Reviews of Sanofi’s diabetes drug Tzield and Disc Medicine’s blood-disorder medicine bitopertin stalled
Tzield pushed back after adverse event reports; bitopertin delayed two weeks amid efficacy and abuse concerns
Eli Lilly’s weight-loss pill gets April 10, 2026 decision target
By Patrick Wingrove
Jan 15 (Reuters) - The U.S. Food and Drug Administration has delayed reviews of two drugs chosen for the Trump administration’s new fast-track program after agency scientists flagged safety and efficacy concerns, including the death of a patient while taking one of the medicines, internal documents seen by Reuters show.
FDA reviewers pushed back by two weeks Disc Medicine’s (IRON.O) experimental drug for a rare blood disorder following concerns about trial data and its risk for abuse.
They also stalled their review of French drugmaker Sanofi’s (SASY.PA) Tzield for late-stage type 1 diabetes by more than a month over adverse event reports, including two related to seizure and blood clotting and one death.
Unveiled in June, the FDA Commissioner’s National Priority Voucher Program promised decisions in one or two months on a limited number of drugs deemed critical to public health or national security, or if they were manufactured in the U.S. or offered at low prices. That would cut four to six months off the fastest priority approval process.
The delays have not been previously reported. Disc Medicine and Sanofi declined to comment on the details of the FDA’s reviews.
Andrew Nixon, a spokesperson for the U.S. Department of Health and Human Services, said the FDA does not comment on applications under review but allows its divisions flexibility to adjust time lines.
<h3>DECISION DELAYS ON TWO OTHER DRUGS</h3>
Two other drugs tapped for the speedy review program have also been pushed by weeks or longer beyond the original target date. A decision on Boehringer Ingelheim’s zongertinib for lung cancer is currently expected mid-February, and Eli Lilly’s (LLY.N) weight-loss pill is now due April 10, according to documents.
A Lilly spokesperson confirmed approval could land in the second quarter, based on current FDA guidance. A Boehringer spokesperson said a decision is expected in the near future, without commenting on the delay.
The four drugs are among at least seven in the program that have started their approval process, according to documents.
Since announcing the first of the selected drugs in October, the agency has said 18 medicines will receive the speedy treatment, including two from Merck (MRK.N) . Most reviews are slated to start in 2026 with two others scheduled for 2027 and 2028. Only one drug, a generic antibiotic, has been approved under the program so far.
Two regulatory experts said the delays of several drugs, as described to them by Reuters, was reassuring as the new program’s one- to two-month target raised questions over whether reviews would be rigorous.
“It is a very good sign the FDA in this program is willing to say: ‘Hold on, we’re not actually sure this product should be allowed on the market’,” said Holly Fernandez Lynch, a health policy professor at the University of Pennsylvania.
Lynch and others said they still have concerns about the program politicizing drug reviews, since the administration of President Donald Trump selects the medicines and approval rests with a panel of high-ranking FDA officials rather than traditional reviewers.
Aaron Kesselheim, a professor of medicine at Harvard Medical School, said the agency risked wasting resources by awarding vouchers to drugs still in early development, as their true potential and effectiveness had yet to be assessed.
Companies are allowed up to two years to submit their applications after receiving vouchers, Nixon said.
<h3>SAFETY AND EFFICACY CONCERNS</h3>
Internal documents show FDA reviewers had slated November 21, 2025 as the decision date for Sanofi’s bid to expand Tzield’s use to new patients.
In one document seen by Reuters, the FDA said its action on Tzield was delayed due to what it deemed a treatment-related death. The agency’s public database of adverse events lists only a September 2025 report of a 30-year-old man who suffered a seizure and other adverse reactions.
The FDA and Sanofi declined to provide more information about the death.
Regulators also asked Sanofi for more details on several serious post-launch side effects they deemed possibly tied to the drug, including a December 2024 seizure and a blood-clotting episode last May, documents show.
A Sanofi spokesperson said they rigorously assess any serious adverse event reports and continue to work closely with the FDA on Tzield’s expanded approval application.
The agency also extended to February 10 its accelerated approval review of Disc Medicine’s bitopertin, being developed for patients whose blood disorder makes them extremely sensitive to sunlight.
The delay followed agency concerns over whether pain-free time in the sun - a secondary goal used in clinical trials - was a statistically solid measure of efficacy, or if other data could still justify approval by showing the drug was likely to work based on biomarkers, documents show.
FDA staff responsible for scheduling drugs that have a potential for abuse or addiction were also examining whether bitopertin posed any abuse risks, according to documents.
Reuters could not confirm details of bitopertin’s abuse potential, which could lead to restrictions on the drug.
Disc CEO John Quisel said in an interview that the bitopertin data highlighted a solid safety profile and multiple medical benefits. He cited a sharp drop in the toxic metabolite that causes the disease - the primary goal of two mid-stage trials - and in phototoxic reactions.
“We feel very good about our data package and its potential,” Quisel said, “but of course final approval is at the FDA’s discretion.”
Drugs tapped for the FDA’s Commissioner National Priority Voucher program
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The U.S. FDA has delayed reviews of Sanofi’s diabetes drug Tzield and Disc Medicine’s blood-disorder medicine bitopertin due to safety and efficacy concerns, including a patient death linked to Tzield. The review for Tzield has been postponed by over a month, while bitopertin's review is delayed by two weeks. The FDA's new fast-track program, aimed at expediting drug approvals, has faced scrutiny as several drugs have experienced significant delays. Experts express concern over the program's potential politicization and the rigorousness of reviews.

EXCLUSIVE-US FDA delays two drug reviews in new voucher program after safety, efficacy concerns