A study published in *JAMA* found that pharmaceutical companies have increasingly accumulated extra patents on small-molecule medicines, a practice that can keep cheaper generic versions off the market for longer. These “patent thickets” often cover changes beyond a drug’s active ingredient, and may extend periods of limited price competition without corresponding clinical advances.

Researchers examined 1,981 US-approved small-molecule drugs from 1990 to 2019, identifying 10,940 patents; 84 per cent were nonprimary patents. The average number of patents per drug rose from 2.1 to 6.9, while the average patent-covered period grew from two years to 6.1 years. The study did not directly measure delays to generic availability, and its authors say the findings may understate current patent activity; they suggest stronger scrutiny and legal reforms to curb minor add-on patents.