Genentech Inc. Gets Idec Stake: The company has acquired a more than 7% stake in San Diego-based Idec Pharmaceuticals Corp. as part of an agreement to develop a drug to treat tumors. The deal calls for Genentech, a South San Francisco-based biotechnology firm, to eventually acquire an additional $17.5 million in Idec stock. The size of that stake will be determined by the future price of Idec shares. Based on Thursday's stock price, it would be about 28.5%. The companies said the deal has a potential value of about $57 million. The companies plan to promote the drug for lymphoma, a tumor made of tissues that hold white blood cells, in the United States and Canada, with Idec receiving a share of the profits. Genentech has rights to promote the drug throughout the rest of the world, excluding Asia, where it has some option rights.