Mersana grabs a $35M round, posts ex-Millennium chief Protopapas at helm

Anna Protopapas

For more than a year now, NEA general partner David Mott has helmed Mersana Therapeutics, a Cambridge, MA-based biotech that has been working on next-gen antibody-drug conjugates. But this morning he's handing the reins over to longtime biotech vet Anna Protopapas (while remaining chairman) after organizing a $35 million B round that will be announced later this morning.

The B round also involved a personal investment from Elliott Sigal, the former R&D chief at Bristol-Myers Squibb ($BMY) and now a partner at NEA. Rock Springs Capital Management is also coming in as a new investor alongside Pfizer Venture Investments and Fidelity Biosciences.

Protopapas' last job was as president of Millennium, the iconic Boston biotech which has educated generations of biotech execs. Protopapas stepped aside from Millennium at the beginning of last October as Takeda was involved in remaking the unit over as Takeda Oncology. Her departure followed Takeda's first pact with Mersana. And now she'll be going back to work with some of her old colleagues at the redubbed unit, pursuing one of several partnerships the biotech has inked in recent years. Merck KGaA signed a $792 million deal with Mersana last summer.

"I'm excited about the Mersana technology," Protopapas told FierceBiotech ahead of today's release. "It overcomes a lot of challenges with first-generation ADCs."

Even without any additional partnership money coming in, Protopapas says that the B round funds a runway that stretches out into early 2017. Its first program should be in clinical development before the end of this year and there's enough of a cash commitment to get a second program into the clinic as well.

Mersana's investors have been drawn in by new "armed antibody" technology that promises to do the first generation of therapies in the class one better. It's relying on new linker technology which the biotech bills as more flexible and also more stable. One or more drug payloads can be dropped into the target cell with these Fleximers.

"You can really fine-tune the linker and the payload to the appropriate target," says Protopapas.

The technology was spotlighted in Mersana's 2012 award as a Fierce 15 company. Takeda initially signed on as a partner about a year ago and expanded the pact with a $300 million deal in January. Tillman Gerngross's Adimab, meanwhile, has been working with Mersana on developing new antibodies for their ADCs.

ADCs have been pioneered by companies like Roche ($RHHBY), its partner ImmunoGen ($IMGN) and Seattle Genetics ($SGEN). The focus now is on better design and going after some hard-to-hit tumor targets in oncology.

Special Report: FierceBiotech's 2012 Fierce 15 - Mersana Therapeutics

Suggested Articles

CNS Pharma says berubicin is the first anthracycline drug to cross the blood-brain barrier and could transform treatment of the highly invasive brain tumor.

Grid Therapeutics is planning to start trials of its lead cancer immunotherapy GT103 next year after raising $5 million in second-round financing.

The IPO comes as the Flagship startup prepares to test its lead inflammatory disease and anticancer microbial strains in humans.