Our Take
The FDA is clearing a backlog of decisions that broke its own earlier commitments to companies—a correction that matters more than the individual resubmission.
Why it matters
Gene therapy companies operating under prior FDA guidance now have clarity that rejections based on policy shifts, not new safety data, can be revisited. This affects the timeline and cost calculus for any therapy in a similar position.
Do this week
Gene therapy counsel and regulatory affairs teams: audit your company's pre-2025 FDA feedback letters for language signaling prior agreement versus new concern, and flag candidates for resubmission requests before Q2 closes.
Regenxbio will resubmit Hunter syndrome gene therapy
Regenxbio announced it will resubmit its gene therapy candidate for Hunter syndrome (mucopolysaccharidosis type II) following FDA guidance that the rejection decision conflicted with prior agreements between the agency and the company. The move is part of a broader FDA effort to clear rejections issued during the Makary administration that appeared to contradict earlier commitments to drugmakers.
Hunter syndrome is a rare genetic disorder affecting fewer than 1,000 patients in the US annually. Regenxbio's therapy, based on the company's NAV technology platform for gene delivery, had faced rejection despite what the company characterizes as alignment with FDA feedback on the proposed development program.
Policy reversals create legitimate grounds for resubmission
The FDA's acknowledgment that certain rejections contradicted prior guidance signals a shift in how the agency will handle decisions made under prior leadership. This is not a rare-disease carve-out or a change in the science. It is a procedural reset.
For Regenxbio and similar companies, the practical consequence is straightforward: rejections based on regulatory interpretation rather than new safety or efficacy evidence can now be contested and reversed. This reduces the sunk cost of a rejection and shortens the calendar to resubmission.
The broader implication reaches beyond Hunter syndrome. Any gene therapy or small biotech company with a rejection letter from 2024 or earlier should review whether the stated reasons align with the FDA's prior written feedback to that company. If misalignment exists, a resubmission request is now more likely to succeed.
What to do with this precedent
Regulatory affairs teams should pull every rejection letter issued in the past 18 months and cross-reference it against the company's IND file, meeting minutes, and any written FDA correspondence that predates the rejection. Look specifically for language in the rejection that contradicts earlier feedback on study design, endpoints, or regulatory strategy.
If that gap exists, prepare a resubmission package that opens with a point-by-point comparison of prior FDA guidance versus the stated reason for rejection. Frame it as a clarification request, not a challenge to the agency's authority. The FDA has already shown it is willing to reverse course on consistency grounds; your job is to make the inconsistency explicit.
Time matters. As the backlog clears and the Makary-era rejections are resolved, the window for claiming administrative error will narrow. Move on this in the next 60 days if you have a candidate.