The FDA just gave Disc Medicine Inc. (IRON) a bit of homework before making a final call on its experimental drug bitopertin. Regulators pushed their decision date to Feb. 10, adding roughly two weeks to the review timeline while they figure out some thorny questions about how to measure success.

Bitopertin targets erythropoietic protoporphyria, a rare blood disorder that makes patients extremely sensitive to sunlight. The complications? Regulators aren't convinced that "pain-free time in the sun"—a secondary endpoint used in clinical trials—is statistically solid enough to prove the drug works. They're wondering if biomarker data might be a better foundation for approval.

There's another wrinkle too. According to internal documents cited by Reuters on Thursday, FDA staff responsible for evaluating drugs with abuse potential have been asked to examine whether bitopertin poses any risk of misuse or addiction. That adds another layer to an already complex review process.

Analyst Douglas Tsao at H.C. Wainwright isn't particularly worried. He noted Friday that the company wasn't aware of a specific FDA action date before the Reuters report dropped, though the implied Jan. 27 timing lines up with prior FDA guidance for the CNPV program and management's expectation of a late-January or early-February decision. Disc received CNPV designation back in October.

This isn't the first time bitopertin has faced skepticism. In December, STAT News reported that Vinay Prasad, head of the FDA's Center for Biologics Evaluation and Research, expressed doubts about the drug's efficacy under the CNPV program. But since bitopertin is under CBER review, management says it's unclear what role, if any, Prasad actually plays in the decision-making process.

Disc has described its interactions with the FDA as following a "regular" review process, though conversations have been more frequent because of the accelerated timeline.

"Another leak belies internal controversies within the FDA; we still remain confident that approval will occur," Tsao said Friday. He added that even if the company receives a Complete Response Letter—which he considers unlikely—any delay would be "relatively modest."

H.C. Wainwright continues to think "it is likely noise" and maintains its Buy rating with a price forecast of $118.

IRON Price Action: Disc Medicine stock was up 2.59% at $72.88 at publication Friday.