Targeting the mSWI/SNF Complex in POU2F-POU2AF Transcription Factor-Driven Malignancies

The POU2F3-POU2AF2/3 (OCA-T1/2) transcription factor complex is the master regulator of the tuft cell lineage and tuft cell-like small cell lung cancer (SCLC). Here, we found that the POU2F3 molecular subtype of SCLC (SCLC-P) exhibits an exquisite dependence on the activity of the mammalian switch/sucrose non-fermentable (mSWI/SNF) chromatin remodeling complex. SCLC-P cell lines were sensitive to nanomolar levels of a mSWI/SNF ATPase proteolysis targeting chimera (PROTAC) degrader when compared to other molecular subtypes of SCLC. POU2F3 and its cofactors were found to interact with components of the mSWI/SNF complex. The POU2F3 transcription factor complex was evicted from chromatin upon mSWI/SNF ATPase degradation, leading to attenuation of downstream oncogenic signaling in SCLC-P cells. A novel, orally bioavailable mSWI/SNF ATPase PROTAC degrader, AU-24118, demonstrated preferential efficacy in the SCLC-P relative to the SCLC-A subtype and significantly decreased tumor growth in preclinical models. AU-24118 did not alter normal tuft cell numbers in lung or colon, nor did it exhibit toxicity in mice. B cell malignancies which displayed a dependency on the POU2F1/2 cofactor, POU2AF1 (OCA-B), were also remarkably sensitive to mSWI/SNF ATPase degradation. Mechanistically, mSWI/SNF ATPase degrader treatment in multiple myeloma cells compacted chromatin, dislodged POU2AF1 and IRF4, and decreased IRF4 signaling. In a POU2AF1-dependent, disseminated murine model of multiple myeloma, AU-24118 enhanced survival compared to pomalidomide, an approved treatment for multiple myeloma. Taken together, our studies suggest that POU2F-POU2AF-driven malignancies have an intrinsic dependence on the mSWI/SNF complex, representing a therapeutic vulnerability.

Novel CDK12/13 Inhibitors AU-15506 and AU-16770 Are Potent Anti-Cancer Agents in EGFR Mutant Lung Adenocarcinoma with and without Osimertinib Resistance

Osimertinib is a third-generation epidermal growth factor receptor and tyrosine kinase inhibitor (EGFR-TKI) approved for the treatment of lung adenocarcinoma patients harboring EGFR mutations. However, acquired resistance to this targeted therapy is inevitable, leading to disease relapse within a few years. Therefore, understanding the molecular mechanisms of osimertinib resistance and identifying novel targets to overcome such resistance are unmet needs of cancer patients. Here, we investigated the efficacy of two novel CDK12/13 inhibitors, AU-15506 and AU-16770, in osimertinib-resistant EGFR mutant lung adenocarcinoma cells in culture and xenograft models in vivo. We demonstrate that these drugs, either alone or in combination with osimertinib, are potent inhibitors of osimertinib-resistant as well as -sensitive lung adenocarcinoma cells in culture. Interestingly, only the CDK12/13 inhibitor in combination with osimertinib, although not as monotherapy, suppresses the growth of resistant tumors in xenograft models in vivo. Taken together, the results of this study suggest that inhibition of CDK12/13 in combination with osimertinib has the potential to overcome osimertinib resistance in EGFR mutant lung adenocarcinoma patients.

Abstract 4030: Generation of profound anti-tumor immunity by AUR-109, a spectrum-selective tyrosine kinase inhibitor, either as a single agent or in combination with immune checkpoint inhibitors

AUR-109 is an orally bioavailable clinical stage receptor tyrosine kinase inhibitor (RTK) that inhibits the activity of proangiogenic and oncogenic pathway-related RTKs including DDR1, FGFR, VEGFR, PDGFR, and RET. DDR1 instigates immune exclusion by promoting collagen fiber alignment thereby altering extracellular matrix (ECM) components in tumor immune microenvironment (TIME). DDR1 expression inversely correlated with reduced immune cell infiltration in TIME leading to exhaustion of tumor-fighting immune cells, tumor escape, EMT and metastasis. FGFRs induce the expression the PD-L1 and VEGFRs promote the proliferation of regulatory T cells (Treg), inhibit T-cell development and maturation of dendritic cells. These findings suggest that the spectrum-selective inhibition of these RTKs by AUR-109 has the potential to strongly modulate the anti- tumor immune response. Clinically successful immune checkpoint inhibitors (ICI) (anti-PD1, anti-PD-L1, and anti-CTLA4 antibodies) block the pathways that inhibit immune cell activation thus stimulating immune responses against the tumor cells. Although ICIs show improved survival in patients with many types of cancers, they suffer from the lack of response in majority of patients along with the development of resistance to therapy. To overcome the resistance and improve the efficacy, a number of combinations of PD-1 blockade with other anticancer therapies are being evaluated. We have undertaken a detailed characterization of the anti-tumor immune response by AUR-109 either as a single agent or in combination with anti-PD1 antibodies. The effect of AUR-109 on CD4 T cells and Treg cells was evaluated in the Renca subcutaneous tumor model. Immune cell population in the blood and tumor microenvironment were analyzed by FACS. Anti-tumor efficacy was analyzed in both subcutaneous and orthotopic Renca syngeneic tumor models. AUR-109 treatment resulted in an increase of total and CD4 T cells. Higher ratio of total T cells to regulatory T cells was observed indicating that there is an increase in effector T cells. In the TILs, there was decrease in the expression of PD-1 and PD-L1 with a concomitant increase in IFN-γ expression on CD8 T cells and NK cells indicating a profound immune activation caused by AUR-109 within the tumor. These results demonstrate the therapeutic potential of AUR-109 in combination with PD-1 blockade in preclinical models and the results from the ongoing combination studies will be presented.

Citation Format: Girish Daginakatte, Saravanan Thiyagarajan, Kiran Aithal, Mamon Dey, Reshma Reghu, Monalisha Mandal, Kavitha Nellore, Susanta Samajdar, Murali Ramachandra. Generation of profound anti-tumor immunity by AUR-109, a spectrum-selective tyrosine kinase inhibitor, either as a single agent or in combination with immune checkpoint inhibitors. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4030.

Activation of targetable inflammatory immune signaling is seen in myelodysplastic syndromes with SF3B1 mutations

Background

Mutations in the SF3B1 splicing factor are commonly seen in myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML), yet the specific oncogenic pathways activated by mis-splicing have not been fully elucidated. Inflammatory immune pathways have been shown to play roles in the pathogenesis of MDS, though the exact mechanisms of their activation in splicing mutant cases are not well understood.

Methods

RNA-seq data from SF3B1 mutant samples was analyzed and functional roles of interleukin-1 receptor-associated kinase 4 (IRAK4) isoforms were determined. Efficacy of IRAK4 inhibition was evaluated in preclinical models of MDS/AML.

Results

RNA-seq splicing analysis of SF3B1 mutant MDS samples revealed retention of full-length exon 6 of IRAK4, a critical downstream mediator that links the Myddosome to inflammatory NF-kB activation. Exon 6 retention leads to a longer isoform, encoding a protein (IRAK4-long) that contains the entire death domain and kinase domain, leading to maximal activation of NF-kB. Cells with wild-type SF3B1 contain smaller IRAK4 isoforms that are targeted for proteasomal degradation. Expression of IRAK4-long in SF3B1 mutant cells induces TRAF6 activation leading to K63-linked ubiquitination of CDK2, associated with a block in hematopoietic differentiation. Inhibition of IRAK4 with CA-4948, leads to reduction in NF-kB activation, inflammatory cytokine production, enhanced myeloid differentiation in vitro and reduced leukemic growth in xenograft models.

Conclusions

SF3B1 mutation leads to expression of a therapeutically targetable, longer, oncogenic IRAK4 isoform in AML/MDS models.

Funding

This work was supported by Cincinnati Children's Hospital Research Foundation, Leukemia Lymphoma Society, and National Institute of Health (R35HL135787, RO1HL111103, RO1DK102759, RO1HL114582), Gabrielle's Angel Foundation for Cancer Research, and Edward P. Evans Foundation grants to DTS. AV is supported by Edward P. Evans Foundation, National Institute of Health (R01HL150832, R01HL139487, R01CA275007), Leukemia and Lymphoma Society, Curis and a gift from the Jane and Myles P. Dempsey family. AP and JB are supported by Blood Cancer UK (grants 13042 and 19004). GC is supported by a training grant from NYSTEM. We acknowledge support of this research from The Einstein Training Program in Stem Cell Research from the Empire State Stem Cell Fund through New York State Department of Health Contract C34874GG. MS is supported by a National Institute of Health Research Training and Career Development Grant (F31HL132420).

