Mersana Therapeutics and Takeda Pharmaceutical Company Limited announced that they have entered a new, expanded, strategic partnership.  Under the terms of the agreement,  Takeda obtains the rights to Mersana’s lead product candidate, XMT-1522, outside the United States and Canada. XMT-1522 has the potential to address significant unmet needs and improve patient outcomes in multiple oncology indications.

The new agreement between the companies, signed in January, also expands an existing collaboration to provide Takeda with additional access to Mersana’s Fleximer® antibody-drug conjugate or ADC platform technology and grants Mersana an option, at the end of Phase I, to co-develop and co-commercialize one of these programs in the United States. In addition, the companies will co-develop new payloads for use with ADCs.

HER2-expressing tumors
XMT-1522 is a novel, investigational, Fleximer-based antibody-drug conjugate targeting HER2-expressing tumors, including breast, gastric and non-small cell lung cancers. The Fleximer immunoconjugate technology carries approximately 15 proprietary auristatin payload molecules. Preclinical data suggest that XMT-1522 may have anti-tumor activity in patients with HER2 low-expressing cancers as well as in patients with HER2 high-expressing cancers that do not respond to currently available HER2-targeting therapies. Mersana anticipates filing an Investigational New Drug application or IND for XMT-1522 with the U.S. Food and Drug Administration (FDA) in mid-2016.

“We believe XMT-1522 has the potential to make a dramatic difference for HER2 low-expressing patients who currently have limited treatment options, and are confident that our Fleximer-based technology can address significant patient needs not currently met by other ADC platform technologies,” said Anna Protopapas, President and Chief Executive Officer, Mersana. “Takeda’s knowledge of oncology and commitment to ADCs as a key therapeutic approach make the company the best partner for us to progress our transformative platform and advance XMT-1522 into the clinic.”

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During a poster session at the 2015 San Antonio Breast Cancer Symposium (SABCS), being held December 8-12, 2015 in San Antonio, Texas, scientists confirmed positive preclinical data for XMT-1522. According to Donald A. Bergstrom, M.D., Ph.D., Chief Medical Officer of Mersana, the drug candidate demonstrated significant anti-cancer activity in both HER2-positive and HER2 low-expressing tumor models refractory to currently available therapies.“These results demonstrate XMT-1522’s potential to expand the population of breast cancer patients for whom HER2-targeted therapy is appropriate, from the 20% currently diagnosed with HER2-positive breast cancer to the full range of patients with HER2 expression,” Bergstrom added.[1]

Development and commercialization
Takeda and Mersana will co-develop XMT-1522, and Mersana will lead execution of the Phase I trial. The company will also retain full commercial rights in the United States and Canada while Takeda will have rights in rest of world. Beyond development and commercialization of XMT-1522, the expanded partnership also grants Takeda access to additional targets within Mersana’s Fleximer-based ADC platform, with Mersana retaining the right to select one program at the end of Phase 1 for co-development and co-commercialization in the United States. Takeda and Mersana will also work together, leveraging Takeda’s proprietary small molecule libraries, to identify and develop novel payloads that both parties will be able to use in new ADC therapies.

“This is our third collaboration with Mersana in less than two years. We see great potential for Mersana’s Fleximer technology, combined with our oncology expertise and resources, to extend the benefits of targeted therapy with ADCs to underserved cancer patient populations,” noted Andrew Plump M.D., Ph.D., Chief Medical and Scientific Officer, Takeda. “We, along with the global oncology community, have made great strides in our fight against cancer, and we know that achieving our aspiration to cure cancer relies on great partnerships and innovation. We look forward to progressing these collaborations and, together, advancing the science of cancer care.”

Upfront payment
Takeda signed agreements with Mersana through its wholly owned subsidiary, Millennium Pharmaceuticals, under which, Mersana will receive an upfront payment of US$40 million and an additional payment of $20 million upon clearance of the IND for XMT-1522 by the FDA. Subject to the success of the XMT-1522 and ADC programs, Mersana is eligible to receive milestone payments of more than $750 million combined, as well as royalties. Takeda will also invest up to $20 million in equity in future rounds of Mersana financing.

Other collaborations
To advancing the company’s own pipeline, Mersana is accelerating the development of novel, Felximer-based, antibody-drug conjugate therapies through strategic collaborations with leading pharmaceutical and biotech companies.  In addition to the latest, expanded, agreement with Takeda, Mersana collaborates with Merck KGaA, and Asana BioSciences.

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