Through its savvy but legal exploitation of the U.S. patent system, Humira’s manufacturer, AbbVie, blocked competitors from entering the market. For the next six years, the drug’s price kept rising. Today, Humira is the most lucrative franchise in pharmaceutical history. AbbVie orchestrated the delay by building a formidable wall of intellectual property protection and suing would-be competitors before settling with them to delay their product launches until this year. Over the past 20 years, AbbVie and its former parent company increased Humira’s price about 30 times, most recently by 8 percent this month. Since the end of 2016, the drug’s list price has gone up 60 percent to over $80,000 a year, according to SSR Health, a research firm. AbbVie did not invent these patent-prolonging strategies; companies like Bristol Myers Squibb and AstraZeneca have deployed similar tactics to maximize profits on drugs for the treatment of cancer, anxiety and heartburn. But AbbVie’s success with Humira stands out even in an industry adept at manipulating the U.S. intellectual-property regime.

“Humira is the poster child for many of the biggest concerns with the pharmaceutical industry,” said Rachel Sachs, a drug pricing expert at Washington University in St. Louis. “AbbVie and Humira showed other companies what it was possible to do.”