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 3592: Targeting SWI/SNF ATPases in enhancer-addicted human cancers

In mammalian cells, DNA is wrapped around histone octamers (collectively referred to as nucleosomes) which form a physical barrier to all DNA-based processes. The switch/sucrose non-fermentable (SWI/SNF) is a multi-subunit chromatin remodeling complex that uses energy from ATP hydrolysis to reposition or eject nucleosomes at non-coding regulatory elements, thereby enabling access to the underlying DNA for transcriptional activation. Notably, the SWI/SNF complex plays a crucial role in chromatin remodeling and is recurrently altered in over 20% of human cancers, with the revised complex in cancer cells enabling central oncogenic gene programs. Yet, no studies have assessed the therapeutic efficacy of complete SWI/SNF inactivation across human cancers. Here, we developed a proteolysis targeting chimera (PROTAC) degrader of ATPase subunits of the SWI/SNF complex, SMARCA2 and SMARCA4. In a panel with over 90 normal and cancer cell lines from 18 different lineages, we found MYC-driven multiple myeloma and androgen receptor (AR)/forkhead box A1 (FOXA1)-positive prostate and breast cancers to be preferentially sensitive to dual SMARCA2 and SMARCA4 degradation relative to benign prostate as well as other cancer cell lines, including cancer cell lines with inactivating SMARCA4 mutations. We found complete SWI/SNF ATPase degradation to instantaneously compact the cis-regulatory elements that are bound and activated by transcription factors that drive cancer proliferation, namely MYC, IRF4, TCF3, AR, FOXA1, and ERG. This ensued in parallel untethering of these oncogenic drivers from the chromatin, with subsequent chemical decommissioning of their core enhancer circuitry and attenuation of downstream gene programs. Furthermore, using chromatin conformation assays we found SWI/SNF inactivation to disrupt super-enhancer and promoter DNA looping interactions that wire supra-physiologic expression of the MYC, AR, ERG, IRF4, and TCF3 oncogenes themselves, thereby tempering their expression in cancer cells. Treatment with the SMARCA2/4 degrader alone induced potent inhibition of tumor growth in cell line-derived xenograft models of multiple myeloma, as well as prostate cancer, and synergized with AR antagonists, inducing disease remission in several drug-resistant disease models. Notably, no major toxicities were seen in mice upon prolonged treatment with the SMARCA2/4 degrader, including no indications of thrombocytopenia, gastrointestinal goblet cell depletion, or germ cell degeneration—all being major toxicities associated with the BRD4-targeting therapeutics. To our knowledge, this study is the first preclinical proof of concept that targeted obstruction of chromatin accessibility at non-coding regulatory elements can be a potent therapeutic strategy in enhancer-addicted tumors, warranting the safety and efficacy assessments of SWI/SNF inhibitors and degraders in human clinical trials.

Citation Format: Abhijit Parolia, Lanbo Xiao, Yuanyuan Qiao, Pushpinder Bawa, Sanjana Eyunni, Eleanor Young, Rahul Mannan, Sandra E. Carson, Yu Chang, Yuping Zhang, James George, Mustapha Jaber, Fengyun Su, Rui Wang, Sanjita Sasmal, Leena Khare, Subhendu Mukerjee, Chandrasekhar AbbinenI, Kiran Aithal, Xuhong Cao, Yuzhuo Wang, Susanta Samajdar, Murali Ramachandra, Arul M. Chinnaiyan. Targeting SWI/SNF ATPases in enhancer-addicted human 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 3592.

Abstract 3500: AUR103 an oral small molecule CD47 antagonist in combination with azacytidine and bortezomib exhibits potent anti-tumor activity in myeloma and leukemia models in vitro and in vivo

The CD47/signal regulatory protein alpha axis is a critical regulator of myeloid cell activation and serves as an immune checkpoint for macrophage mediated phagocytosis. Targeting CD47-SIRPα axis is emerging as one of the promising new immunotherapy approaches that targets innate immune response. Number of clinical trials are in progress to evaluate CD47/SIRPα blocking therapies. Most of these molecules are either anti-CD47 antibodies or SIRPα-Fc recombinant proteins. We have developed a novel small molecule CD47 antagonist, AUR103 as a therapeutic agent for solid and hematological cancers. AUR103 is efficacious as a single agent in tumors with high expression of “eat-me” signals and synergizes well in combination with tumor-targeting antibodies. We hypothesized that agents capable of inducing “eat-me” signals such as calreticulin (CRT) a pro-phagocytic signal, will synergize with AUR103 to enhance phagocytosis and antitumor activity. Here, we report the anti-tumor efficacy of AUR103 in combination with azacytidine and bortezomib in acute myeloid leukemia and multiple myeloma model of cancer, respectively.In the phagocytosis assay, HL-60 human myeloid leukemia or NCI-H929 human multiple myeloma cells were treated with azacytidine or bortezomib for 48 hours. Cells were stained with CFSE and were further treated with AUR103. Cells were then added to human macrophages and allowed to undergo phagocytosis. Phagocytosis of target cells was measured by detecting cells that were double positive for APC and CFSE by FACS. HL-60 cells were orthotopically implanted in NOD SCID mice while NCI-H929 multiple myeloma cells were sub-cutaneously implanted in NOD SCID mice. Tumor bearing mice were treated with AUR103 (10 and 30 mg/kg, b.i.d, and po) as a single agent or in combination with azacytidine (5 mg/kg i.p., twice weekly) or bortezomib (0.4 mg/kg i.v., twice weekly). AUR103 in combination with azacytidine and bortezomib significantly enhanced phagocytosis of HL-60 and NCI-H929 tumor cells, respectively when compared to individual treatments. In the combination efficacy studies, AUR103 combination treatments with azacytidine and bortezomib were well tolerated without any signs of toxicity. In the HL-60 orthotopic model, AUR103 combination with azacytidine significantly reduced the engraftment of HL-60 tumor cells. AUR103 combination with bortezomib resulted in enhanced tumor growth inhibition in NCI-H929 tumor model when compared to individual treatments. These results demonstrate the therapeutic potential of AUR103 in combination with agents that are capable of inducing “eat-me” or pro-phagocytic signals.

Citation Format: Girish C. Daginakatte, Sasikumar Pottayil, Sudarshan Naremaddepalli, Gundala Chennakrishnareddy, Prasad Bilugudi, Sai Krishna Tangella, Sandeep Patil, Nagesh Gowda, Kiran Aithal, Wesley Roy Balasubramanian, Amit Dhudashiya, Samiulla Dodheri, Kavitha Nellore, Susanta Samajdar, Murali Ramachandra. AUR103 an oral small molecule CD47 antagonist in combination with azacytidine and bortezomib exhibits potent anti-tumor activity in myeloma and leukemia models in vitro and in vivo [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 3500.

Abstract 5469: Targeting SWI/SNF ATPases in enhancer-addicted prostate cancer

The switch/sucrose non-fermentable (SWI/SNF) complex plays a crucial role in chromatin remodeling and is recurrently altered in over 20% of human cancers. Here, we developed a proteolysis targeting chimera (PROTAC) degrader of ATPase subunits of the SWI/SNF complex, SMARCA2 and SMARCA4. Intriguingly, we found androgen receptor (AR)/forkhead box A1 (FOXA1)-positive prostate cancer to be exquisitely sensitive to dual SMARCA2 and SMARCA4 degradation relative to benign prostate as well as other cancer cell lines, including those with inactivating SMARCA4 mutations. Mechanistically, SWI/SNF inhibition rapidly compacts the cis-regulatory elements that are bound and activated by transcription factors that drive cancer proliferation, namely AR, FOXA1, ERG, and MYC. This ensues in chromatin untethering of these oncogenic drivers, chemical decommissioning of their core enhancer circuitry, and attenuation of downstream gene programs. Furthermore, we found SWI/SNF inhibition to disrupt super-enhancer and promoter DNA looping interactions that wire supra-physiologic expression of the AR, FOXA1, and MYC oncogenes, thereby tempering their expression in cancer cells. Monotherapy with the SMARCA2/4 degrader induced potent inhibition of tumor growth in cell line-derived xenograft models of prostate cancer and remarkably synergized with AR antagonists, inducing disease remission in models of castration-resistant prostate cancer. We also found the combinatorial treatment to significantly inhibit the growth of enzalutamide resistant disease using in vitro as well as patient-derived xenograft models. Notably, no major toxicities were seen in mice upon prolonged treatment with the SMARCA2/4 degrader, including no indications of thrombocytopenia, gastrointestinal goblet cell depletion, or germ cell degeneration. Taken together, these results suggest that impeding enhancer accessibility through SWI/SNF ATPase inactivation represents a novel therapeutic approach in enhancer addicted human cancers.

Citation Format: Lanbo Xiao, Abhijit Parolia, Yuanyuan Qiao, Pushpinder Bawa Pushpinder, Sanjana Eyunni, Rahul Mannan, Sandra E. Carson, Yu Chang, Xiaoju Wang, Yuping Zhang, Josh Vo, Steven Kregel, Stephanie A. Simko, Andrew D. Delekta, Mustapha Jaber, Heng Zheng, Ingrid Apel, Lisa McMurry, Fengyun Su, Rui Wang, Sylvia Wang, Sanjita Sasmal, Leena K. Satyam, Subhendu Mukherjee, Chandrasekhar AbbinenI, Kiran Aithal, Mital S. Bhakta, Jay Ghurye, Xuhong Cao, Nora M. Navone, Alexey Nesvizhskii, Rohit Mehra, Ulka Vaishampayan, Marco Blanchette, Yuzhuo Wang, Susanta Samajdar, Murali Ramachandra, Arul M. Chinnaiyan. Targeting SWI/SNF ATPases in enhancer-addicted prostate cancer [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 5469.

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.

Small Molecule Agents Targeting PD-1 Checkpoint Pathway for Cancer Immunotherapy: Mechanisms of Action and Other Considerations for Their Advanced Development

Pioneering success of antibodies targeting immune checkpoints such as programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) has changed the outlook of cancer therapy. Although these antibodies show impressive durable clinical activity, low response rates and immune-related adverse events are becoming increasingly evident in antibody-based approaches. For further strides in cancer immunotherapy, novel treatment strategies including combination therapies and alternate therapeutic modalities are highly warranted. Towards this discovery and development of small molecule, checkpoint inhibitors are actively being pursued, and the efforts have culminated in the ongoing clinical testing of orally bioavailable checkpoint inhibitors. This review focuses on the small molecule agents targeting PD-1 checkpoint pathway for cancer immunotherapy and highlights various chemotypes/scaffolds and their characterization including binding and functionality along with reported mechanism of action. The learnings from the ongoing small molecule clinical trials and crucial points to be considered for their clinical development are also discussed.

