MK-0457, a Novel Multikinase Inhibitor, Has Activity in Refractory AML, Including Transformed JAK2 Positive Myeloproliferative Disease (MPD), and in Philadelphia-Positive ALL.

Background. MK-0457 (VX-680) is a small-molecule inhibitor of aurora kinases A, B, and C, FLT3, BCR-ABL, and JAK2. MK-0457 exhibits nanomolar level broad-spectrum preclinical anti-tumor activity. Specifically, MK-0457 inhibits proliferation of patient-derived AML cells in vitro, and improves survival of a Ba/F3 FLT3 ITD murine model of systemic AML. A Phase I study of MK-0457 is being conducted in patients with a broad range of hematological malignancies, including acute myeloid and lymphoid leukemias.

Methods. After IRB approval, 15 consenting patients with relapsed/refractory AML and ALL, ECOG performance status ≤ 2, and adequate organ function were enrolled using a standard dose escalation scheme with 3 patients/dose level until dose-limiting toxicity (DLT), followed by 6 patients/level. MK-0457 was administered by continuous 5-day intravenous infusion every 2 to 3 weeks. DLT was defined as grade 3 or higher non-hematologic toxicity during cycle 1. Pharmacokinetics (PKs) were collected pre-dose through 168 h and analyzed for MK-0457 by HPLC/mass spec.

Results. Thirteen patients with AML and 2 patients with ALL were enrolled at 8, 12, 20, 24, and 28 mg/m²/hr. Among AML patients, two had a diploid karyotype and the remainder had complex unfavorable cytogenetic abnormalities. Two AML patients had a prior JAK2-positive MPD, transformed to AML, and then received MK-0457 as their 1^st AML treatment. One AML patient received MK-0457 as first salvage, three as second salvage, and the remainder as salvage attempt three or higher. Both ALL patients failed prior multiagent chemotherapy; one of these patients had Philadelphia (Ph)-positive ALL and progressed after prior BCR-ABL inhibitor therapy, including dasatinib. The latter patient carried the BCR-ABL inhibitor resistance mutation, T315I. Four of 5 AML patients without baseline grade 3/4 myelosuppression in one cell line developed grade 4 neutropenia, including both JAK2-positive AML patients. Normalization of the platelet count during cycle one occurred in one MPD patient with thrombocytosis at baseline (~800 x 10³/mL); Grade 3 thrombocytopenia occurred during cycle one in the other MPD patient with a normal baseline. The Ph+-ALL patient had eradication of peripheral blood blasts at the end of 2 cycles of therapy. No MK-0457 attributable extramedullary grade 2 or above adverse events were seen. Mild hair thinning was seen in some patients at dose levels 20 mg/m²/hr and above. Preliminary PK analysis showed dose-dependent linearity at steady state, with a biexponential decay at the end of infusion characterized by a rapid a decay followed by a slower b decay (t_1/2 10–20 hrs).

Conclusions. MK-0457 at well tolerated doses achieves myelosuppression in refractory AML and ALL patients. Its activity in JAK2+ transformed AML patients may be partially attributable to JAK2 inhibitory activity. The role of aurora kinase inhibition in the above responses is not yet established. As neither maximum tolerated dose nor dose limiting toxicity has been defined to date, dose finding on this Phase I study of MK-0457 is on-going in the acute leukemia population with 36 mg/m²/hr as the current dose level under investigation.