Merck & Co. (NYSE: MRK) added to its product pipeline with the $500 million acquisition Afferent Pharmaceuticals, a privately held biotechnology company in San Mateo, California. Afferent develops therapeutic candidates targeting the P2X3 receptor, for the treatment of common, poorly-managed neurogenic conditions.

Afferent’s lead candidate, AF-219, is a selective, non-narcotic, orally administered P2X3 antagonist. It is currently being evaluated in a Phase 2b clinical trial for the treatment of refractory, chronic cough, as well as in a Phase 2 clinical trial in idiopathic pulmonary fibrosis with cough.

Merck, which is known as MSD outside the United States and Canada, paid $500 million in cash upfront. Afferent shareholders will be eligible to receive a total of up to an additional $750 million associated with the achievement of certain clinical development and commercial milestones for multiple indications and candidates.

This deal is expected to close in the third quarter of 2016.