Discovery of MAP855, an Efficacious and Selective MEK1/2 Inhibitor with an ATP-Competitive Mode of Action

Mutations in MEK1/2 have been described as a resistance mechanism to BRAF/MEK inhibitor treatment. We report the discovery of a novel ATP-competitive MEK1/2 inhibitor with efficacy in wildtype (WT) and mutant MEK12 models. Starting from a HTS hit, we obtained selective, cellularly active compounds that showed equipotent inhibition of WT MEK1/2 and a panel of MEK1/2 mutant cell lines. Using a structure-based approach, the optimization addressed the liabilities by systematic analysis of molecular matched pairs (MMPs) and ligand conformation. Addition of only three heavy atoms to early tool compound 6 removed Cyp3A4 liabilities and increased the cellular potency by 100-fold, while reducing log P by 5 units. Profiling of MAP855, compound 30, in pharmacokinetic-pharmacodynamic and efficacy studies in BRAF-mutant models showed comparable efficacy to clinical MEK1/2 inhibitors. Compound 30 is a novel highly potent and selective MEK1/2 kinase inhibitor with equipotent inhibition of WT and mutant MEK1/2, whose drug-like properties allow further investigation in the mutant MEK setting upon BRAF/MEK therapy.

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.

Structural and binding studies of cyclin-dependent kinase 2 with NU6140 inhibitor

Cyclin-dependent kinase 2 (CDK2) is an established target protein for therapeutic intervention in various diseases, including cancer. Reported inhibitors of CDK2 target the ATP-binding pocket to inhibit the kinase activity. Many small molecule CDK2 inhibitors have been discovered, and their crystal structure with CDK2 or CDK2-cyclin A complex has been published. NU6140 is a CDK2 inhibitor with moderate potency and selectivity. Herein, we report the cocrystal structure determination of NU6140 in complex with CDK2 and confirmation of the binding using various biophysical methods. Our data show that NU6140 binds to CDK2 with a Kd of 800 nM as determined by SPR and stabilizes the protein against thermal denaturation (ΔT_m -5°C). The cocrystal structure determined in our study shows that NU6140 binds in the ATP-binding pocket as expected for this class of compounds and interacts with Leu83 and Glu81 with regular hydrogen bonds and with Asp145 via water-mediated H-bond. Based on these data, we propose structural modifications of NU6140 to introduce new interactions with CDK2 that can improve its potency while retaining the selectivity.

Abstract 1266: Discovery and preclinical evaluation of a novel covalent inhibitor of FABP5 for cancer therapy

Dysregulated fatty acid metabolism is thought to be a hallmark of cancer, wherein fatty acids function both as an energy source and as signals for enzymatic and transcriptional networks contributing to malignancy. Fatty acid-binding protein 5 (FABP5) is an intracellular protein that facilitates transport of fatty acids and plays a role in regulating the expression of genes associated with cancer progression such as cell growth, survival, and metastasis. Overexpression of FABP5 has been reported to contribute to an aggressive phenotype and a poor survival correlation in several cancers. Therefore, inhibition of FABP5 is considered as a therapeutic approach for cancers. Phenotypic screening of a library of covalent compounds for selective sensitivity of cancer cells followed by medicinal chemistry optimization resulted in the identification of AUR104 with desirable properties. Chemoproteomic-based target deconvolution revealed FABP5 as the cellular target of AUR104. Covalent adduct formation with Cys43 of FABP5 by AUR104 was confirmed by mass spectrometry. Target occupancy studies using a biotin-tagged AUR104 demonstrated potent covalent binding to FABP5 in both cell-free and cellular conditions. Ligand displacement assay with a fluorescent fatty acid probe confirmed the competitive binding mode of AUR104 with fatty acids. Binding at the fatty acid site and covalent bond formation with Cys43 were also demonstrated by crystallography. Furthermore, AUR104 showed a high degree of selectivity against a broad safety pharmacology panel of enzymes and receptors. AUR104 exhibited potent anti-proliferative activity in a large panel of cell lines derived from both hematological and solid cancers with a high degree of selectivity over normal cells. Anti-proliferative activity in lymphoma cell lines correlated with inhibition of MALT1 pathway activity, cleavage of RelB/Bcl10 and secretion of cytokines, IL-10 and IL-6. AUR104 displayed desirable drug-like properties and dose-dependent oral exposure in pharmacokinetic studies. Oral dosing with AUR104 resulted in dose-dependent anti-tumor activity in DLBCL (OCI-LY10) and NSCLC (NCI-H1975) xenograft models. In a repeated dose MTD studies in rodents and non-rodents, AUR104 showed good tolerability with an exposure multiple of >500 over cellular EC50 for up to 8 hours. In summary, we have identified a novel covalent FABP5 inhibitor with optimized properties that showed anti-tumor activity in in vitro and in vivo models with acceptable safety profile. The data presented here strongly support clinical development of AUR104.

Citation Format: Dinesh Chikkanna, Leena Khare Satyam, Sunil Kumar Pnaigrahi, Vinayak Khairnar, Manoj Pothuganti, Lakshmi Narayan Kaza, Narasimha Raju Kalidindi, Vijaya Shankar Nataraj, Aditya Kiran Gatta, Narasimha Rao Krishnamurthy, Sandeep Patil, DS Samiulla, Kiran Aithal, Vijay Kamal Ahuja, Nirbhay Kumar Tiwari, KB Charamannna, Pravin Pise, Thomas Anthony, Kavitha Nellore, Sanjeev Giri, Shekar Chelur, Susanta Samajdar, Murali Ramachandra. Discovery and preclinical evaluation of a novel covalent inhibitor of FABP5 for cancer therapy [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 1266.

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 1713: Novel, potent and orally bioavailable small molecule CD73 inhibitors for cancer immunotherapy

CD73 is a cell surface ectoenzyme, which is overexpressed in many types of human and mouse cancers. CD73 is the primary enzymatic producer of immunosuppressive adenosine in the tumor microenvironment, and high CD73 expression is associated with significantly poorer prognosis in several tumor types. Inhibition of either adenosine generation or signaling by inhibiting CD73 have been shown to be effective therapeutic approaches. Here we sought to discover and develop novel and orally bioavailable small molecule inhibitors that target CD73. Aurigene's non-nucleotide small molecule exhibit potent inhibition of CD73 in respective biochemical and cellular assays. High potency translated into rescue of AMP induced repression of IFN-Υ and IL-2 in human PBMCs. Lead compounds exhibited desirable drug-like properties including solubility, Caco2 permeability, lack of CYP inhibition and excellent oral pharmacokinetic exposure. In summary, we have identified small molecule inhibitors with good drug like properties, which showed good in vitro potency and excellent PK. Evaluation of these lead compounds in syngeneic tumor model along with in vivo toxicity studies are currently under way.

Citation Format: Chandregowda Venkateshappa, Kishore Narayanan, Prasath Kothandaraman, Garima Priyadarshani, Rashmi Nair, Megha Goyal, Vijay Kamal Ahuja, Sagar Dadhania, AB Aravind, DS Samiulla, Girish Daginakkatte, Thomas Antony, Kavitha Nellore, Sunil Panigrahi, Dinesh Chikkanna, Susanta Samajdar, Murali Ramachandra. Novel, potent and orally bioavailable small molecule CD73 inhibitors for cancer immunotherapy [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 1713.

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.

PD-1 derived CA-170 is an oral immune checkpoint inhibitor that exhibits preclinical anti-tumor efficacy

Small molecule immune checkpoint inhibitors targeting PD-1 and other pathways may offer advantages including ease of dosing, ability to manage immune-related adverse events (irAEs) due to their shorter pharmacokinetic exposure and opportunity to target more than one pathway for improving efficacy. Here we describe the identification and characterization of CA-170, an amino acid inspired small molecule inhibitor of PD-L1 and VISTA derived from the interface of PD-1 and PD-L1. CA-170 exhibited potent rescue of proliferation and effector functions of T cells inhibited by PD-L1/L2 and VISTA with selectivity over other immune checkpoint proteins as well as a broad panel of receptors and enzymes. Observed blocking of PD-L1 signaling and binding to PD-L1 in the cellular context without preventing the assembly of PD-1:PD-L1 complex support the formation of a defective ternary complex as the mechanism of action of CA-170. Oral administration of CA-170 resulted in increased proliferation and activation of T cells in the tumor, and significant anti-tumor efficacy in a number of immunocompetent mouse tumor models either as a single agent or in combination with approved therapeutics. These results prompted the advancement of CA-170 to human clinical trials.

Discovery of CA-4948, an Orally Bioavailable IRAK4 Inhibitor for Treatment of Hematologic Malignancies

Small molecule potent IRAK4 inhibitors from a novel bicyclic heterocycle class were designed and synthesized based on hits identified from Aurigene's compound library. The advanced lead compound, CA-4948, demonstrated good cellular activity in ABC DLBCL and AML cell lines. Inhibition of TLR signaling leading to decreased IL-6 levels was also observed in whole blood assays. CA-4948 demonstrated moderate to high selectivity in a panel of 329 kinases as well as exhibited desirable ADME and PK profiles including good oral bioavailability in mice, rat, and dog and showed >90% tumor growth inhibition in relevant tumor models with excellent correlation with in vivo PD modulation. CA-4948 was well tolerated in toxicity studies in both mouse and dog at efficacious exposure. The overall profile of CA-4948 prompted us to select it as a clinical candidate for evaluation in patients with relapsed or refractory hematologic malignancies including non-Hodgkin lymphoma and acute myeloid leukemia.

