Based in Cambridge, Massachusetts, biopharmaceutical company Mersana Therapeutics (NASDAQ:MRSN) announced positive interim data from its phase 1 clinical study of XMT-1536 for the treatment of ovarian cancer. The expansion portion of the study involving 20 evaluable patients with ovarian cancer achieved a 35% objective response rate including a 10% complete response rate. Objective response rate refers to the attainment of a pre-specified level of tumor reduction. An additional patient showed an unconfirmed partial response.

The XMT-1536 therapy was well-tolerated by the patients and no new safety issues arose. According to management, other product candidates from different companies have witnessed dose-limiting toxicities such as severe neutropenia, neuropathy, and ocular toxicity.

The drug was also evaluated in seven non-small cell lung cancer (NSCLC) adenocarcinoma patients, but the company concluded that more data is necessary to assess the antitumor activity in lung cancer.

Mersana Therapeutics SEC Filings

Disease control rate of 80% is encouraging

Mersana uses its proprietary antibody-drug conjugates (ADC) platforms to develop new ADCs to improve the lives of people that are battling cancer. The company’s other product candidate, XMT-1592, is targeting NaPi2b-expressing tumors and is in the dose escalation portion of a separate phase 1 study.

The expansion portion of the XMT-1536 study involves patients with ovarian, fallopian tube, or primary peritoneal cancer who had received as many as four lines of prior therapy in addition to patients with NSCLC adenocarcinoma. The patients received doses of either 36mg or 43mg every four weeks. Forty percent of the ovarian cancer patients achieved stable disease (SD) and the disease control rate (DCR) was 80%. Disease control rate includes patients who experienced a complete response, partial response, or stable disease status.

President and CEO Anna Protopapas said, “These data demonstrate not only that XMT-1536, our first-in-class Dolaflexin ADC targeting NaPi2b, can deliver confirmed complete responses, partial responses and durable stable disease in platinum-resistant ovarian cancer, but also that these responses can deepen over time in a patient population with poor prognosis and limited treatment options.”

Looking ahead

The company will be presenting the data along with Dr. Debra Richardson from the Stephenson Cancer Center at the University of Oklahoma at the American Society of Clinical Oncology’s 2020 Virtual Scientific Program on May 29th, 2020 at 8:00am ET. It also plans to present more mature data from the ongoing study during the second half of this year.

Mersana Therapeutics stock jumped 69% to $18.19 in very heavy volume on May 27th in response to the favorable proof of concept data. The stock is up 135% year-to-date and is closing back in on its May 2018 all-time high of $23.96. The small cap biotechnology company is scheduled to report second quarter financial performance on August 13th.

Mersana Therapeutics SEC Filings


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