months) as compared to patients treated without matched therapy (9 months). Matched therapy patients also showed a better overall response rate of 27% vs. 5% in unmatched patients. Another criteria measured was the time-to-treatment failure which was again longer with matched targeted therapy, 5.2 months compared to 3.1 months with systemic therapy. The results of the study were published recently in Clinical Cancer Research. Essentially, the study concluded that there is a better chance of drug response and longer survival in patients who have been administered drugs according to their molecular signature. This is indeed good news for patients suffering from the disease.

So, how does the success of matched-therapy translate to the clinic? “What we propose is the optimization of treatment by taking into consideration multiple factors, including the genetics and molecular status of tumors, and that the process becomes a part of regular clinical practice,” explains Dr. Tsimberidou.

When Dr. Tsimberidou and her colleagues at MD Anderson Cancer Center started the phase I clinical trial for personalized medicine in 2007, they faced numerous challenges. The biggest challenge she describes was “dealing with the inertia of the existing system”. “It is easy for an insurance company to approve payment for a CAT-scan, but it is still challenging to cover the cost of a new biopsy and tumor molecular analysis from a patient who has suffered from cancer for over 10 years. Hopefully, there will be a shift in the approach.” How could a shift in the approach be achieved? “Researchers need to continue to carefully design prospective clinical trials, including small phase II clinical studies with targeted agents against tumor molecular aberrations.” She emphasizes that “resources–time, energy and funds–to conduct clinical trials are very limited. Using the approach of matched therapy earlier during the course of the disease could give better results.”

Dr. Tsimberidou states, “The most important thing is that we need to take advantage of the available technology to make advances in tumor molecular profiling and drug discovery. We need the technologists, molecular biologists, health care professionals and regulators to work together and expedite the use of the existing technology to identify tumor abnormalities and to discover novel drugs. We need to access, learn and share with each other to determine what the optimal therapeutic approach for every patient is.”

According to the American Cancer Society, the probability that an individual will develop or die from cancer over the course of a lifetime (lifetime risk) in the United States is less than a 1 in 2 for men; and a little more than 1 in 3 for women. Thanks to passionate and committed researchers like Dr. Tsimberidou, personalized medicine-based cancer treatments might take us a few steps closer to curing the disease. Dr. Tsimberidou concludes, “We have to develop innovative treatment protocols and to offer the best treatment possible for each of our patients”.

Reporter

Ritu Saxena, Ph.D.

Author, Reporter, Curator @ Leaders in Pharmaceutical Business Intelligence

http://pharmaceuticalintelligence.com/

Research article:

Personalized medicine in a phase I clinical trials program: the MD anderson cancer center initiative.

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Nanotechnology and HIV/AIDS Treatment

Posted in Bio Instrumentation in Experimental Life Sciences Research, Biomarkers & Medical Diagnostics, BioSimilars, Disease Biology, Small Molecules in Development of Therapeutic Drugs, Human Immune System in Health and in Disease, Infectious Disease & New Antibiotic Targets, Nanotechnology for Drug Delivery, Pharmaceutical R&D Investment, Regulated Clinical Trials: Design, Methods, Components and IRB related issues, Uncategorized, tagged AIDS, antiretroviral drugs, CD4, CD4+ T cells, CD8, CD8+ T cells, Clinical tr, Clinical Trials, CXCR4, gene therapy, HAART, highly active antiretroviral therapy (HAART), HIV, immunoresponse, liposome, macrophages, nanosuspension, nanotechnology, nanotherapeutic, PEG, PLGA, polymeric system, retroviral, RNAi, siRNA, T cells on December 25, 2012| 5 Comments »

Nanotechnology and HIV/AIDS Treatment

Author: Tilda Barliya, PhD

AIDS was first reported in 1981 followed by the identification of HIV as the cause of the disease in 1983 and is now a global pandemic that has become the leading infectious killer of adults worldwide. By 2006, more than 65 million people had been infected with the HIV virus worldwide and 25 million had died of AIDS (Merson MH. The HIV-AIDS pandemic at 25 – the global response. (1, 2). This has caused tremendous social and economic damage worldwide, with developing countries, particularly Sub-Saharan Africa, heavily affected.

A cure for HIV/AIDS has been elusive in almost 30 years of research. Early treatments focused on antiretroviral drugs that were effective only to a certain degree. The first drug, zidovudine, was approved by the US FDA in 1987, leading to the approval of a total of 25 drugs to date, many of which are also available in fixed-dose combinations and generic formulations for use in resource-limited settings (to date, only zidovudine and didanosine are available as true generics in the USA).

However, it was the advent of a class of drugs known as protease inhibitors and the introduction of triple-drug therapy in the mid-1990s that revolutionized HIV/AIDS treatment (3,4). This launched the era of highly active antiretroviral therapy (HAART), where a combination of three or more different classes of drugs are administered simultaneously.

Challenges of HIV/AIDS treatment

HIV resides in latent cellular and anatomical reservoirs where current drugs are unable to completely eradicate the virus.
Macrophages are major cellular reservoirs, which also contribute to the generation of elusive mutant viral genotypes by serving as the host for viral genetic recombination.
Anatomical latent reservoirs include secondary lymphoid tissue, testes, liver, kidney, lungs, the gut and the brain.
The major challenge facing current drug regimens is that they do not fully eramacrdicate the virus from these reservoirs; requiring patients take medications for life. Under current treatment, pills are taken daily, resulting in problems of patient adherence. The drugs also have side effects and in some people the virus develops resistance against certain drugs.

Current treatment in HIV/AIDS

The use of the HAART regimen, particularly in the developed world, has resulted in tremendous success in improving the expectancy and quality of lives for patients. However, some HAART regimens have serious side effects and, in all cases, HAART has to be taken for a lifetime, with daily dosing of one or more pills. Due to the need to take the medication daily for a lifetime, patients fail to adhere to the treatment schedule, leading to ineffective drug levels in the body and rebound of viral replication.Some patients also develop resistance to certain combinations of drugs, resulting in failure of the treatment. The absence of complete cure under current treatment underscores the great need for continued efforts in seeking innovative approaches for treatment of HIV/AIDS.

Drug resistance is mainly caused by the high genetic diversity of HIV-1 and the continuous mutation it undergoes. This problem is being addressed with individualized therapy, whereby resistance testing is performed to select a combination of drugs that is most effective for each patient (5). In addition, side effects due to toxicities of the drugs are also a concern. There are reports that patients taking HAART experience increased rates of heart disease, diabetes, liver disease, cancer and accelerated aging. Most experts agree that these effects could be due to the HIV infection itself or co-infection with another virus, such as co-infection with hepatitis C virus resulting in liver disease. However, the toxicities resulting from the drugs used in HAART could also contribute to these effects.

Under current treatment, complete eradication of the virus from the body has not been possible. The major cause for this is that the virus resides in ‘latent reservoirs’ within memory CD4⁺ T cells and cells of the macrophage–monocyte lineage. A major study recently found that, in addition to acting as latent reservoirs, macrophages significantly contribute to the generation of elusive mutant viral genotypes by serving as the host for viral genetic recombination (6). The cells that harbor latent HIV are typically concentrated in specific anatomic sites, such as secondary lymphoid tissue, testes, liver, kidney, lungs, gut and the CNS. The eradication of the virus from such reservoirs is critical to the effective long-term treatment of HIV/AIDS patients.

Therefore, there is a great need to explore new approaches for developing nontoxic, lower-dosage treatment modalities that provide more sustained dosing coverage and effectively eradicate the virus from the reservoirs, avoiding the need for lifetime treatments.

Nanotechnology for HIV/AIDS treatment

The use of nanotechnology platforms for delivery of drugs is revolutionizing medicine in many areas of disease treatment.

Nanotechnology-based platforms for systemic delivery of antiretroviral drugs could have similar advantages.

Controlled-release delivery systems can enhance their half-lives, keeping them in circulation at therapeutic concentrations for longer periods of time. This could have major implications in improving adherence to the drugs.
Nanoscale delivery systems also enhance and modulate the distribution of hydrophobic and hydrophilic drugs into and within different tissues due to their small size. This particular feature of nanoscale delivery systems appears to hold the most promise for their use in clinical treatment and prevention of HIV. Specifically, targeted delivery of antiretroviral drugs to CD4⁺ T cells and macrophages as well as delivery to the brain and other organ systems could ensure that drugs reach latent reservoirs
Moreover, by controlling the release profiles of the delivery systems, drugs could be released over a longer time and at higher effective doses to the specific targets. Figure 1. Various nanoscale drug delivery systems.