Discovery of CA-4948, an Orally Bioavailable IRAK4 Inhibitor for Treatment of Hematologic Malignancies

Small molecule potent IRAK4 inhibitors from a novel bicyclic heterocycle class were designed and synthesized based on hits identified from Aurigene's compound library. The advanced lead compound, CA-4948, demonstrated good cellular activity in ABC DLBCL and AML cell lines. Inhibition of TLR signaling leading to decreased IL-6 levels was also observed in whole blood assays. CA-4948 demonstrated moderate to high selectivity in a panel of 329 kinases as well as exhibited desirable ADME and PK profiles including good oral bioavailability in mice, rat, and dog and showed >90% tumor growth inhibition in relevant tumor models with excellent correlation with in vivo PD modulation. CA-4948 was well tolerated in toxicity studies in both mouse and dog at efficacious exposure. The overall profile of CA-4948 prompted us to select it as a clinical candidate for evaluation in patients with relapsed or refractory hematologic malignancies including non-Hodgkin lymphoma and acute myeloid leukemia.

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.

Structure of cyclin-dependent kinase 2 (CDK2) in complex with the specific and potent inhibitor CVT-313

CVT-313 is a potent CDK2 inhibitor that was identified by screening a purine-analogue library and is currently in preclinical studies. Since this molecule has the potential to be developed as a CDK2 inhibitor for cancer therapy, the potency of CVT-313 to bind and stabilize CDK2 was evaluated, together with its ability to inhibit aberrant cell proliferation. CVT-313 increased the melting temperature of CDK2 by 7°C in thermal stabilization studies, thus indicating its protein-stabilizing effect. CVT-313 inhibited the growth of human lung carcinoma cell line A549 in a dose-dependent manner, with an IC50 of 1.2 µM, which is in line with the reported biochemical potency of 0.5 µM. To support the further chemical modification of CVT-313 and to improve its biochemical and cellular potency, a crystal structure was elucidated in order to understand the molecular interaction of CVT-313 and CDK2. The crystal structure of CDK2 bound to CVT-313 was determined to a resolution of 1.74 Å and clearly demonstrated that CVT-313 binds in the ATP-binding pocket, interacting with Leu83, Asp86 and Asp145 directly, and the binding was further stabilized by a water-mediated interaction with Asn132. Based on the crystal structure, further modifications of CVT-313 are proposed to provide additional interactions with CDK2 in the active site, which may significantly increase the biochemical and cellular potency of CVT-313.

Ternary complex formation of AFN-1252 with Acinetobacter baumannii FabI and NADH: Crystallographic and biochemical studies

Acinetobacter baumannii is an opportunistic Gram-negative bacterial pathogen, associated mostly with hospital-acquired infections. The emergence of drug resistance strains made it necessary to explore new pathways for the development of more effective antibiotics. Enoyl CoA reductase (FabI), a key enzyme in the fatty acid biosynthesis (FAS) pathway, has emerged as a potential target for antibacterial drug development. Earlier reports show that the lead SaFabI inhibitor AFN-1252 can inhibit FabI from other organisms including Escherichia coli and Burkholderia pseudomallei, but with differential potency. In the present work, we show that AFN-1252 is a moderate inhibitor of AbFabI with an IC₅₀ of 216 nM. AFN-1252 stabilized AbFabI with a 4.2°C increase in the melting temperature (T_m ) and, interestingly, the stabilization effect was significantly increased in presence of the cofactor NADH (∆T_m  = 17°C), suggesting the formation of a ternary complex AbFabI: AFN-1252: NADH. X-ray crystallography studies of AbFabI co-crystalized with AFN-1252 and NADH confirmed the ternary complex formation. The critical interactions of AFN-1252 with AbFabI and NADH identified from the co-crystal structure may facilitate the design and development of new drugs against A. baumannii infections by targeting the FAS pathway.

Abstract 4148: An orally bioavailable small molecule antagonist of TIM-3 signaling pathway shows potent anti-tumor activity

Activation of anti-tumor immune response by specific inhibition of PD1 pathway using monoclonal antibodies has now become of the mainstay in cancer therapy as evidenced by its widespread use in an expanding list of indications. Although these antibodies show impressive durable clinical activity, low response rates are witnessed in a large number of cancers, including colorectal cancer that remain largely refractory to PD-1 blockade. Upregulation of alternative immune checkpoints such as T cell immunoglobulin and mucin-domain containing-3 (TIM-3) and VISTA contributes to the lack of response in patients not responding to therapies with anti-PD-1/PD-L1 antibodies. TIM-3 is a co-inhibitory receptor expressed on IFN-γ-producing T cells, FoxP3+ Treg cells and innate immune cells. Synergistic effects in restoring the anti-tumor immunity in preclinical models upon dual blockade of TIM-3 and PD-1 has provided a strong rationale for developing TIM-3 agents for use in combination with PD1 agents in the clinic. We sought to discover and develop an orally available small molecule antagonist targeting TIM3- signaling pathways. Unlike antibodies an oral agent potentially offers the convenience, flexibility to adjust dose and schedule to address any emergent adverse events and ease of combination therapy. Because TIM-3 shares sequence and structural similarity with the B7 family ligands, a focused library of compounds mimicking the interaction of checkpoint proteins of B7 family was screened towards the functional antagonism of TIM-3. Further optimization of the hit compounds resulted in lead compounds targeting TIM-3 pathway with desirable potency and selectivity. Lead compounds exhibited potent functional activity comparable to that obtained with an anti-TIM-3 antibody in rescuing the effector functions in human PBMC-based assays. Additionally, an advanced lead compound exhibited desirable drug-like properties including solubility, metabolic stability and pharmacokinetics with good oral bioavailability. In a syngeneic tumor models, once a day oral dosing of the advanced lead compound resulted in significant tumor growth inhibition as a single agent and in combination with anti-PD1 antibody that correlated well with immune PD in the tumor. The findings reported here support the development of the oral TIM-3 antagonist for use in the clinic.

Citation Format: Pottayil G. Sasikumar, Sudarshan S. Naremaddepalli, Raghuveer K. Ramachandra, Nagesh Gowda, Srinivaskumar Devarapalli, Sreenivas Adurthi, Jiju Mani, Rashmi Nair, Amit A. Dhudashiya, Dodheri S. Samiulla, Nagaraj M. Gowda, Murali Ramachandra. An orally bioavailable small molecule antagonist of TIM-3 signaling pathway shows potent anti-tumor activity [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 4148.

Abstract 4418: Pharmacological characterization of a preclinical candidate covalently inhibiting CDK12

Cyclin-dependent kinase 12 (CDK12) is a transcription-associated protein that plays a critical role in DNA damage response, splicing, pre-mRNA processing and is crucial for maintaining genomic stability. CDK12 associated with Cyclin K (CycK) regulates transcription elongation by phosphorylating RNA polymerase II (RNAP II) at Serine 2 (pS2) in the C-terminal domain (CTD). Overexpression of CDK12 in various tumor types suggests the possibility that CDK12 has oncogenic properties, similarly to other transcription-associated kinases. Considering its critical role in transcription and RNA processing, CDK12 is emerging as a potential therapeutic target for cancer. Multiple series of potent and selective CDK12 covalent inhibitors were identified by structure-guided and iterative medicinal chemistry approaches. Early lead compounds were optimized towards achieving high on target potency with good selectivity and desirable drug like properties including pharmacokinetic profile to achieve anti-tumour activity. Optimization of early lead compounds from two distinct chemical series resulted in very potent and highly selective CDK12 covalent inhibitors with desirable oral bioavailability. The covalent mode of action for these biochemically potent compounds has been confirmed by CDK12 target engagement assay in the cellular context. These selective inhibitors showed significant anti-proliferative activity in TNBC and other cancer cell lines including those harbouring ETS fusion. Importantly, cell killing is observed in cancer cells but not in normal cells (RWPE1) with short time (2h) and long-time (72h) exposure of these compounds. Anti-proliferative activity is well correlated with the inhibition of pS2 and down-regulation of a number of DNA damage response genes including BRCA1, RAD51, ATM and FANCI. Consistent with the inhibition of genes involved in DNA damage repair, a highly synergistic anti-proliferative activity was observed when treated in combination with cisplatin and PARP inhibitors. Based on the robust efficacy as a single agent in a TNBC mouse xenograft model with one of the optimized leads, the preclinical candidate exhibiting a greater degree of selectivity is being evaluated for efficacy and tolerability in relevant preclinical models.

Citation Format: Ramulu Poddutoori, Sujatha Rajagopalan, Subhendu Mukherjee, Sivapriya Marappan, Samiulla D. S., Sasirekha Sivakumar, Shilpa S Nayak, Ravindra M V, Devaraja TS, Srinivas Kondela, Suraj Tgore, Amit A Dhudashiya, Charamanna K. B, Aravind A B, Amith A, Pavithra S, Hema Sankar Pathange, Thomas Antony, Mahaboobi Jaleel, Sanjeev Giri, Girish Daginakatte, Kavitha Nellore, Shekar Chelur, Murali Ramachandra, Susanta Samajdar. Pharmacological characterization of a preclinical candidate covalently inhibiting CDK12 [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 4418.

