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What is a Complete Response Letter (CRL)?
A Complete Response Letter (CRL) is the FDA's formal notice that it will not approve a drug application in its current form. It's not a permanent rejection — it lists the deficiencies the company must address before the FDA can approve.
Common CRL reasons
EfficacyData didn't convincingly show the drug works
SafetyUnresolved safety signal or risk/benefit concern
Manufacturing (CMC)Facility or chemistry/quality issues — often third-party
Manufacturing/CMC and inspection CRLs are often the most fixable — a strong efficacy package can survive a facility finding. An efficacy CRL is usually the hardest.
What happens after a CRL?
The company resubmits after addressing the issues; the FDA then sets a new review clock (Class 1 resubmission ≈ 2 months, Class 2 ≈ 6 months). Stocks often crash on a CRL, then trade the run-up into the resubmission — the 'fallen-angel' pattern. Browse real examples in our CRL archive.