Posts Tagged ‘Dacarbazine’

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.


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).


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.


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).


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.


  1. Eggermont AM and Kirkwood JM, Eur J Cancer, Aug 2004;40(12):1825-36
  2. Douglas JG and Margolin K, Semin Oncol, Oct 2002;29(5):518-24
  3. Chapman PB, et al, ASCO 2011, Abstract LBA4
  4. Margolin KA, et al, Cancer, 1 Aug 2004;101(3):435-8
  5. Verma S, et al, Curr Oncol, April 2008; 15(2): 85–89
  6. Agarwala S, Am J Clin Dermatol, 2003;4(5):333-46
  7. Schwartzentruber DJ, et al, N Engl J Med, 2 Jun 2011;364(22):2119-27
  8. Chudnovsky Y, et al, J Clin Invest, Apr 2005;115(4):813-24.
  9. National Cancer Institute (National Institute of Health)
  10. Clinical Trials reported on the U.S. Institute of Health
  11. New Medicine Oncology KnowledgeBase (nm|OK)

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

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


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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


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.


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



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.


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.


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.



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