Abstract 4086: Preclinical evaluation of pharmacokinetics, pharmacodynamics and efficacy of the dual CD73-A2AR Inhibitors

As a potent immunosuppressor adenosine is essential for maintaining tissue homeostasis and preventing an overzealous immune response during inflammation and infection. However, adenosine generated within the tumor microenvironment by the action of ecto-nucleotidases including CD73 hinders the immune reaction towards cancer cells by signaling through adenosine receptors such as high affinity A2AR expressed on immune cells. Inhibitions of either adenosine generation or signaling by inhibiting CD73 or A2AR have been shown to be effective therapeutic approaches. Interestingly, the co-blockade of CD73 and A2AR results in a more pronounced anti-tumor activity than blockade of either, likely due to increased CD73 expression upon A2AR inhibition and compensatory activity of other adenosine receptors such as A2BR. In view of this, we sought to discover and develop small molecule inhibitors that dually target CD73 and A2AR with oral bioavailability for ease of administration and use in combination with other anti-cancer therapies. Aurigene’s dual inhibitors exhibit potent inhibition of both A2AR and CD73 in respective biochemical and cellular assays. High potency translated into rescue of NECA or AMP induced repression of IFNΥ and IL2 in human PBMCs. Lead compounds exhibited desirable drug-like properties including solubility, permeability, lack of CYP inhibition, and pharmacokinetic exposure. In Syngeneic tumour model, treatment with lead compounds resulted in significant tumour growth inhibition while correlating well with tumour drug levels and modulation of pharmacodynamic markers. In summary, we have identified first-in-class dual inhibitors with good drug like properties, which showed significant antitumor efficacy. Evaluation of these lead compounds in additional tumour models and in vivo toxicity studies is currently under way.

Citation Format: Dinesh Chikkanna, Kishore Narayanan, Sunil Panigrahi, Garima Priyadarshini, Megha Goyal, Jiju Mani, DS Samiulla, Sagar dadhania, AB Aravind, Girish Daginakatte, Thomas Anthony, Kavitha Nellore, Susanta Samajdar, Murali Ramachandra. Preclinical evaluation of pharmacokinetics, pharmacodynamics and efficacy of the dual CD73-A2AR Inhibitors [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 4086.

Abstract 3844: Anti-tumor efficacy of SMARCA degraders in pre-clinical models of cancer

SMARCA2/BRM and SMARCA4/BRG1 are the mutually exclusive DNA-dependent ATPases within the SWI/SNF complexes, which function in mobilizing nucleosomes to regulate transcription, DNA replication and repair, and higher-order chromosome dynamics. SMARCA4 is mutated in a number of cancers, which generally lack targetable oncogenes. Genetic silencing studies have established a requirement of SMARCA2 for survival of tumor cells lacking SMARCA4. SMARCA4-deficient patient population represents 10%-20% of NSCLC cases, ∼5% pancreatic cancer patients and ∼10% ovarian cancer patients where SMARCA2 is overexpressed. Interestingly, SMARCA4 is highly expressed without mutation in certain tumor types, where overexpression contributes to increased proliferation and survival. SMARCA4 knockdown in these tumors leads to inhibition of proliferation and also increase sensitivity to known chemotherapeutic agents, supporting the validity of targeting 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 bromodomain have failed to show such an anti-proliferative phenotype. These findings triggered us to evaluate chemical degradation as an alternate approach to target SMARCA2/4 altered cancers. Optimization of bifunctional molecules with binding moieties for SMARCA2/4 and E3 ligase to induce proteasome-mediated degradation resulted in the identification of selective SMARCA2 and SMARCA4 degraders. These degraders showed selectivity against other bromodomain containing proteins such as BRD4, CBP and p300 in Western blot analysis. Functional analysis of a preferential SMARCA2 degrader in a panel of cell lines indicated a potent anti-proliferative activity in the context of SMARCA4 mutation. Additionally, these compounds displayed acceptable drug-like properties including solubility, metabolic stability and pharmacokinetics in mice. Dose-dependent tumor growth inhibition was observed in a SMARCA4-deficient lung cancer xenograft model and a syngeneic model of lymphoma at well-tolerated doses. Observed efficacy was correlated with the target degradation in the tumor supporting the potential to further develop them for cancer therapy. Based on the reported vulnerability of SMARCA4-deficient cell lines of diverse tumor origin to agents targeting PARP, PI3K/AKT and EZH2, combination effects with SMARC2 degrader are being interrogated.

Citation Format: Leena Khare Satyam, Sanjita Sasmal, Manoj K. Pothuganti, Sreevidya M.R., Ashokk Ettam, Sireesha Nunna, Marla Roshaiah, Shankaraiah Chithaluru, Rangarao Pallepati, Amitkumar A. Pawar, Leela P. Narukulla, Raghunadh A. Sripathi, Suraj Tgore, Rakesh P. Nankar, Charamanna KB, Nagesh Gowda S, Kiran Aithal, Samiulla DS, Subhendu Mukherjee, Shekar Chelur, Kavitha Nellore, Girish Daginakatte, Murali Ramachandra, Susanta Samajdar. Anti-tumor efficacy of SMARCA degraders in pre-clinical models of cancer [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 3844.

A Rationally Designed Peptide Antagonist of the PD-1 Signaling Pathway as an Immunomodulatory Agent for Cancer Therapy

Pioneering success of antibodies targeting immune checkpoints such as PD-1 and CTLA4 has opened novel avenues for cancer immunotherapy. Along with impressive clinical activity, severe immune-related adverse events (irAE) due to the breaking of immune self-tolerance are becoming increasingly evident in antibody-based approaches. As a strategy to better manage severe adverse effects, we set out to discover an antagonist targeting PD-1 signaling pathway with a shorter pharmacokinetic profile. Herein, we describe a peptide antagonist NP-12 that displays equipotent antagonism toward PD-L1 and PD-L2 in rescue of lymphocyte proliferation and effector functions. In preclinical models of melanoma, colon cancer, and kidney cancers, NP-12 showed significant efficacy comparable with commercially available PD-1-targeting antibodies in inhibiting primary tumor growth and metastasis. Interestingly, antitumor activity of NP-12 in a preestablished CT26 model correlated well with pharmacodynamic effects as indicated by intratumoral recruitment of CD4 and CD8 T cells, and a reduction in PD-1⁺ T cells (both CD4 and CD8) in tumor and blood. In addition, NP-12 also showed additive antitumor activity in preestablished tumor models when combined with tumor vaccination or a chemotherapeutic agent such as cyclophosphamide known to induce "immunologic cell death." In summary, NP-12 is the first rationally designed peptide therapeutic targeting PD-1 signaling pathways exhibiting immune activation, excellent antitumor activity, and potential for better management of irAEs.

ODM-203, a Selective Inhibitor of FGFR and VEGFR, Shows Strong Antitumor Activity, and Induces Antitumor Immunity

Alterations in the gene encoding for the FGFR and upregulation of the VEGFR are found often in cancer, which correlate with disease progression and unfavorable survival. In addition, FGFR and VEGFR signaling synergistically promote tumor angiogenesis, and activation of FGFR signaling has been described as functional compensatory angiogenic signal following development of resistance to VEGFR inhibition. Several selective small-molecule FGFR kinase inhibitors are currently in clinical development. ODM-203 is a novel, selective, and equipotent inhibitor of the FGFR and VEGFR families. In this report we show that ODM-203 inhibits FGFR and VEGFR family kinases selectively and with equal potency in the low nanomolar range (IC₅₀ 6-35 nmol/L) in biochemical assays. In cellular assays, ODM-203 inhibits VEGFR-induced tube formation (IC₅₀ 33 nmol/L) with similar potency as it inhibits proliferation in FGFR-dependent cell lines (IC₅₀ 50-150 nmol/L). In vivo, ODM-203 shows strong antitumor activity in both FGFR-dependent xenograft models and in an angiogenic xenograft model at similar well-tolerated doses. In addition, ODM-203 inhibits metastatic tumor growth in a highly angiogenesis-dependent kidney capsule syngenic model. Interestingly, potent antitumor activity in the subcutaneous syngenic model correlated well with immune modulation in the tumor microenvironment as indicated by marked decrease in the expression of immune check points PD-1 and PD-L1 on CD8 T cells and NK cells, and increased activation of CD8 T cells. In summary, ODM-203 shows equipotent activity for both FGFR and VEGFR kinase families and antitumor activity in both FGFR and angigogenesis models.

Data on comparative studies of lineaments extraction from ASTER DEM, SRTM, and Cartosat for Jilledubanderu River basin, Anantapur district, A.P, India by using remote sensing and GIS

The data deals with the functions that automatically extracted lineaments from the Cartosat, ASTER and SRTM of Digital Elevation Model (DEM) of different spatial resolutions, in the software ArcGIS 10.4. The extracted lineaments result shows the ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) DEM gives the lowest number of lineaments reflects Cartosat and SRTM (Shuttle Radar Topography Mission) DEM shows a medium number of lineaments. Cartosat DEM is most appropriate for extraction of contours precisely rather than ASTER and SRTM. This study reveals the Cartosat DEM data is best to use extraction of lineaments in the Indian provinces, offers at most comprehensive geological structural info amongst all the data sets. The extracted lineaments lengths and densities are determined by the statistical method. Based on the data generated lineament density and rose diagram. Cartosat DEM data are the best suited for studying very small areas as through geological and structural information can be mined by using this data.

