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Live Notes, Real Time Conference Coverage 2020 AACR Virtual Meeting April 28, 2020 Session on Novel Targets and Therapies 2:35 PM

Reporter: Stephen J. Williams, PhD

 

Session VMS.ET04.01 – Novel Targets and Therapies

Targeting chromatin remodeling-associated genetic vulnerabilities in cancer: PBRM1 defects are synthetic lethal with PARP and ATR inhibitors

Presenter/AuthorsRoman Merial Chabanon, Daphné Morel, Léo Colmet-Daage, Thomas Eychenne, Nicolas Dorvault, Ilirjana Bajrami, Marlène Garrido, Suzanna Hopkins, Cornelia Meisenberg, Andrew Lamb, Theo Roumeliotis, Samuel Jouny, Clémence Astier, Asha Konde, Geneviève Almouzni, Jyoti Choudhary, Jean-Charles Soria, Jessica Downs, Christopher J. Lord, Sophie Postel-Vinay. Gustave Roussy, Villejuif, France, The Francis Crick Institute, London, United Kingdom, Institute of Cancer Research, London, United Kingdom, Sage Bionetworks, Seattle, WA, Institute of Cancer Research, London, United Kingdom, Institute of Cancer Research, London, United Kingdom, Institut Curie, Paris, France, Université Paris-Sud/Université Paris-Saclay, Le Kremlin-Bicêtre, France, Gustave Roussy Cancer Campus and U981 INSERM, ATIP-Avenir group, Villejuif, FranceDisclosures R.M. Chabanon: None. D. Morel: None. L. Colmet-Daage: None. T. Eychenne: None. N. Dorvault: None. I. Bajrami: None. M. Garrido: None. S. Hopkins: ; Fishawack Group of Companies. C. Meisenberg: None. A. Lamb: None. T. Roumeliotis: None. S. Jouny: None. C. Astier: None. A. Konde: None. G. Almouzni: None. J. Choudhary: None. J. Soria: ; Medimmune/AstraZeneca. ; Astex. ; Gritstone. ; Clovis. ; GSK. ; GamaMabs. ; Lilly. ; MSD. ; Mission Therapeutics. ; Merus. ; Pfizer. ; PharmaMar. ; Pierre Fabre. ; Roche/Genentech. ; Sanofi. ; Servier. ; Symphogen. ; Takeda. J. Downs: None. C.J. Lord: ; AstraZeneca. ; Merck KGaA. ; Artios. ; Tango. ; Sun Pharma. ; GLG. ; Vertex. ; Ono Pharma. ; Third Rock Ventures. S. Postel-Vinay: ; Merck KGaA. ; Principal investigator of clinical trials for Gustave Roussy.; Boehringer Ingelheim. ; Principal investigator of clinical trials for Gustave Roussy.; Roche. ; Principal investigator of clinical trials for Gustave Roussy. Benefited from reimbursement for attending symposia.; AstraZeneca. ; Principal investigator of clinical trials for Gustave Roussy.; Clovis. ; Principal investigator of clinical trials for Gustave Roussy.; Bristol-Myers Squibb. ; Principal investigator of clinical trials for Gustave Roussy.; Agios. ; Principal investigator of clinical trials for Gustave Roussy.; GSK.AbstractAim: Polybromo-1 (PBRM1), a specific subunit of the pBAF chromatin remodeling complex, is frequently inactivated in cancer. For example, 40% of clear cell Renal Cell Carcinoma (ccRCC) and 15% of cholangiocarcinoma present deleterious PBRM1 mutations. There is currently no precision medicine-based therapeutic approach that targets PBRM1 defects. To identify novel, targeted therapeutic strategies for PBRM1-defective cancers, we carried out high-throughput functional genomics and drug screenings followed by in vitro and in vivo validation studies.
Methods: High-throughput siRNA-drug sensitization and drug sensitivity screens evaluating > 150 cancer-relevant small molecules in dose-response were performed in Pbrm1 siRNA-transfected mouse embryonic stem cells (mES) and isogenic PBRM1-KO or -WT HAP1 cells, respectively. After identification of PBRM1-selective small molecules, revalidation was carried out in a series of in-house-generated isogenic models of PBRM1 deficiency – including 786-O (ccRCC), A498 (ccRCC), U2OS (osteosarcoma) and H1299 (non-small cell lung cancer) human cancer cell lines – and non-isogenic ccRCC models, using multiple clinical compounds. Mechanistic dissection was performed using immunofluorescence, RT-qPCR, western blotting, DNA fiber assay, transcriptomics, proteomics and DRIP-sequencing to evaluate markers of DNA damage response (DDR), replication stress and cell-autonomous innate immune signaling. Preclinical data were integrated with TCGA tumor data.
Results: Parallel high-throughput drug screens independently identified PARP inhibitors (PARPi) as being synthetic lethal with PBRM1 defects – a cell type-independent effect which was exacerbated by ATR inhibitors (ATRi) and which we revalidated in vitro in isogenic and non-isogenic systems and in vivo in a xenograft model. PBRM1 defects were associated with increased replication fork stress (higher γH2AX and RPA foci levels, decreased replication fork speed and increased ATM checkpoint activation), R-loop accumulation and enhanced genomic instability in vitro; these effects were exacerbated upon PARPi exposure. In patient tumor samples, we also found that PBRM1-mutant cancers possessed a higher mutational load. Finally, we found that ATRi selectively activated the cGAS/STING cytosolic DNA sensing pathway in PBRM1-deficient cells, resulting in increased expression of type I interferon genes.
Conclusion: PBRM1-defective cancer cells present increased replication fork stress, R-loop formation, genome instability and are selectively sensitive to PARPi and ATRi through a synthetic lethal mechanism that is cell type-independent. Our data provide the pre-clinical rationale for assessing PARPi as a monotherapy or in combination with ATRi or immune-modulating agents in molecularly-selected patients with PBRM1-defective cancers.

