Allergan plc (NYSE: AGN) agreed to buy Tobira Therapeutics Inc. (Nasdaq: TBRA) for as much as $1.7 billion to gain a late-stage experimental drug to treat liver diseases, one of the most anticipated categories in biotechnology.

Allergan recently agreed to buy Vitae Pharmaceuticals Inc. (Nasdaq: VTAE), after the company terminated its merger with Pfizer Inc. (NYSE: PFE). In other pharmaceutical deal, Sunovion Pharmaceuticals Inc. is acquiring Cynapsus Therapeutics Inc. (Nasdaq: CYNA).

Allergan will pay $28.35 a share for Tobira in cash, according to a statement, or about $533 million based on the number of shares outstanding. The drugmaker also agreed to pay up to $49.84 a share if Tobira hits certain sales and regulatory goals. Even if Tobira fails to hit the goals, the lower price is six times its $4.74 closing price on Sept. 19.

Tobira, based in San Francisco, is developing several treatments for non-alcoholic steatohepatitis -- known as Nash, a severe type of non-alcoholic fatty liver disease. The hefty premium shows how important therapies for the disease have become for biotech companies, with Gilead Sciences Inc. (Nasdaq: GILD) and Intercept Pharmaceuticals Inc. (Nasdaq: ICPT) both working on experimental therapies to treat it.