Executive Summary

Shares in San Diego-based oncology company MEI Pharma dropped by 69% on Nasdaq 23 March to close at $1.93 after it reported disappointing Phase II top-line data for its oral histone deacetylase (HDAC) inhibitor, Pracinostat, in one of its potential indications, myelodysplastic syndrome (MDS). In the 102-patient study, the combination of Pracinostat and azacitidine showed no difference in the rate of complete remission, the study's primary endpoint, compared with azacitidine alone in patients with previously untreated intermediate-2 or high-risk MDS. The event-driven endpoints, including duration of response, event and progression free survival and overall survival, are immature but there were no new or unexpected toxicities observed in the study. Future development of the product in MDS will now rest on analyses of the entire dataset as well as subset data. "Specifically, we are trying to fully assess the impacts of discontinuations on clinically important efficacy outcomes, including duration of response, event and progression-free survival and overall survival," said president and CEO Dr Daniel Gold. However, it seems likely that the company's attention will be more focused on its potential in acute myeloid leukemia (AML), for which Phase II data were reported at ASH in December.