P11.24 CR13626, an oral tyrosine kinase inhibitor crossing the blood brain barrier, reduces tumour growth and prolongs survival in a mouse model of glioblastoma

Abstract BACKGROUND Glioblastoma multiforme (GBM) is the most malignant primary brain cancer. Several mutations and alterations of key cellular pathways including tyrosine kinases (TKs) are involved in GBM etiopathogenesis. Currently there is no cure for GBM. Tumour heterogeneity and the presence of the blood brain barrier (BBB), with efflux transporters, are some of the causes of failure of novel therapeutic agents. Thus, appropriate target selectivity and pharmacokinetics (including brain penetration) are critical issues for the generation of potential drug candidates. The main in-vitro and in-vivo properties and antitumour activity of CR13626, a novel brain penetrant TK inhibitor, are presented. MATERIAL AND METHODS CR13626 inhibitory activity against a panel of 173 kinases was assessed. The effect on cellular proliferation was verified in different 2D human glioblastoma cell lines (U87MG, U373, U87MG vIII) and in a U87MG 3D spheroid model by ViaCount assays. The in-vivo antitumour activity was determined in a mouse model of glioblastoma based on the orthotopic injection of U87MG-Luciferase GBM cells in nude mice: oral treatment started on day 9 post-implantation and continued for 10 days (50 mg/kg/daily). Tumour progression was evaluated through the measurement of bioluminescence (BLI) at the end of dosing (day 19) and during follow-up (day 26–33). Survival was also monitored. The pharmacokinetics and brain exposure of CR13626 were assessed by LC/MS/MS in plasma and brain homogenate tissues of CD1 and tumour-bearing nude mice. RESULTS CR13626 potently inhibited FYN, YES, KDR and EGFR kinases, relevant for GBM development, with IC50 values of 69 nM, 3.6 nM, 82 nM and 6 nM, respectively. The compound reduced the proliferation of different human glioblastoma cell lines (GI50 1–3 µM). In CD1 mice, CR13626 had a good oral bioavailability (72%) and brain penetration (brain/plasma ratio of 1.4). In-vivo BLI analysis indicated a time-dependent reduction of tumour growth, reaching 60% on the last BLI evaluation 33 days post-implantation (i.e. 15 days after the end of dosing). Tumour growth inhibition translated into an increase of 25% of the median survival time of animals treated with CR13626 compared to the vehicle group (p<0.05). The observed antitumour effects agreed with the exposure of tumour-bearing mice to CR13626, which was above the TKs in-vitro IC50 values. CONCLUSION The combined abilities of CR13626 to inhibit the activity of TKs involved in GBM development, to cross the BBB, and to reduce tumour growth in-vivo leading to increased survival, warrant its further development as a drug candidate in GBM.