1057 – Targeting MTHFD2 using first-in-class inhibitors kills haematological and solid cancer through thymineless-induced replication stress

Presenter/AuthorsThomas Helleday. University of Sheffield, Sheffield, United KingdomDisclosures T. Helleday: None.AbstractSummary
Thymidine synthesis pathways are upregulated pathways in cancer. Since the 1940s, targeting nucleotide and folate metabolism to induce thymineless death has remained first-line anti-cancer treatment. Recent discoveries that showing cancer cells have rewired networks and exploit unique enzymes for proliferation, have renewed interest in metabolic pathways. The cancer-specific expression of MTHFD2 has gained wide-spread attention and here we describe an emerging role for MTHFD2 in the DNA damage response (DDR). The folate metabolism enzyme MTHFD2 is one of the most consistently overexpressed metabolic enzymes in cancer and an emerging anticancer target. We show a novel role for MTHFD2 being essential for DNA replication and genomic stability in cancer cells. We describe first-in-class nanomolar MTHFD2 inhibitors (MTHFD2i), with protein co-crystal structures demonstrating binding in the active site of MTHFD2 and engaging with the target in cells and tumours. We show MTHFD2i reduce replication fork speed and induce replication stress, followed by S phase arrest, apoptosis and killing of a range of haematological and solid cancer cells in vitro and in vivo, with a therapeutic window spanning up to four orders of magnitude compared to non-transformed cells. Mechanistically, MTHFD2i prevent thymidine production leading to mis-incorporation of uracil into DNA and replication stress. As MTHFD2 expression is cancer specific there is a potential of MTHFD2i to synergize with other treatments. Here, we show MTHFD2i synergize with dUTPase inhibitors as well as other DDR inhibitors and demonstrate the mechanism of action. These results demonstrate a new link between MTHFD2-dependent cancer metabolism and replication stress that can be exploited therapeutically.
Keywords
MTHFD2, one-carbon metabolism, folate metabolism, DNA replication, replication stress, synthetic lethal, thymineless death, small-molecule inhibitor, DNA damage response

 

 

1060 – Genetic and pharmacologic inhibition of Skp2, an E3 ubiquitin ligase and RB1-target, has antitumor activity in RB1-deficient human and mouse small cell lung cancer (SCLC)