Abstract LB-258: Identification of SMARCA2/4 degraders for the treatment of SMARCA4-mutant and other cancers

The SWI/SNF complexes consist of one of two mutually exclusive DNA-dependent ATPases, BRG1/SMARCA4 or BRM/SMARCA2, together with core and accessory subunits that function in mobilizing nucleosomes to regulate transcription, DNA replication and repair, and higher-order chromosome dynamics. SMARCA2 (BRM) and SMARCA4 (BRG1), contain a bromodomain and an ATPase domain. The mammalian SWI/SNF complex functions as a tumor suppressor in many human malignancies. In addition to an essential role in pluripotency and development, genetic lesions of SWI/SNF complexes have been strongly linked to cancer development as components are mutated in many cancers. In some tumor types, mutations within the SWI/SNF complex lead to context specific vulnerabilities such as the requirement of SMARCA2 for survival of tumour cells lacking SMARCA4. This finding of SMARCA2/4 synthetic lethal relationship translates in vivo which emphasizes SMARCA2 as a promising therapeutic target for the treatment SMARCA4-mutant cancers. Moreover, the SMARCA4-deficient patient population generally lacks targetable oncogenes (such as mutant EGFR or ALK translocations), which further emphasizes the potential of developing SMARCA2 inhibitors. Previously, contrary to genetic silencing of SMARCA2 leading to potent anti-proliferative activity in SMARCA4-deficient cancer cell lines, pharmacological studies with a cell permeable probe capable of binding to SMARCA2 and SMARCA4 have failed to show such an anti-proliferative phenotype. These findings support that the ATPase domain, but not the bromodomain of SMARCA2, is the tractable therapeutic target for SMARCA4-deficient cancer. Significant hurdle in developing potent and selective ATPase inhibitors that must compete with intracellular concentrations of ATP (2-10 mM) triggered us to evaluate chemical degrader as an alternate approach. Herein we report the identification and characterization of potent SMARCA2/4 degraders. Design and SAR-based optimization of bifunctional molecules with binding moities for SMARCA2/4 and E3 ligase to induce proteosome-mediated degradation yielded compounds that potently degraded SMARCA2 alone or both SMARCA2 and SMARCA4. Selective binding to SMARCA2/4 was confirmed in biochemical assays followed by assessement of their cellular degradation potency in Western blot analysis. Selective degradation of SMARCA2/4 over other bromodomain containing protein such as BRD4 and CBP/p300 was also observed. Functional analysis of these compounds in a panel of cell lines indicated that the degradation of SMARCA2 or SMARCA2/4 resulted in potent anti-proliferative activity in selected cell lines that was not strictly dependent upon SMARCA4 status. Additionally, these compounds displayed reasonable drug-like properties including solubility, metabolic stability and pharmacokinetics in mice supporting their potential to fully evaluate the impact of SMARCA2/4 degradation and to develop them as a novel therapeutic approach.

Citation Format: Sanjita Sasmal, Leena K. Satyam, Manoj K. Pothuganti, Ashokk Ettam, Sireesha Nunna, Mohammed A. Shareef, Sreevalsam Gopinath, Subhendu Mukherjee, Murali Ramachandra, Susanta Samajdar. Identification of SMARCA2/4 degraders for the treatment of SMARCA4-mutant and other cancers [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 LB-258.

Abstract 1392: Preclinical In vivo evaluation of efficacy, pharmacokinetics and pharmacodynamics of novel PRMT5 inhibitors in multiple tumor models

PRMT5 is a typical type II methyltransferase, transferring two methyl groups to arginine, leading to symmetric dimethylation of the substrate. It can symmetrically methylate histones H2AR3, H3R2, H3R8, and H4R3 and can also methylate many non-histone proteins contributing to tumorigenesis by regulating cell cycle progression, DNA repair, cell growth, apoptosis, and inflammation. Overexpression of PRMT5 is reported in several human malignancies including lymphoma, glioma, melanoma, lung, breast, ovarian, and prostate cancers. Elevated levels correlate with poor prognosis in NSCLC, ovarian cancers, and GBM. Therefore, PRMT5 is considered an attractive target for cancer therapy. We sought to discover and develop PRMT5 inhibitors with the “best-in-class” profile with an emphasis on improved permeability for their potential use in solid tumors. Utilizing structure-guided drug design and SAR-based approaches, we have optimized two chemical series of substrate competitive PRMT5 inhibitors. Determination of co-crystal structures with several de novo designed hits aided in the identification of lead compounds that exhibited potent inhibition of PRMT5. Lead compounds AU-574 and AU-755 were highly active in inhibiting proliferation of a number of cell lines derived from solid tumors that correlated well with cellular H4R3Me2s inhibition, confirming the mechanism. Lead compounds exhibited desirable drug-like properties including solubility, permeability, lack of CYP inhibition, and pharmacokinetic exposure. In xenograft models of Z-138 (lymphoma) and H-358 (lung cancer), treatment with lead compounds resulted in significant tumor growth inhibition while correlating with tumor drug levels and modulation of H4R3Me2s as the pharmacodynamic effect. In summary, we have identified PRMT5 inhibitors with “best-in-class" drug-like properties including optimized permeability and antitumor efficacy. Evaluation of these lead compounds in in vitro selectivity screening and in toxicity studies in higher species is currently under way.

Citation Format: Dinesh Chikkanna, Sunil Kumar Panigrahi, Sujatha Rajagopalan, Srinivasa Raju Sammeta, Darshan Chawla, Pavithra S, Samiulla D.S, Angelene Prasanna, Priyabrata Chand, Kiran Aithal, Sai Sudheer Marri, Naveen Kumar, Srinivasa Rao Ganipisetty, Raju Mutyala, Kasieswara Rao, Thomas Antony, Girish Daginakatte, Anirudha Lakshminarasimhan, Mohan R, Narasihmarao K, Shekar Chelur, Chetan Pandit, Susanta Samajdar, Murali Ramachandra. Preclinical In vivo evaluation of efficacy, pharmacokinetics and pharmacodynamics of novel PRMT5 inhibitors in multiple tumor models [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 1392.

Abstract 3852: Combination efficacy and safety profile of an orally bioavailable small molecule agent targeting CD47/SIRPα axis

Introduction: Most of the immunotherapies currently approved in the clinic target immune checkpoint proteins that suppress T-cell responses. There is growing evidence that the innate immune system also plays an important role in the initiation and propagation of enduring antitumor responses. Targeting CD47-SIRPα axis is emerging as one of the promising new immunotherapy approaches that targets innate immune response. A number of clinical trials are in progress to evaluate CD47/SIRPα blocking therapies. Most of these molecules are either anti-CD47 antibodies or SIRPα-Fc recombinant proteins. We are developing a novel small molecule CD47 antagonist, AUR-104, as therapeutic agent for solid and hematalogical cancers. AUR-104 is a CD47 antagonist that disrupts CD47- SIRPα interaction and enhances phagocytosis of tumor cells. AUR-104 exhibits good drug-like properties and demonstrates antitumor activity in several pre-clinical tumor models. Here, we report the anti-tumor efficacy of AUR-104 in combination with tumor specific antibodies in pre-clinical models of cancer and also present the safety profile of AUR-104 in rodents.

Materials and Methods: Syngeneic murine tumor models: MC38 colon carcinoma cells were subcutaneously implanted in C57BL/6J mice while A20 B-cell lymphoma cells were implanted in BALB/c mice. Tumor bearing mice were treated with AUR-104 (30 mg/kg, b.i.d, and po) as a single agent or in combination with anti-PD1 antibody (100 µg/animal) or anti-PDL1 antibody (200 µg/animal). Tumor volumes were recorded with calliper's measurement over period of treatment.

A single dose maximum tolerated dose (MTD) study in BALB/c mouse followed by a 14-day repeat dose toxicity study in BALB/c mouse: Adult male and female BALB/c, are dosed with AUR-104 at ascending doses up to the limit dose. End points monitored include clinical observations, toxicokinetic parameters, body weights, food consumption, hematology, clinical pathology investigations, organ weights and histopathology of selected tissues.

Results: AUR-104 combination treatment with anti-PD1 antibody significantly enhanced anti-tumor efficacy in MC38 colon carcinoma model. Combination study with anti-PDL1 antibody in A20 tumor model is in progress. Preliminary observations from efficacy studies indicate that AUR-104 combination treatments with antibodies are well tolerated without any signs of toxicity. Advance in vitro safety evaluation and in vivo 14 day repeat day toxicity study in mice are being initiated. In summary, AUR-104 plus anti-PD1 antibody was a well-tolerated drug combination that exhibited a much greater in vivo antitumor response as compared to the single agent treatments. These results demonstrate the therapeutic potential of CD47 antagonist AUR-104 in combination with other tumor specific antibodies for the treatment of cancer.

Citation Format: Girish Daginakatte, Sasikumar Pottayil, Gundala Chennakrishna, Wesley Roy Balasubramanian, Sudarshan Naremaddepalli, Archana Bhumireddy, Sandeep Patil, Kavitha Nellore, Priyabrata Chand, Kiran Aithal, Amit Dhudashiya, Samiulla DS, Rajesh Eswarappa, Murali Ramachandra. Combination efficacy and safety profile of an orally bioavailable small molecule agent targeting CD47/SIRPα axis [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 3852.

