Development of an orally bioavailable mSWI/SNF ATPase degrader and acquired mechanisms of resistance in prostate cancer

Mammalian switch/sucrose nonfermentable (mSWI/SNF) ATPase degraders have been shown to be effective in enhancer-driven cancers by functioning to impede oncogenic transcription factor chromatin accessibility. Here, we developed AU-24118, an orally bioavailable proteolysis-targeting chimera (PROTAC) degrader of mSWI/SNF ATPases (SMARCA2 and SMARCA4) and PBRM1. AU-24118 demonstrated tumor regression in a model of castration-resistant prostate cancer (CRPC) which was further enhanced with combination enzalutamide treatment, a standard of care androgen receptor (AR) antagonist used in CRPC patients. Importantly, AU-24118 exhibited favorable pharmacokinetic profiles in preclinical analyses in mice and rats, and further toxicity testing in mice showed a favorable safety profile. As acquired resistance is common with targeted cancer therapeutics, experiments were designed to explore potential mechanisms of resistance that may arise with long-term mSWI/SNF ATPase PROTAC treatment. Prostate cancer cell lines exposed to long-term treatment with high doses of a mSWI/SNF ATPase degrader developed SMARCA4 bromodomain mutations and ABCB1 (ATP binding cassette subfamily B member 1) overexpression as acquired mechanisms of resistance. Intriguingly, while SMARCA4 mutations provided specific resistance to mSWI/SNF degraders, ABCB1 overexpression provided broader resistance to other potent PROTAC degraders targeting bromodomain-containing protein 4 and AR. The ABCB1 inhibitor, zosuquidar, reversed resistance to all three PROTAC degraders tested. Combined, these findings position mSWI/SNF degraders for clinical translation for patients with enhancer-driven cancers and define strategies to overcome resistance mechanisms that may arise.

Development of an orally bioavailable mSWI/SNF ATPase degrader and acquired mechanisms of resistance in prostate cancer

Mammalian switch/sucrose non-fermentable (mSWI/SNF) ATPase degraders have been shown to be effective in enhancer-driven cancers by functioning to impede oncogenic transcription factor chromatin accessibility. Here, we developed AU-24118, a first-in-class, orally bioavailable proteolysis targeting chimera (PROTAC) degrader of mSWI/SNF ATPases (SMARCA2 and SMARCA4) and PBRM1. AU-24118 demonstrated tumor regression in a model of castration-resistant prostate cancer (CRPC) which was further enhanced with combination enzalutamide treatment, a standard of care androgen receptor (AR) antagonist used in CRPC patients. Importantly, AU-24118 exhibited favorable pharmacokinetic profiles in preclinical analyses in mice and rats, and further toxicity testing in mice showed a favorable safety profile. As acquired resistance is common with targeted cancer therapeutics, experiments were designed to explore potential mechanisms of resistance that may arise with long-term mSWI/SNF ATPase PROTAC treatment. Prostate cancer cell lines exposed to long-term treatment with high doses of a mSWI/SNF ATPase degrader developed SMARCA4 bromodomain mutations and ABCB1 overexpression as acquired mechanisms of resistance. Intriguingly, while SMARCA4 mutations provided specific resistance to mSWI/SNF degraders, ABCB1 overexpression provided broader resistance to other potent PROTAC degraders targeting bromodomain-containing protein 4 (BRD4) and AR. The ABCB1 inhibitor, zosuquidar, reversed resistance to all three PROTAC degraders tested. Combined, these findings position mSWI/SNF degraders for clinical translation for patients with enhancer-driven cancers and define strategies to overcome resistance mechanisms that may arise.

Abstract 4114: Evaluation of AU-18069, a novel small molecule CBP/p300 bromodomain inhibitor for the treatment of cancers

Background: E1A binding protein (p300) and its paralog CREB binding protein (CBP or CREBBP) are ubiquitously expressed acetyl transferases (HAT) that also act as co-activators for number of transcription factors including HIF1a, BRCA-1, p53, c-Myc and androgen receptor (AR). Both CBP and p300 possess bromodomain (BRD) and a lysine acetyltransferase (KAT) domain. These two closely related epigenetic modulators are known to play an oncogenic role in a variety of cancers. Functional synthetic lethal screens have identified preferential killing in CBP-deficient and/or MYC-dependent hematological cancer cells by suppression of the paralogue p300. CBP/p300 BRD inhibitor could also prevent AR and ER signaling, thereby potentially inhibiting growth of AR and ER -dependent cancer cells. Thus, targeting CBP/p300 represents an attractive approach for developing personalized cancer therapies.

