AB Science: 67% Response Rate in Phase 1 for AB8939 Combined with Venetoclax in AML

A 67% Response Rate Observed in Six Heavily Pretreated Patients

Stage 3 treated six patients at two dose levels of AB8939 (16 mg/m² and 21.3 mg/m²) in combination with venetoclax administered over a 14-day cycle. Four of the six patients achieved an objective response (one complete remission with incomplete hematologic recovery and three partial responses), corresponding to an overall response rate (ORR) of 67%. The remaining two patients exhibited stable disease, resulting in a disease control rate (DCR) of 100%. These responses were achieved after just one treatment cycle in patients heavily pretreated receiving second to fourth line treatments. Two of the responding patients had previously progressed under venetoclax combined with other chemotherapies. All six treated patients have highly challenging cytogenetic profiles, including complex karyotype, TP53 mutation, NRAS mutation, monosomy 5 and 7, and MECOM rearrangement.

Satisfactory Tolerance Paving the Way to the Next Phase

The combination of AB8939 and venetoclax was well tolerated, with no dose-limiting toxicity or hematological toxicity observed at either dose level. This tolerance allowed AB Science to select the recommended dose for phase 2 (RP2D). The next stage, called stage 4, will evaluate the triple combination of AB8939 + venetoclax + azacitidine. Concurrently, AB Science plans to initiate an extension study involving approximately 15 patients with AML eligible for AB8939 + venetoclax at the appropriate dose. The company has also engaged in discussions with the European Medicines Agency (EMA) and the Food and Drug Administration (FDA) about three potential registration study pathways: the combination as a first-line treatment in elderly patients and/or those with genetic anomalies, as a second or third line for all patients, or AB8939 as monotherapy in MECOM in the second or third line.