Johnson & Johnson, the US healthcare products group, is to take a $1bn (£600m) minority stake in Elan and commit at least $500m more to help fund development of the lossmaking Irish-American’s biotech company’s late-stage products for Alzheimer’s disease.

The US group will acquire an 18.4 per cent stake in Elan, and assume majority control of its two leading experimental Alzheimer’s products, which are being developed in a partnership with Wyeth, a large US drugs company.