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.

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.