London: Pfizer Inc is taking a 3 per cent stake in Sosei Group Corp. and has entered into a drug discovery collaboration with the Japanese company’s UK unit to develop new medicines. Pfizer will purchase $33 million of newly issued Sosei shares, representing about 3 per cent of the enlarged Sosei share capital, the Tokyo-based company said in a statement today. Pfizer will pay a 7,950 yen ($65) per share, a 25 per cent premium to Friday’s closing price. For Sosei’s UK unit Heptares, based in Hertfordshire, England, the partnership with Pfizer adds to pacts with AstraZeneca Plc, Merck & Co. and Takeda Pharmaceutical Co. Last week, Teva Pharmaceutical Industries Ltd. said it would collaborate with Heptares to develop drugs for migraines.