As tensions around the FDA continue to escalate, a Republican U.S. senator has announced an investigation into recent approval rejections for rare disease candidates, according to Bloomberg News.
Wisconsin Sen. Ron Johnson is asking to see several of the complete response letters that have been delivered of late and also told Bloomberg that he may call on top FDA leaders to testify before the Senate’s Permanent Subcommittee on Investigations, which Johnson chairs.
The probe comes on the heels of heightened interactions between gene therapy developer uniQure and the FDA as an unnamed senior agency official—widely believed to be the now-departing Vinay Prasad, M.D.—defended the FDA’s demand that the biotech launch another sham-controlled trial for its Huntington’s disease candidate. The one-time uniQure therapy is given directly into the brain through small holes in the skull.
Now, Johnson is categorizing the request for a new trial as “bureaucratic idiocy,” according to Bloomberg.
“You’re expecting people to go through sham surgeries where they get holes drilled in their heads?” Johnson said to the outlet. “That’s just unbelievable.”
On March 2, uniQure leaders argued that a sham-controlled study “could impose significant risks and burden to patients—some might even consider this trial design to be unethical.”
A few days later, the anonymous FDA official denied that the control group would require that patients get holes drilled in their heads.
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“We asked uniQure to take their product and randomize patients to getting the treatment the way they give the treatment, which requires a skin incision, a hole in the skull and an intracranial injection of the product, versus a control arm, where all they do is anesthetize the patient and put one to three nicks in the scalp,” the unknown official said on March 5. “We did not ask them to compare against a partial sham burr hole.”
One day later, news broke that Prasad would be departing his role as the FDA’s top regulator of vaccines and cell and gene therapies at the end of April—the second time the leader has left the agency. A search is currently underway for Prasad’s successor.
“The stories are so outrageous,” Johnson said to Bloomberg. “It just appears that they’re looking for excuses to say no.”
In response, Department of Health and Human Services spokesperson Andrew Nixon told Fierce that the FDA “stands by the scientists evaluating these applications and each rationale is explained in detail through CRL’s, which, for the first time, are made available to the public.”
Under the second Trump administration, the drug regulator pledged to publicly release CRLs at the same time they are issued to sponsoring companies, part of what the FDA calls a push toward “radical transparency.” The agency has released batches of certain rejection letters, but it has not been consistent in what is published and when.
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“The number of FDA approvals and rejections under this administration are consistent with historical data over the last decade. In fact, CBER had a record number of approvals in December,” HHS’ Nixon said.
The agency did not provide the referenced data behind this claim when asked.
When asked about the intensifying pushback from the rare disease community, the HHS spokesperson said, “Our obligation is to patients and public health, and we remain committed to a regulatory approach that brings safe, effective individualized treatments to patients who urgently need them.”
He also cited the agency’s plausible mechanism framework, which is draft guidance for an approval pathway that could see custom CRISPR therapies formally embraced by the agency.
“This FDA is doing more than any other time in history to help speed up the development of ultra-rare disease cures for the American people,” the spokesperson said.
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In late February, a panel of physicians, biotech leaders and patient advocates took aim at the FDA during a Senate hearing chaired by Sen. Rick Scott, R-Fla., on how the agency’s bureaucracy affects innovation.
Sen. Johnson spoke during that hearing, which included a discussion of the FDA’s November rejection of Biohaven’s experimental drug, troriluzole, for spinocerebellar ataxia.
“I wrote six letters to FDA leadership between 2023 and 2025, cosigned by 17 ataxia colleagues asking FDA to review the application again and work with Biohaven to make the drug available [and], if necessary, performing post-marketing studies. I never heard back,” Jeremy Schmahmann, M.D., a neurology professor at Harvard Medical School and founding director of Massachusetts General Hospital’s Ataxia Center, said during the hearing.
Johnson told Bloomberg that he is also upset about the spinocerebellar ataxia rebuff, adding that he doesn’t understand why FDA officials aren’t listening to specialists who say rare disease candidates are helping their patients.
The senator will be holding a press conference alongside patients and families who are losing access to ataluren, also known as Translarna, a treatment designed to treat Duchenne muscular dystrophy (DMD). In mid-February, drugmaker PTC Therapeutics revealed that it withdrew its FDA application for Translarna in nonsense mutation DMD after receiving feedback from the regulator.
As of publication, Johnson’s office has not responded to Fierce Biotech’s inquiries for additional comment.
