The senator, who has long advocated for expanding access to experimental therapies, reportedly called the FDA’s request for a sham surgery–controlled Phase 3 trial for uniQure’s Huntington’s disease gene therapy “bureaucratic idiocy.”
Sen. Ron Johnson (R-WI) is launching an investigation into recent FDA denials of rare disease therapies after a spate of highly publicized rejections during the past year.
Johnson is seeking complete response letters sent to the developers of these therapies to learn the rationale behind the rejections, according to Bloomberg News, which reported the news on Tuesday. The senator is also considering having senior FDA officials, including Commissioner Marty Makary, appear before the Senate’s Permanent Subcommittee on Investigations, which he chairs.
“The stories are so outrageous,” Johnson told the publication on Monday. “It just appears that they’re looking for excuses to say no.”
Reports of Johnson’s investigation follow a chaotic week in which uniQure revealed that the FDA is insisting upon a sham surgery–controlled Phase 3 trial before reviewing the Huntington’s disease gene therapy AMT-130. The request runs contrary to guidance provided to uniQure in 2024, according to the company.
In September 2025, uniQure announced that AMT-130 slowed disease progression by 75% after three years in a pivotal trial. Five weeks later, however, the FDA told uniQure it “no longer agrees” that data from the company’s Phase 1/2 trial, which compared the gene therapy to a natural history arm, are “adequate to provide the primary evidence in support of a BLA submission.”
Johnson called the FDA’s request for a new trial of AMT-130 “bureaucratic idiocy,” Bloomberg reported.
“You’re expecting people to go through sham surgeries where they get holes drilled in their heads?” Johnson said. “That’s just unbelievable.”
The agency has refuted this characterization of the sham surgery, with a senior FDA official telling a selection of reporters last week that surgeons would only need to “put one to three nicks in the scalp.” The senior official was later revealed to be Center for Biologics and Evaluation Director Vinay Prasad.
UniQure represents a trend noted by industry analysts and other experts of a stricter regulator—particularly when it comes to investigational therapies for rare diseases. Under the leadership of Prasad, “CBER rejected at least five cell and gene therapies that we believe could have received approval under prior FDA officials,” H.C. Wainwright analysts said in a note Tuesday morning.
The analysts expressed optimism, however, that Prasad’s upcoming departure at the end of April—announced on Friday—may turn the tide.
“His departure . . . may signal a moderation in the interpretive posture applied to filing-stage programs relying on external comparator controls, single-arm datasets, or surrogate endpoints, in our view,” H.C. Wainwright analysts said in a Tuesday morning note. “Prasad’s departure removes the single most consequential individual variable driving regulatory uncertainty across the gene therapy and rare disease space, in our view.”
Johnson is a long-time advocate of expanding access to experimental therapies for people with terminal or rare diseases, according to Bloomberg, previously saying that patients should be given “hope and the freedom to try.”
Johnson is not the first U.S. senator to question the FDA’s decision-making.
“One of the greatest challenges innovators face is that the FDA’s process for reviewing products can be an unpredictable ‘black box,’” Sen. Bill Cassidy, chairman of the Senate’s Health, Education, Labor and Pensions Committee, wrote in an 18-page report published in February.
A Department of Health and Human Services spokesperson defended the FDA’s recent decisions, telling Bloomberg that the number of drug approvals and rejections under this Trump administration is “consistent with historical data over the last decade.”
The FDA approved 56 novel therapeutics in 2025, and Jefferies analysts in a January note said the agency’s approval and rejection rates were within historical norms. The 46 approvals under the Center for Drug Evaluation and Research were down from 49 in 2024, according to the firm, while nods under CBER—which oversees cell and gene therapies—remained flat.