Optional treatments:

Antiretroviral drugs
Gene Therapy
Immune Therapy
Prevention

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The use of nanotechnology systems for delivery of antiretroviral drugs has been extensively reviewed by Nowacek et al. and Amiji et al. (7,8).

In a recent study based on polymeric systems, nanosuspensions (200 nm) of the drug rilpivirine (TMC278) stabilized by polyethylene. A series of experiments by Dou et al. showed that nanosuspension of the drug indinavir can be stabilized by a surfactant system comprised of Lipoid E80 for effective delivery to various tissues. The indinavir nanosuspensions were loaded into macrophages and their uptake was investigated. Macrophages loaded with indinavir nanosuspensions were then injected intravenously into mice, resulting in a high distribution in the lungs, liver and spleen. More significantly, the intravenous administration of a single dose of the nanoparticle-loaded macrophages in a rodent mouse model of HIV brain infection resulted in significant antiviral activity in the brain and produced measureable drug levels in the blood up to 14 days post-treatment.polypropylene glycol (poloxamer 338) and PEGylated tocopheryl succinate ester (TPGS 1000) were studied in dogs and mice. A single-dose administration of the drug in nanosuspensions resulted in sustained release over 3 months in dogs and 3 weeks in mice, compared with a half-life of 38 h for free drug. These results serve as a proof-of-concept that nanoscale drug delivery may potentially lower dosing frequency and improve adherence.

Active targeting strategies have also been employed for antiretroviral drug delivery. Macrophages, which are the major HIV reservoir cells, have various receptors on their surface such as formyl peptide, mannose, galactose and Fc receptors, which could be utilized for receptor-mediated internalization. The drug stavudine was encapsulated using various liposomes (120–200 nm) conjugated with mannose and galactose, resulting in increased cellular uptake compared with free drug or plain liposomes, and generating significant level of the drug in liver, spleen and lungs. Stavudine is a water-soluble drug with a very short serum half-life (1 h). Hence, the increased cellular uptake and sustained release in the tissues afforded by targeted liposomes is a major improvement compared with free drug. The drug zidovudine, with half-life of 1 h and low solubility, was also encapsulated in a mannose-targeted liposome made from stearylamine, showing increased localization in lymph node and spleen. An important factor to consider here is that although most of the nucleoside drugs such as stavudine and zidovudine have short serum half-lives, the clinically relevant half-life is that of the intracellular triphosphate form of the drug. For example, despite zidovudine’s 1 h half-life in plasma, it is dosed twice daily based on intracellular pharmacokinetic and clinical efficacy data. Therefore, future nanotechnology-based delivery systems will have to focus in showing significant increase of the half-lives of the encapsulated drugs to achieve a less frequent dosing such as once weekly, once-monthly or even less.

Gene Therapy for HIV/AIDS

In addition to improving existing antiretroviral therapy, there are ongoing efforts to discover alternative approaches for treatment of HIV/AIDS. One promising alternative approach is gene therapy, in which a gene is inserted into a cell to interfere with viral infection or replication. Other nucleic acid-based compounds, such as DNA, siRNA, RNA decoys, ribozymes and aptamers or protein-based agents such as fusion inhibitors and zinc-finger nucleases can also be used to interfere with viral replication.

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RNAi is also considered to have therapeutic potential for HIV/AIDS. Gene silencing is induced by double stranded siRNA, which targets for destruction

he mRNA of the gene of interest. For HIV/AIDS, RNAi can either target the various stages of the viral replication cycle or various cellular targets involved in viral infection such as CD4, CCR5, and/or CXCR4, the major cell surface co-receptors responsible for viral entry. HIV replicates by reverse transcription to form DNA and uses the DNA to produce copies of its mRNA for protein synthesis; siRNA therapy could be used to knock down this viral mRNA. As with other gene therapy techniques, delivery of siRNA to specific cells and tissues has been the major challenge in realizing the potential of RNAi.

New nanotechnology platforms are tackling this problem by providing nonviral alternatives for effective and safe delivery. The first nontargeted delivery of siRNA in humans via self-assembling, cyclodextrin polymer-based nanoparticles for cancer treatment have recently entered Phase I clinical trials.

Although at an early stage, nonviral delivery of siRNA for treatment of HIV infection is also gaining ground. A fusion protein, with a peptide transduction domain and a double stranded RNA-binding domain, was used to encapsulate and deliver siRNA to T cells in vivo. CD4- and CD8-specific siRNA delivery caused RNAi responses with no adverse effects such as cyto-toxicity or immune stimulation. Similarly, a protamine-antibody fusion protein-based siRNA delivery demonstrated that siRNA knockdown of the gag gene can inhibit HIV replication in primary T cells.

Single-walled nanotubes were shown to deliver CXCR4 and CD4 specific siRNA to human T cells and peripheral blood mononuclear cells. Up to 90% knockdown of CXCR4 receptors and up to 60% knockdown of CD4 expression on T cells was observed while the knockdown of CXCR4 receptors on peripheral blood mononuclear cells was as high as 60%. In a separate study, amino-terminated carbosilane dendrimers (with interior carbon-silicon bonds) were used for delivery of siRNA to HIV-infected lymphocytes.

These pioneering studies demonstrate that nonviral siRNA delivery is possible for HIV/AIDS treatment. However, more work needs to be done in optimizing the delivery systems and utilizing designs for efficient targeting and intracellular delivery. The recent developments in polymer- and liposome-based siRNA delivery systems could be optimized for targeting cells that are infected with HIV, such as T cells and macrophages. Moreover, since HIV mutates and has multiple strains with different genetic sequences, combination siRNA therapy targeting multiple genes should be pursued. For these applications, nanotechnology platforms with capability for co-delivery and targeting need to be developed specifically for HIV-susceptible cells. A macrophage and T-cell-targeted and nanotechnology-based combination gene therapy may be a promising platform for efficient HIV/AIDS treatment.

Immunotherapy for HIV/AIDS

The various treatment approaches described above focus on treating HIV/AIDS by directly targeting HIV at the level of the host cell or the virus itself. An alternative approach is immunotherapy aimed at modulating the immune response against HIV. CD8⁺ cytotoxic T-cell responses to acute HIV infection appear to be relatively normal, while neutralizing antibody production by B cells is delayed or even absent.

Immunotherapy is a treatment approach involving the use of immunomodulatory agents to modulate the immune response against a disease. Similar to vaccines, it is based on immunization of individuals with various immunologic formulations; however, the purpose is to treat HIV-infected patients as opposed to protect healthy individuals (preventive vaccines will be discussed in an upcoming section). The various immunotherapy approaches for HIV/AIDS could be based on delivering cytokines (such as IL-2, IL-7 and IL-15) or antigens. The development of cellular immunity, and to a large degree humoral immunity, requires antigen-presenting cells (APCs) to process and present antigens to CD4⁺and CD8⁺ T cells. Dendritic cells (DCs) are the quintessential professional APCs responsible for initiating and orchestrating the development of cellular and humoral (antibody) immunity.

Various polymeric systems have been explored for in vivo targeting of DCs and delivery of small molecules, proteins or DNAs showing potential for immunotherapy. Poly(ethylene glycol) (PEG) stabilized poly(propylene sulfide) polymer nanoparticles accumulated in DCs in lymph nodes. Following nanoparticle injection, DCs containing nanoparticles accumulated in lymph nodes, peaking at 4 days with 40–50% of DCs and other APCs having internalized nanoparticles.

In another study, nanoparticles of the copolymer poly(D,L-lacticide-co-glycolide) (PLGA) showed efficient delivery of antigens to murine bone marrow-derived DCs in vitro, suggesting their potential use in immunotherapy. More recently, a very interesting work showed that HIV p24 protein adsorbed on the surface of surfactant-free anionic poly(D,L-lactide) (PLA) nanoparticles were efficiently taken-up by mouse DCs, inducing DC maturation. he p24-nanoparticles induced enhanced cellular and mucosal immune responses in mice. Although this targeting is seen in ex vivo-generated DCs and not in vivo DCs, the efficient delivery of the antigen to DCs through the nanoparticles is an important demonstration that may eventually be applied to in vivo DC targeting.

Clinical Trial

he most clinically advanced application of nanotechnology for immunotherapy of HIV/AIDS is the DermaVir patch that has reached Phase II clinical trials (9). DermaVir is a targeted nanoparticle system based on polyethyleimine mannose (PEIm), glucose and HIV antigen coding DNA plasmid formulated into nanoparticles (~100 nm) and administered under a patch after a skin preparation. The nanoparticles are delivered to epidermal Langerhans cells that trap the nanoparticles and mature to become highly immunogenic on their way to the lymph nodes. Mature DCs containing the nanoparticles present antigens to T cells inducing cellular immunity. Preclinical studies and Phase I clinical trials showed safety and tolerability of the DermaVir patch, which led the progression to Phase II trials. This is the first nanotechnology-based immunotherapy for HIV/AIDS that has reached the clinic and encourages further work in this area.

