** Shares of cancer drugmaker Verastem VSTM.O rise 3% to $6.89 in afternoon trading

** VSTM says the U.S. FDA approved its combo therapy to treat patients with a rare type of ovarian cancer

** The therapy, under the brand name Avmapki Fakzynja Co-pack, is for adults with low-grade serous ovarian cancer who have received prior treatment and have a mutated KRAS gene

** Jefferies analyst Kelly Shi said the therapy has shown better results than traditional chemotherapy and a commonly used treatment, Novartis' NOVN.S trametinib, sparking "strong adoption enthusiasm" among doctors

** Therapy will be available in one week - VSTM

** As of last close, stock up 29% YTD

(Reporting by Kamal Choudhury in Bengaluru)

((Kamal.Choudhury@thomsonreuters.com;))