6. Sensipar

Sensipar is only one of several Amgen meds facing new or potential competition from generics and biosimilars. (Amgen)

Company: Amgen
2018 U.S. sales: $1.43 billion
Use: Calcium reducer
Competition expected: Midyear or later

Nearly a year after a patent expiration, Amgen's Sensipar continues to dodge generic competition—apart from a couple of days last year, that is. And thanks to the lack of copycats, the drug pulled in $1.43 billion in 2018 U.S. sales.

But Sensipar could face a full generics launch any day, the company notes in SEC filings. That’s because copycat drugmakers have FDA approvals in hand, and as Amgen well knows, one or more of them might decide to roll out those versions “at risk” despite ongoing patent litigation.

Teva did just that late last year, albeit briefly. The generics giant rolled out its copy for a matter of days and reaped tens of millions in sales, Bernstein analyst Ronny Gal figures, as buyers scrambled to stock up. That launch could have triggered others—because of acceleration clauses in Amgen's previous deals with would-be Sensipar copycats—so the branded drugmaker chose to settle with Teva, too, and quickly, the analyst wrote.

Some generics makers haven't settled yet. Sensipar's composition of matter patent expired in March, but Amgen's still fighting in court with "a number of generic companies" seeking to market their copies, Amgen said in a third-quarter SEC filing. During the company's fourth-quarter conference call, Chief Financial Officer David Meline said Amgen anticipates litigation "would conclude by around midyear.”

So for now, market watchers are waiting to see how competition to Sensipar will play out this year.

“We are confident in the strength of our intellectual property,” Meline added on the fourth-quarter call. “However, uncertainty as to the timing and intensity of competition will remain until the outcome of litigation becomes clear.” Sensipar's remaining patents expire in 2026, according to the FDA Orange Book.

Gal wrote after Amgen reported 2018 results that the company assumed midyear generic Sensipar competition in calculating the low range of its 2019 sales guidance. His team thinks there's a 40% chance generics won't launch until the fourth quarter of 2019 or later.

RELATED: Locked in a Sensipar patent fight, Teva rolled its generic anyway—and then Amgen settled

There are more than a dozen generic companies seeking to knock off Sensipar, the analyst wrote after the brief Teva launch; Amgen has settled with most of them. Under the deal with Teva, the Israeli drugmaker can’t launch until 2021—or sooner, if other generics reach market. Thanks to the brief launch by Teva and other factors, Meline said Amgen expects lower sales for Sensipar this year "in any scenario."

Aside from Sensipar, Amgen is facing biosimilar competition to Neulasta and Epogen, as well as a potential threat to its big-selling Enbrel for inflammatory conditions. Amgen executives recently said the litigation over Enbrel's patents will take some time to play out, so it is unclear when copycats might reach the market. Novartis has already won FDA approval for its Enbrel biosimilar, called Erelzi.

6. Sensipar