Dr. Reddy’s Laboratories Ltd., India’s biggest drugmaker, is developing eight generic medicines using biotechnology and plans to release one for sale a year, challenging companies such as Roche Holding NV and Amgen Inc. Reddy’s may double the number of people in its biotech division to about 340 in the next two years and plans to spend about $20 million bolstering production capacity there, Chief Executive Officer G.V. Prasad said yesterday. [...] Reddy’s, which had sales of $1.42 billion in the year ended March 31, generates less than 5 percent of revenue from biotech drugs. Biotechnology, or the use of cellular material to make medicines, may contribute as much as 30 percent to revenue within a decade as the company starts selling Reditux outside India and patents on other biologics expire, allowing Reddy’s to copy them.