The FDA suspends or revokes approval of an approved gene-editing therapy due to off-target side effects before

Question

Six frontier AI models put this at 8% by 5 Oct 2029. Full reasoning from every model.

WillHappen.ai · Accepted Answer

8% — the median of 6 frontier models, resolving by 2029-10-05.

Answer

Gemini (Google): 4% — Low patient uptake and slow onset of oncogenesis make detecting and acting on off-target effects before 2028 extremely improbable. Casgevy has treated only dozens of commercial patients, generating too small an exposure pool for rare off-target events by 2028. FDA post-market withdrawals take years of investigation; black box warnings or clinical holds precede full suspension. A confirmed case of secondary malignancy tied directly to CRISPR off-target cleavage would drastically increase these odds.

Answer

Claude (Anthropic): 9% — FDA rarely revokes approvals; it usually demands label changes or partial holds instead of full suspension. Only a handful of approved gene-editing therapies exist (Casgevy, Lyfgenia, others), limiting the event space before 2029. FDA historically prefers REMS updates, black-box warnings, or voluntary market withdrawal over formal suspension even after serious adverse events. A clear off-target mutagenesis signal causing cancer or death in treated patients would be the main trigger that could change this.

Answer

GPT (OpenAI): 18% — This turns on a confirmed patient-harm signal being attributable to off-target editing strongly enough for FDA action. FDA has approved only a small number of editing therapies, and marketed products face years of sparse real-world exposure before rare harms emerge. FDA can impose a clinical hold quickly, but withdrawing an approved BLA typically requires a clear causal safety pattern and due process. A replicated cluster of clonal malignancies or heritable/off-target mutations in treated patients would sharply raise the odds.

Answer

Grok (xAI): 7% — FDA post-market action on Casgevy-class products from off-target data by end-2027. FDA needs clear post-approval evidence of off-target harm (cancers/mutations) by late 2027; Casgevy has ~3 years of use with none reported. Historical FDA full suspensions/revocations are rare (<1% of approvals, almost never gene therapies); this sits below because off-target risk was already accepted with… A cluster of unexpected malignancies in treated patients would most raise the odds.

Answer

DeepSeek (DeepSeek): 9% — No approved gene-editing therapy has shown off-target harm in humans, and FDA has never pulled one on this basis. Casgevy and Lyfgenia (Dec 2023) are the only approved gene-editing therapies; both use ex vivo editing, which limits off-target risk. FDA would need post-market evidence of harm, a safety signal review, and a formal suspension order — a multi-year process with no precedent. The base rate for FDA revoking an accelerated approval over safety is roughly 1-2 per year across all drugs, but none for gene editing.

Answer

Qwen (Alibaba): 7% — Off-target effects are real but no approved gene-editing therapy has shown signal severe enough to trigger suspension in ~3 years. Casgevy and Lyfgenia (both approved Dec 2023) have post-marketing surveillance running; no FDA safety signal has emerged as of mid-2026. FDA suspension/revocation of any biologic is rare—fewer than 10 cases in 20 years—and requires a clear, attributable adverse event pattern, not theoretical risk. A black-swan off-target event in a treated patient would need to be causally linked and severe enough to prompt action; base rate of this in the remaining ~2 years is…

The FDA suspends or revokes approval of an approved gene-editing therapy due to off-target side effects before 2028.

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