Experimental Results: Multiple potent and selective CBP/p300 BRD inhibitors that are structurally unrelated to known inhibitors were identified by iterative medicinal chemistry and SAR based approaches. The lead compound AU-18069 was optimized towards attaining good potency, selectivity, physicochemical properties and DMPK profile. AU-18069 potently inhibited proliferation of a wide range of cell lines derived from prostate cancer, breast cancer and CBP mutant/MYC-dependent hematological cancers. The lead compound demonstrated good PK profile in rodents as well as in dogs. Excellent anti-tumor efficacy was achieved in leukemia and lymphoma xenograft models at well-tolerated doses. Significant downregulation of c-Myc was observed in a single dose PK-PD study.

Conclusion: Lead candidate AU-18069 demonstrated that selective CBP/p300 bromodomain inhibitors are efficacious in models of hematologic malignancies and solid cancers in vitro and in vivo. Further evaluation of efficacy in other xenograft models, as a single agent as well as in combination with other agents is planned. Long term toxicological and safety pharmacology evaluation in different species and other IND enabling studies are in progress to support progression of this compound to clinical trials.

Citation Format: Chandrasekhar Abbineni, Saravanan Thiyagarajan, Aravind A B, Amit A Dhudashiya, Sivapriya Marappan, Naveen Kumar R, Raghavendra N R, Mamon Dey, Avinash Kumar, Uma Bharathi B V, Girish Aggunda Renukappa, N Venkata Siva Reddy, Asha Babu, Aakanksha J Shetty, Amith A, Narasimha Rao K, Suraj T Gore, Mahaboobi Jaleel, Ramesh S Senaiar, Vijaya Shankar Nataraj, Subhendu Mukherjee, Samiulla D S, Thomas Antony, Girish Daginakatte, Rajesh Eswarappa, Kavitha Nellore, Shekar Chelur, Murali Ramachandra, Susanta Samajdar. Evaluation of AU-18069, a novel small molecule CBP/p300 bromodomain inhibitor for the treatment of cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4114.

Abstract 3729: Discovery of orally bioavailable SMARCA2/4 dual degraders for treatment of acute myeloid leukemia

Background: The BAF (SWI/SNF) chromatin remodeling complex comprises of two mutually exclusive ATPases, SMARCA2 (BRM) and SMARCA4 (BRG1), that affect the mobilization and positioning of nucleosomes on DNA and thereby regulates important cellular functions including transcription, DNA recombination, DNA repair and chromosome decatenation during mitosis. SMARCA4 is frequently overexpressed in several types of cancers. Overexpression has been linked to increased proliferation and survival, as well as aggressive tumors and poor prognosis. SMARCA4 knockdown in these tumors lead to inhibition of proliferation and increased sensitivity to known chemotherapeutic agents, supporting the validity of targeting SMARCA4. Genetic silencing studies have established that the oncogenic activity of tumors lacking SMARCA4 is primarily driven by SMARCA2-containing residual SWI/SNF complex, suggesting the importance of dual inhibition of SMARCA2 and SMARCA4. While SMARCA4 is known to play a vital role in maintaining the oncogenic transcription program and driving proliferation in leukemia, the impact of dual SMARCA2 and SMARCA4 inhibition/degradation in acute myeloid leukemia (AML) is largely unexplored.

Methods and Results: As part of the initial design plan, selective SMARCA2/4 Bromodomain inhibitors and specific ligands of several E3 ligases were chosen to arrive at different degrader designs. A choice of linkers and different exit vectors were considered to construct a variety of hetero bifunctional molecules. Our proprietary ternary complex modeling algorithm, ALMOND (ALgorithm for MOdeling Neosubstrate Degraders) helped in prioritizing the designs. Short listed compounds were synthesized and profiled in multiple cellular assays to understand their degradation potential. Several compounds that degrade SMARCA2, SMARCA4 & PBRM1 with pico molar DC50 were identified. These compounds have shown very potent anti-proliferative activity in both SMARCA2/4 proficient (MV-4-11, VCaP etc) and SMARCA4 mutant cell lines (SK-MEL-5 & RERF-LC-A1 etc). Further, potent compounds were optimized for their pharmacokinetic properties. Multiple lead compounds with low IV clearance and good oral bioavailability in rodents were identified. Advanced lead compounds are currently being evaluated in rodent tolerability and PK-PD experiments to select doses for the efficacy study.

Conclusions: Highly potent degraders of SMARCA2, SMARCA4 & PBRM1 were identified by conjugating selective SMARCA2/4 Bromodomain inhibitors and several E3 ligase specific ligands. Further optimization of the linkers resulted in compounds with improved pharmacokinetic profile and very good oral bioavailability in rodents. Highly potent and orally available degraders of SMARCA2, SMARCA4 are efficacious in AML xenograft models and advanced profiling of candidate molecule is in progress.

