Abstract 4219: Efficacy of CR13626, a novel oral brain penetrant multi-kinase inhibitor, in a mouse model of glioblastoma
Authors: Galimberti Chiara , Piepoli Tiziana , Montagna Giuseppe M. , Zerbi Silvia , Letari Ornella , Artusi Roberto , Colovic Milena , Persiani Stefano , Caselli Gianfranco , Rovati Lucio C. 
Published: September 2020

BACKGROUND: Currently there is no cure for glioblastoma (GBM), the most malignant primary brain cancer. Glioblastoma etiopathogenesis involves mutations and alterations of key signaling pathways including tyrosine kinases (TKs). Notably, aberrant activation of receptor tyrosine kinases (RTKs) such as EGFR (amplified in 40% of glioblastoma cases) and KDR represents one of the driving forces for cellular proliferation and angiogenesis. The ability to cross the blood brain barrier (BBB) and appropriate pharmacodynamics (target selectivity) and pharmacokinetics (brain penetration) are critical issues for the generation of potential drug candidates against glioblastoma. CR13626 is a novel brain penetrant small molecule able to inhibit different TKs relevant to the development of this cancer. The present study describes the in vitro and in vivo properties of CR13626 and its antitumor activity in a mouse model of glioblastoma.

METHODS: We identified the TKs targeted by CR13626 against a panel of 173 kinase enzymes. The effects of CR13626 on cellular proliferation were assessed in different 2D human GBM cell lines (U87MG, U373, U87MG vIII) by ViaCount, and in U87MG 3D spheroids by CellTiter-Glo 3D viability assay. The antitumor activity in vivo was determined in an orthotopic mouse model of GBM based on the injection of U87MG-Luciferase cells in nude mice. Animals were orally treated with CR13626 (50 mg/kg/daily) for 10 days, starting on day 9 post-implantation. Measurement of bioluminescence (BLI) at day 19 (end of dosing) and during follow-up (days 26-33) allowed the monitoring of tumor progression. CR13626 pharmacokinetics and brain exposure were assessed by LC/MS/MS in plasma and brain homogenate tissues of CD1 and tumor-bearing nude mice.

RESULTS: CR13626 potently inhibited tyrosine kinases relevant to GBM development, with IC50 values in the nanomolar range: FYN (69 nM), YES (3.6 nM), KDR (82 nM) and EGFR (6 nM). CR13626 reduced the growth of different human glioblastoma cell lines with GI50 values in the range 1-3 µM. In vivo, CR13626 treatment led to a time-dependent reduction of tumor growth, reaching 60% on the last BLI evaluation 33 days post-implantation (i.e. 15 days after the end of dosing). A 25% significant increase in the median survival of animals compared to the vehicle group was also observed. The antitumor effects of CR13626 were in line with the exposure of tumor-bearing mice to the compound. Pharmacokinetic studies in CD1 mice showed good oral bioavailability (72%) and brain penetration (brain/plasma ratio of 1.4) for CR13626.

CONCLUSION: The ability of CR13626 to cross the BBB without being a substrate of efflux transporters that mediate tumor resistance, to simultaneously inhibit the activity of different TKs involved in GBM development, and to reduce tumor growth eventually leading to an increased survival of animals, warrant its further development as a drug candidate in glioblastoma.

Citation Format: Chiara Galimberti, Tiziana Piepoli, Giuseppe M. Montagna, Silvia Zerbi, Ornella Letari, Roberto Artusi, Milena Colovic, Stefano Persiani, Gianfranco Caselli, Lucio C. Rovati. Efficacy of CR13626, a novel oral brain penetrant multi-kinase inhibitor, in a mouse model of glioblastoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4219.