1. Lantus

Lantus
For the second year in a row, sales of Lantus dropped year over year in 2016.

Company: Sanofi
2016 U.S. sales: $3.9 billion
Drug class: Basal insulin

Lantus has led the way, both in diabetes sales and in Sanofi sales, for years now, pumping out more than $7 billion worldwide for the company at its peak. But now, the stalwart basal insulin is on the wane. For the second year in a row, sales of Lantus (insulin glargine) dropped year over year in 2016, as U.S. payers pushed for higher rebates and rivals stole market share, partly by striking deals with payers.

And as of December, Lantus has even more competition in the U.S., in the form of its first biosimilar, Basaglar. Biosimilars aren’t traditional generics, of course, so their list prices are expected to run 15% to 20% lower than the brand, rather than the enormous discounts offered by small-molecule copycats. Still, Eli Lilly and Boehringer Ingelheim apparently made some aggressive deals with payers, because Basaglar won exclusive spots on at least two key formularies, UnitedHealth and CVS Heatlh.

Losing share to a biosimilar isn’t good for the top line, but losing it to your own follow-up drug is—and some of Lantus’ market stake has gone to Sanofi’s longer-acting basal insulin, Toujeo. Since Toujeo launched in April 2015, Sanofi has been working hard to switch as many patients as possible over to the newer medication, in hopes of bridging its Lantus sales gap. But Toujeo’s sales still pale in comparison to Lantus itself: €475 million in the U.S. last year, €630 million worldwide.

Lantus faces other new competition in the basal insulin world, too: Novo Nordisk’s Tresiba, which launched last January armed with some Lantus-beating clinical trial data. One potential rival, however, failed to make the grade; Eli Lilly pulled the plug on its long-acting insulin peglispro after pivotal trial data raised safety questions.

1. Lantus