Abstract 2384: Preclinical evaluation of PD and efficacy of novel potent selective and orally bioavailable CDK12 covalent inhibitors in TNBC model

Cyclin-dependent kinase 12 (CDK12) is a transcription-associated kinase that participates in various cellular processes such as DNA damage response, splicing and pre-mRNA processing. In association with Cyclin K (CycK), CDK12 regulates transcription elongation by phosphorylating RNA polymerase II (RNAP II) at Serine 2 in the C-terminal domain (CTD). Overexpression of CDK12 in various tumor types suggests the possibility that CDK12 has oncogenic properties, similarly to other transcription-associated kinases. Considering its critical role in transcription and RNA processing CDK12 is emerging as a potential therapeutic target for cancer. Multiple series of potent and selective CDK12 covalent inhibitors were identified by iterative medicinal chemistry efforts and SAR-based approaches. Early compounds were optimized towards attaining good physicochemical properties, high potency, good selectivity and desirable pharmacokinetic profile to achieve anti-tumour activity. Very potent and highly selective CDK12 inhibitors have been identified from two distinct chemical series. The covalent mode of action for these biochemically potent compounds has been confirmed by CDK12 target engagement assay in the cellular context. These selective inhibitors showed significant anti-proliferative activity in TNBC and other cancer cell lines, which correlated with inhibition of pS2 (RNAP II), a bonafide CDK12 substrate and target engagement. In vivo target engagement, PD and efficacy data for optimized compounds with good oral bioavailability in a TNBC (HCC-70) xenograft model along with will be presented.

Citation Format: Ramulu Poddutoori, Sujatha Rajagopalan, Subhendu Mukherjee, Sivapriya Marappan, Samiulla D S, Sasirekha Sivakumar, Shilpa S. Nayak, Ravindra M. V, Hadianawala Murtuza, Devaraja T. S, Srinivas Kondela, Suraj Tgore, Amit A. Dhudashiya, Charamanna K. B, Thomas Antony, Girish Daginakatte, Sanjeev Giri, Shekar Chelur, Murali Ramachandra, Chetan Pandit, Susanta Samajdar. Preclinical evaluation of PD and efficacy of novel potent selective and orally bioavailable CDK12 covalent inhibitors in TNBC model [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 2384.

Abstract B165: Potent selective and orally bioavailable inhibition of CDK12 by novel covalent inhibitors

Background: Cyclin-dependent kinase 12 (CDK12) coordinately regulates the transcription, splicing, and alternative splicing of several large pre-mRNAs. Defective CDK12 kinase activity has been associated with genomic instability and downregulation of genes in the DNA damage response (DDR) pathway. In addition, CDK12 depletion impairs alternate splicing, a process being increasingly implicated in cancer progression. Associated with Cyclin K (CycK), CDK12 regulates transcription elongation by phosphorylating RNA polymerase II (RNAP II) at S2 in the C-terminal domain (CTD). Considering its role in transcription and RNA processing to maintain genomic stability/integrity in cancer, CDK12 is emerging as a potential therapeutic target to treat cancer. Experimental Procedures: Potent and selective CDK12 inhibitors were identified from multiple series by iterative medicinal chemistry efforts and SAR-based approaches. Early compounds were optimized towards attaining good physicochemical properties, high potency, good selectivity, and desirable pharmacokinetic profile to achieve antitumor activity.Summary: Very potent and highly selective compounds were identified from two distinct chemical series that are highly potent in inhibiting CDK12 in biochemical assays. Proving their covalent mode of action, these orally exposed compounds demonstrated robust engagement of CDK12 in a cellular context. Several of these potent and selective CDK12 inhibitors showed potent antiproliferative activity in various cancer cell lines derived from different origin, accompanied by robust CDK12 engagement and inhibition of pS2 (RNAP II). Further optimization of potency and ADME properties of initial lead compounds is in progress. Tolerability and efficacy studies are ongoing with selected early leads to test their impact on tumor growth inhibition in xenograft models. Conclusion: We identified novel, selective, and orally bioavailable covalent inhibitors of CDK12 from multiple distinct series with desirable drug-like properties, which are being evaluated for antitumor activity in xenograft models.

Citation Format: Ramulu Poddutoori, Sujatha Rajagopalan, Subhendu Mukherjee, Sivapriya Marappan, Samiulla D S, Venkateswarlu Kasturi, Sasirekha Sivakumar, Shilpa Nayak, Ravindra M V, Suraj Tgore, Amit Dhudashiya, Charamanna K B, Thomas Antony, Mahaboobi M, Sanjeev Giri, Girish C. Daginakatte, Shekar Chelur, Murali Ramachandra, Chetan Pandit, Susanta Samajdar. Potent selective and orally bioavailable inhibition of CDK12 by novel covalent inhibitors [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B165.

Abstract A174: Novel inhibitors of protein arginine methyltransferase 5 (PRMT5) for the treatment of solid tumors

PRMT5 is a typical type II methyltransferase, transferring two methyl groups to arginine, leading to symmetric dimethylation of the substrate. It can symmetrically methylate histones H2AR3, H3R2, H3R8, and H4R3 and can also methylate many non-histone proteins contributing to tumorigenesis by regulating cell cycle progression, DNA repair, cell growth, apoptosis, and inflammation. Overexpression of PRMT5 is reported in several human malignancies including lymphoma, glioma, melanoma, lung, breast, ovarian, and prostate cancers. Elevated levels correlate with poor prognosis in NSCLC, ovarian cancers, and GBM. Therefore, PRMT5 is considered an attractive target for cancer therapy. We sought to discover and develop PRMT5 inhibitors with the “best-in-class” profile with an emphasis on improved brain permeability for their potential use in solid tumors including glioblastoma. Utilizing structure-guided drug design and SAR-based approaches, we have optimized two chemical series of substrate competitive PRMT5 inhibitors. Determination of co-crystal structures with several de novo designed hits aided in the identification of lead compounds that exhibited potent inhibition of PRMT5. Lead compounds were highly active in inhibiting proliferation of a number of cell lines derived from solid tumors that correlated well with cellular H4R3Me2s inhibition, confirming the mechanism. Lead compounds exhibited desirable drug-like properties including solubility, permeability, lack of CYP inhibition, and pharmacokinetic exposure. A substantial improvement in brain permeability over reported PRMT5 inhibitors was noted in rodent pharmacokinetic studies. In a xenograft model of lung cancer, treatment with lead compounds resulted in significant tumor growth inhibition while correlating with tumor drug levels and modulation of H4R3Me2s as the pharmacodynamic effect. In summary, we have identified PRMT5 inhibitors with “best-in-class" drug-like properties including optimized brain permeability and antitumor efficacy. Evaluation of the efficacy of these lead compounds in additional xenograft models including glioblastoma is currently under way.

Citation Format: Dinesh Chikkanna, Sunil Kumar Panigrahi, Sujatha Rajagopalan, Srinivasa Raju Sammeta, Anirudha Lakshminarasimhan, Mohan R, Narasihmarao K, Darshan Chawla, Harsha Bhat, Venkateswarlu Kasturi, Samiulla D.S, Angelene Prasanna, Kiran Aithal, Priyabrata Chand Chand, Naveen Kumar, Sai Sudheer Marri, Srinivasa Rao Ganipisetty, Kasieswara Rao N, Raju Mutyala, Nageswara Rao Neerukattu, Nithesh K, Ramya Amin, Priyanka Machhindra Gorade, Thomas Antony, Girish Daginakatte, Shekar Chelur, Chetan Pandit, Susanta Samajdar, Murali Ramachandra. Novel inhibitors of protein arginine methyltransferase 5 (PRMT5) for the treatment of solid tumors [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A174.

Abstract B006: Functional antagonism of VSIG8-mediated immune suppression by oral VISTA agents

With the remarkable success of antibodies focusing on PD-1/PD-L1, the immune checkpoint blockade approach has established itself as a cornerstone to cancer therapy. While PD-1/PD-L1 antibodies primarily focus on T cells to achieve antitumor efficacy, other cells in the tumor microenvironment such as myeloid cells, including MDSCs, also play a role in immune evasion, thus contributing to the lack of response in 70-80% of patients. To overcome the immune resistance induced by MDSCs, V-domain Ig suppressor of T-cell activation (VISTA) expressed predominantly on myeloid cells and tumor-infiltrating lymphocytes is considered as an ideal target. Recent findings also support the role of VISTA pathway in clearance of apoptotic bodies and prevention of autoimmunity. VISTA is reported to mediate immune suppression through homophillic interaction as well as interaction with V-Set and immunoglobulin domain containing 8 (VSIG8). We sought to discover and develop an orally available, small-molecule VISTA antagonist targeting both VISTA and VSIG8 pathways. Unlike antibodies targeting VISTA in early clinical trials, an oral agent potentially offers the convenience and flexibility to adjust the dose and schedule to address any emergent adverse events and ease of combination therapy. Since VISTA belongs to B7 family and the extracellular Ig domain of VISTA shares significant sequence homology with the B7 family ligands PD-L1 and PD-L2, a focused library of compounds mimicking the interaction of checkpoint proteins of B7 family was designed and synthesized. Screening and analysis of the resulting library led to the identification of hits capable of functional disruption of the checkpoint protein(s) signaling, depending upon the pockets of sequence similarity of interacting proteins. Further optimization resulted in lead compounds targeting both VISTA and VSIG8 signaling pathways with desirable drug-like properties including good oral bioavailability. Potent functional activity comparable to that obtained with an anti-VISTA or anti-VSIG8 antibody in rescuing effector functions was observed with the lead compound along with selectivity against other immune checkpoint proteins. An advanced lead compound exhibited sustained immune PD in tumor-bearing animals including desirable impact on myeloid and T cells in both circulation and tumor. The advanced lead compound also exhibited significant efficacy in syngeneic preclinical tumor models of melanoma and colon cancers upon once-a-day oral dosing with excellent tolerability. Further development of the oral VISTA antagonist is under way towards advancing it to the clinic.

