Dr Daver on Initial Efficacy and Safety Data With Bexmarilimab Plus Azacitidine in Higher-Risk MDS

"This is really the first time that we're seeing a 13-plus month OS rate [in the relapsed/refractory population]. Again, it's a single-arm study, so we have to be cautious. What's even more impressive is that actually almost half of these patients had a TP53 mutation, so if anything, this is a higher risk group than what we had studied [previously]. This could be very important pathway for drug development."

Naval G. Daver, MD, a professor and director of the Leukemia Research Alliance Program in the Department of Leukemia at The University of Texas MD Anderson Cancer Center, highlighted efficacy data from the phase 1/2 BEXMAB study (NCT05428969) evaluating bexmarilimab (FP-1305) plus standard-of-care (SOC) azacitidine in patients with relapsed/refractory higher-risk myelodysplastic syndrome (MDS).

Early findings from BEXMAB, which were presented at the 2025 ASCO Annual Meeting, showed that patients with relapsed/refractory disease achieved an overall response rate (ORR) of 63%, and the median overall survival (OS) was consistent with previously reported data from this population.

In treatment-naive patients with higher-risk MDS, the combination of bexmarilimab and azacitidine resulted in an overall response rate (ORR) of 72%, with a complete remission (CR) rate of 28%. In the relapsed/refractory cohort—particularly those previously treated with hypomethylating agents (HMAs)—the combination yielded an ORR of 63%, with a CR plus marrow CR rate near 30% based on IWG 2006 criteria. These results compare favorably with prior data from azacitidine-based doublets, including azacitidine plus venetoclax, which have shown lower response rates in similar patient populations, he stated.

Importantly, the median overall survival (OS) estimate in the relapsed/refractory population was reported at 13.4 months. This represents a substantial improvement compared with historical benchmarks of 6 to 8 months in this post-HMA setting, previously established by MD Anderson studies published in 2012 and 2014, Daver noted. He emphasized that no dose-limiting toxicities were observed, and the regimen demonstrated a favorable tolerability profile, underscoring its feasibility in a high-risk population.

Notably, 40.6% of patients in the relapsed/refractory cohort harbored TP53 mutations—a subgroup historically associated with poor outcomes. Among patients with TP53-mutated disease, median OS was 9.3 months, which is considered favorable. For those without TP53 mutations, the median OS had not yet been reached at the time of analysis, suggesting a durable benefit. Daver concluded that these outcomes signal the potential of bexmarilimab, a macrophage immune checkpoint inhibitor targeting Clever-1, as a promising novel agent in MDS, warranting further clinical investigation in randomized studies.