Millennium Pharmaceuticals, Inc., a wholly-owned subsidiary of Takeda Pharmaceutical Company Limited has exercised an option to license commercial rights for its first novel Fleximer® antibody-drug conjugate or ADC developed as part of their collaboration with Mersana Therapeutics, announced earlier this year.

Mersana’s next-generation Fleximer technology is based on the company’s proprietary biodegradable polymer system, and includes a wide variety of linkers that allow for the attachment of an extensive range of anti-tumor payloads. As an example, once loaded with drug(s), Fleximer is then attached through a stable linker that is different from the drug linker(s) to the antibody or antibody alternative to create a Fleximer-ADC.

Unique properties
These novel linker systems are designed to be stable in the bloodstream and to release the drug payloads once inside the targeted cell. In comparison to currently available approaches, the Fleximer-ADC technology provides several key advantages. Among these benefits is the ability to deliver diverse payloads, he opportunity to significantly increase drug loading per antibody, significantly improved physicochemical properties and facile manufacturing. Today these properties not achievable with direct conjugation ADC technologies.  Mersana’s proprietary polymer payload platforms include Dolaflexin™, an auristatin-polymer conjugate; Vindeflexin™, a vindesine-polymer conjugate; and Cytoflexin™, a tubulysin-polymer conjugate.

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Commercial license
Under the original April 2014 agreement, Millennium/Takeda provided an upfront payment to Mersana for the right to utilize Fleximer technology to develop novel ADC candidates for indications in oncology. Mersana is currently conducting research and creating ADCs that are conjugates of Takeda’s antibodies and Mersana’s diverse payload platforms, which combine a cytotoxic payload with the Fleximer polymer and custom linkers. In addition to providing antibodies, Takeda is responsible for product development, manufacturing and commercialization of any Fleximer-ADC products.

Over the past seven months, Mersana and Millennium/Takeda have been conducting pre-clinical, proof-of-concept studies for several Fleximer-ADCs against an undisclosed oncology target using  Mersana’s Fleximer-ADC technology. With the exercise of the commercial license, Mersana receives a license fee and is eligible for development and regulatory milestone payments and royalties on net sales.

“Our productivity and Takeda’s license for the Fleximer-ADC’s commercial rights speak to the Fleximer polymer and proprietary conjugation technology providing an optimal platform for the development of next-generation ADCs,” said Timothy B. Lowinger, Ph.D., Chief Scientific Officer of Mersana. “Not only is Mersana delivering unique, highly differentiated Fleximer-ADCs to our industry-leading partners, but we are actively developing an internal pipeline with superior antibodies conjugated to our payload platforms, as well.”

“The collaboration with Mersana has progressed rapidly and has proven beneficial for our discovery research efforts,” noted Christopher Claiborne, Ph.D., Head of the Oncology Drug Discovery Unit at Takeda. “We have been impressed with the results generated through use of the Fleximer platform, and we are looking forward to the continued success of this collaboration.”