Table 1

Summary of nanotechnology-based treatment approaches for HIV/AIDS.

Type of therapy	Therapeutic agent (drug or gene)	Nanotechnology delivery platform	Development stage	Refs.
Antiretroviral therapy	Rilpivirine (TMC278)	Poloxamer 338/TPGS 1000	Preclinical	[35]
	Indinavir	Liposome-laden macrophages	Preclinical	[36–38]
	Stavudine	Mannose- and galactose-targeted liposome	Preclinical	[39–41]
	Zidovudine	Mannose-targeted liposome	Preclinical	[42]
	Efavirenz	Mannose-targeted dendrimer	Preclinical	[43,45]
	Lamivudine	Mannose-targeted dendrimer	Preclinical	[46]
Nanomaterials	Fullerene derivatives	–	Preclinical	[49–55]
	Dendrimers	–	Preclinical	[56,57]
	Silver nanoparticles	–	Preclinical	[58,59]
	SDC-1721/gold nanoparticles	Gold nanoparticles	Preclinical	[60]
Gene therapy	siRNA	Peptide fusion proteins, protamine–antibody fusion proteins, dendrimers, single walled carbon nanotubes, peptide–antibody conjugates	Preclinical	[77–81]
Immunotherapy	P24 protein	Poly (D,L-lactide) nanoparticles/dendritic cells	Preclinical	[98]
Immunotherapy	Plasmid DNA	Mannose-targeted polyethyleimine polymers	Phase II clinical trials	[99]

Note: to open the references in the table 1, please go to ref 1 in this post to see full ref info.

Nanotechnology for HIV/AIDS prevention

The search for a safe and effective HIV/AIDS vaccine has been challenging in the almost three decades since the discovery of the disease. Recently, high-profile clinical trial failures have prompted great debate over the vaccine research, with some suggesting the need for a major focus on fundamental research, with fewer efforts on clinical trials.

The major challenges in the development of a preventive HIV/AIDS vaccine have been the extensive viral strain and sequence diversity, viral evasion of humoral and cellular immune responses, coupled with the lack of methods to elicit broadly reactive neutralizing antibodies and cytotoxic T cells. The challenge associated with delivery of any exogenous antigen (such as nanoparticles) to APCs, is that exogenous antigens require specialized ‘cross-presentation’ in order to be presented by MHC class I and activate CD8⁺cytotoxic T cells.

his requirement for cytosolic delivery of antigens and cross-presentation represents yet another hurdle for HIV intracellular antigen vaccine, but potentially an advantage of nanodelivery. Humoral responses (neutralizing antibodies produced by B cells) are generated to intact antigen presented on the surface for the virus, or nanoparticles, but these humoral responses typically require ‘help’ from CD4⁺ T cells, but rather both. Nanoparticles have potential as adjuvants and delivery systems for vaccines. Table 2 present the different approaches.

Table 2

Summary of nanotechnology developments for prevention of HIV/AIDS.

Type of preventive agent	Antigen/adjuvant or drug	Nanotechnology platform	Development stage	Refs.
Protein or peptide vaccine	gp41, gp120, gp160, p24, Env, Gag, Tat	Liposomes, nanoemulsion, MF59, PLA nanoparticles, poly(γ-glutamic acid) nanoparticles	Preclinical	[108–111] [119–120] [122–125] [128–130]
DNA vaccine	env, rev, gag, tat, CpG ODN	Liposomes, nanoemulsion, PLA nanoparticles	Preclinical	[115,121]
Inactivated viral particle	Inactivated HIV viral particle	Polystyrene nanospheres	Preclinical	[126–127]
Microbicides	L-lysine dendrimer	L-lysine dendrimer	Phase I/II	[136–138]
		PLGA nanoparticles
	PSC-RANTES	PLGA	Preclinical	[139]
	siRNA	Nanoparticles, lipids, cholesterol conjugation	Preclinical	[141–144]

ODN: Oligonucleotides; PLA: Poly(D,L-lactide); PLGA: Poly(D,L-lacticide-co-glycolide).

Note: to open the references in the table 2, please go to ref 1 in this post to see full ref info.

Summary

Nanotechnology can impact the treatment and prevention of HIV/AIDS with various innovative approaches. Treatment options may be improved using nanotechnology platforms for delivery of antiretroviral drugs. Controlled and sustained release of the drugs could improve patient adherence to drug regimens, increasing treatment effectiveness.

While there is exciting potential for nanomedicine in the treatment of HIV/AIDS, challenges remain to be overcome before the potential is realized. These include toxicity of nanomaterials, stability of nanoparticles in physiological conditions and their scalability for large-scale production. These are challenges general to all areas of nanomedicine and various works are underway to tackle them.

Another important consideration in investigating nanotechnology-based systems for HIV/AIDS is the economic aspect, as the hardest hit and most vulnerable populations reside in underdeveloped and economically poor countries. In the case of antiretroviral therapy, nanotherapeutics may increase the overall cost of treatment, reducing the overall value. However, if the nanotherapeutics could improve patient adherence by reducing dosing frequency as expected, and furthermore, if they can eradicate viral reservoirs leading to a sterile immunity, these advantages may effectively offset the added cost.

Ref:

1. Mamo T, Moseman EA., Kolishetti N., Salvadoe-Morales C., Shi J., Kuritzkes DR., Langer R., von-Adrian U and Farokhzad OF. Emerging nanotechnology approaches for HIV/AIDS treatment and prevention. Nanomedicine (Lond) 2010; 5(2): 269-295.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2861897/

2. Merson MH. The HIV-AIDS pandemic at 25 – the global response. N Engl J Med.2006;354(23):2414–2417

3. Walensky RP, Paltiel AD, Losina E, et al. The survival benefits of AIDS treatment in the United States. J Infect Dis. 2006;194(1):11–19

4. Richman DD, Margolis DM, Delaney M, Greene WC, Hazuda D, Pomerantz RJ. The challenge of finding a cure for HIV infection. Science. 2009;323(5919):1304–1307)

5.Sax PE, Cohen CJ, Kuritzkes DR. HIV Essentials. Physicians’ Press; Royal Oak, MI, USA: 2007.

6. Lamers SL, Salemi M, Galligan DC, et al. Extensive HIV-1 intra-host recombination is common in tissues with abnormal histopathology. PLoS One. 2009;4(3):E5065.

7. Vyas TK, Shah L, Amiji MM. Nanoparticulate drug carriers for delivery of HIV/AIDS therapy to viral reservoir sites. Expert Opin Drug Deliv. 2006;3(5):613–628.

8. Amiji MM, Vyas TK, Shah LK. Role of nanotechnology in HIV/AIDS treatment: Potential to overcome the viral reservoir challenge. Discov Med. 2006;6(34):157–162

9. Lori F, Calarota SA, Lisziewicz J. Nanochemistry-based immunotherapy for HIV-1. Curr Med Chem. 2007;14(18):1911–1919

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Nanotechnology: Detecting and Treating metastatic cancer in the lymph node

Posted in Bio Instrumentation in Experimental Life Sciences Research, Biomarkers & Medical Diagnostics, BioSimilars, CANCER BIOLOGY & Innovations in Cancer Therapy, Disease Biology, Small Molecules in Development of Therapeutic Drugs, Imaging-based Cancer Patient Management, Nanotechnology for Drug Delivery, Pharmaceutical R&D Investment, Regulated Clinical Trials: Design, Methods, Components and IRB related issues, Technology Transfer: Biotech and Pharmaceutical, tagged Cancer - General, Cancer cell, cancer cell spread, Clinical Trials, contrast agents, Drug delivery, Fluorescence, ICG, imaging, indocyanine green (ICG), Lung cancer, Lymph node, lymph nodes, mapping, metastasis, nanoparticles, nanotechnology, near-Infrared Light (NIR), NIR, QDs, Quantom dots (QDs), Sentinel lymph node, sentinel lymph node (SLN), SLN on December 19, 2012| 6 Comments »

Author: Tilda Barliya PhD

Metastasis, the spread of cancer cells from a primary tumour to seed secondary tumours in distant sites, is one of the greatest challenges in cancer treatment today. For many patients, by the time cancer is detected, metastasis has already occurred. Over 80% of patients diagnosed with lung cancer, for example, present with metastatic disease. Few patients with metastatic cancer are cured by surgical intervention, and other treatment modalities are limited. Across all cancer types, only one in five patients diagnosed with metastatic cancer will survive more than 5 years. (1,2).

