Although Geron Corp.’s imetelstat met its primary and key secondary endpoints in a phase III study, the U.S. FDA is questioning the magnitude and durability of the effect of the first-in-class telomerase inhibitor as a second-line treatment of transfusion-dependent anemia in adults with low- to intermediate-1 risk myelodysplastic syndromes. The agency’s concerns resulted in more than an 12% stock tumble March 12 after the FDA released its briefing document two days ahead of an Oncology Drugs Advisory Committee meeting, in which the panel will be asked to vote on whether imetelstat’s benefits outweigh its risks.