Citation Format: Pottayil G. Sasikumar, Sudarshan S. Naremaddepalli, Raghuveer K. Ramachandra, Nagesh Gowda, Manikyala Rao Yerramsetti, Srinivasa Rao Bandireddy, Sreenivas Adurthi, Jiju Mani, Rashmi Nair, Amit A. Dhudashia, Samiulla S. Dodheri, Nagaraj M. Gowda, Murali Ramachandra. Functional antagonism of VSIG8-mediated immune suppression by oral VISTA agents [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B006.

Abstract LB-317: Identification of a novel preclinical candidate for CDK7 inhibition

Cyclin-dependent kinase 7 (CDK7) is an important constituent of the cellular transcriptional machinery, where it phosphorylates the C-terminal domain (CTD) of RNAP polymerase II (RNAPII). Because many tumor types are critically dependent on transcription for maintenance of their oncogenic state, pharmacological modulation of CDK7 kinase activity is considered as an approach to treat cancer. Multiple series of covalent CDK7 inhibitors were identified by iterative medicinal chemistry efforts and SAR based approach. These compounds were optimized towards attaining good physicochemical properties, high potency, good selectivity and desirable pharmacokinetic profile to achieve anti-tumor activity. We have now identified a pre-clinical candidate AU-BGB-002 which is highly potent in inhibiting CDK7 in biochemical as well as cellular assays while fully efficiently engaging the target. In a panel of kinases, AU-BGB-002 shows selectivity for CDK7. A panel of cell lines derived from a diverse set of indications are sensitive to AU-BGB-002. AU-BGB-002 exhibits excellent drug-like characteristics including solubility, permeability, metabolic stability and good oral bioavailability. When tested in a xenograft model, AU-BGB-002 treatment resulted in dose dependent tumor growth inhibition in AML xenograft model with tumor stasis at a dose of 10 mg/kg. Potent inhibiton of tumor growth was accompanied by complete target engagement and suppression of pS5RNAPII RNAPolII Ser5 phosphorylation in a parallel PK-PD study. Efficacy studies in additional xenograft models, advanced DMPK and toxicity studies are ongoing for this compound. In summary, we have identified a novel and selective CDK7 covalent inhibitor candidate with desirable drug-like properties that shows excellent efficacy in an AML xenograft model. Findings presented here support further development of AU-BGB-002 for the treatment of cancer.

Citation Format: Leena K. Satyam, Ramulu Poddutoori, Subhendu Mukherjee, Sivapriya Marappan, Sreevalsam Gopinath, Aravind Basavaraju, Lakshmi Narayana Kaza, Manoj Kumar Pothuganti, Shilpa Nayak, Nandish C, Amith A, Ravindra MV, Dabbeeru Madhu Babu, Nagaraju A, Suraj Tgore, Thomas Antony, Chetan Pandit, Murali Ramachandra, Shekar Chelur, Girish Daginakatte, Susanta Samajdar. Identification of a novel preclinical candidate for CDK7 inhibition [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-317. doi:10.1158/1538-7445.AM2017-LB-317

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 5108: Potent small molecule compounds that selectively inhibit proliferation of ABC-DLBCL cell lines

Diffuse large B cell lymphoma (DLBCL), which accounts for 25% of all lymphomas cases, has been classified into molecular subtypes including germinal center B cell like (GCB) DLBCL, activated B cell-like (ABC) DLBCL, and primary mediastinal B cell lymphoma (PMBL). Among these subtypes, patients with ABC-DLBCLs have the worst prognosis because of the high chemo-resistance, and require effective therapies.

Mucosa-Associated Lymphoid Tissue Lymphoma Translocation 1 (MALT1) protease activity is linked to the pathogenesis of ABC-DLBCL. Therefore, a focused library of covalent compounds selected based on molecular docking on the reported crystal structure was screened for selective sensitivity to ABC-DLBCL, but not GCB-DLBCL cell lines. Optimization of initial hits resulted in the identification of lead compounds with an anti-proliferative EC50 of <100 nM selectively in ABC-DLBCL cell lines. Consistent with the previously reported role of MALT1 inhibitors, lead compounds also showed anti-proliferative activity in selected melanoma and NSCLC cell lines. The anti-proliferative activity of the lead compounds correlated well with the inhibition IL-6, a downstream marker of MALT1 signaling, in ABC-DLBCL cell line such as OCI-LY3. The lead compounds exhibited excellent drug-like properties including solubility, metabolic stability, lack of CYP inhibition, permeability and desired dose-dependent oral exposure in pharmacokinetic studies. In a repeated dose MTD study, the lead compounds showed good tolerability with an exposure multiple of >10 over cellular EC50 for up to 8 hours. The lead compounds showed dose-dependent tumor growth inhibition in a xenograft model upon oral dosing.

In summary, we have identified novel and potent MALT1 inhibitors capable of selectively inhibiting proliferation of DLBCL cell lines with optimized drug-like properties including oral bioavailability. The data presented here strongly support further development of these compounds for DLBCL and other indications.

Citation Format: Leena Khare Satyam, Dinesh Chikkanna, Vinayak Khairnar, Manoj Pothuganti, Sunil Panigrahi, Anirudha Lakshminarasimhan, Narasimha Rao, Wesley Balasubramanian, Sandeep Patil, Sreevalsam Gopinath, Gunta Upendra, Jwala Nagaraj, Kiran Aithal, Vijay Ahuja, Sanjeev Giri, Chetan Pandit, Murali Ramachandra. Potent small molecule compounds that selectively inhibit proliferation of ABC-DLBCL cell lines [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 5108. doi:10.1158/1538-7445.AM2017-5108

Simulation study of Hemodynamic in Bifurcations for Cerebral Arteriovenous Malformation using Electrical Analogy

BACKGROUND AND OBJECTIVE

Cerebral Arteriovenous Malformation (CAVM) hemodynamic is disease condition, results changes in the flow and pressure level in cerebral blood vessels. Measuring flow and pressure without catheter intervention along the vessel is big challenge due to vessel bifurcations/complex bifurcations in Arteriovenous Malformation patients. The vessel geometry in CAVM patients are complex, composed of varying diameters, lengths, and bifurcations of various angles. The variations in the vessel diameter and bifurcation angle complicate the measurement and analysis of blood flow features invasively or non-invasively.

METHODS

In this paper, we proposed a lumped model for the bifurcation for symmetrical and asymmetrical networks in CAVM patients. The models are created using MATLAB Simulation software for various bifurcation angles. Each bifurcation angle created using electrical network- RLC. The segmentation and pre-processing of bifurcation vessels are implemented using adaptive segmentation. The proposed network address clinicians problem by measuring hemodynamic non-invasively. The method is applicable for any types of bifurcation networks with different bifurcation angles in CAVM patients.

RESULTS

In this work, we constructed a mathematical model, measured hemodynamic for 23 patients (actual and simulated cases) with 60 vessel bifurcation angles variations. The results indicate that comparisons evidenced highly significant correlations between values computed by the lumped model and simulated mechanical model for both networks with p < 0.0001. A P value of less than 0.05 considered statistically significant.

CONCLUSION

In this paper, we have modelled different bifurcation types and automatically display pressure and flow non-invasively at different node and at different angles of bifurcation in the complex vessel with help of bifurcation parameters, using lumped parameter model. We have simulated for different bifurcation angles and diameters of vessel for various imaging modality and model extend for different organs. This will help clinicians to measure haemodynamic parameters noninvasively at various bifurcations, where even catheter cannot be reached.

The Multi-kinase Inhibitor Debio 0617B Reduces Maintenance and Self-renewal of Primary Human AML CD34+ Stem/Progenitor Cells

Acute myelogenous leukemia (AML) is initiated and maintained by leukemia stem cells (LSC). LSCs are therapy-resistant, cause relapse, and represent a major obstacle for the cure of AML. Resistance to therapy is often mediated by aberrant tyrosine kinase (TK) activation. These TKs primarily activate downstream signaling via STAT3/STAT5. In this study, we analyzed the potential to therapeutically target aberrant TK signaling and to eliminate LSCs via the multi-TK inhibitor Debio 0617B. Debio 0617B has a unique profile targeting key kinases upstream of STAT3/STAT5 signaling such as JAK, SRC, ABL, and class III/V receptor TKs. We demonstrate that expression of phospho-STAT3 (pSTAT3) in AML blasts is an independent prognostic factor for overall survival. Furthermore, phospho-STAT5 (pSTAT5) signaling is increased in primary CD34⁺ AML stem/progenitors. STAT3/STAT5 activation depends on tyrosine phosphorylation, mediated by several upstream TKs. Inhibition of single upstream TKs did not eliminate LSCs. In contrast, the multi-TK inhibitor Debio 0617B reduced maintenance and self-renewal of primary human AML CD34⁺ stem/progenitor cells in vitro and in xenotransplantation experiments resulting in long-term elimination of human LSCs and leukemia. Therefore, inhibition of multiple TKs upstream of STAT3/5 may result in sustained therapeutic efficacy of targeted therapy in AML and prevent relapses. Mol Cancer Ther; 16(8); 1497-510. ©2017 AACR.