** Shares of drug developer Halozyme Therapeutics HALO.O gain ~13% to $51.5 premarket

** Co withdraws offer to buy German drug developer Evotec EVTG.DE for 11 euro per share, or 2 billion euros ($2.09 billion)

** U.S.-listed shares of Evotec EVO.O down about 17% at $4.43 before the bell

** HALO CEO Helen Torley says EVO "has been unwilling to engage with us to explore a potential combination and a company spokesperson has publicly commented that its goal is to remain an independent company"

** Adds that multiple requests to meet with the chairwoman of EVO's supervisory board were not accepted

** HALO announced its proposal to buy EVO on Nov 14

** As of last close, HALO up ~24% YTD and EVO down ~53% YTD

($1 = 0.9589 euros)

(Reporting by Bhanvi Satija in Bengaluru)

((Bhanvi.Satija@thomsonreuters.com; Outside U.S. +91 9873062788;))