Metastatic Cancer

Metastatic cancer is cancer that has spread from the place where it first started to another place in the body.
Metastatic cancer has the same name and same type of cancer cells as the original cancer.
The most common sites of cancer metastasis are the lungs, bones, and liver.
Treatment for metastatic cancer usually depends on the type of cancer and the size, location, and number of metastatic tumors.

How do cancer cells spread (3)

Local invasion: Cancer cells invade nearby normal tissue.
Intravasation: Cancer cells invade and move through the walls of nearby lymph vessels or blood vessels.
Circulation: Cancer cells move through the lymphatic system and the bloodstream to other parts of the body.

The ability of a cancer cell to metastasize successfully depends on its individual properties; the properties of the noncancerous cells, including immune system cells, present at the original location; and the properties of the cells it encounters in the lymphatic system or the bloodstream and at the final destination in another part of the body. Not all cancer cells, by themselves, have the ability to metastasize. In addition, the noncancerous cells at the original location may be able to block cancer cell metastasis. Furthermore, successfully reaching another location in the body does not guarantee that a metastatic tumor will form. Metastatic cancer cells can lie dormant (not grow) at a distant site for many years before they begin to grow again, if at all.

Although cancer therapies are improving, many drugs are not reaching the sites of metastases, and doubt remains over the efficacy of those that do. Methods that are effective for treating large, well-vascularized tumours may be inadequate when dealing with small clusters of disseminated malignant cells.

We expect that the expanding capabilities of nanotechnology, especially in targeting, detection and particle trafficking, will enable novel approaches to treat cancers even after metastatic dissemination.

Lymph nodes, which are linked by lymphatic vessels, are distributed throughout the body and have an integral role in the immune response. Dissemination of cancer cells through the lymph network is thought to be an important route for metastatic spread. Tumor proximal lymph nodes are often the first site of metastases, and the presence of lymph node metastases signifies further metastatic spread and poor patient survival.

As such, lymph nodes have been targeted using cell-based nanotechnologies

Lymph nodes are small, bean-shaped organs that act as filters along the lymph fluid channels. As lymph fluid leaves the organ (such as breast, lung etc) and eventually goes back into the bloodstream, the lymph nodes try to catch and trap cancer cells before they reach other parts of the body. Having cancer cells in the lymph nodes suggests an increased risk of the cancer spreading. It is thus very important to evaluate the involvement of lymph nodes when choosing the best possible treatment for the patient.

Although current mapping methods are available such as CT and MRI scans, PET scan, Endobronchial Ultrasound, Mediastinoscopy and lymph node biopsy, sentinel lymph node (SLN) mapping and nodal treatment in lung cancer remain inadequate for routine clinical use.

Certain characteristics are associated with preferential (but not exclusive) nanoparticle trafficking to lymph nodes following intravenous administration.

Targeting is often an indirect process, as receptors on the surface of leukocytes bind nanoparticles and transfer them to lymph nodes as part of a normal immune response. Several strategies have been used to enhance nanoparticle uptake by leukocytes in circulation. Coating iron-oxide nanoparticles with carbohydrates, such as dextran, results in the increased accumulation of these nanoparticles in lymph nodes. Conjugating peptides and antibodies, such as immunoglobulin G (IgG), to the particle surface also increases their accumulation in the lymphatic network. In general, negatively charged particles are taken up at faster rates than positively charged or uncharged particles. Conversely, ‘stealth’ polymers, such as polyethylene glycol (PEG), on the surface of nanoparticles, can inhibit uptake by leukocytes, thereby reducing accumulation in the lymph nodes.

Lymph node targeting may be achieved by other routes of administration. Tsuda and co-workers reported that non-cationic particles with a size range of 6–34nm, when introduced to the lungs (intrapulmonary administration), are trafficked rapidly (<1 hour) to local lymph nodes. Administering particles <80 nm in size subcutaneously also results in trafficking to lymph nodes. Interestingly, some studies have indicated that non-pegylated particles exhibit enhanced accumulation in the lymphatics and that pegylated particles tend to appear in the circulation several hours after administration.

Over the last twenty years, sentinel lymph node (SLN) imaging has revolutionized the treatment of several malignancies, such has melanoma and breast cancer, and has the potential to drastically improve treatment in other malignancies, including lung cancer. Several attempts at developing an easy, reliable, and effective method for SLN mapping in lung cancer have been unsuccessful due to unique difficulties inherent to the lung and to operating in the thoracic cavity.

An inexpensive method offering rapid, intraoperative identification of SLNs, with minimal risk to both patient and provider, would allow for improved staging in patients. This, in turn, would permit better selection of patients for adjuvant therapy, thus reducing morbidity in those patients for whom adjuvant treatment is inappropriate, and ensuring that those who need this added therapy actually receive it. (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3109504/)

Current methods for SLN identification involve the use of radioactivity-guided mapping with technetium-99m sulfur colloid and/or visual mapping using vital blue dyes. Unfortunately these methods can be inadequate for SLN mapping in non-small cell lung cancer (NSCLC) The use of vital blue dyes is limited in vivo by poor visibility, particularly in the presence of anthracotic mediastinal nodes, thereby decreasing the signal-to-background ratio (SBR) that enables nodal detection. Similarly, results with technetium-99m sulfur colloid have been mixed when used in the thoracic cavity, where hilar structures and aberrant patterns of lymphatic drainage make detection more difficult.

Although Nomori et al. have reported an 83% nodal identification rate following a preoperative injection of technetium-99 colloid, there is an associated increased risk of pneumothorax and bleeding with this method. Further, the recently completed CALGB 140203 multicenter Phase 2 trial investigating the use of intraoperative technetium-99m colloid found an identification rate of only 51% with this technique. Clearly a technology with greater accuracy, improved SBR, and less potential risk to surgeon and patient would be welcome in the field of thoracic oncology.

Near-infrared (NIR) fluorescence imaging has the potential to meet this difficult challenge.

Near-Infrared Light

NIR light is defined as that within the wavelength range of 700 to 1000 nm. Although NIR light is invisible to the naked eye, it can be thought of as “redder” than UV and visible light.

Absorption, scatter, and autofluorescence are all significantly reduced at redder wavelengths. For instance, Hemoglobin, water, lipids, and other endogenous chromophores, such as melanin, have their lowest absorption within the NIR spectrum, which permits increased photon depth penetration into tissues
In addition, imaging can also be affected by photon scatter, which describes the reflection and/or deflection of light when it interacts with tissue. Scatter, on an absolute scale, is often ten-times higher than absorption. However, the two major types of scatter, Mie and Rayleigh, are both reduced in the NIR, making the use of NIR wavelengths especially important for the reduction of photon attenuation.
living tissue has extremely high “autofluorescence” in the UV and visible wavelength ranges due to endogenous fluorophores, such as NADH and the porphyrins. Therefore, UV/visible fluorescence imaging of the intestines, bladder, and gallbladder is essentially precluded. However, in the NIR spectrum, autofluorescence is extremely low, providing the black imaging background necessary for optimal detection of a NIR fluorophore within the surgical field
Additionally, optical imaging techniques, such as NIR fluorescence, eliminate the need for ionizing radiation. This, combined with the availability of a NIR fluorophore already FDA-approved for other indications and having extremely low toxicity (discussed below), make this a potentially safe imaging modality.

The main disadvantage is that it’s invisible to the human eye, requiring special imaging-systems to “see” the NIR fluorescence.

Currently there are three intraoperative NIR imaging systems in various stages of development:

The SPY system^™ (Novadaq, Canada) – utilizes laser light excitation in order to obtain fluorescent images. The Spy^™ system has been studied for imaging patency of vascular anastamoses following CABG and organ transplantation
The Photodynamic Eye^™(Hamamatsu, Japan) – is presently available only in Japan
The Fluorescence-Assisted Resection and Exploration (FLARE^™) system ()- developed by the authors’ laboratory utilizes NIR light-emitting diode (LED) excitation, eliminating the need for a potentially harmful laser. Additionally, the FLARE^™system has the advantage of being able to provide simultaneous color imaging, NIR fluorescence imaging, and color-NIR merged images, allowing the surgeon to simultaneously visualize invisible NIR fluorescence images within the context of surgical anatomy.

