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 IrishAmerican'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.