Mersana Therapeutics Announces Topline Data from UPLIFT Clinical Trial in Patients with Platinum-Resistant Ovarian Cancer and Strategic Reprioritization

• UPLIFT clinical trial did not meet its primary endpoint
• Company realigns focus and significantly reduces expenses to extend cash runway into 2026
• Conference call today at 8:00 a.m. ET
  

CAMBRIDGE, Mass., July 27, 2023 (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 the UPLIFT clinical trial of upifitamab rilsodotin (UpRi) did not meet its primary endpoint. UpRi is an ADC targeting the sodium-dependent phosphate transport protein NaPi2b and was developed utilizing the company’s Dolaflexin platform.

UPLIFT was a single-arm clinical trial that enrolled platinum-resistant ovarian cancer patients with one to four prior treatment regimens. The primary endpoint for UPLIFT was the investigator-assessed objective response rate (ORR) in the NaPi2b-positive population. NaPi2b-positive status was defined by a tumor proportion score (TPS) of ≥75%. Secondary endpoints for the trial included the investigator-assessed ORR among all patients in the trial, duration of response (DOR), and safety and tolerability. The trial also included an assessment of ORR and DOR by independent radiology review (IRR).

UPLIFT enrolled a total of 268 patients, 141 of whom were determined to be NaPi2b positive. The median prior lines of systemic therapy among all patients was three, with 31% of the population having received four prior lines of treatment. Additionally, 84% of patients received prior bevacizumab and 69% received prior PARP inhibitor treatment.

Top-line results from UPLIFT as of the May 31, 2023 data cutoff date are as follows:

NaPi2b-Positive Population (n=141)

	Investigator Assessment	IRR Assessment
ORR, n (%) [95% confidence interval]	22 (15.6%) [10.0%, 22.7%]	23 (16.3%) [10.6%, 23.5%]
Partial Response, n (%)	20 (14.2%)	16 (11.3%)
Complete Response, n (%)	2 (1.4%)	7 (5.0%)
Median DOR, months	7.4	Not Reached