One of the central hypotheses of modern targeted cancer treatment paradigm is that aberrant activation and/or over-expression of oncogenic kinases drive intrinsic cancer cell proliferation and survival and is the causative event in cancer initiation and progression. The numerous examples of effective cancer therapies targeting specific kinases are testaments to its validity. In recent years, the demonstrations of profound and broad antitumor responses to immune checkpoint inhibitors, such as anti-PD1/PD-L1 or anti-CTLA-4, have confirmed and emphasized the crucial role immune evasion plays in creating a permissive condition for disease progression. Because protein kinases are known to regulate the majority of cellular functions, we hypothesize that Just as cancer cells frequently usurp the kinase signaling machinery to promote uncontrolled proliferation and survival, they may similarly hijack key immunokinase signaling machinery to suppress immune detection and elimination. We prioritized 6 key kinases that play profound roles in sustaining immunosuppressive cells in the tumor microenvironment (AXL, DDR1, DDR2, FMS, KIT and MER) and design inhibitors that potently, selectively and collectively counteract their action. AGX-73, optimized for drug-like properties, is a small molecule compound currently undergoing IND evaluation as potential clinical candidate for first-in-human trial. In in vitro assay, carried out at high ATP concentration (100 μM), AGX-73 inhibited the activity of recombinant human AXL, DDR1, DDR2, FMS, KIT and MER with IC50 values of 30, 12, 0.63, 96, 54, and 40 nM, respectively, but was highly selective against a panel of 374 kinases. Importantly, in in vitro primary macrophage assays, AGX-73 promoted M1 macrophage polarization and increased the secretion of IL-6 and TNFα. In contrast, AGX-73 suppressed the activation of M2 macrophages and decreased the secretion of IL-10. In vivo, in the MC38 colon carcinoma model, AGX-73 treatment reduced the number of tumor-associated macrophages (TAMs), from 46 to 22% of the total CD45+ cells in the tumors. Moreover, the M1/M2 ratio was favorably increased, from 1.3 to 1.8. AGX-73 demonstrated robust antitumor activity in multiple syngeneic tumor models. In the MC38 model, AGX-73 administered orally was active at multiple dose levels, from 30-150 mg/kg, QDx14, yielding %TGI that ranged from 55-92%. Importantly, AGX-73 treatment produced greater antitumor effects in immunocompetent mice than in immunodeficient mice (88 vs. 65% TGI at 90 mg/kg), suggesting the involvement of a functional immune system in its optimal antitumor activity. Of the 13 syngeneic tumor models tested in immunocompetent mice (150 mg/kg, QDx14), eleven were sensitive with TGI>50% (range 45-122%). In combination with anti-PD1 (10 mg/kg) in the MC38 model, AGX-73 produced synergistic activity at multiple dose levels evaluated when compared with either single agent alone. In nonclinical ADME studies, AGX-73 demonstrated favorable drug-like properties: including good bioavailability (F>50% in mouse, rat and monkey) and systemic exposure following oral administration in multiple species, acceptable metabolic stability, lack of significant drug-drug interaction liabilities (transporters, CYP inhibition, CYP induction). IND toxicologic studies are currently in progress.
Citation Format: Francis Y.F. Lee, Wen-Lian Wu, Zhi-Qiang Yang, John Tan. AGX-73, a novel small molecule multi-immunokinase inhibitor, has robust antitumor activity in murine syngeneic tumor models as a single agent and in combination with anti-PD1 checkpoint inhibitor [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr C082. doi:10.1158/1535-7163.TARG-19-C082