** Shares of drug developer Summit Therapeutics SMMT.O rise 6.2% to $23.50 premarket

** Co says it is collaborating with Pfizer PFE.N to study its experimental drug ivonescimab in combination with several of Pfizer's targeted cancer therapies called antibody drug conjugates (ADCs) across different types of tumors

** Under the agreement, SMMT will provide ivonescimab for the studies, which PFE will conduct

** Studies expected to start mid-year

** SMMT's drug has previously showed better survival rates in some lung cancer patients in a trial in China, outdoing Merck's MRK.N blockbuster Keytruda

** Stock has risen 5x in the last 12 months after outperforming Keytruda - the world's biggest drug with more than $29 billion in sales last year - in those studies

(Reporting by Padmanabhan Ananthan)

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