On Wednesday (5-29), the Food and Drug Administration approved the drug topotecan for the treatment of ovarian cancer in patients who do not respond well to chemotherapy and other treatments. SmithKline Beehcam Pharmaceuticals will begin selling the drug under the name Hycamtin in several weeks. The drug inhibits an enzyme that is essential for tumor growth and is expected to help women in advanced stages of the disease. Its 17 percent rate of shrinking tumors is comparable to that of the widely-used ovarian cancer drug taxol, but the side effects of topotecan may be more severe. Approximately 26,700 women are diagnosed with ovarian cancer each year, and 14,800 lose their lives fighting the disease.