Forest Laboratories has terminated its partnership with Daiichi Sankyo to co-promote the Japanese firm's antihypertensive combination treatment Azor in the USA, so it can concentrate on marketing its own products.

Forest is to post a one-time charge of $44.1 million, which is made a $26.6 million payment to Daiichi Sankyo related to the termination and $17.5 million for the unamortised portion of an initial payment. The pact to promote Azor, which is a combination of Pfizer’s off-patent calcium channel blocker Norvasc (amlodipine) and Daiichi Sankyo's angiotensin receptor blocker Benicar (olmesartan) and was approved in the USA last September, followed on from an earlier agreement to promote the latter, signed in 2002.

Howard Solomon, chief executive at Forest, said that "our decision to reallocate resources to our currently marketed products causes us to forego the opportunity to continue to participate in the promotion of Daiichi Sankyo's excellent product Azor". As for the original Benicar partnership, Forest will end co-promoting that drug at the end of May but will be entitled to income from Benicar profits until March 31, 2014.

Mr Solomon added that that the termination of any active promotion for Azor or Benicar leaves “the equivalent of an additional 500-person sales force which Forest requires” for the support of its products, notably the antidepressant Lexapro (escitalopram) and Namenda (memantine) for Alzheimer's disease. Both lose US patent protection early next decade.

As for Daiichi Sankyo, it will take sole responsibility for marketing Azor beginning in July. The company added that it has “expanded its cardiovascular sales capability in recent years” and is adding additional capacity in preparation of the potential launch of its investigational anti-platelet agent prasugrel, which is partnered with Eli Lilly.