Amgen

(AMGN) - Get Report

agreed to buy Avidia, a privately held biopharmaceutical company, in a $290 million deal.

The transaction should close in the fourth quarter. Amgen will gain Avidia's lead product candidate, an experimental treatment for inflammation and autoimmune diseases that's in Phase 1 clinical trials.

Amgen will also pay up to $90 million if Avidia achieves certain milestones. Shares of Amgen were down 38 cents, or 0.5%, at $71.17 Friday.