Near-Infrared Fluorescent Nanoparticle Contrast Agents

The ideal contrast agent for SLN mapping would be anionic and within 10–50 nm in size in order to facilitate rapid uptake into lymphatic vessels with optimal retention within the SLN.

Due to the lack of endogenous NIR tissue fluorescence, exogenous contrast agents must be administered for in vivo studies. The most important contrast agents that emit within the NIR spectrum are the heptamethine cyanines fluorophores, of which indocyanine green (ICG) is the most widely used, and fluorescent semiconductor nanocrystals, also known as quantum dots (QDs).

ICG is an extremely safe NIR fluorophore, with its only known toxicity being rare anaphylaxis. The dye was FDA approved in 1958 for systemic administration for indicator-dilution studies including measurements of cardiac output and hepatic function. Additionally, it is commonly used in ophthalmic angiography. When given intravenously, ICG is rapidly bound to plasma albumin and cleared from the blood via the biliary system. Peak absorption and emission of ICG occur at 780 nm and 830 nm respectively, within the window where in vivo tissue absorption is at its minimum. ICG has a relatively neutral charge, has a hydrodynamic diameter of only 1.2 nm, and is relatively hydrophobic. Unfortunately, this results in rapid transport out of the SLN and relatively low fluorescence yield, thereby decreasing its efficacy in mapping techniques. However, noncovalent adsorption of ICG to human serum albumin (HSA), as occurs within plasma, results in an anionic nanoparticle with a diameter of 7.3 nm and a three-fold increase in fluorescence yield markedly improving its utility in SLN mapping.
QDs consist of an inorganic heavy metal core and shell which emit within the NIR spectrum. This structure is then surrounded by a hydrophilic organic coating which facilitates aqeuous solubility and lymphatic distrubtion. QDs have been extensively studied and are ideal for SLN mapping as their hydrodynamic diameter can be customized to the appropriate size within a narrow distribution (15–20 nm), they can be engineered to have an anionic surface charge, and exhibit an extremely high SBRs with significant photostability. Unfortunately, safety concerns due to the presence of heavy metals within the QDs so far have precluded clinical application

Human Clinical Trials and NIR SLN mapping

Several studies have investigated the clinical use of indocyanine green without adsorption to HSA for NIR fluorescence-guided SLN mapping in breast and gastric cancer with good success (9-13).

Kitai et al. first examined this technique in 2005 in breast cancer patients, and was able to identify a SLN node in 17 of 18 patients using NIR fluorescence rather than the visible green color of ICG (9). Sevick-Muraca et al. reported similar results using significantly lower microdoses of ICG (10 – 100 μg), successfully identifying the SLN in 8 of 9 patients (11). Similar to these subcutaneous studies, 56 patients with gastric cancer underwent endoscopic ICG injection into the submucosa around the tumor 1 to 3 days preoperatively or injection directly into the subserosa intraoperatively with identification of the SLN in 54 patients (13).

Recently, Troyan et al. have completed a pilot phase I clinical trial examining the utility of NIR imaging the ICG:HSA nanoparticle fluorophore for SLN mapping/biopsy in breast cancer using the FLARE^™system. In this study, 6 patients received both ^99mTc-sulfur colloid lymphoscintigraphy along with ICG:HSA at micromolar doses. SLNs were identified in all patients using both methods. In 4 of 6 patients the SLNs identified were the same, while in the remaining two, lymphoscintigraphy identified an additional node in one patient and ICG:HSA identified an additional SLN in the other. Irrespective, this study demonstrates that NIR SLN mapping with low dose ICG:HSA is a viable method for intraoperative SLN identification.

Nanotechnology and Drug Delivery in Lung cancer

We previously explored Lung cancer and nanotechnology aspects as polymer nanotechnology has been an area of significant research over the past decade as polymer nanoparticle drug delivery systems offer several advantages over traditional methods of chemotherapy delivery

see: (15) http://pharmaceuticalintelligence.com/2012/11/08/lung-cancer-nsclc-drug-administration-and-nanotechnology/ (16) http://pharmaceuticalintelligence.com/2012/12/01/diagnosing-lung-cancer-in-exhaled-breath-using-gold-nanoparticles/

As the importance of micrometastatic lymphatic spread of tumor becomes clearer, there has been much interest in the use of nanoparticles for lymphatic drug delivery. The considerable focus on developing an effective method for SLN mapping for lung cancer is indicative of the importance of nodal spread on overall survival.

Our lab is investigating the use of image-guided nanoparticles engineered for lymphatic drug delivery. We have previously described the synthesis of novel, pH-responsive methacrylate nanoparticle systems (14). Following a simple subcutaneous injection of NIR fluorophore-labeled nanoparticles 70 nm in size, we have shown that we can deliver paclitaxel loaded within the particles to regional draining lymph nodes in several organ systems of Yorkshire pigs while simultaneously confirming nodal migration using NIR fluorescent light. Future studies will need to investigate the ability of nanoparticles to treat and prevent nodal metastases in animal cancer models. Additionally, the development of tumor specific nanoparticles will potentially allow for targeting of chemotherapy to small groups of metastatic tumor cells further limiting systemic toxicities by narrowing the delivery of cytotoxic drugs.

Ref:

1. http://www.nature.com.rproxy.tau.ac.il/nrc/journal/v12/n1/pdf/nrc3180.pdf

2. http://www.nature.com/nrc/focus/metastasis/index.html

3. http://www.cancer.gov/cancertopics/factsheet/Sites-Types/metastatic

4. http://www.cancerresearchuk.org/cancer-help/about-cancer/what-is-cancer/body/the-lymphatic-system

5. http://www.macmillan.org.uk/Cancerinformation/Cancertypes/Lymphnodessecondary/Secondarycancerlymphnodes.aspx

6. Khullar O, Frangioni JV and Colson YL. Image-Guided Sentinel Lymph Node Mapping and Nanotechnology-Based Nodal Treatment in Lung Cancer using Invisible Near-Infrared Fluorescent Light. Semi Thorac Cardiovasc Surg 2009 :21 (4); 309-315. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3109504/

7. Stacker SA, Achen MG, Jussila L, Baldwin ME and Alitalo K. Metastasis: Lymphangiogenesis and cancer metastasis. Nature Reviews Cancer 2002 2, 573-583. http://www.nature.com/nrc/journal/v2/n8/full/nrc863.html

8. Schroeder A., Heller DA., Winslow MM., Dahlman JE., Pratt GW., Langer R., Jacks T and Anderson DG.. Nature Reviews Cancer 2012; 12(1), 39-50. Treating metastatic cancer with nanotechnology. http://www.nature.com.rproxy.tau.ac.il/nrc/journal/v12/n1/pdf/nrc3180.pdf

http://www.nature.com.rproxy.tau.ac.il/nrc/journal/v12/n1/full/nrc3180.html

9. Kitai T, Inomoto T, Miwa M, et al. Fluorescence navigation with indocyanine green for detecting sentinel lymph nodes in breast cancer. Breast Cancer. 2005;12:211–215.

10. Ogasawara Y, Ikeda H, Takahashi M, et al. Evaluation of breast lymphatic pathways with indocyanine green fluorescence imaging in patients with breast cancer. World journal of surgery.2008;32:1924–1929.

11. Sevick-Muraca EM, Sharma R, Rasmussen JC, et al. Imaging of lymph flow in breast cancer patients after microdose administration of a near-infrared fluorophore: feasibility study. Radiology.2008;246:734–741.

12. Miyashiro I, Miyoshi N, Hiratsuka M, et al. Detection of sentinel node in gastric cancer surgery by indocyanine green fluorescence imaging: comparison with infrared imaging. Ann Surg Oncol.2008;15:1640–1643.

13. Tajima Y, Yamazaki K, Masuda Y, et al. Sentinel node mapping guided by indocyanine green fluorescence imaging in gastric cancer. Ann Surg. 2009;249:58–62.

