Mersana Therapeutics Reports Preclinical Data from Immunosynthen STING-Agonist ADC Platform and Pipeline

• Immunosynthen ADCs activate the STING pathway in both tumor-resident immune cells and in the tumor cells, resulting in robust anti-tumor activity and offering a differentiated approach from other innate immune activators 

CAMBRIDGE, Mass., Nov. 11, 2020 (GLOBE NEWSWIRE) -- Mersana Therapeutics, Inc. (NASDAQ:MRSN), a clinical-stage biopharmaceutical company focused on discovering and developing a pipeline of antibody-drug conjugates (ADCs) targeting cancers in areas of high unmet medical need, today announced that preclinical mechanistic data from its novel Immunosynthen STING-Agonist ADC platform is available as a live e-poster in the virtual poster hall at the 35th Annual Meeting of the Society for Immunotherapy of Cancer (SITC) taking place from November 9-14, 2020.

“These data highlight the novel research undertaken by our scientists to elucidate the mechanism of activation of the STING pathway in the tumor. It has been widely believed that the STING pathway is silenced in cancer cells; however, these data show that the anti-tumor activity of STING-agonist ADCs involves the activation of the STING pathway in both tumor-resident immune cells and in tumor cells, both in an antigen binding-dependent manner. This targeted one-two punch provides the potential for enhanced anti-tumor activity with a STING-agonist ADC when compared to other innate immune pathways that activate only the immune cells” said Timothy B. Lowinger, Ph.D., Chief Science and Technology Officer of Mersana Therapeutics.

“Building on our expertise in ADC design and optimization, we have developed the Immunosynthen STING-Agonist ADC platform and have validated its potential across multiple targets,” said Anna Protopapas, President and Chief Executive Officer of Mersana Therapeutics. “We look forward to providing a more thorough overview of the platform as well as our pipeline of Immunosynthen STING-agonist ADCs during our webinar on November 16, 2020.”

This preclinical research demonstrates that the anti-tumor activity of STING-agonist ADCs involves the activation of the STING pathway in tumor cells as well as tumor-resident immune cells. This dual-targeted delivery is achieved through target receptor internalization into tumor cells, and Fcγ receptor (FcγR)-mediated internalization into immune cells, facilitated by ADC binding to the tumor antigen.

The contribution of both cell types to efficacy was demonstrated by evaluating STING pathway activation by, and anti-tumor activity of ADCs harboring either wild type (wt) or mutant Fc (deficient in FcγR binding), in both wt and STING knockout (ko) cancer cells, using immune cell – tumor cell co-cultures and in vivo tumor models. Together, these findings demonstrate the direct contribution of STING activation of both immune cells and tumor cells to the antitumor activity of Immunosynthen ADCs.

Details of the poster display are as follows:

Poster Title: Tumor cell-intrinsic STING pathway is activated in the presence of cues from immune cells and contributes to the anti-tumor activity of tumor cell-targeted STING agonist antibody-drug conjugates
Abstract Number: 620
E-poster Available: 9 a.m. – 5 p.m. ET, November 11-14, 2020.
Location: Virtual Poster Hall

About Mersana Therapeutics
Mersana Therapeutics is a clinical-stage biopharmaceutical company using its differentiated and proprietary ADC platforms to rapidly develop novel ADCs with optimal efficacy, safety and tolerability to meaningfully improve the lives of people fighting cancer. Mersana’s lead product candidate, XMT-1536, is in the expansion portion of a Phase 1 proof-of-concept clinical study in patients with ovarian cancer and NSCLC adenocarcinoma. XMT-1592, Mersana’s second ADC product candidate targeting NaPi2b-expressing tumors, was created using Mersana’s customizable and homogeneous Dolasynthen platform and is in the dose escalation portion of a Phase 1 proof-of-concept clinical study. The Company’s early stage programs include a B7-H4 targeting ADC, as well as a STING-agonist ADC developed using the Company’s Immunosynthen platform. In addition, multiple partners are using Mersana’s Dolaflexin platform to advance their ADC pipelines.

Forward-Looking Statements

This press release contains “forward-looking” statements within the meaning of federal securities laws. These forward-looking statements are not statements of historical facts and are based on management’s beliefs and assumptions and on information currently available to management. Forward-looking statements include information concerning the Company’s business strategy and the design, progression and timing of its clinical trials. Forward-looking statements generally can be identified by terms such as “aims,” “anticipates,” “believes,” “contemplates,” “continues,” “could,” “estimates,” “expects,” “goal,” “intends,” “may,” “on track,” “plans,” “possible,” “potential,” “predicts,” “projects,” “seeks,” “should,” “target,” “will,” “would” or similar expressions and the negatives of those terms. Forward-looking statements represent management’s beliefs and assumptions only as of the date of this press release. The Company’s operations involve risks and uncertainties, many of which are outside its control, and any one of which, or combination of which, could materially affect its results of operations and whether the forward-looking statements ultimately prove to be correct. Factors that may materially affect the Company’s results of operations and whether these forward-looking statements prove to be correct include, among other things, that preclinical testing may not be predictive of the results or success of ongoing or later preclinical or clinical trials, that the development and testing of the Company’s product candidates and new platforms will take longer and/or cost more than planned, and that the identification of new product candidates will take longer than planned, as well as those listed in the Company’s Annual Report on Form 10-K filed on February 28, 2020, with the Securities and Exchange Commission (“SEC”), the Company’s Quarterly Report on Form 10-Q filed on May 8, 2020, with the SEC and subsequent SEC filings. In addition, while we expect that the COVID-19 pandemic might adversely affect the Company’s preclinical and clinical development efforts, business operations and financial results, the extent of the impact on the Company’s operations and the value of and market for the Company’s common stock will depend on future developments that are highly uncertain and cannot be predicted with confidence at this time, such as the ultimate duration of the pandemic, travel restrictions, quarantines, physical distancing and business closure requirements in the U.S. and in other countries, and the effectiveness of actions taken globally to contain and treat the disease. Except as required by law, the Company assumes no obligation to update these forward-looking statements publicly, or to update the reasons actual results could differ materially from those anticipated in the forward-looking statements, even if new information becomes available in the future.

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