This Phase IIb study (BEXERA) will evaluate the safety and efficacy of bexmarilimab (FP-1305), an antibody targeting Clever-1, given in combination with azacitidine compared with azacitidine plus placebo in adults with treatment-naïve higher-risk myelodysplastic syndromes (HR-MDS). Participants will be randomized to receive bexmarilimab at one of two dose levels (1 mg/kg or 3 mg/kg) plus azacitidine, or placebo plus azacitidine. The primary aim is to select the recommended dose of bexmarilimab for subsequent development based on a predefined integration of clinical response and safety/tolerability.