** U.S. drug developer CERo Therapeutics' CERO.O shares rise 7.2% to $3.55 in premarket trade

** Co says its experimental drug for a type of blood drug, CER-1236 cleared a key safety milestone, allowing higher dosing in its ongoing clinical trial

** CERO's CER-1236 is being tested in patients with acute myeloid leukemia, a fast-growing cancer of the blood and bone marrow

** CERO says no serious side effects in initial patient group, clears path for higher dose

** Safety panel clears start of second cohort with higher initial dose - CERO

** CERO says it is not for sale, correcting recent media report

** Co says focus remains on dose escalation trial, not seeking partnerships

** Up to last close, stock down ~97% YTD

(Reporting by Sahil Pandey)

((Sahil.Pandey@thomsonreuters.com))