Citation Format: Chandrasekhar Abbineni, Leena Khare, Bilash Kuila, Abdul Rawoof Khaji, Dhaytadak Bhagwan Mahadeo, Sandeep Vitthal Dukare, Bhagya M S Kumar, Suraj T Gore, Vijay Kamal Ahuja, Amit A Dhudashiya, Raghavendra N R, Nagesh Gowda, Charamanna K B, Kiran Aithal B, Samiulla D S, Subhendu Mukherjee, Thomas Antony, Sanjeev Giri, Shekar Chelur, Kavitha Nellore, Girish Daginakatte, Murali Ramachandra, Susanta Samajdar. Discovery of orally bioavailable SMARCA2/4 dual degraders for treatment of acute myeloid leukemia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3729.

Targeting SWI/SNF ATPases in enhancer-addicted prostate cancer

The switch/sucrose non-fermentable (SWI/SNF) complex has a crucial role in chromatin remodelling1 and is altered in over 20% of cancers2,3. Here we developed a proteolysis-targeting chimera (PROTAC) degrader of the SWI/SNF ATPase subunits, SMARCA2 and SMARCA4, called AU-15330. Androgen receptor (AR)+ forkhead box A1 (FOXA1)+ prostate cancer cells are exquisitely sensitive to dual SMARCA2 and SMARCA4 degradation relative to normal and other cancer cell lines. SWI/SNF ATPase degradation rapidly compacts cis-regulatory elements bound by transcription factors that drive prostate cancer cell proliferation, namely AR, FOXA1, ERG and MYC, which dislodges them from chromatin, disables their core enhancer circuitry, and abolishes the downstream oncogenic gene programs. SWI/SNF ATPase degradation also disrupts super-enhancer and promoter looping interactions that wire supra-physiologic expression of the AR, FOXA1 and MYC oncogenes themselves. AU-15330 induces potent inhibition of tumour growth in xenograft models of prostate cancer and synergizes with the AR antagonist enzalutamide, even inducing disease remission in castration-resistant prostate cancer (CRPC) models without toxicity. Thus, impeding SWI/SNF-mediated enhancer accessibility represents a promising therapeutic approach for enhancer-addicted cancers.

Design, synthesis, and biological evaluation of phenyl thiazole-based AR-V7 degraders

Multiple Splice variants of AR have been reported in the past few years. These splice variants are upregulated in most cases of CRPC resulting in poor prognosis. Most of these variants lack the ligand binding domain (LBD) but still bind to DNA resulting in constitutive activation of downstream targets. The AR-V7 splice variant has been characterized extensively and current clinical trials in CRPC are exploring the use of AR-V7 as a biomarker. New therapeutic molecules that selectively target AR-V7 are also being explored. However, there is a dearth of information available on the selectivity, phenotypic responses in AR-V7 dependent cell lines and pharmacokinetic properties of such molecules. Using our proprietary computational algorithms and rational SAR optimization, we have developed a potent and selective AR-V7 degrader from a known AR DNA binding domain (DBD) binder. This molecule effectively degraded AR-V7 in a CRPC cell line and demonstrated good oral bioavailability in mouse PK studies. This tool compound can be used to evaluate the pharmacological effects of AR-V7 degraders. Further exploration of SAR can be pursued to develop more optimized lead compounds.

Abstract 1144: Orally bioavailable SMARCA2 degraders with exceptional selectivity and potency

Background: SMARCA2 (BRM) and SMARCA4 (BRG1) are two mutually exclusive DNA-dependent ATPases of the SWI/SNF complex, which function in mobilizing nucleosomes to regulate transcription, DNA replication/repair and chromosome dynamics. SMARCA4 is known to be mutated in number of cancers lacking targetable oncogenes, with SMARCA4-mutant patient population representing 10%-20% of NSCLC, 100% small cell ovarian cancer (hypercalcemic type), 28% skin cancer, 16% glioma and 14% colon cancer. Genetic studies have established the necessity of SMARCA2 for survival of tumor cells lacking SMARCA4. Although genetic silencing of SMARCA2 leads to potent anti-proliferative activity in SMARCA4-deficient cancer cell lines, pharmacological studies with a probe capable of binding to SMARCA2 and SMARCA4 bromodomains have failed to recapitulate such anti-proliferative effects. This prompted us to evaluate targeted protein degradation as an alternate approach to target SMARCA4 altered cancers.

Methods and Results: A variety of hetero bi-functional molecules were synthesized by conjugating selective SMARCA2/4 bromodomain inhibitors with either VHL or CRBN E3-ligase specific ligands. Rational design approach guided by our proprietary ternary complex modeling algorithm, ALMOND (ALgorithm for MOdeling Neosubstrate Degraders) resulted in the identification of highly selective SMARCA2 degraders. The lead compound, AU-19820 showed > 10000-fold selectivity for SMARCA2 degradation versus other homologous proteins in tested cell lines. AU-19820 demonstrated potent anti-proliferative activity in SMARCA4 mutant but not in SMARCA2/4 proficient cell lines. This compound displayed favorable IV PK profile in rodents along with clean CYP profile. Additionally, the lead compound exhibited significant tumor growth inhibition in RERF-LC-A1 (SMARCA4 mutant lung cancer) xenograft model when dosed via i.v. route. Efficacious exposures were well tolerated with excellent tumor penetration. The compound also demonstrated moderate oral bioavailability in mouse. Efforts are in progress to improve this further by SAR modifications and exploiting prodrug approach.

