Allergan figured Kythera's drug Kybella could provide a "pivotal entry point" for expanding the use of facial aesthetics in men, CEO Brent Saunders said at the time. (Allergan)

Deal size:
$2.1 billion
Date announced: June 17, 2015

Hot off the presses after its Actavis merger in March 2015, Allergan wasn't done spending money. Just three months later, it opted to pick up Kythera and its up-and-coming chin-fat drug, Kybella, in a $2.1 billion deal.

Then and for years to come, Allergan repeatedly touted the drug as a long-term growth booster for its aesthetics franchise––but things haven't exactly gone according to plan.

Four years after the Kythera buy, Kybella posted just $5.6 million in global sales in the third quarter. Even worse, those sales amounted to $1.2 million less than the same quarter last year––a disheartening 17.6% drop.

And that's only the most recent depressing quarter for a drug that once held high hopes for Allergan's future.

When Allergan inked its deal, Kybella seemed to fit right into its burgeoning aesthetics business, led, of course, by the wrinkle injection Botox.

In fact, Allergan figured the drug might just be able to give Botox itself a boost. Kybella could provide a "pivotal entry point" for expanding the use of facial aesthetics in men, Allergan CEO Brent Saunders pointed out in a statement.

Within a year, though, analysts were already growing concerned about Kybella's chances. They pointed to a 4% rate of facial nerve injury in trial patients and instead of quoting blockbuster forecasts, tagged the drug at around $400 million in peak sales—if everything went as planned.

Allergan moved ahead in 2016 with a round of DTC ads and plans to expand the drug's label with indications in bra-line and ankle fat. And Kybella managed to bring in $50 million that year, including $12 million in the fourth quarter.

RELATED: Did Allergan lose its $2.1B Kythera bet, or can chin-fat drug Kybella make its mark?