Mersana Therapeutics – 2012 Fierce 15

Nicholas Bacopoulos, CEO of Mersana Therapeutics

Based: Cambridge, MA
Founded: 2001
CEO: Nicholas Bacopoulos
Focus: Antibody-drug conjugates
Website: www.mersana.com

The Scoop: Mersana Therapeutics has turned more than a decade of research of its polymer platform for drug delivery into an emerging force in the hot field of antibody-drug conjugates (ADCs). The biotech grabbed some early validation for its preclinical work on ADC technology in a potential $270 million deal with Endo Pharmaceuticals ($ENDP) early this year. Fighting malignancies appears to be the top opportunity for the armed antibody drugs, and deep-pocketed New Enterprise Associates (NEA) led Mersana's $27 million Series A-1 round announced in July to fuel the biotech's work in building a pipeline of anti-cancer ADCs. While Mersana still has a lot to prove, expect the developer to surface often in the news as more industry players tap its technology to mount powerful and targeted attacks on disease.

What Makes it Fierce?

Mersana Therapeutics has restyled itself as a next-generation player in the ADC game, finding a nice alignment between a sizzling area in biotech and a polymer-based drug conjugation tech. Based on the early research of biochemist Mikhail "Misha" Papisov at Massachusetts General Hospital, the tech offers a vehicle for carrying a variety of compounds while overcoming the stability and solubility challenges that have hampered previous approaches to combining small molecules and antibodies.

Prior to this year, however, Mersana was largely quiet about its work in matching its "Fleximer" polymer with antibodies. Its earlier work focused on compounds such as XMT-1107, which marries its polymer tech with an analog of the highly toxic cancer drug fumagillin that causes CNS side effects as a standalone agent. Yet the company found perhaps an even larger opportunity in the ADC field, which has risen as one of the most promising areas of cancer drug development in recent years, with Seattle Genetics ($SGEN) gaining FDA approval for one such drug called Adcetris for treating two kinds of lymphoma in August 2011 and Roche ($RHHBY) generating promising Phase III data for its lead ADC called T-DM1 with partner ImmunoGen ($IMGN).

"Having done the conjugates with small molecules, we felt that we were close to creating our own ADC technology," Mersana CEO Nicholas Bacopoulos told FierceBiotech. "And indeed, when we combined antibodies and small molecules with our platform, we got some very efficient and very active ADCs and that's what formalized the decision."

Preclinical studies gave early evidence of the potential of its ADCs. In oncology, the drugs are generally defined as an antibody linked to cytotoxic agents, combining the tumor-homing prowess of the former with the cancer-killing properties of the latter. Mersana offers a new way of building the compounds, using its polymer chains as a "backbone" to which a targeted antibody and multiple molecules of an anti-cancer toxin or other drugs are strongly linked--rather than linking the antibody directly to the cytotoxin, which presents solubility hurdles that Mersana's ADCs avoid, Bacopoulos explained.

Endo Pharmaceuticals agreed to pay milestones of up to $270 million to Mersana for use of the biotech's platform to study armed antibodies against an undisclosed cancer target. The two companies were mum on the upfront fee paid to Mersana, but the endorsement from the pact raised the small biotech's profile in the ADC game and Bacopoulos says his company has entered into talks with other pharma suitors with interest in alliances.

In July, Mersana put together a $27 million Series A-1 round with marquee backing from new investors NEA and the venture fund of drug giant Pfizer ($PFE). The round, which brought the biotech's total venture haul to $77 million, gives the company financial firepower to build its own pipeline of armed antibodies build on its platform. David Mott, the NEA general partner and ex-CEO of AstraZeneca's ($AZN) biotech unit MedImmune, stepped up to chairman of Mersana and made the startup the first biotech investment from his firm's new $2.6 billion fund.

"We were looking for what would be the leading next-generation antibody-drug conjugate company… and that led us to Mersana," Mott told FierceBiotech. "We think that their Fleximer polymer technology has real advantages that could further open up the field beyond what Seattle Genetics, ImmunoGen and Genentech have achieved so far." 

On the heels of the financing announcement came news that Mersana joined forces with antibody discovery shop Adimab (a 2010 Fierce 15 company), forming an alliance that provides each of the startups with the ability to offer pharma partners a single and unique source for both targeted antibodies and the chemical components to assemble ADCs--one-stop shopping for armed antibodies. Tillman Gerngross, co-founder and CEO of Adimab, said in an interview that his group evaluated a number of technologies before committing to a partnership with Mersana.

Partners are taking a calculated gamble on Mersana. While the biotech has tested its earlier small-molecule conjugates in human studies, the company's antibody conjugates have never been tested in humans. Bacopoulos says the Series A-1 round provides his company with the capital to advance its own pipeline of ADCs to investigational new drug (IND) approval, meaning the next step would be to test the compounds in patients.

Investors: PureTech Ventures (which is the founding backer that worked early on with MGH's Papisov and others to launch the company), Fidelity Biosciences, ProQuest Investments, Rho Ventures, Cape Family Fund, Harris & Harris Group, Lansing Brown Investments, Pfizer Venture Investments and New Enterprise Associates.

-- Ryan McBride (Email | Twitter)

Mersana Therapeutics – 2012 Fierce 15
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