Abstract 2643: Discovery and characterization of a selective TrkA inhibitor for the treatment of TrkA-driven cancers

Abstract

Abstract Kinase gene fusions have been implicated as oncogenic drivers promoting cell survival and proliferation. TrkA gene fusions have been reported in a number of cancer types including lung, colorectal, papillary thyroid, sarcoma, cholangiocarcinoma and other tumors. We have identified novel, potent, selective and orally bioavailable TrkA inhibitors for the treatment of TrkA-driven cancers. One of the inhibitors, GVK-TrkI showed potent activity with an IC50 of 0.8 nM and 1.5 nM in the cell based assays for WT TrkA (AD293 cells expressing TrkA) and TPM3-NTRK1 fusion (KM12 cells) respectively. Potent activity of 12.5 nM IC50 was observed in TrkA Z-lyte kinase assay. Significant change in TrkA Z-lyte kinase IC50 was not observed at multiple ATP concentrations ranging from 100 uM to 1 mM suggesting non-ATP competitive mode of inhibition. Excellent selectivity (>1000x) was observed towards TrkB and TrkC in the cell based assays. GVK-TrkI inhibited TrkA autophosphorylation in a concentration dependent manner up to 24 h in KM12 cells in vitro. GVK-TrkI inhibited cell proliferation in KM12 cells with a GI50 of 34 nM while exhibiting no activity in cell lines without TrkA fusion. Comparable activity was observed in Ba/F3 cell line expressing MPRIP-NTRK1 fusion, demonstrating inhibition of TrkA driven cell proliferation irrespective of the N-terminal fusion with a different gene, MPRIP. In the KM12 xenograft model, treatment with GVK-TrkI at various doses and dosing regimens of 20 mpk bid, 50 mpk bid and 100 mpk qd resulted in dose dependent inhibition with almost 100% tumor growth inhibition (TGI) at 100 mpk qd with 3 out of 8 mice showing complete tumor regression. Besides, at 50 mpk in various dosing regimens of qd, bid and bid alternate day showed good correlation of TGI with compound exposure. GVK-TrkI was well-tolerated, causing no weight loss or death compared with vehicle control. Based on the evidence of ATP binding site mutations contributing to clinical resistance with kinase inhibitor drugs, GVK-TrkI is predicted to be effective as a second generation TrkA inhibitor with a non-ATP binding site mechanism compared to pan-Trk inhibitors currently being pursued in clinic. These results suggest that GVK-TrkI is an effective therapeutic option in TrkA driven cancers with TrkA gene fusions, activating mutations and cancers with NGF/TrkA overexpression resulting in constitutive activation of TrkA pathway. Citation Format: Vijaya G. Tirunagaru, Kumaragurubaran Nagaswamy, Sayan Mitra, Srinivas Maddi, Ram Sudheer Adluri, Hemant Joshi, Jang B. Gupta. Discovery and characterization of a selective TrkA inhibitor for the treatment of TrkA-driven cancers. [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 2643.