U.S. regulators have approved the first generic version of one of the first very effective – and expensive – cancer drugs, Gleevec, which costs about $10,000 a month. The Food and Drug Administration granted a subsidiary of Indian drugmaker Sun Pharmaceutical Industries Ltd. approval to sell generic Gleevec, known as imatinib mesylate, in 100-milligram and 400-milligram pills for chronic myeloid leukemia.