May 20 (Reuters) - Zymeworks Inc said on Friday its board had rejected investment firm All Blue Capital's $773 million acquisition offer, saying it undervalued the cancer therapy developer.

Reuters in April reported All Blue's $10.50 per share bid to Zymeworks that represented a 116% premium to the stock's last closing price at that time.

Shares of Canada-based Zymeworks - which develops antibody treatments for types of cancer and has no approved products on the market - had lost nearly 70% of their value in 2022 before the offer.

Shares of biotech companies have had a rough few months, with investors targeting the private markets more than the public, as equity markets suffer from fears of aggressive monetary policy tightening to tame soaring inflation.

"This non-binding, unsolicited activist proposal was timed opportunistically during a period of substantial market dislocation, and prior to several important near-term events," Zymeworks Chief Executive Officer Kenneth Galbraith said. (Reporting by Manas Mishra in Bengaluru; Editing by Shinjini Ganguli)