Patent Evergreening

What It Means

Patent evergreening is a strategy used primarily by pharmaceutical companies to extend the effective commercial life of a product beyond the expiration of its original patent. Rather than developing entirely new drugs, companies file successive patents on incremental modifications — new formulations, different dosages, alternative delivery methods, metabolites, polymorphs, or combinations with other drugs. Each new patent can add years of protection, delaying generic entry and maintaining pricing power. Common evergreening tactics include converting an immediate-release drug to an extended-release formulation, developing a single-enantiomer version of a racemic drug (as AstraZeneca did converting Prilosec to Nexium), combining an established drug with a new active ingredient, and discovering new therapeutic uses for existing molecules. Each of these modifications can support new patent claims that extend protection even as the original compound patent expires. The practice is legal but controversial. Proponents argue that continued innovation on existing drugs — better formulations, reduced side effects, new indications — provides genuine patient benefits and reflects real R&D investment. Critics contend that many evergreening patents cover trivial modifications that do not represent meaningful innovation, and that their primary purpose is to delay competition and maintain artificially high prices. The FTC and academic researchers have documented patterns where the cumulative effect of evergreening can extend effective exclusivity by 5-15 years beyond the original patent term. In patent portfolio analysis, the presence of evergreening patterns — clusters of continuation applications and formulation patents surrounding a core compound patent — is an indicator that a company is actively managing its patent cliff risk.

Frequently Asked Questions