14. Griset AP, Walpole J, Liu R, et al. Expansile nanoparticles: synthesis, characterization, and in vivo efficacy of an acid-responsive drug delivery system. J Am Chem Soc. 2009;131:2469–2471

15. http://pharmaceuticalintelligence.com/2012/11/08/lung-cancer-nsclc-drug-administration-and-nanotechnology/

16. http://pharmaceuticalintelligence.com/2012/12/01/diagnosing-lung-cancer-in-exhaled-breath-using-gold-nanoparticles/

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Nitric Oxide and it’s impact on Cardiothoracic Surgery

Posted in Bio Instrumentation in Experimental Life Sciences Research, BioSimilars, Cardiac & Vascular Repair Tools Subsegment, Cardiovascular Pharmacogenomics, Disease Biology, Small Molecules in Development of Therapeutic Drugs, Exec Compensation in the Cardiac & Vascular Repair Tools Subsegment, Nitric Oxide in Health and Disease, Regulated Clinical Trials: Design, Methods, Components and IRB related issues, Stents & Tools, tagged arterial disease, Atherosclerosis, cardiothoracic surgery, cardiovascular, Clinical Trials, endothelial, hyperplasia, Inhaled NO, L-arginine, local delivery, neointimal hyperplasia, nitric oxide, NO, restenosis, Stent, systemic delivery, vascular, vascular smooth muscle cells (VSMC) on December 15, 2012| 9 Comments »

Nitric Oxide and it’s impact on Cardiothoracic Surgery

Author, curator: Tilda Barliya PhD

In the past few weeks we’ve had extensive in-depth series about nitric oxide (NO) and it’s role in renal function and donors in renal disorders, coagulation, endothelium and hemostasis. This inspired this new post regarding the impact of NO on cardiothoratic surgery. You can read and follow up on these posts here: http://pharmaceuticalintelligence.com/category/nitric-oxide-in-health-and-disease/

Atherosclerosis in the form of peripheral arterial disease (PAD) affects approximately eight million Americans, which includes 12 to 20% of individuals over the age of 65. Approximately 20% of patients with PAD have typical symptoms of lower extremity claudication, rest pain, ulceration, or gangrene, and one-third have atypical exertional symptoms.Persons with PAD have impaired function and quality of life even if they do not report symptoms and experience a decline in lower extremity function over time. Cardiovascular disease is the major cause of death in patients with intermittent claudication; the annual rate of cardiovascular events (myocardial infarction, stroke, or death from cardiovascular causes) is 5 to 7%. Thus, PAD represents a significant source of morbidity and mortality. (1) (http://www.medscape.com/viewarticle/569812).

Several options exist for treating atherosclerotic lesions, including:

percutaneous transluminal angioplasty with and without stenting,
endarterectomy
bypass grafting

Unfortunately, patency rates for each of these procedures continue to be suboptimal secondary to the development of neointimal hyperplasia. A universal feature of all vascular surgical procedures is the removal of or damage to the endothelial cell monolayer that occurs whether the procedure performed is endovascular or open. This endothelial damage leads to a decreased or absent production of nitric oxide (NO) at the site of injury.

he relationship between NO and the cardiovascular system has proven to be a landmark discovery, and the scientists credited for its discovery were awarded the Nobel Prize in Medicine in 1998. Since its discovery, NO has proven to be one of the most important molecules in vascular homeostasis. In fact, the term endothelial dysfunction has now become synonymous with the reduced biologic activity of NO.

NO produced by endothelial cells has been shown to have many beneficial effects on the vasculature.

As described above,

NO stimulates vascular smooth muscle cells (VSMC) relaxation, which leads to vessel vasodilatation.
NO has opposite beneficial affects on endothelial cells compared with VSMCs.
Whereas NO stimulates endothelial cell proliferation and prevents endothelial cell apoptosis, it inhibits VSMC growth and migration and stimulates VSMC apoptosis.
NO also has many thromboresistant properties, such as inhibition of platelet aggregation, adhesion, and activation; inhibition of leukocyte adhesion and migration; and inhibition of matrix formation

As stated before, the endothelial cell monolayer is often removed or damaged during the time of vascular procedures, which leads to a local decrease in the production of NO. It is now understood that this loss of local NO synthesis by endothelial cells at the site of vascular injury is one of the inciting events that allows platelet aggregation, inflammatory cell infiltration, and VSMC proliferation and migration to occur in excess, which, taken together, leads to neointimal hyperplasia.

Reendothelialization of the injured artery can restore proper function to the artery and potentially halt the restenotic process. Many studies have attempted to improve the patency of bypass grafts and stents by coating them with endothelial cells in the hope that this would restore the thromboresistant nature of native blood vessels.

Unfortunately, although it has been possible to coat these devices with endothelial cells, these cells do not behave like normal endothelial cells and their NO production is often diminished or absent. Because the vasoprotective properties of endothelial cells are largely carried out by NO alone, investigators are engaged in research to improve the bioavailability of NO at the site of vascular injury in an attempt to reduce the risk of thrombosis and restenosis after successful revascularization. The overall goal of using a NO-based approach is to reproduce the same thromboresistive moiety observed with normal NO production.

Why of delivering NO to the injured site:

Systemic delivery
Local delivery

Systemic Delivery

One simple mechanism by which to deliver NO to the body is via inhalational therapy. Inhaled NO has been used clinically in the past to selectively reduce pulmonary vascular resistance in patients with pulmonary hypertension, as well as a potential therapy for patients with acute respiratory distress syndrome. Because the gas is delivered only to the pulmonary system and has a very short half-life, it was thought that there would be no systemic effects of the drug. Subsequently, studies in the mid- to late 1990s suggested that inhaled NO had beneficial antiplatelet and antileukocyte properties without adverse systemic side effects (2,3)

To test if inhaled NO had any beneficial systemic properties specifically on the vasculature, Lee and colleagues evaluated the effect of inhaled NO on neointimal hyperplasia in rats undergoing carotid balloon injury, Unfortunately, the treatment was required for the full 2 weeks to see any difference between the treatment and the control group, thereby limiting its clinical utility.

Despite some of the early animal studies, investigations with healthy human volunteers failed to reproduce these findings.I t was speculated that despite the obvious effects of inhaled NO on the pulmonary vasculature, systemic bioavailability could not be reliably achieved because of the immediate binding and depletion of NO by hemoglobin as soon as it entered the systemic circulation.

Hamon and colleagues tested the ability of orally supplementing l-arginine (2.25%), the precursor to NO, in the drinking water of rabbits to reduce the formation of neointimal hyperplasia after injuring the iliac arteries with a balloon. This amount of l-arginine is approximately sixfold higher than normal daily intake. When the arteries were studied 4 weeks after injury, the l-arginine-fed group exhibited less neointimal hyperplasia and greater acetylcholine-induced relaxation compared with the control animals. The authors speculated that the improved outcomes were due to increased bioavailability of NO secondary to the l-arginine-supplemented diets. To test the ability of this supplemented diet to reduce neointimal hyperplasia in a vein bypass graft model, Davies and colleagues fed rabbits l-arginine (2.25%) 7 days prior to and 28 days after common carotid vein bypass grafts. A 51% decrease in the formation of neointimal hyperplasia was demonstrated in the l-arginine-fed groups, and their vein grafts exhibited preserved NO-mediated relaxation.

Despite some of the positive findings in animals, similar studies in humans have failed to show any benefit with l-arginine supplementation. Shiraki and colleagues studied the effects of short-term high-dose l-arginine on restenosis after PTCA. Thirty-four patients undergoing cardiac catheterization and PTCA for angina pectoris received 500 mg of l-arginine administered through the cardiac catheter immediately prior to PTCA and 30 g per day of l-arginine administered via the peripheral vein for 5 days after PTCA. No significant statistical differences in restenosis were observed between the two groups (34% vs 44%). The authors speculated that the lack of effect was secondary to the fact that although the levels of l-arginine in the plasma increased significantly, NO and cyclic guanosine monophosphate (cGMP) did not. (4)

Table 1. Comparison of Different Nitric Oxide Donor Drugs Currently Used for Clinical or Research Purposes
Drug	Mechanism of NO Release	Unique Properties
Diazeniumdiolates	Spontaneous when in contact with physiologic fluidsNO release follows first-order kinetics	Stable as solidsVarious reliable half-lives depending on the structure of the nucleophile it is attached to
Diazeniumdiolates		Nitrosamines can form as by-products
S-Nitrosothiols	Copper ion-mediated decomposition	Stable as a solid
	Direct reaction with ascorbate	Must be protected from light
	Homeolytic cleavage by light	Present in circulating blood
	Homeolytic cleavage by light	Potential for unlimited NO release
Sydnonimines	Requires enzymatic cleavage by liver esterases to form active metabolite	Stable as a solidMust be protected from light
Sydnonimines	Requires molecular oxygen as an electron acceptor	Requires alkaline pHReleases superoxide as a by-product, which may have negative effects
l-Arginine	Substrate for NOS genes	Stable as a solid
		Ease of administration
		Dependent on presence of NOS for NO production
Sodium nitroprusside	Requires a one-electron reduction to release NO	Stable as a solid
	Requires a one-electron reduction to release NO	Must be protected from light
	Light can induce NO release	Must be given intravenously
	Light can induce NO release	Releases cyanide as a by-product
Organic nitrates	Either by enzymatic cleavage or nonenzymatic bioactivation with sulfhydryl or thiol groups	Stable as a solid
		Must be protected from light
		Ease of administration
		Development of tolerance limits efficacy
NO-releasing aspirin	Require enzymatic cleavage to break the covalent bond between the aspirin and the NO moiety	Stable as a solid
		Ease of administration
		Inherent benefits of aspirin also
		Does not affect systemic blood pressure

Despite the ease of administration, the reliability of drug delivery, and the relative safety of these NO-donating drugs, there are limitations associated with systemic administration. One such limitation is that NO is rapidly inactivated by hemoglobin in the circulating blood, resulting in limited bioavailability. Furthermore, in attempts to increase the amount of drug delivered to obtain the desired clinical effect, unwanted systemic circulatory effects (eg, vasodilation) and unwanted hemostatic effects (eg, bleeding) often preclude administration of biologically effective doses of NO.

