Merck & Co has agreed an upfront payment of €110m (around $140m) to buy German biotech AiCuris' portfolio of drugs to treat human cytomegalovirus (CMV) infection.
In addition to this sum, Bayer spin-out AiCuris stands to receive up to €334.5m in development, regulatory, and commercialisation milestone payments, as well as royalties on sales.
The lead drug candidate covered by the deal is letermovir (AIC246), an orally-active compound which has successfully completed a phase IIb trial for the treatment and prevention of CMV infection in transplant patients.
Letermovir works by inhibiting an enzyme called CMV viral terminase, and Merck has also bought a follow-up compound targeting the same enzyme and various other phase I candidates that work in a different way.
Letermovir has been granted orphan drug status in the EU and the US, and has also been earmarked for fast-track review by the FDA.
Dr Roger Pomerantz, head of infectious disease R&D at Merck Research Laboratories, said: "There is a significant need for additional medicines for the treatment of [CMV] infection, which is one of the most common viral infections affecting organ and bone marrow transplant patients."
"This portfolio complements Merck's broad antiviral portfolio," he added. Merck currently has two antiviral candidates in clinical testing, namely hepatitis C virus (HCV) protease inhibitor vaniprevir in phase III and follow-up MK-5172 in phase II.
This is the first major licensing deal for privately-held AiCuris, which was formed as a spin-out from Bayer's anti-infectives unit in 2006 and has already advanced seven compounds into the clinic.
In addition to its CMV portfolio, the company is also seeking licensing partners for a drug targeting Herpes simplex virus (HSV) called AIC316, also heading into phase III testing, as well as two immune modulators being developed for viral hepatitis and fibrosis and autoimmune diseases.