Conclusions: Potent and extremely selective SMARCA2 protein degraders were identified by conjugating SMARCA2/4 inhibitors with known VHL or CRBN ligands. SMARCA2 vs SMARCA4 selectivity handles have been very well explored with expandable SAR. Lead compound also displayed a synthetic lethality phenotype in SMARCA4 mutant cancer models while sparing SMARCA2/4 proficient ones. Further optimization of the oral bioavailability and evaluation of efficacy through oral route as well as intermittent IV dosing are planned.

Citation Format: Chandrasekhar Abbineni, Leena Khare Satyam, Bilash Kuila, Ashok Ettam, Khaji Abdul Rawoof, Sreevidya MR, Sandeep Vitthal Dukare, Suraj T. Gore, Rakesh P. Nankar, Vijay Kamal Ahuja, Charamanna KB, Megha Goyal, Kiran Aithal, Samiulla DS, Subhendu Mukherjee, Thomas Antony, Sanjeev Giri, Shekar Chelur, Kavitha Nellore, Girish Daginakatte, Murali Ramachandra, Susanta Samajdar. Orally bioavailable SMARCA2 degraders with exceptional selectivity and potency [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1144.

Abstract 1143: Evaluation of AU-18069, a novel small molecule CBP/p300 bromodomain inhibitor for the treatment of cancers

Background: E1A binding protein (p300) and its paralog CREB binding protein (CBP or CREBBP) are ubiquitously expressed acetyl transferases (HAT) that also act as co-activators for number of transcription factors including HIF1a, BRCA-1, p53, c-Myc and androgen receptor (AR). Both CBP and p300 possess bromodomain (BRD) and a lysine acetyltransferase (KAT) domain. These two closely related epigenetic modulators are known to play oncogenic roles in a variety of cancers. Functional synthetic lethal screens have identified preferential killing in CBP-deficient and MYC-dependent hematological cancer cells by suppression of the paralogue p300. CBP/p300 BRD inhibitor could also prevent its coactivator function at AR, thereby potentially inhibit growth of AR-dependent prostate cancer cells. Thus, targeting CBP/p300 represents an attractive approach for developing personalized therapies.

Experimental procedures and Results: Multiple potent and selective CBP/p300 BRD inhibitors that are structurally unrelated to known inhibitors have been identified by iterative medicinal chemistry and SAR based approaches. The lead compound, AU-18069 was optimized towards attaining good potency, physicochemical properties and DMPK profile. AU-18069 potently inhibited viability and proliferation of a wide range of cell lines derived from prostate cancer, CBP mutant and MYC-dependent hematological cancers and demonstrated improved PK profile in rodent models in comparison with a compound, currently in clinical trials. Excellent efficacy with significant tumor growth inhibition (TGI) was observed in MV4-11 xenograft model at well-tolerated doses along with downregulation of cMYC in a single dose PK-PD study. AU-18069 also showed modulation of different immune phenotypes including CD4+ T cell subsets.

In summary, our lead candidate AU-18069 demonstrated that selective CBP/p300 bromodomain inhibitors are potent in models of hematologic malignancies and solid tumors in vitro and in vivo. Further evaluation of immune activation potential, efficacy studies in various xenograft models, long term toxicological evaluation in different species and other IND enabling studies are in progress.

Citation Format: Chandrasekhar Abbineni, Saravanan Thiyagarajan, Ramesh S Senaiar, Subhendu Mukherjee, Mahaboobi Jaleel, Sivapriya Marappan, Raghavendra N R, Girish Aggunda Renukappa, Aravind A B, Naveen Kumar R, Venkata Siva Reddy, Asha Babu, Akhila Srinivas, Prasad Yadlapalli, Suraj T Gore, Pathange Hemasankar, Mamon Dey, Samiulla D S, Chandranath D Naik, Thomas Antony, Kavitha Nellore, Shekar Chelur, Girish Daginakatte, Mikko Myllymäki, Gerd Wohlfahrt, Murali Ramachandra, Susanta Samajdar. Evaluation of AU-18069, a novel small molecule CBP/p300 bromodomain inhibitor for the treatment of cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1143.

