US drug maker Gilead Sciences is to pay $400 million to Nimbus Therapeutics for its subsidiary Nimbus Apollo and its Acetyl-CoA Carboxylase (ACC) inhibitor program.

The ACC program includes an experimental treatment – NDI-010976 – for the fatty liver disease known as non-alcoholic steatohepatitis, or NASH, as well as liver cancer and other diseases.

NDI-010976 works by blocking ACC, which is involved in making fatty acids and regulating the breakdown of fatty acids in cells. It won a fast track designation from the Food and Drug Administration in February and results from an early-stage trial will be presented next month.

Nimbus will get another $800 million if Nimbus Apollo’s drug development program meets certain milestones in testing results and drug approval and sales.

Norbert Bischofberger, Gilead’s chief scientific officer, said the acquisition of Nimbus’ ACC-inhibitor program was a timely and important opportunity to accelerate efforts in addressing unmet needs in NASH.

The disease, which affects up to 15 million Americans and can cause inflammation, cell damage, progressive scarring and cirrhosis, is expected to become the major reason for liver transplants by 2020. Analysts have estimated that the market for NASH drugs could eventually be worth $35 billion.

After its success with the two blockbuster hepatitis C treatments Harvoni and Sovaldi, Gilead has been sitting on $26.2 billion in cash and equivalents and looking to boost its portfolio before revenue from its hepatitis C drugs starts declining.

Prices have already started to fall in the US because of increasing competition and pressure from insurers for bigger discounts off their list prices. A course of treatment with Sovaldi costs around $84,000 and Harvoni $94,000.

Last month, however, Gilead lost a high-profile patent dispute with US rival Merck over sofosbuvir, the active ingredient in Sovaldi and Harvoni, and is now liable for more than $2 billion in damages plus royalties.