Ponatinib (AP24534), a Multitargeted Pan-FGFR Inhibitor with Activity in Multiple FGFR-Amplified or Mutated Cancer Models

Members of the fibroblast growth factor receptor family of kinases (FGFR1-4) are dysregulated in multiple cancers. Ponatinib (AP24534) is an oral multi-targeted tyrosine kinase inhibitor (TKI) being explored in a pivotal phase 2 trial in patients with chronic mylogenous leukemia due to its potent activity against BCR-ABL. Ponatinib has also been shown to inhibit the in vitro kinase activity of all 4 FGFRs, prompting us to examine its potential as an FGFR inhibitor. In Ba/F3 cells engineered to express activated FGFR1-4 ponatinib potently inhibited FGFR-mediated signaling and viability with IC50s <40 nM, with substantial selectivity over parental Ba/F3 cells. In a panel of 14 cell lines representing multiple tumor types (endometrial, bladder, gastric, breast, lung and colon), and containing FGFRs dysregulated by a variety of mechanisms, ponatinib inhibited FGFR-mediated signaling with IC50s <40 nM and inhibited cell growth with GI50s of 7-181 nM. Daily oral dosing of ponatinib (10-30 mg/kg) to mice reduced tumor growth and inhibited signaling in all 3 tumor models examined. Importantly, the potency of ponatinib in these models is similar to that previously observed in BCR-ABL-driven models and plasma levels of ponatinib that exceed the IC50s for FGFR1-4 inhibition can be sustained in patients. These results demonstrate that ponatinib is a potent pan-FGFR inhibitor and provide strong rationale for its evaluation in patients with FGFR-driven cancers.