Mersana Therapeutics Nabs $35 Million And A New CEO

March 2, 2015

By Alex Keown, BioSpace.com Breaking News Staff

CAMBRIDGE, Mass. –Mersana Therapeutics, Inc., a manufacturer of antibody drug conjugates, nabbed $35 million in financing and named a new president and CEO on Monday.

The $35 million, raised through Series B-1 financing, will be used to fund the advancement of the company's pipeline products, which is based on the antibody-drug conjugate Fleximer platform used to target cancerous cells. Mersana will seek its first investigational new drug filing based on the Fleximer platform later this year. The platform allows for the attachment of an extensive range of anti-tumor payloads to Fleximer. The ADC is designed to remain stable in the bloodstream and to release the drug payloads once inside the targeted cell.

The company is banking on the Fleximer platform's ability to deliver diverse payloads, significantly increase drug loading per antibody and improved physicochemical properties and facile manufacturing.

In January Mersana announced a continuing partnership with Takeda Pharmaceuticals (TKPYY) to expand its Fleximer research. Since 2014 the two companies have been conducting pre-clinical, proof-of-concept studies for several Fleximer-ADCs against an undisclosed oncology target under a research license to Mersana's Fleximer-ADC technology. Takeda has already exercised an option to license commercial rights for the first drug candidate developed under this collaboration, which was announced in October 2014. The deal has a potential to earn more than $300 million if it's successful.

Takeda provided an upfront payment to Mersana for the right to harness Fleximer technology to develop ADC candidates for oncology use. Mersana is conducting research and creating ADCs that are conjugates of Takeda's antibodies and Mersana's platforms, which combine a cytotoxic payload with the Fleximer polymer and custom linkers.

Mersana's proprietary polymer payload platforms include the auristatin-polymer conjugate Dolaflexin; Vindeflexin, a vindesine-polymer conjugate; and Cytoflexin, a tubulysin-polymer conjugate.

Mersana also entered into a working relationship with Merck & Co. (MRK) last year to use Fleximer technology to generate ADCs for multiple undisclosed targets. Both parties have agreed to test a variety of ADCs by utilizing Mersana's platform technologies and several cytotoxic agents as conjugates.

In addition to the new funding, the Mersana announced it had tapped Anna Protopapas, former president of Millennium Pharmaceuticals, a division of Takeda Pharmaceutical Company, to lead Mersana for the foreseeable future. Protopapas, who has worked with Mersana and its pipeline while at Millennium, said she was excited about the future of the company's Fleximer platform.

"Mersana's Fleximer-ADCs are a best-in-class approach which overcomes the limitations of other ADC technologies. I am very encouraged by the results to date and look forward to working alongside the team at Mersana to translate the technology into important therapies for patients," Protopapas said in a press release.

During her time at Millennium, Protopapas led the company's oncology business. Protopapas was also vice president of global business development, where she was responsible for all global acquisitions, partnering, licensing and venture investing.

In addition to serving as president and CEO, Protopapas will serve on the company's board of directors. Joining her on the board will be Elaine V. Jones, Ph.D., Executive Director of Pfizer Venture Investments.

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