Abstract 1754: First in class orally bioavailable BETBRD degraders

Background: Inhibition of Bromodomain and extra-terminal (BET) family proteins by small molecules is actively being pursued as a therapeutic strategy in the clinics. Targeted protein degradation is an emerging therapeutic modality that has shown initial promise in the clinic. BET protein degradation has inherent advantages over inhibition viz. expansion of indication scope and amenability to intermittent dosing schedules. While many BET degraders have been disclosed earlier, inferior pharmacokinetic properties limit their further development.

Methods and Results: We have designed and synthesized various hetero bi-functional molecules by conjugating novel and selective BET BRD ligands with VHL or CRBN ligands. This exercise led to the identification of several potent and selective BRD4 protein degraders with activity in a wide range of hematological and solid tumor cell lines. We have profiled one of the lead compounds extensively in vitro to gain insights on the mechanism of action. The lead compound showed lasting effect on BET protein abundance post compound washout while leading to apoptosis. This compound has favorable IV PK profile in rodents had has clean CYP and hERG profiles. Additionally, the lead compound exhibited significant tumor growth inhibition in MV4-11 xenograft model when dosed via i.v. route. Both QD and Q48h dosing regimens were well tolerated and produced efficacy in mouse models. Further SAR in the linker portion resulted in compounds with lower iv clearance and oral bioavailability either as prodrugs or as such. The proteomics study revealed a high selectivity towards BET proteins for the lead compound.

Conclusions: Potent and selective BET protein degraders were identified by conjugating novel BET BRD ligands with both VHL and CRBN ligands. Optimization of these first generation BET degraders led to improved metabolic stability, translating into low iv clearance in rodents. Further evaluation of these compounds as prodrugs resulted in good oral exposures. Lead compounds from both the series have low iv clearance and are orally bioavailable in a simple formulation. We believe these compounds serve as valuable tools to fully understand the clinical scope of BET degraders.

Citation Format: Chandrasekhar Abbineni, Mahaboobi Jaleel, Subhendu Mukherjee, Sivapriya Marappan, Nirbhay Kumar Tiwari, DS Samiulla, AB Aravind, Naveen R Kumar, Indu Bansal, Raghurami B Reddy, NVM Rao Bandaru, Akhila Srinivas, Janith Mary Maben, Suraj Tgore, Avainash Kumar, Rakesh P. Nankar, Chandranath D. Naik, Thomas Antony, Kavitha Nellore, Sanjeev Giri, Girish Daginakatte, Shekar Chelur, Olli Törmäkangas, Gerd Wohlfahrt, Mari Björkman, Elina Mattila, Laura Ravanti, Anu Moilanen, Murali Ramachandra, Susanta Samajdar. First in class orally bioavailable BETBRD degraders [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1754.

Abstract 1753: Targeting cancer with selective cbp/p300 bromodomain inhibitors

Background: The Bromodomain (BRD) and Extra-Terminal domain (BET) family of proteins are key regulators of epigenetic control. Although pan BET Inhibitors show good clinical activity, progressive disease was seen after several months of treatment in clinical responders, likely due to secondary resistance mechanisms. The plausible resistance mechanisms are increased expression of TCF7L2, c-Myc, Survivin and PIM1. Cyclic AMP response element binding protein (CREB)-binding protein (CBP) and E1A interacting protein of 300 kDa (EP300 or p300) are two closely related histone acetyl transferases with oncogenic roles in a variety of cancers. They are known to be co-activators of several key transcription factors that contribute to tumor progression including HIF1a, BRCA-1, p53, c-Myc and androgen receptor (AR). Studies have indicated that p300 is also upregulated in SPOP-mutated prostate cancer. Thus, targeting CBP/p300 represents an attractive approach for developing novel therapies.

Methods and Results: Multiple potent and selective CBP/p300 bromodomain inhibitors that are structurally unrelated to known inhibitors were identified by iterative medicinal chemistry and SAR based approaches. The compounds were optimized towards attaining good physicochemical properties and DMPK profile. The anti-proliferative activity of the lead compounds was studied across multiple tumor types in a 3-day assay. The lead compounds potently inhibited viability of a wide range of hematological and solid tumor cell lines including prostate cancer cell lines VCaP and 22Rv1. In H929 cell line the lead compounds showed dose-dependent inhibition of cMYC and increase in cPARP. In a single dose PK-PD study in MV4-11 xenograft model, the compounds showed modulation of cMYC and Survivin.

Conclusions: In summary, our studies demonstrate that selective CBP/p300 bromodomain inhibitors are potent in models of hematologic malignancies and solid tumors in-vitro. Profiling of efficacy in xenograft models, and further toxicological evaluation are in progress.

