** J.P.Morgan upgrades drug developer Mersana Therapeutics
Inc MRSN.O to "overweight" from "neutral"
** Brokerage says MRSN's late-stage study testing its
experimental drug, UpRi, to treat a type of ovarian cancer is
"highly powered"
** JPM believes concerns related to safety risks around
pneumonitis are "overblown" in a disease of high unmet needs
** Adds UpRi has potential to become "key standard of care
option in a significant piece of ovarian cancer market" - JPM
** All 8 brokerages covering stock rate it "buy" or higher;
their median PT is $14.5
** Up to Wednesday's close, MRSN up ~16.4% in past 12 months
(Reporting by Mariam Sunny)
((Mariam.ESunny@thomsonreuters.com;))