Alrizomadlin (APG-115) Alone or Combined with Azacitidine (AZA) in Patients (pts) with Relapsed or Refractory (R/R) Acute Myeloid Leukemia (AML) or Relapsed or Progressive Higher-Risk Myelodysplastic Syndrome (HR-MDS): Phase 1b Trial Results

*Drs. Yifan Zhai and Jianxiang Wang are co-corresponding authors. Background Pts with R/R AML and HR-MDS failing hypomethylating agents have limited therapeutic options and relatively dismal outcomes with available therapies. Investigational alrizomadlin is a novel, orally active, potent, small-molecule selective inhibitor that destabilizes the p53-MDM2 complex and activates p53-mediated apoptosis in tumor cells and has shown apoptotic activity in AML and MDS xenograft models, alone and combined with AZA. Here, we present safety and efficacy results of this therapy in these pts. Methods This open-label dose escalation and expansion trial included adults with R/R AML or relapsed/progressed HR-MDS (IPSS-R ≥ 4.5). MTD and RP2D of alrizomadlin ± AZA were determined by dose escalation. Alrizomadlin (100/150/200/250 mg) was administered orally on Days (D) 1-7 in 28-day cycles. In the combination dose escalation group, alrizomadlin (100/150/200 mg) + AZA (75 mg/m 2) was administered orally once daily on D 1-7 in 28-day cycles and at the combination RP2D during dose expansion. Responses were assessed per revised International Working Group (IWG) Response Criteria 2003, ELN 2017 classifications for AML, and IWG 2006 for MDS. Extensive pharmacokinetic (PK) analyses were performed. Results As of June 1, 2023, 29 pts were enrolled in China. In the monotherapy group, 21 pts (median [range] age, 65 [32-76] years; 76.2%, R/R AML) had a median (range) of 2 (1-10) prior lines of therapy. In the combination group, 8 pts (median [range] age of 69.5 [20-76] years; 50%, R/R AML) had a median (range) of 2 (1-4) prior lines of therapy. In both groups, common any-grade treatment-related adverse events (TRAEs; ≥ 20%) were hematologic- and gastrointestinal-related toxicities, hypokalemia, and dizziness, and most grade ≥ 3 TRAEs were hematologic toxicities. No grade ≥ 3 gastrointestinal toxicities were reported (Figure 1). One DLT, a pulmonary embolism (PE), was reported among 6 evaluable patients at the alrizomadlin 100 mg + AZA dose level: a 59-year-old pt with MDS had a prior COVID-19 infection and abnormal coagulation function before (and during) study treatment. The study investigator attributed the PE to the pt's COVID-19 infection, age, primary disease, and long-term bed rest. One pt in each arm discontinued treatment because of AEs. In pts with AML, the overall response rate (ORR) was defined as complete remission (CR) + CR with incomplete hematologic recovery (CRi) + partia