Presenter/Authors
Hongling ZhaoVineeth SukrithanNiloy IqbalCari NicholasYingjiao XueJoseph LockerJuntao ZouLiang ZhuEdward L. Schwartz. Albert Einstein College of Medicine, Bronx, NY, Albert Einstein College of Medicine, Bronx, NY, Albert Einstein College of Medicine, Bronx, NY, University of Pittsburgh Medical Center, Pittsburgh, PA, Albert Einstein College of Medicine, Bronx, NY
Disclosures
 H. Zhao: None. V. Sukrithan: None. N. Iqbal: None. C. Nicholas: None. Y. Xue: None. J. Locker: None. J. Zou: None. L. Zhu: None. E.L. Schwartz: None.
Abstract
The identification of driver mutations and their corresponding targeted drugs has led to significant improvements in the treatment of non-small cell lung cancer (NSCLC) and other solid tumors; however, similar advances have not been made in the treatment of small cell lung cancer (SCLC). Due to their aggressive growth, frequent metastases, and resistance to chemotherapy, the five-year overall survival of SCLC is less than 5%. While SCLC tumors can be sensitive to first-line therapy of cisplatin and etoposide, most patients relapse, often in less than 3 months after initial therapy. Dozens of drugs have been tested clinically in SCLC, including more than 40 agents that have failed in phase III trials.
The near uniform bi-allelic inactivation of the tumor suppressor gene RB1 is a defining feature of SCLC. RB1 is mutated in highly aggressive tumors, including SCLC, where its functional loss, along with that of TP53, is both required and sufficient for tumorigenesis. While it is known that RB1 mutant cells fail to arrest at G1/S in response to checkpoint signals, this information has not led to effective strategies to treat RB1-deficient tumors, and it has been challenging to develop targeted drugs for tumors that are driven by the loss of gene function.
Our group previously identified Skp2, a substrate recruiting subunit of the SCF-Skp2 E3 ubiquitin ligase, as an early repression target of pRb whose knockout blocked tumorigenesis in Rb1-deficient prostate and pituitary tumors. Here we used genetic mouse models to demonstrate that deletion of Skp2 completely blocked the formation of SCLC in Rb1/p53-knockout mice (RP mice). Skp2 KO caused an increased accumulation of the Skp2-degradation target p27, a cyclin-dependent kinase inhibitor, and we confirmed this was the mechanism of protection in the RP-Skp2 KO mice by using the knock-in of a mutant p27 that was unable to bind to Skp2. Building on the observed synthetic lethality between Rb1 and Skp2, we found that small molecules that bind to and/or inhibit Skp2 induced apoptosis and inhibited SCLC cell growth. In a panel of SCLC cell lines, growth inhibition by a Skp2 inhibitor was not correlated with sensitivity/resistance to etoposide. Targeting Skp2 also had in vivo antitumor activity in mouse tumors and human patient-derived xenograft models of SCLC. Using the genetic and pharmacologic approaches, antitumor activity was seen in vivo in established SCLC primary lung tumors, in liver metastases, and in chemotherapy-resistant tumors. The identification and validation of an actionable target downstream of RB1 could have a broad impact on treatment of SCLC and other advanced tumors with mutant RB1, for which there are currently no targeted therapies available.

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Live Notes, Real Time Conference Coverage 2020 AACR Virtual Meeting April 27, 2020 Symposium New Drugs on the Horizon Part 1 4:50- 6:00 pm

Reporter: Stephen J. Williams, PhD.

SESSION VSY.DDT01 – New Drugs on the Horizon: Part 1

April 27, 2020, 4:50 PM – 6:05 PM
Virtual Meeting: All Session Times Are U.S. EDT

Session Type
Virtual Symposium
Track(s)
Experimental and Molecular Therapeutics,Drug Development
10 Presentations
4:50 PM – 6:00 PM
– CochairAndrew J. Phillips. C4 Therapeutics, Watertown, MA

4:50 PM – 6:00 PM
– CochairMichael Brands. Bayer Pharma AG, Berlin, Germany

4:50 PM – 4:54 PM
– IntroductionAndrew J. Phillips. C4 Therapeutics, Watertown, MA

4:54 PM – 5:14 PM
DDT01-01 – A first-in-class Menin-MLL1 antagonist for the treatment of MLL-r and NPM1 mutant leukemias Jerry McGeehan. Syndax Pharmaceuticals, Inc., Waltham, MA