Citation Format: Mahaboobi Jaleel, Ramesh S. Senaiar, Chandrasekhar Abbineni, Girish A. Renukappa, Subhendu Mukherjee, Sivapriya Marappan, DS Samiulla, AB Aravind, Naveen R. Kumar, Venkata Siva N. Reddy, Asha Babu, Akhila P. Srinivas, Prasad Yadlapalli, Suraj Tgore, Raghavendra NR, Chandranath D. Naik, Sanjeev Giri, Thomas Antony, Kavitha Nellore, Shekar Chelur, Girish Daginakatte, laura Ravanti, Mikko Myllymäki, Gerd Wohlfahrt, Elina Mattila, Stefan Karlsson, Mari Björkman, Reetta Riikonen, Tarja Ikonen, Laura Leimu, Chira Mälmström, Timo Korjamo, Anu Moilanen, Murali Ramachandra, Susanta Samajdar. Targeting cancer with selective cbp/p300 bromodomain inhibitors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1753.

Abstract 3827: Antitumor activity of ODM-207, a novel BET bromodomain inhibitor, in nonclinical models of ER+ breast cancer as single agent and as a combination treatment

Introduction: The bromodomain and extraterminal (BET) family of proteins are chromatin readers that promote the transcription of several important cell identity genes. BET proteins also control expression of many genes that play an essential role in the pathogenesis of human cancer, including cell-cycle and proliferation-regulating genes. The small-molecule BET inhibitors block BET binding to chromatin and have shown antitumor activity in a variety of pre-clinical cancer models. In this study, we evaluated the anticancer activity of the novel BET inhibitor, ODM-207, in ER+ breast cancer models as a single agent and in combination with other cancer drugs.

Methods: ER+ breast cancer cell lines were studied for sensitivity to ODM-207 and the in vivo efficacy was assessed using the ER+ Ma3366 patient-derived xenograft model. For gene expression analyses, breast cancer cells were treated with ODM-207 or reference BET inhibitor JQ1 and differentially expressed genes were analyzed by RNA-sequencing. The ability of ODM-207 to regulate anticancer signaling pathways was validated by western blotting. Synergistic drug interactions were profiled using five-concentration dose response matrices.

Results: ODM-207 is a novel BET inhibitor structurally distinct from JQ1 that shows antiproliferative activity in a broad panel of cancer cell lines. The strongest antitumor activity could be observed in hormone-dependent prostate and breast cancer models. In this study, we show that ODM-207 effectively inhibits the proliferation of ER+ breast cancer cell lines by inducing cell cycle arrest in G0/G1-phase. Additionally, ODM-207 suppresses the growth of ER+ patient-derived breast cancer xenograft tumors. ODM-207 as well as JQ1 targeted several pathways important for cancer progression such as MYC, estrogen response and cell cycle gene signatures. The inhibition of key cell cycle regulators, such as CDK4 and Cyclin D1, were further verified. The cyclin D1:CDK4/6 axis plays a significant role in the development, and currently, treatment of ER+ breast cancer together with endocrine therapy. Interestingly, ODM-207 was shown to synergize with palbociclib in vitro in ER+ breast cancer cell lines: the combination of ODM-207 and CDK4/6 inhibitor palbociclib achieved greater cell proliferation inhibition than either drug alone at sub IC50 concentrations. Notably, the ODM-207 and palbociclib combination did not cause the induction of an obvious senescent-like phenotype as compared to palbociclib alone, but rather affected cell survival cellular assays.

Conclusions: In summary, ODM-207, which is currently in Phase I clinical trials for treating solid tumors, causes significant growth inhibition in pre-clinical models of ER+ breast cancer and enhances antiproliferative activity of palbociclib, providing a rationale for development of a combination therapy.

Citation Format: Julia Lindqvist, Mari Björkman, Reetta Riikonen, Daniel Nicorici, Elina Mattila, Mahaboobi Jaleel, Chandrasekhar Abbineni, Anu-Maarit Moilanen. Antitumor activity of ODM-207, a novel BET bromodomain inhibitor, in nonclinical models of ER+ breast cancer as single agent and as a combination treatment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3827.

Abstract 3970: Therapeutic targeting of estrogen receptor positive breast cancer with the BET bromodomain inhibitor ODM-207

Introduction: The bromodomain and extraterminal (BET) family of proteins are chromatin readers that recognize and bind to specific acetylated histones and promote the transcription of several important cell identity genes. BET bromodomain inhibitors have shown promising antitumor activity in a variety of pre-clinical cancer models, as BET inhibition abrogates the transcription of several key oncogenes in a cell type-specific manner. It is known that inhibition of BET proteins effectively inhibits the proliferation of estrogen receptor positive (ER+) breast cancer cells, at least in part through repression of ER and MYC signaling. However, many additional cancer-associated genes are likely to underlie the growth inhibitory effects of BET inhibitors in breast cancer. The purpose of this study was to determine the anticancer activity of the novel BET bromodomain inhibitor ODM-207 in pre-clinical ER+ breast cancer models, and further, to look for cancer-associated signaling pathways suppressed by BET inhibitors.