Because NO produces systemic side effects, lower doses of NO have been used in many of the human studies. One of the reasons for the differences observed between the animal studies and the human studies was the 10- to 50-fold lower doses of drugs used in the human studies compared with the animal studies. Thus, local delivery of NO may achieve improved results.

Local Delivery

The local delivery of drugs allows for the administration of the maximally effective dose of a drug without the unwanted systemic side effects. Because the target vessels are easily accessible during most vascular procedures, a local pharmacologic approach to administer a drug during the intervention can be easily performed.

Suzuki and colleagues performed a prospective, randomized, single-center clinical trial. (7)

The study population consisted of patients with symptomatic ischemic heart disease who were undergoing coronary artery stent placement. After stent deployment, l-arginine (600 mg/6 mL) or saline (6 mL) was locally delivered via a catheter over 15 minutes. The patients were followed with serial angiography and intravascular ultrasonography to assess for neointimal thickness for up to 6 months. The authors found that in the l-arginine-treated groups, there was slightly less neointimal volume, but this was not statistically significant.

Because it was not known if the addition of l-arginine actually translated to increased NO production, several studies have focused on the addition of NO donors directly to the site of injury.However, Critics of some of the highlighted animal studies point out that the evaluation of neointimal hyperplasia was performed radiographically, which could be subjectively biased. Furthermore, infusing the drug through a catheter for an extended period of time during the procedure to achieve an effect is not clinically feasible. Because of this, other studies have aimed to develop a clinically applicable approach to deliver NO locally to the site of injury.

Hydrogels
Vascular grafts
Gene therapy

represents another method by which to locally increase the level of NO at the site of vascular injury, tested in different multiple creative animal models. Thought, most of this studies shown great preliminary results, only the gene therapy moved forward into randomized clinical trial in humans using gene therapy to reduce neointimal hyperplasia.

In December 2000, the Recombinant DNA Advisory Committee at the National Institutes of Health voted unanimously to proceed with the first phase of clinical evaluation of iNOS lipoplex-mediated gene transfer, called REGENT-1: Restenosis Gene Therapy Trial. (8). The primary objective of this multicenter, prospective, single-blind, dose escalation study was to obtain safety and tolerability information of iNOS-lipoplex gene therapy for reducing restenosis following coronary angioplasty. As of 2002, 27 patients had been enrolled overseas and the process had been determined to be safe. To date, no results have been published as it appears that this trial lost its funding and closed. On April 5, 2002, a notification was issued that the trial had been closed without enrolling any individuals in the United States.

Unfortunately, despite the promising findings shown with NOS therapy, the field of gene therapy has been mottled by two widely known complications. One case occurred as the result of administering a large viral load that led to the death of a patient. In addition, in France, there were at least two cases of malignancy following retroviral gene therapy. (9)

Summary

Atherosclerosis in the form of coronary artery disease and peripheral vascular disease continues to be a major source of morbidity and mortality. Unfortunately, the procedures and materials that are currently used to alleviate these disease states are temporary at best because of the inevitable injury to the native endothelium and the subsequent impairment of NO release. Since the discovery of NO and its role in vascular biology, a main focus in vascular research has been to create novel mechanisms to use NO to combat neointimal hyperplasia. To date, numerous animal studies have restored NO production to the vasculature and have shown that this inhibits neointimal hyperplasia, improves patency rates, and is safe to the animal. Clinical studies using these novel NO-releasing compounds in humans are on the horizon.

Ref:

1. Daniel A. Popowich, Vinit Varu, Melina R. Kibbe. Nitric Oxide: What a Vascular Surgeon Needs to Know. Vascular. 2007;15(6):324-335. (http://www.medscape.com/viewarticle/569812).

2. Gries A, Bode C, Peter K, et al. Inhaled nitric oxide inhibits human platelet aggregation, P-selectin expression, and fibrinogen binding in vitro and in vivo Circulation 1998;97:1481-7.

3. Lee JS, Adrie C, Jacob HJ, et al. Chronic inhalation of nitric oxide inhibits neointimal formation after balloon-induced arterial injury Circ Res 1996;78:337-42.

4. Shiraki T, Takamura T, Kajiyama A, et al. Effect of short-term administration of high dose l-arginine on restenosis after percutaneous transluminal coronary angioplasty J Cardiol 2004;44:13-20.

5. David A. Fullerton, MD, Robert C. McIntyre, Jr, MD. Inhaled Nitric Oxide: Therapeutic Applications in Cardiothoracic Surgery. Ann Thorac Surg 1996;61:1856-1864. http://ats.ctsnetjournals.org/cgi/content/abstract/61/6/1856

6. Owen I.Miller,Swee Fong Tang, Anthony Keech,Nicholas B.Pigott, Elaine Beller and David S. Celemajer. Inhaled nitric oxide and prevention of pulmonary hypertension after congenital heart surgery: a randomised double-blind study. The Lancet,2000:356; 9240 Pages 1464 – 1469, http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(00)02869-5/abstract

7. Suzuki T, Hayase M, Hibi K, et al. Effect of local delivery of l-arginine on in-stent restenosis in humans Am J Cardiol 2002;89:363-7.

8. von der Leyen HE, Chew N. Nitric oxide synthase gene transfer and treatment of restenosis: from bench to bedside Eur J Clin Pharmacol 2006;62:83-89

9. Barbato JE, Tzeng E. iNOS gene transfer for graft disease Trends Cardiovasc Med 2004;14:267-72.

10. E. Matevossian, A. Novotny, C. Knebel, T. Brill, M. Werner, I. Sinicina, M. Kriner, M. Stangl, S. Thorban, and N. Hüser. The Effect of Selective Inhibition of Inducible Nitric Oxide Synthase on Cytochrome P450 After Liver Transplantation in a Rat Model. Transplantation Proceedings 2008, 40, 983–985. http://211.144.68.84:9998/91keshi/Public/File/29/40-4/pdf/1-s2.0-S0041134508004181-main.pdf

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Paclitaxel: Pharmacokinetic (PK), Pharmacodynamic (PD) and Pharmacogenpmics (PG)

Author: Tilda Barliya PhD

In response to the previous post:

Paclitaxel vs Abraxane (albumin-bound paclitaxel)

http://pharmaceuticalintelligence.com/2012/11/17/paclitaxel-vs-abraxane-albumin-bound-paclitaxel/

Pharmacogenomics properties are presented, below.

Paclitaxel is a mitotic inhibitor used in cancer chemotherapy. It was discovered in a U.S. National Cancer Institute program at the Research Triangle Institute (North Carolina) in 1967 when Monroe E.Wall and Mansukh C.Wani isolated it from the bark of the Pacific yew tree, Taxus brevifolia and named it taxol. Later it was discovered that endophytic fungi in the bark synthesize paclitaxel.

Paclitaxel is currently being indicated to lung, breast and ovarian cancer as well as head and neck cancer, and advanced forms of Kaposi’s sarcoma.