  • Their inhibitor binds to C terminus of Menin MLL1 which is required for AML progression
  • MLL-4 is from a translocation causing a fusion protein; the inhibitor block leukemic transcription program
  • anti transcription program when Menin inhibitor is used; displaces Menin from chromatin

menin mllr

 

 

 

  • worked in tumor models
  • their inhibitors have good antiproliferative activity seems has good bio-availability in rat and dog
  • they have active QT signal (cardiac tox) screen program in their clinical studies
  • initial pre phase1 have not found the max effective dose
  • not a complete response so may have to look at combination

 

5:14 PM – 5:17 PM
– Discussion

5:17 PM – 5:37 PM
DDT01-02 – BAY 2416964: The first Aryl Hydrocarbon Receptor (AhR) inhibitor to enter phase I clinical development as a novel cancer immunotherapy. Ilona Gutcher, Christina Kober, Julian Röwe, Ulrike Roehn, Lars Roese, Florian Prinz, Detlef Stoeckigt, Benjamin Bader, Matyas Gorjanacz, Rafael Carretero, Norbert Schmees, Horst Irlbacher, Helge Roider, Katharina Sahm, Hilmar Weinmann, Ingo V. Hartung, Bertolt Kreft, Rienk Offringa, Michael Platten. Bayer AG, Berlin, Germany, Bayer AG, Germany, DKFZ, Heidelberg, Germany

  • has a more proinflammatory effect in vivo than other I/O inhibitors
  • rescues TNF alpha immunomodulation
  • further increases IL2 and IFN gamma when combined with I/O inhibitor so by a different mechanism
  • looking to use in NSCLC
  • prelim tox looks fine

5:37 PM – 5:40 PM
– Discussion

5:40 PM – 6:00 PM
DDT01-03 – IPN60090: A potent and selective inhibitor of glutaminase being developed for KEAP1/NFE2L2 mutant NSCLC and ASNS-low HGSOC patients. Jeffrey J. Kovacs. UT MD Anderson Cancer Center, Houston, TX

  • Being developed for NSCLC and high grade serous ovarian cancer
  • glutaminolysis repsonsible for many of the building blocks of cell function
  • these compounds had selective antiproliferative but was focus on GLS1
  • good PK and bioavailability; mouse half life is short but dog is longer so estimated human is 8 hours
  • increased pentose phosphate pathway; reliance on GLS1 activity promotes metabolic reprogramming
  • the inhibitor significantly reduced glutathione in responder cell lines; responders had higher level of ROS
  • use ribose pathway and pentose shunt to help deal with REDOX
  • get a antitumor response in KEAP mut PDX models and these PDX respond poorly to I/O checkpoint inhibitors
  •  ASN2 was higher in nonresponders (alt. formation of Gln) as well as GPT2
  • ASN2 high expressing nonresponding OVCA lines; need low ASN2 in OVCA for response
  • so given metabolic plasticity used shRNA screens after inhibitor
  • PI3K turned up so can use mTORC inhibitor in combo; works well with GLS1 inhibitor to inhibit tumorigenesis
  • they are looking at other combos including std. chemo and I/O checkpoints
  • currently doing dose escalation clinical study

6:00 PM – 6:04 PM
– Discussion

6:04 PM – 6:05 PM
– Closing Remarks Michael Brands. Bayer Pharma AG, Berlin, Germany

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Outstanding Questions in Trends in Pharmacological Sciences – Serendipity in Cancer Drug Discovery: Rational or Coincidence?

 Reporter: Aviva Lev-Ari, PhD, RN

Volume 37, Issue 6, p435–450, June 2016

 

  • Why drug discovery should not rely on specific targets?
  • Are single targets not druggable?
  • What is the reason for the failure of drugs based on targeted therapy in clinical trials at advanced stages
  • Why are existing drugs, which are multitargeted, not considered for reinvestigation in other diseases?

SOURCE

Serendipity in Cancer Drug Discovery: Rational or Coincidence?

Sahdeo Prasad, Subash C. Gupta, Bharat B. Aggarwal3,correspondence
3Current address: Bharat B Aggarwal Founding Director, Anti-inflammation Research Institute, San Diego, CA, USA.

See article in

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