Mersana Therapeutics Inc, based in Cambridge, MA, USA and Takeda Pharmaceutical Company Limited have expanded their ongoing collaboration to create novel Fleximer® antibody-drug conjugate (ADC) drug candidates to include additional oncology-relevant targets.

Mersana focuses on engineering antibody-drug conjugates (ADCs) designed to maximize the potential of new and established therapeutic classes.

Biodegradable polymer system
The company’s next-generation Fleximer® antibody-drug conjugate (ADC) technology is based on the company’s proprietary biodegradable polymer system known as Fleximer and a wide variety of linkers that allow for the attachment of an extensive range of anti-tumor payloads to Fleximer. 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.

The company’s novel linker systems are designed to be stable in the bloodstream and to release the drug payloads once inside the targeted cell. The Fleximer-ADC technology provides several key advantages over currently available approaches. For example, the technology offers researchers the ability to deliver diverse payloads, the opportunity to significantly increase drug loading per antibody as well as significantly improved physicochemical properties and facile manufacturing.

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Proprietary polymer payload platforms
In addition to the Fleximer-ADC technology, Mersana has developed proprietary polymer payload platforms include Dolaflexin™ (an auristatin-polymer conjugate), Vindeflexin™ (a vindesine-polymer conjugate) and Cytoflexin™ (a tubulysin-polymer conjugate).

Takeda signed an agreement with Mersana through its wholly owned subsidiary Millennium Pharmaceuticals Inc. Under that agreement 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. Mersana remains eligible to receive milestone payments and royalties on worldwide net sales of any resulting ADC products. When Takeda exercised its option for commercial rights to the first ADC product Mersana received a license fee.

Based on the ongoing agreement, Mersana is eligible to receive additional upfront and milestone payments potentially totaling over $300 million under the expanded collaboration subject to future success of the programs. The partners’ collaboration was announced in April 2014 and since then Mersana and Takeda 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 expansion of our collaboration with Mersana is a testament to the importance of partnership in innovating new treatments for cancer,” noted Christopher Claiborne Ph.D. Head of the Oncology Drug Discovery Unit at Takeda. “Now encompassing multiple therapeutic targets and potential drug candidates we look forward to further advancing the next-generation of ADCs under our expanded collaboration with Mersana with the goal of bringing new therapies to patients around the world.”

“We are delighted to expand our relationship with Takeda and are excited about the prospects of Fleximer-ADC candidates that have progressed well into preclinical development” said Eva M. Jack Chief Business Officer of Mersana Therapeutics. “Our highly productive strategic partnership with Takeda affords us the ability to advance potential new medicines with superior properties closer to the clinic as well as enhance our Fleximer platform.”