The administration of paclitaxel (Taxol®) through intravenous infusions was achieved by using Cremophor® EL as a vehicle to entrap the drug in micelles and keep it in solution, which affects the disposition of paclitaxel and is responsible for the nonlinear pharmacokinetics of the drug, especially at higher dose levels. (http://www.futuremedicine.com/doi/pdf/10.2217/pgs.10.32)

Although Nonlinear pharmacokinetics (dose-dependented kinetics) may occur in all aspects of pharmacokinetics (absorption, distribution, and/or elimination), it focus on the in the metabolism or MichaelisMenten (MM) kinetics of the drug. http://archive.ajpe.org/legacy/pdfs/aj650212.pdf

Briefly, it is known that some of these adverse effects such as hypersensitivity reactions were diminished with the administration of corticosteroids and H1 and H2 antihistamine premedication, and by reducing the incidence of grade 3/4 neutropenia with the administration of granulocyte colony-stimulating factors (G-CSF) and shortening paclitaxel infusion time from 24 to 3 h. However, the neurotoxicity, which was believed to be caused by either paclitaxel or Cremophor EL, could not be controlled and became the dose-limiting toxicity of the drug. It was later on found that paclitaxel itself was responsible to the neurotoxicity effects (http://annonc.oxfordjournals.org/content/6/7/699.abstract)

Pharmacokinetics and Pharmacodynamics

The selection of pharmacokinetic (PK) parameter end points and basic model types for exposure-toxicity relationships of paclitaxel is usually based on tradition rather than physiological relevance.

pharmacokinetic (PK)-pharmacodynamic (PD) relationships for paclitaxel are still most commonly described with empirically-designed threshold models, which have little or no mechanistic basis and lack usefulness when applied to conditions (eg, schedules, vehicles, or routes of administration) different from those from which they were originally derived. (http://jco.ascopubs.org/content/21/14/2803.long). As such, the AUC of the unbound paclitaxel is highly important as a pharmacokinetic parameter to describe exposure-neutropenia relationships (the unbound ptx was not evaluated yet). (http://clincancerres.aacrjournals.org.rproxy.tau.ac.il/content/1/6/599.full.pdf+html)

The clearance of Cremophor EL in patients was found to be time-dependent, resulting in disproportional increases in systemic exposure being associated with shortening of infusion from 3 hours to 1 hour.

One study (http://clincancerres.aacrjournals.org/content/1/6/599), compare the pharmacokinetics and pharmacodynamics (PD) of paclitaxel between Phase I trials of 3- and 24-h infusions and to determine the most informative pharmacokinetic parameter to describe the PD. The study had 3 main goals

(a) to compare the PK and PD of paclitaxel between Phase I studies of 3- and 24-h infusion,
(b) to examine the relationship between PK and PD
(c) to determine the most informative pharmacokinetic parameter to describe the PD.

Note: Although this study was conducted in ~1993-1995, is has been cited extensively and paved the was to other clinical trials with similar results.

27 patients were treated in a Phase I study of paclitaxel by a 3-h infusion at one of six doses: 105, 135, 180, 210, 240, and 270 mg/m2. Pharmacokinetic data were obtained from all patients. Paclitaxel concentrations were measured in the plasma and urine using HPLC. Similar eligibility criteria were designed for the 24-hr infusion with these doses were 49.5, 75, 105, 135, and 180 mg/m2 . Plasma and urine samples for pharmacokinetic evaluation of paclitaxel were collected.

Pharmacokinetic Analysis: Pharmacokinetic parameters, Cmax, AUC, t112, and MRT were obtained by a noncompartmental moment method. Cmax was actually observed peak concentration. AUC and MRT were computed by trapezoidal integration with extrapolation to infinite time.

Pharmacodynamic Analysis: The pharmacokinetic/pharmacodynamic relationships were modeled with the sigmoid maximum effect

Results:

Pharmacokinetic analysis:

The drug plasma concentration increased throughout the 3-h infusion period and began to decrease immediately upon cessation of the infusion with t112 of 9.9-16.0 h and MRT of 6.47-10.24 h (Fig. 1). Both Cmax and AUC increased with increasing doses (r = 0.865, P <0.001 for Cmax r 0.870, P < 0.001 for AUC), although the pharmacokinetic behavior appeared to be nonlinear (Fig. 2). The mean Cmax and AUC at a dose of 270 mg/m2 were more than 3-fold greater than those at a dose of 135 mg/m2. CL and V, decreased with increasing doses (Table 1). The urinary excretion of paclitaxel over 75 h was less than 15% of the dose administered, which indicated that non-renal excretion is the primary route of drug elimination.

The urinary excretion of paclitaxel over 75 h was less than 15% of the dose administered, which indicated that non-renal excretion is the primary route of drug elimination.

Comparison of PD between 3-h and 24-h Infusion

Groups. AUC and duration of plasma concentration (h) above (7>) 0.05-0.1 LM correlated with the % D in granulocytes with p values less than 0.05. The best parameter predicting granulocytopenia was T> 0.09 pM with the minimum of the Akaike Information Criterion. In the 24-h schedule, dose, AUC, and T > 0.04-0.07 pM were demonstrated to correlate with the % D in granulocytes. The best parameter predicting granulocytopenia in the 24-h schedule was T > 0.05 p.M.

Nonhematological toxicities such as peripheral neuropathy, hypotension, and arthralgialmyalgia mainly observed in the 3-h infusion group had no relationship with Cm or AUC which are much higher in the 3-h infusion group, although peripheral neuropathy and musculoskeletal toxicity have been suggested to be associated with AUC on a 6- (12) or 24-h (29) schedule.

Pharmacogenomics:

In the past, the major adverse effects encountered with Taxol were severe hypersensitivity reactions, mainly attributed to Cremophor EL; hematologic toxicity, primarily appearing in the form of severe neutropenia; and neurotoxicity, mainly seen as cumulative sensory peripheral neuropathy. The mechanism for the neurotoxicity has been demonstrated to involve ganglioneuropathy and axonopathy caused by dysfunctional microtubules in dorsal root ganglia, axons and Schwann cells.

Variability in paclitaxel pharmacokinetics has been associated with the adverse effects of the drug. Thus, polymorphisms in genes encoding paclitaxel-metabolizing enzymes, transporters and therapeutic targets have been suggested to contribute to the interindividual variability in toxicity and response.

Further characterization of genes involved in paclitaxel elimination and drug response was performed, including the identification of their most relevant genetic variants. The organic anion transporting polypeptide (OATP) 1B3 was identified as a key protein for paclitaxel hepatic uptake and polymorphisms in the genes encoding for paclitaxel metabolizing enzymes and transporters (CYP2C8, CYP3A4) CYP3A5, P-glycoprotein and OATP1B3) (http://www.futuremedicine.com/doi/pdf/10.2217/pgs.10.32)

***It is important to note that the allele frequencies for many of these polymorphisms are subject to important ethnicity specific differences, with some alleles exclusively present in specific populations (e.g., the Caucasian CYP2C8*3).

For the CYP2C8 gene, two alleles common in Caucasians that result in amino acid changes CYP2C8*3 (R139K; K399R) and CYP2C8*4 (I264M), were described. The former has been shown to possess an altered activity, while the latter does not seem to have functional
consequences. In addition, two CYP2C8 haplotypes were recently shown to confer an increased and reduced metabolizing activity, respectively.

CYP3A5 was found to be highly polymorphic owing to CYP3A5*3, CYP3A5*6 and CYP3A5*7 , with the latter two being African-specific polymorphisms.

Pharmacogenetic studies comparing the most relevant polymorphisms in these genes and paclitaxel pharmacokinetics have rendered contradictory results, with some studies finding no associations while others reported an effect for ABCB1, CYP3A4 or CYP2C8 polymorphisms on specific pharmacokinetic parameters.

Again, with respect to paclitaxel neurotoxicity risk, some studies have rendered positive results for ABCB1 , CYP2C8 and CYP3A5 polymorphisms, while others found no significant associations.

Note: These differences might be caused by underpowered studies and by differences in the patients under study.

Changes affecting microtubule structure and/or composition have been shown to affect paclitaxel efficacy, probably by reducing drug–target affinity. Mainly, resistance to tubulin-binding agents has been associated with an overexpression of b-tubulin isotype III,
which seems to be caused by a deregulation of the microRNA family 200.

However, the clinical utility of these findings remains to be established; furthermore, the identification of biomarkers that could be used to individualize paclitaxel treatment remains a challenge.

In summary,

Pharmacokinetics: Paclitaxel seems to have a non-linear (=dose-dependent) PK parameters.
Pharmcokinetics- Pharmacodynamics: Previous clinical trials did NOT take into account the unbound concentrations of Ptx and therefore in the PK analysis, therefore newly designed clinical trials should take that into consideration. This is very important since the neurotoxicity is attributed to ptx and not its vehicle Cremophor (as shown in the PD analysis)
Difficult to compare between the 3hr and 24hr infusion schedule as most clinical trials did NOT used similar dose-regime making the comparison very hard.
Pharmacogenetics: Different polymorphisms seems to attribute to the been suggested to contribute to the interindividual variability in toxicity and response.
Prospective pharmacogenetic-guided clinical trials will be required in order to accurately establish the utility of the identified markers/strategies for patients and healthcare systems.