Patent Portfolios Protecting 10 Top-Selling Prescription Drugs

Importance Brand-name drugs are sold at high prices in the US during market exclusivity periods protected by patents. Multiple overlapping patents protecting a drug are known as patent thickets and can effectively delay the emergence of price-lowering generic competition for many years. Objective To evaluate the composition of patent thickets of 10 top-selling prescription drugs in the US and compare the characteristics of drug patents filed during development with those filed on these products after US Food and Drug Administration (FDA) approval. Design and Setting This cross-sectional study examined US patent thickets of the 10 prescription drugs with the highest US net sales revenue in 2021 using information on issued patents and patent applications as of June 30, 2022, obtained from a public database by the Initiative for Medicines, Access, and Knowledge. Data were analyzed from September 2022 to June 2023. Main Outcomes and Measures Prevalence of patents filed before and after FDA approval; types of claims present in issued patents (ie, chemical composition, method of use, process or synthesis, formulation, and delivery device); and patent thicket density (number of active patents at a given time). Results The 10 top-selling prescription drugs in the US for 2021 included 4 small-molecule drugs and 6 biologics. These 10 drugs were linked to 1429 patents and patent applications: 742 (52%) issued patents, 218 (15%) pending applications, and 469 (33%) abandoned applications. Almost three-quarters of patent applications (1028 [72%]) were filed after FDA approval. The postapproval proportion was higher for biologics (80%) than for small-molecule drugs (58%). Postapproval filing of patent applications peaked in the first 5 years after FDA approval for small-molecule drugs and 12 years after FDA approval for biologics. Of 465 patents issued for applications filed after FDA approval, 189 (41%) had method of use claims, 127 (27%) had formulation claims, and 103 (22%) had process or synthesis claims, while 86 (19%) had chemical composition claims and 46 (10%) had device claims. Patent thicket density peaked 13 years after FDA approval, at which time these 10 drugs were protected by a median (IQR) of 42 (18-83) active patents, 66% of which were filed after FDA approval. Conclusions and Relevance This study found that among the 10 top-selling prescription drugs in the US in 2021, patents filed after FDA approval and containing claims covering aspects other than the active ingredient of the drug contributed to patent thickets. Scrutiny of patent applications and of patents filed after FDA approval is needed to facilitate timely generic or biosimilar competition.