4. Eliquis

Eliquis saw a 22% sales jump in 2019, around $1.38 billion more than the prior year. (Pfizer)

Companies: Pfizer, Bristol Myers Squibb
Used for: Blood clots
2019 sales: $7.71 billion

Pfizer and Bristol Myers Squibb’s Eliquis got a bit of a scare in December after the FDA approved the first generic version of their partnered blood thinner. But the companies’ aggressive patent litigation should stave off most copycats until 2026, leaving Eliquis with plenty of room to grow this year.

The Pfizer-BMS alliance is poised to add $1.08 billion in Eliquis sales this year to its already formidable $7.71 billion in 2019, according to EvaluatePharma. That bump could bring Eliquis' sales in 2020 up to $8.79 billion. 

That increase is certainly within reason, given Eliquis’ recent sales growth: The drug saw a 22% jump in 2019—around $1.38 billion more than the prior year.

Pfizer attributed the growth to Eliquis’ booming market share in the warfarin alternative market, where the drug easily leads the way, as well as the overall oral anticoagulant market, where Eliquis managed to outpace warfarin itself in 2019.

RELATED: First generics to Bristol-Myers and Pfizer's Eliquis are here. But can they launch before 2026?

Despite Eliquis' big year, December marked a sour note after the FDA said it had approved the first two generic challengers for the blood thinner.

However, Bristol has made strenuous efforts to defend Eliquis' patents in recent years, giving most analysts the belief that the drug will hold on to market exclusivity until those patents expire in 2026. 

Take 2017, for example:  After 25 generics companies told Bristol that they had filed for FDA approval of their copycats, the alliance erected a patent wall, launching lawsuits against all those drugmakers. The following August, the U.S. Patent and Trademark Office granted Eliquis a key composition of matter patent, extending it from February 2023 to November 2026.

In its most recent annual report filed in February, Bristol said the partners had reached a settlement with "a number" of generics challengers. A Bristol spokesperson told FiercePharma in December that the company has signed agreements with Mylan and Micro Labs.

RELATED: Pfizer points to newer meds—including Ibrance—as post-Upjohn cash engines

4. Eliquis