Methodology and results: ODM-207 is a novel, highly selective BET bromodomain inhibitor structurally distinct from JQ1 and its benzodiazepine-related derivatives. In this study, we show that ODM-207 effectively inhibits the proliferation of ER+ breast cancer cell lines when measured by cell viability assays as well as suppresses the growth of patient-derived xenograft tumors. Furthermore, we wanted to investigate the anticancer signaling pathways regulated by ODM-207 as well as the prototypical BET inhibitor JQ1 in breast cancer cells. For this purpose, we performed RNA sequencing on two ER+ breast cancer cell lines after 24h treatment with the aforementioned BET inhibitors. We found that both BET inhibitors targeted several genes and pathways important for breast cancer progression. For example, the targets included CDK4 and CDK6, two cell cycle kinases fundamental for the development and treatment of ER+ breast cancer. The RNA sequencing results were further validated in vitro, and were utilized as a basis for combination therapy assessment.

Conclusions: Our results indicate that the novel BET bromodomain inhibitor ODM-207, which is currently in Phase I clinical trials for treating solid tumors, causes significant growth inhibition and cell cycle arrest in pre-clinical models of ER+ breast cancer, and regulates multiple crucial signaling pathways involved in breast cancer cell cycle and survival.

Citation Format: Julia Lindqvist, Mari Björkman, Reetta Riikonen, Daniel Nicorici, Elina Mattila, Chandrasekhar Abbineni, Mahaboobi Jaleel, John Eriksson, Pekka Kallio, Anu-Maarit Moilanen. Therapeutic targeting of estrogen receptor positive breast cancer with the BET bromodomain inhibitor ODM-207 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3970.

Abstract LB-113: Immune-mediated anti-tumor activity with a clinical stage BET bromodomain inhibitor ODM-207 in pre-clinical models

Background: ODM-207 is a potent and selective BET inhibitor that is structurally unrelated to the benzodiazepine-based inhibitors including JQ1, I-BET762, and OTX015. Phase I clinical trials have now been initiated with this agent based on its potent anti-tumor activity in various in vitro and in vivo models of hematologic malignancies and solid tumors. In view of the recent publications implicating a role for BET protein BRD4 in the suppression of PD-L1 expression, an immune checkpoint ligand for PD-1, we sought to evaluate ODM-207 for its effect on immune-mediated anti-tumor efficacy in pre-clinical models.

Methods and Results: Mouse splenocytes were stimulated with anti-CD3 and anti-CD28 in the presence or absence of ODM-207 for four days and changes in immune cell population were analyzed by FACS. Results revealed an increase in the level of activated cytotoxic CD8+ T cells as indicated by increased intracellular IFNγ and granzyme B with ODM-207 treatment. After confirming the lack of direct anti-proliferative activity on the mouse colon carcinoma cell line CT26, in vivo evaluation of ODM-207 was carried out in the syngeneic CT26 subcutaneous tumor model established in BALB/c mice. Daily oral administration of ODM-207 at 30 mg/kg was well tolerated in this model and resulted in a statistically significant inhibition of tumor growth. Interestingly, the tumor growth inhibition observed with ODM-207 was comparable to that with a commercially available anti-mouse PD1 antibody. Studies to characterize the immune changes in the tumor and anti-tumor activity of ODM-207 in combination with an anti-mouse PD1 antibody are currently underway and the results will be presented.

Conclusions: In summary, these studies demonstrate the anti-tumor activity of BET inhibitor in a syngeneic model of colon carcinoma in the absence of a direct anti-proliferative activity on tumor cells. Observed tumor growth inhibition correlated with the in vitro activation of cytotoxic CD8+ T cells supporting the immune-mediated effect leading to tumor growth inhibition. In view of the remarkable success with the immune-based therapeutic approaches, these findings are relevant in devising appropriate strategies for the continued clinical development of ODM-207.

Citation Format: Pratima Deshpande, Ravi Krishna Babu, Prashant Yallappa Vadnal, Mahaboobi Jaleel, Murali Ramachandra, Chandrasekhar Abbineni, Susanta Samajdar, Anu-Maarit Moilanen, Pekka Kallio. Immune-mediated anti-tumor activity with a clinical stage BET bromodomain inhibitor ODM-207 in pre-clinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-113. doi:10.1158/1538-7445.AM2017-LB-113

Abstract 118: Targeting cancer with a novel BET bromodomain inhibitor ODM-207

Background: Bromodomain and extra-terminal (BET) family proteins are dual bromodomain-containing epigenetic readers that bind to acetylated-lysine residues at gene promoter and enhancer elements in histones and recruit protein complexes to promote transcriptional elongation. Recent evidence demonstrates that BET bromodomain inhibition leads to anti-proliferative activity in pre-clinical models of many hematological malignancies and solid tumors. Selective inhibition of BET bromodomains by small molecule inhibitors has emerged as a promising therapeutic strategy for the treatment of cancer. In this study, we evaluated the antitumor activity of ODM-207, a novel, potent and highly selective BET bromodomain inhibitor.

