Cambridge, Massachusetts-based Mersana Therapeutics Inc, a provider of Fleximer antibody-drug conjugate technology, has secured $35 million in Series B-1 financing. New Enterprise Associates led the round with participation from Rock Springs Capital Management, Elliott Sigal, former head of R&D at Bristol-Myers Squibb, Pfizer Venture Investments and Fidelity Biosciences. Also, Mersana has appointed Anna Protopapas as president and CEO. And, Protopapas and Dr. Elaine V. Jones, executive director of Pfizer Venture Investments, have been added to Mersana’s board of directors.