Corvus Pharmaceuticals Inc., which was quietly incorporated late last year with a $33.5 million series A, doubled down in its second raise, closing a $75 million series B from a syndicate led by Rock Springs Capital Management that included Fidelity Management and Research Co., Blackrock, accounts managed by T. Rowe Price, Jennison Associates on behalf of certain clients, Roche Venture Fund, Cormorant Asset Management, Sphera Funds Management, Venbio Select and Cowen Private Investments.