Methods and Results: ODM-207 is a potent and selective BET inhibitor that is structurally unrelated to the benzodiazepine like inhibitors such as JQ1, I-BET762, and OTX015. We tested the preclinical activity of ODM-207 across multiple tumor types in a 4-day growth inhibition in vitro assay. ODM-207 potently inhibits cell viability of a wide range of hematological and solid tumor cell lines. ODM-207 also shows potent antiproliferative effects in patient-derived cancer cells representing various tumor types. In VCaP prostate cancer cell lines, ODM-207 induced apoptosis consistent with increased expression of pro-apoptotic regulators, whereas potent antiproliferative effects associated with cell cycle arrest and cellular senescence were seen in e.g. LNCaP prostate cancer cell line. To gain insight on mechanisms of acquired BET inhibitor resistance, we generated a cell line with resistance to BET-inhibition by culturing LNCaP prostate cancer cells with increasing concentrations of OTX015, a potent and selective BET-inhibitor. Interestingly, ODM-207 is also able to inhibit proliferation and downregulate Myc levels in cells that have acquired resistance to BET-inhibitors OTX015 and I-BET762. In xenograft models, oral treatment with ODM-207 significantly inhibits tumor growth at a dose which is well tolerated.

Conclusions: In summary, these studies demonstrate that ODM-207 is a potent inhibitor of BET proteins in models of hematologic malignancies and solid tumors in vitro and in vivo and support its clinical development for the treatment of cancer.

Citation Format: Anu-Maarit Moilanen, Mari Björkman, Reetta Riikonen, Chandrasekhar Abbineni, Mahaboobi Jaleel, Sivapriya Marappan, Tarja Ikonen, Girish Daginakatte, Aravind A B, Elina Mattila, Juha Rantala, Susanta Samajdar, Murali Ramachandra, Pekka Kallio. Targeting cancer with a novel BET bromodomain inhibitor ODM-207 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 118. doi:10.1158/1538-7445.AM2017-118

Abstract 671: Identification of potent BET bromodomain inhibitors for treatment of cancer

Epigenetic mechanisms are essential for normal development and maintenance of tissue-specific gene expression. Histone lysine acetylation is one of the most abundant epigenetic modifications central to control of gene transcription. Bromodomains are the only known readers of this specific lysine acetylation code, playing an important role in transcriptional regulation of diverse cellular processes such as inflammatory gene expression, mitosis and viral/host interactions. Recently, the human BET family bromodomains which consists of BRD2, BRD3, BRD4 and BRDT has emerged as new druggable target class for the development of specific protein interaction inhibitors, enabling a novel strategy for the development of new therapies for various diseases. Here we report the identification of potent BET bromodomain inhibitors using structure based drug design principle. Multiple distinct series of compounds have been identified with low nM potency in biochemical binding assay. Crystal structures of BRD4 in complex with hit compounds have been solved to assist in optimization. The lead compounds showed very good cell based activity and favorable ADME properties. The compounds demonstrated dose dependent inhibition of c-Myc expression confirming the mechanism of action. Further optimization of these compounds and profiling in relevant pre-clinical disease models is in progress.

Citation Format: Sanjita Sasmal, Rajeev Kumar Shrimali, Chandrasekhar Abbineni, Kamala Kumari Arumalla, Anirudha Lakshminarasimhan, Karthikeyan Narasingapuram Arumugam, Nirbhay Kumar Tiwari, Narasimha K. Rao, Aravind AB, Subramanya Hosahalli. Identification of potent BET bromodomain inhibitors for treatment of cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 671. doi:10.1158/1538-7445.AM2013-671

A mild and convenient indium(III) chloride-catalyzed synthesis of thioglycosides

The efficiency of glycosidation reactions generally involves a high chemical yield, as well as high/complete stereo- and regioselectivity. All these depend on the compatibility of the reactivity of glycosyl donors and acceptors. Among glycosyl donors, thioglycosides are widely used because of their high degree of stability in many organic reactions. Although there are number of methods available for the preparation of thioglycosides, all of them have one or more disadvantages, especially concerning the time factor and cumbersome workup procedures. Here we report a convenient and high-yielding method for the preparation of thioglycosides.

Novel thieno oxazine analogues as antihyperglycemic and lipid modulating agents

A series of phenyl acetic acid and alpha-hydroxy propionic acid derivatives were synthesized. In vivo studies of the compounds indicated compound 2c as the most potent in one of the series, which has both glucose and lipid lowering properties. The syntheses and biological studies have been discussed.