Phase 1/2a study of the IRAK4 inhibitor CA-4948 as monotherapy or in combination with azacitidine or venetoclax in patients with relapsed/refractory (R/R) acute myeloid leukemia or lyelodysplastic syndrome
As of December 16th, 2021, 49 patients have been treated in the phase 1 portion, of whom 43 started by September 30th, allowing 2 on-study disease assessments. The median number of prior therapies was 2 (range 1-5). Four monotherapy dose levels of CA-4948 were tested (200 to 500 mg orally BID). No dose-limiting toxicities were observed at 200 mg and 300 mg BID. No Grade 4 or 5 treatment-related AEs (TRAEs) were reported, and all the TRAEs were manageable. Reversible, manageable Grade 3 rhabdomyolysis occurred in 1/26 (4%) patients at 300 mg BID, 2/17 (12%) at 400 mg BID, and 1/3 (33%) at 500 mg BID. RP2D was determined as 300 mg BID. Of 43 patients starting before Sept 30th, 2021, 14 had SF3B1, U2AF1 or FLT3 mutations and demonstrated more promising efficacy. In the 5 evaluable AML patients with spliceosome mutations, 40% reached CR/CRh (1 CR, 1 CRh), both with study duration >6 months. In the 7 spliceosome-mutated HR-MDS patients, 57% reached marrow CR, including 1 with RBC transfusion independence and 1 proceeding to HSCT. One of the three FLT3-mutated AML reached CR, and 2 became FLT3-negative. Among the 29 patients without SF3B1/U2AF1/FLT3 mutations, 1 reached CR and 2 PR. Phase 1b and Phase 2a are ongoing. RNA-seq on selected samples showed decrease in relative expression of IRAK4-long isoforms with response to CA-4948. Conclusions: CA-4948 is well tolerated and effective in heavily pretreated AML and HR-MDS patients, especially in those with U2AF1/SF3B1/FLT3 mutations. No dose-limiting myelosuppression was reported, suggesting CA-4948 may be a candidate for combination therapy. Accrual of Phases 1b and 2a is ongoing.