Biogen Idec is to acquire Stromedix, a privately-held company founded by a former research chief of the US biotech major, in a deal that could be worth over $560 million.

Cashwise, Biogen will fork out an upfront fee of $75 million and additional contingent value payments of up to $487.5 million based on "the achievement of certain development and approval milestones across multiple indications". The drug at the heart of the deal is Stromedix’s STX-100, a monoclonal antibody that selectively disrupts the TGF-beta pathway, which plays a central role in fibrotic disease.

Stromedix, which has also identified "a series of clinical biomarkers that reflects the biological activity of STX-100", says the compound is entering a Phase II trial in patients with idiopathic pulmonary fibrosis. This "almost uniformly fatal disease" causes patients to experience difficulty breathing due to scarring of the lung.

More than 200,000 patients in the USA and Europe have IPF, and there is no Food and Drug Administration treatment approved for the disease, though Intermune's Esbriet (pirfenidone) is available this side of the Atlantic. Biogen says STX-100 has "potential in several additional fibrotic indications given its selective mechanism of action".

Douglas Williams, head of R&D at Biogen, said STX-100 "has the potential to be a best-in-class therapy and it is an excellent strategic fit". Curiously the drug was initially developed by Biogen and Michael Gilman, founder and chief executive of Stromedix, who led Biogen’s research organisation from 2000 to 2005, licensed the treatment for his new business, which set up in 2007 with Atlas Venture and Frazier Health Care Ventures.

Other venture firms invested in Stromedix, which previously raised $29.4 million in two rounds of funding and Biogen is indeed already a shareholder.