Aptose Biosciences Inc....today announced that the U.S. Food and Drug Administration (FDA) has granted Fast Track designation to HM43239, an oral, myeloid kinome inhibitor, for the treatment of patients with relapsed or refractory (R/R) acute myeloid leukemia (AML) with FLT3 mutation.

Eight of 50 patients achieved clinical response at multiple dose levels including 80 mg, 120 mg, and 160 mg. These include 7 patients with a reported best response of composite complete remission (CRc, including complete remission [CR], complete remission with incomplete platelet recovery [CRp] and complete remission with incomplete hematological recovery [CRi]) and 1 with partial remission (PR). All responses were achieved 1 or 2 cycles after HM43239 was initiated...As of July 14, 2022, HM43239 has delivered CRc at 80 mg, 120mg and 160 mg, and was well tolerated at these dose levels over multiple cycles with no DLTs or drug-related SAEs. Pharmacokinetic data illustrate increasing drug exposures through 120 mg and observed objective responses through 160 mg in both FLT3-WT and FLT3-mutated R/R AML patients even after gilteritinib and midostaurin treatment.

HM43239 delivered multiple complete responses (CR) and demonstrated clinically meaningful benefit in all responders, by either bridging successfully to hematopoietic stem cell transplant (HSCT) or leading to a durable response, as well as a favorable safety profile across all treated patients....Among FLT3 mutant patients treated with 80 mg, 3 of 8 (37.5%) achieved a durable composite complete response (CRc, CR + CRi).