5. Sustiva

Bristol-Myers Squibb building
Bristol’s HIV med Sustiva first won approval in 1998 and is set to lose exclusivity in December, making vulnerable a big chunk of U.S. sales.

Company: Bristol-Myers Squibb
Disease: HIV
2016 U.S. sales: $901 million
U.S. patent expiration date: December 2017

Bristol-Myers generated many a headline in 2016 with its cancer therapies. But it still boasts a hefty antiviral franchise, including the HIV-fighting drug Sustiva, which is set to lose exclusivity in December, according to the company’s 2016 securities filing.

Sustiva, a non-nucleoside reverse transcriptase inhibitor that works by preventing HIV from multiplying, turned in U.S. sales of $901 million, according to earnings results released in late January. Worldwide sales amounted to $1.065 billion.

And a host of generics companies have lined up to challenge that U.S. revenue. Teva Pharmaceutical, Emcure, Strides, Aurobindo and others have earned tentative approvals for copycats, according to Drugs@FDA.

Sustiva’s composition of matter patent expired back in 2013, according to the company, and its method patent for treating HIV fell off in September of the next year. Other patents were in dispute, however, and in October 2014, Bristol-Myers said it had “resolved all outstanding U.S. patent litigation” around the med, the document states.

Bristol previously won pediatric exclusivity on the drug, extending its exclusive market access for six months. That exclusivity expires in November, and the generics are set to hit in December. “Loss of exclusivity in the U.S. for efavirenz is not expected to occur until December 2017,” BMS said with last year’s 10-K.

At $901 million, Sustiva is in the middle of the pack at Bristol-Myers, sales-wise. Its U.S. revenue makes up less than one-twentieth of the company's overall top line.

The company has suffered bigger patent losses before, including Abilify, when went generic just last year. It's counting on newer brands to help it weather this one, including the $3.8 billion drug Opdivo, a cancer immunotherapy.

5. Sustiva