Abstract 4889: The highly specific CSF1R inhibitor DCC-3014 exhibits immunomodulatory and anti-invasive activities in cancer models (2016)

Abstract The role of tumor-associated macrophages (TAMs) in promoting an invasive and immunosuppressed tumor microenvironment is well established. TAMs mediate tumor growth, angiogenesis, invasiveness, and immunosuppression through the secretion and response to a variety of factors. There are few highly specific small molecule inhibitors of CSF1R kinase in clinical development. Such specific CSF1R inhibitors are sought for use in combination with other oncology immune checkpoint inhibitors and/or chemotherapeutic agents. DCC-3014, a highly specific CSF1R inhibitor, was developed based on Deciphera's switch control inhibitor platform. Experimental procedures: DCC-3014 was evaluated in human kinase assays, including CSF1R, highly related kinases FLT3, KIT, and PDGFRa/b, and 300 additional kinases. Cellular studies included evaluation in the monocytic cell lines THP-1, MNFS-60, and a human whole blood assay. DCC-3014 was also evaluated in a human osteoclast TRAP assay. In vivo, DCC-3014 was evaluated in the murine cFOS PK/PD model. DCC-3014 was evaluated as a single agent and in combination with a murine anti-PD1 antibody in the murine syngeneic MC38 colorectal cancer model, a model characterized by high TAM infiltration. Results: DCC-3014 exhibited nanomolar (IC50 5 nM) potency for inhibition of CSF1R, sparing highly related kinases FLT3, KIT, PDGFRa, and PDGFRb, by &amp;gt; 100-fold, and sparing other kinases by &amp;gt; 1,000 fold. Cellular inhibition of CSF1R was resilient to high levels of the CSF1R ligand MCSF (10-1,000 ng/mL), due to its high residency time for binding to CSF1R and its binding mode which maintains CSF1R in a “switch off” state. DCC-3014 inhibited CSF1R in THP-1 monocytes (IC50 11 nM), MNFS-60 monocytes (IC50 4 nM), human osteoclasts (IC50 9 nM), and in a human whole blood monocyte/pERK assay (IC50 260 nM). In vivo, DCC-3014 exhibited sustained inhibition of CSF1R in the murine cFOS PK/PD model, affording 90+% inhibition at 15 mg/kg through 24 h post dose. At steady state (6 days of dosing), DCC-3014 robustly inhibited CSF1R at 3 mg/kg daily. In the MC38 colorectal cancer model, DCC-3014 (10 mg/kg daily) inhibited infiltrating TAMs, repolarized the adaptive immune cell population to an anti-tumoral profile, and depleted circulating CD16+ monocyte populations. Additionally, DCC-3014 was evaluated in combination with a murine anti-PD1 antibody and demonstrated additive effects compared to single agent cohorts. DCC-3014 exhibits optimized biopharmaceutical properties, including a favorable ADME and PK profile in preclinical studies. Conclusion: DCC-3014 is a highly specific CSF1R inhibitor and finds potential utility as a macrophage immunomodulatory agent for clinical evaluation in combination with other immune checkpoint inhibitors or chemotherapeutic agents. DCC-3014 is undergoing IND-enabling activities with a FIH study targeted for 2016. Citation Format: Bryan D. Smith, Cynthia B. Leary, Wei-Ping Lu, Michael D. Kaufman, Daniel L. Flynn. The highly specific CSF1R inhibitor DCC-3014 exhibits immunomodulatory and anti-invasive activities in cancer models. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4889.