Mersana Therapeutics Announces Initiation of the UPGRADE Phase 1 Platinum Combination Cohort for UpRi in Platinum-Sensitive Ovarian Cancer

UPGRADE umbrella study designed to evaluate UpRi in combination with other therapies, starting with carboplatin

CAMBRIDGE, Mass., July 28, 2021 (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 the initiation of patient dosing in UPGRADE, a Phase 1 combination dose escalation umbrella study to evaluate the safety and efficacy of upifitamab rilsodotin (UpRi, previously XMT-1536) in combination with other ovarian cancer therapies. The initial arm of this umbrella study is evaluating carboplatin in combination with UpRi followed by continuation of UpRi monotherapy in patients with platinum-sensitive ovarian cancer.

“The initiation of UPGRADE is another important milestone for Mersana as we work to build UpRi into a foundational medicine in the treatment of ovarian cancer,” said Anna Protopapas, President and Chief Executive Officer of Mersana Therapeutics. “To date, UpRi data has demonstrated clinically meaningful activity and a differentiated tolerability profile without severe neutropenia, peripheral neuropathy or ocular toxicity in patients with heavily pretreated platinum-resistant ovarian cancer. The initiation of the UPGRADE umbrella study is a critical first step in evaluating the potential of UpRi in earlier lines of therapy.”

The UPGRADE Phase 1, open-label, dose-escalation portion of the study will determine the maximum tolerated dose (MTD) and safety and tolerability of a once-every-four-week (Q4W) administration of UpRi in combination with carboplatin for six cycles followed by continuation of UpRi monotherapy in patients with platinum-sensitive high-grade serous ovarian cancer following 1-2 prior platinum-based regimens. Patients will not be preselected for NaPi2b expression; however, archival or fresh tissue will be required for retrospective assessment of expression. Upon completion of the dose-escalation portion of the study, the Company plans to initiate the expansion portion to assess both tolerability and efficacy and inform the further development of UpRi in a broader and earlier-line patient population.

“We are excited to initiate UPGRADE and are beginning with a platinum combination because platinum remains the mainstay therapy in earlier-line platinum-sensitive ovarian cancer. UPGRADE is intended to allow us to assess the advantages of combining with carboplatin for six cycles and replacing paclitaxel, an agent that carries significant toxicities. We will also evaluate the benefit of continuing treatment with UpRi as a single agent beyond the six cycles of combination therapy,” said Arvin Yang, M.D., Ph.D., Senior Vice President and Chief Medical Officer of Mersana Therapeutics. “In the future, we plan to evaluate non-platinum-based combinations in this umbrella study to assess the potential of bringing UpRi to patients who do not benefit from platinum. We believe UpRi’s differentiated tolerability profile without the overlapping toxicities commonly seen with other ADC platforms may provide a significant advantage as a combination therapy for people living with ovarian cancer.”

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, upifitamab rilsodotin (UpRi), is a Dolaflexin ADC targeting NaPi2b and is being studied in UPLIFT, a single-arm registration strategy in patients with platinum-resistant ovarian cancer, as well as in the expansion portion of a Phase 1 proof-of-concept clinical study in patients with 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 XMT-1660, a Dolasynthen ADC targeting B7-H4, as well as XMT-2056, 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, the design, progression and timing of its clinical trials, and the development and potential of our pipeline of innovative ADC candidates. Forward-looking statements generally can be identified by terms such as “aims,” “anticipates,” “believes,” “contemplates,” “continues,” “could,” “designed to,” “efforts,” “estimates,” “expects,” “goal,” “intends,” “may,” “on track,” “opportunity,” “plans,” “poised for,” “possible,” “potential,” “predicts,” “projects,” “promises to be,” “seeks,” “should,” “strategy,” “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 the results of our ongoing or future clinical studies may be inconclusive with respect to the efficacy of our product candidates, that we may not meet clinical endpoints with statistical significance or there may be safety concerns or adverse events associated with our product candidates, that preclinical testing or early clinical results may not be predictive of the results or success of ongoing or later preclinical or clinical studies, that the identification, development and testing of the Company’s product candidates and new platforms will take longer and/or cost more than planned, and that our clinical studies may not be initiated or completed on schedule, if at all, as well as those listed in the Company’s Annual Report on Form 10-Q filed on May 10, 2021, with the Securities and Exchange Commission (“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.

Contact:
Investor & Media Contact
Sarah Carmody, 617-844-8577
scarmody@mersana.com