** Brokerage Piper Sandler initiates coverage on drug developer Compass Therapeutics CMPX.O with an "overweight" rating and a PT of $12

** Brokerage says results from a mid-to-late stage trial, for co's lead drug, tovecimig, could potentially help boost shares

** Adds it will be a "win" if the drug shows more than 23% effect on improving overall response rate, which is the percentage of patients showing response to treatment

** Prior trial data for the drug when studied in combination with a type of chemotherapy paclitaxel in biliary tract cancer was promising

** This suggests its mid-to-late stage trial results (expected in March) should also report efficacy that will support regulatory approval - Piper Sandler

** Estimates peak US sales of $635 million if approved as a second line treatment for biliary tract cancer

** Co is also testing the drug in patients with colorectal cancer

** Stock has risen 71.3% in the past 12 months

(Reporting by Padmanabhan Ananthan)

((Padmanabhan.Ananthan@thomsonreuters.com;))