By Karen Rebelo and Zeba Siddiqui MUMBAI (Reuters) – Investors in India’s $15 billion pharmaceutical industry are favoring smaller firms with little or no exposure to the United States, where increasingly tight regulatory controls have burnt two of the country’s biggest drugmakers over the past month. Heavyweight generics makers, led by Sun Pharma and Dr Reddy’s Laboratories, have long been seen as a conservative bet for domestic and foreign funds eyeing India, as these firms rely on the United States – the world’s biggest pharmaceuticals market – for the bulk of their revenue.