In vitro and in vivo effect of ARQ 531 on Trk family kinases

The tropomycin kinase (Trk) receptor family contain Trk A, B and C that are encoded by the NTRK1, NTRK2, and NTRK3 genes respectively. Trk family kinases have been shown to play a very important role in the development and physiological functions of the nervous system. Recently, chimeric Trk kinases resulted from gene fusions of NTRK genes are involved in initiation and progression of various cancers such as sarcoma, thyroid, salivary gland cancers, etc. Targeting such alteration of Trk family kinases becomes a new avenue for the therapeutic intervention. ARQ 531 has biochemical IC50 values of 1.3 nM, 1.8 nM and 1.8 nM for Trk A, B and C, respectively with targeting a unique set of other kinases. In a cell based assay, ARQ 531 inhibits kinase activity of Trk A, B and C in UOS2 cells overexpressing Trk family kinases with IC50 values of 50.5 nM, 28.0 nM and 4.1 nM respectively. Pathway analysis shows that ARQ 531 abolished autophosphorylation of TMP3-Trk A in colon cancer KM-12 cells after 2-hour treatment, concomitant with marked inhibition of pAKT, pERK and pPLCγ1. Moreover, in Trk A-overexpressing K562 cells, ARQ 531 suppressed phosphorylation of Trk A and its downstream targets AKT and MAPK. Anti-proliferative activity of ARQ 531 has been demonstrated in Ba/F3 system over-expressing fusion Tel-Trk family kinases (ETV6-NTRK1, 2 or 3), exhibiting IC50 value of 300, 481, and 341 nM for Tel-Trk A, B or C respectively. In TMP3-TrkA(TMP3-NTRK1) fusion-driven KM12 cells driven by ARQ 531 strongly suppressed cell proliferation with an IC50 value of 130 nM. Subsequently, apoptotic response was observed in KM-12 cells after treatment of ARQ 531 for 24 hours, which was demonstrated by the increase in cleaved PARP1 and cleaved caspase 3. Significant anti-tumor activity of ARQ 531 was observed in KM-12 xenograft mouse model. In conclusion, ARQ 531 is a potent Trk family kinase inhibitor and the results from preclinical study provides rationale for testing ARQ 531 in a clinical setting, particularly in cancers driven by Trk fusion kinases. Citation Format: Yi Yu, Gabi Schwartz, Pascal Schamber, Ron E. Savage, Sudharshan Eathiraj, Terence Hall, Brian Schwartz. In vitro and in vivo effect of ARQ 531 on Trk family kinases [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 4797.