AstraZeneca is paying Merck & Co $647 million in order to get back the rights to a number of products covered by the firms’ US joint venture.

The Anglo-Swedish drugmaker is exercising an option which will see Merck relinquish the rights to Entocort (budesonide) for Crohn's disease and ulcerative colitis, as well as the antihypertensives Atacand (candesartan cilexetil) and Plendil (felodipine). The agreement also covers certain products still in development, including the oral antiplatelet treatment Brilinta (ticagrelor) and the gastrointestinal drug AZD3355 (lesogaberan).

The value of the payout was calculated in 2008 and this pact has triggered a second option which could see AstraZeneca to repurchase Merck's share in antiulcerant blockbuster Nexium (esomeprazole) and Prilosec (omeprazole). That option is exercisable in 2012, or 2017, “or if combined annual sales of the two products fall below a minimum amount”.

The JV began in 1982 between the Swedish company Astra and Merck and was restructured in 1998 just before the former group merged with Zeneca. Ending the alliance with the US major will mean more cash in AstraZeneca’s pocket; for example the company noted that it made contingent payments in respect of Prilosec and Nexium amounting to $726 million in 2009.