Disc Medicine shares plunge 28% after FDA rejects bitopertin approval
Agency requires Phase 3 APOLLO trial data by late 2026, pushing potential approval to mid-2027
Disc Medicine shares tumbled 28% on Friday after the U.S. Food and Drug Administration issued a Complete Response Letter rejecting the biotechnology company's application for bitopertin, a treatment for a rare genetic blood disorder, until additional clinical data becomes available.
The FDA's decision marks a significant setback for the Watertown, Massachusetts-based company, which had been seeking approval for bitopertin as a treatment for erythropoietic protoporphyria (EPP), a condition that causes severe sensitivity to sunlight. The stock fell to $51.59, wiping out roughly $1 billion in market capitalization and leaving the shares well below their 52-week high of $99.50.
In the regulatory letter, the FDA acknowledged that Disc Medicine's Phase 2 AURORA and BEACON studies demonstrated that bitopertin significantly reduces whole blood metal-free protoporphyrin IX (PPIX) levels, and recognized the strong mechanistic and biological plausibility of using PPIX as a biomarker in protoporphyria. However, the agency concluded that these trials failed to demonstrate a sufficient association between PPIX reduction and clinical endpoints related to sunlight exposure.
"The FDA indicated that results from the ongoing Phase 3 APOLLO study could serve as evidence to support traditional approval for bitopertin in EPP," Disc Medicine stated in its press release. The company completed enrollment for the APOLLO trial in March 2026, ahead of schedule, and anticipates topline data in the fourth quarter of 2026.
The regulatory delay pushes any potential approval timeline to mid-2027, when the company expects an updated FDA decision following its response to the Complete Response Letter. Disc Medicine also plans to request a Type A meeting with the agency to discuss its approach.
The rejection comes despite a review under the FDA's Commissioner's National Priority Voucher program, which granted bitopertin accelerated review. In January, the FDA had postponed its decision by two weeks amid concerns regarding the drug's efficacy.
Analysts had been largely bullish on Disc Medicine's prospects prior to the announcement. As of February 8, thirteen analysts collectively assigned the company a "Moderate Buy" rating, with an average one-year consensus target price of approximately $119.45—more than double the current share price. H.C. Wainwright analyst Douglas Tsao had dismissed reports of potential delays as "likely noise" in late January, reiterating a "Buy" rating with a $118 price target.
The company's financial position provides some cushion against the setback. As of December 31, 2025, Disc Medicine reported approximately $791 million in cash, cash equivalents, and marketable securities, giving it a cash runway into 2029. This financial buffer allows the company to continue operating through the extended development timeline without immediate capital-raising pressures.
However, recent insider selling may raise questions about management's confidence. In the last quarter, executives sold 275,470 shares valued at approximately $25 million, according to regulatory filings. The stock had already been experiencing volatility, with a beta of 2.584 indicating high sensitivity to market movements.
The APOLLO trial is a randomized, double-blind, placebo-controlled Phase 3 study evaluating bitopertin's efficacy, safety, and tolerability in participants with EPP or X-linked protoporphyria. Its primary endpoints include assessing whether bitopertin increases pain-free sunlight exposure and changes in PPIX concentration levels after six months of treatment.
Disc Medicine's pipeline now faces increased scrutiny from investors. The company is a clinical-stage biotechnology focused on developing novel treatments for serious hematologic diseases, with bitopertin representing its most advanced program. The FDA's decision underscores the challenges of developing treatments for rare diseases, where demonstrating clinical benefit on traditional endpoints can prove difficult even when biomarker data appears promising.
For patients with EPP, a condition that can cause debilitating pain and requires strict avoidance of sunlight, the delay represents another obstacle in accessing potential treatments. Current options are limited, creating significant unmet medical need that Disc Medicine aims to address if bitopertin ultimately gains approval.