Abstract 5397: Characterization of INCB053914, a novel pan-PIM kinase inhibitor

The PIM (Proviral Integration sites for Moloney virus) family of constitutively active serine/threonine kinases consists of three members (PIM1, PIM2 and PIM3) that phosphorylate substrates involved in both apoptosis and cellular metabolism. As downstream targets of the JAK/STAT pathway and by having overlapping substrates with the PI3K/AKT pathway, PIM kinases integrate signals from multiple pathways important for the survival and proliferation of malignant cells. Overexpression of PIM kinases has been reported in human hematological cancers with each isoform showing a distinct expression pattern among the various malignancy subtypes, including MM, AML, ALL and NHL. Although the three family members possess overlapping functions that are mutually compensatory, mice deficient for all three PIM kinases exhibit minor phenotypic abnormalities, with smaller overall size at maturity and decreased cellular responses to cytokines. These data suggest that pan-inhibition of the PIM kinase family will have a favorable toxicity profile and may be required for therapeutic benefit in hematological malignancies. INCB053914 is a novel, ATP-competitive, small molecule, pan-inhibitor of PIM kinases. In biochemical assays, INCB053914 is potent against PIM1, PIM2 and PIM3 and highly selective. In cell proliferation assays, INCB053914 is active as a single agent in the majority of cell lines derived from different hematological malignancies, including MM, AML, DLBCL, MCL and T-ALL, with IC50 values ranging from 3 - 300 nM. INCB053914 synergizes with a variety of cytotoxic and targeted agents, reducing the viability of a panel of hematological tumor cell lines. In pharmacodynamic assays, INCB053914 inhibits phosphorylation of S6RP, P70S6K, 4E-BP-1 and BAD, known PIM kinase targets. Following treatment with INCB053914, induction of PIM kinase protein levels was noted in human cancer cell lines. Importantly, this compensatory response does not reduce the activity of the molecule, as effects on downstream signaling and efficacy remain intact when PIM kinase levels are elevated. Induction of PIM kinases after INCB53914 treatment was also evident in whole blood from healthy volunteers and in primary blast cells isolated from patients diagnosed with AML, further supporting the need for pan-PIM kinase inhibition. Taken together, these results indicate that INCB053914 has potent and selective activity against PIM kinases and may be useful as monotherapy or in combination with other ag