The timing of 30-month stay expirations and generic entry: A cohort study of first generics, 2013-2020

Clin Transl Sci. 2021 Sep;14(5):1917-1923. doi: 10.1111/cts.13046. Epub 2021 May 31.


Before the first generic version of a drug is marketed, patent litigation often occurs. The process begins when generic manufacturers notify the US Food and Drug Administration (FDA) of their intent to market a generic copy of a brand-name drug protected by patents, which they allege to be invalid or not infringed (called a Paragraph IV certification). Assuming the brand-name manufacturer responds with litigation within 45 days, a 30-month stay period is triggered, which bars the FDA from authorizing generic entry until the stay period expires or litigation is resolved in favor of the generic manufacturer. To understand whether 30-month stays delay generic entry, we examined the timing of major legal events leading to generic entry for a cohort of 46 generic drugs, including the timing of Paragraph IV certification filings, stay period expirations, the FDA approvals of generics, and generic product launches. We found Paragraph IV certifications were filed a median of 5.2 years after the brand drug's FDA approval. There was a median of 3.2 years between the stay period expiration and subsequent generic launch. Because stay periods generally expire well in advance of when generic entry typically occurs, 30-month stays are unlikely to delay the timing of generic entry. Patent litigation could begin even earlier, however, if litigation was allowed to start immediately following a brand-name drug's FDA approval; but by law currently, the soonest this can begin is 4 years after the brand drug's FDA approval. Study Highlights WHAT IS THE CURRENT KNOWLEDGE ON THE TOPIC? Before generic versions of new drugs reach the market, patent litigation often occurs. Once litigation has been initiated, a 30-month regulatory stay period is triggered that bars the US Food and Drug Administration (FDA) from approving the generic application until litigation resolves or the stay period expires. WHAT QUESTION DID THIS STUDY ADDRESS? What is the timing of key legal events in the regulatory approval process for generic drugs in relation to the eventual launch of the generic product? WHAT DOES THIS STUDY ADD TO OUR KNOWLEDGE? We identified the typical timing of the initiation of patent litigation and expiration of the 30-month stay period prior to the eventual launch of generic products. Litigation is often initiated as soon as legally possible (i.e., 4 years after the launch of the brand product), and stay periods typically expire well before generic entry occurs. HOW MIGHT THIS CHANGE CLINICAL PHARMACOLOGY OR TRANSLATIONAL SCIENCE? Stay periods are unlikely to delay generic entry directly because stay expirations often occur well before the time of generic launch. Allowing the submission of generic drug applications immediately following a brand drug's FDA approval would facilitate earlier patent dispute resolution and prevent unnecessary delays in the anticipated generic product launch date.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Drug Approval / legislation & jurisprudence*
  • Drugs, Generic / standards*
  • Humans
  • Patents as Topic / legislation & jurisprudence*
  • Time Factors
  • United States
  • United States Food and Drug Administration / legislation & jurisprudence
  • United States Food and Drug Administration / standards


  • Drugs, Generic