Sen. Johnson Probing FDA Rare Disease Denials
Senator Ron Johnson (R-WI) is launching a congressional investigation into FDA’s recent decisions to reject or delay treatments for rare diseases, escalating political scrutiny of the agency’s regulatory standards and decision-making.
Johnson, who chairs the Senate Permanent Subcommittee on Investigations, said he is seeking copies of FDA’s complete response letters to understand why certain therapies were turned down. e also said he may call senior agency officials, including commissioner Marty Makary, to testify before Congress.
“The stories are so outrageous,” Johnson told Bloomberg, suggesting the agency may be “looking for excuses to say no.” Two high-profile disputes with FDA appear to be central to Johnson’s inquiry, including cases involving companies Biohaven Ltd. and uniQure N.V..
One involves a therapy from Biohaven aimed at spinocerebellar ataxia, a rare neurodegenerative disorder that progressively impairs coordination and movement. FDA rejected the treatment in late 2025, a decision Johnson said he struggled to understand given support from physicians treating the disease.
Another dispute centers on uniQure’s experimental gene therapy AMT-130 for treating Huntington's disease, a fatal inherited neurological condition affecting tens of thousands of Americans. FDA recently told the company it would need to conduct an additional randomized clinical trial before the therapy could be considered for approval.
The agency specifically recommended a prospective, randomized, sham-surgery-controlled study, a requirement that has drawn criticism from both the company and lawmakers. uniQure argued the design could pose risks and ethical concerns for patients who might undergo invasive procedures without receiving the actual therapy. Johnson sharply criticized the request, calling it “bureaucratic idiocy” and questioning whether regulators were imposing unrealistic demands on patients with life-threatening diseases.
The probe comes amid a wider debate over whether FDA has become more stringent in evaluating therapies for rare diseases, many of which affect very small patient populations and lack effective treatments. Patient advocates and some biotech companies say regulatory requirements can shift late in the development process, forcing companies to run costly additional trials that delay access to new medicines.
HHS has defended the agency’s approach, saying approval decisions are guided by scientific evidence and the need to ensure drugs are safe and effective before reaching patients.
Still, Johnson’s investigation adds to mounting pressure on FDA as it navigates a surge of experimental gene and cell therapies targeting rare conditions — treatments that often rely on small trials and limited data because of the difficulty of studying extremely rare diseases.