The conundrum of drug development in higher-risk MDS: lessons learned from recently failed phase 3 clinical trials

Aside from allogeneic transplantation, the current standard-of-care approach for higher-risk myelodysplastic syndromes/neoplasms (HR-MDS) remains monotherapy with a hypomethylating agent (HMA), including azacitidine, decitabine, or oral decitabine/cedazuridine. Many attempts using HMA-based combinations have failed to improve upon HMA monotherapy. Although promising efficacy was observed in early-phase clinical trials with several agents, subsequent randomized phase 3 trials failed to confirm improvements in complete response rates or overall survival. In this review, we discuss lessons learned from the recently reported negative trials of azacitidine in combination with eprenetapopt (APR-246), magrolimab, pevonedistat, sabatolimab, tamibarotene, and venetoclax. First, we make a case for emphasizing biological classification rather than disease risk status alone to select patients for HR-MDS trials. Second, we argue that patients with TP53-inactivated MDS and chronic myelomonocytic leukemia should be treated in dedicated clinical trials. Alternatively, if TP53-inactivated MDS is included in HR-MDS trials, then randomization stratification by TP53 inactivation status should be considered. Third, we caution against ignoring signals of excessive toxicity and premature discontinuation of investigational agent observed in early-phase trials. Fourth, we show that the International Working Group (IWG) 2006 response criteria, long used in HR-MDS trials, can both overestimate and underestimate the true therapeutic benefit. Instead, we advocate for using the IWG 2023 response criteria to better capture clinically meaningful benefits in HR-MDS. Lastly, we emphasize the need for the scientific community to access patient-level data and samples from failed phase 3 trials in an efficient and expedited fashion to inform the development of subsequent trials.