Boehringer Ingelheim is to buy the privately-owned US biotechnology firm Actimis Pharmaceuticals in a deal that could be worth up to $515 million.

The German drugmaker says that the deal is “a structured buyout” in which Boehringer will acquire shares of Actimis depending on the achievement of “several successive milestones” with the latter’s leading asthma compound AP768. If the latter drug, currently in Phase I, is successfully advanced into Phase III, Boehringer will own 100% of Actimis’ shares. Further financial details were not disclosed.

AP768 interacts with a chemo-attractant receptor-homologous molecule expressed on TH2 mice cells, a novel target for asthma and allergic rhinitis. Previous to the ongoing Phase I study, the compound has been shown to have a more effective mechanism of action across multiple available animal models compared to currently marketed leukotriene receptor antagonists, the firms said.

“Actimis’ compound provides “an innovative addition” to Boehringer’s portfolio of development candidates for the potential treatment of respiratory diseases”, said Andreas Barner, head of R&D at the privately-owned German firm. He added that “for many decades the company has been advancing research in the respiratory area with new medicines, such as Spiriva (tiotropium) for chronic obstructive pulmonary disease.

Actimis chief executive Peter McWilliams said the firm, which was sun off from Bayer in November 2004, and its backers are delighted with “the highly innovative structure of this transaction”. He added that Boehringer “will do a superb job in taking the compound through the critical and demanding further steps in development”.