It’s been a trying 2023 for Mersana Therapeutics and the year doesn’t appear to be ending on a high note. The antibody-drug conjugate (ADC) biotech and Merck KGaA have severed ties for a licensing pact related to one of Mersana’s tech platforms.
The pact, which had been inked in 2014, was terminated Dec. 15 by “mutual agreement,” according to Securities and Exchange Commission documents. The collaboration and commercial license agreement centered around dolaflexin, one of Mersana’s proprietary payload platforms.
Under the 2014 agreement, Merck provided monoclonal antibodies to Mersana so the biotech could generate ADCs and conduct discovery and preclinical development activities. Financial details of the initial agreement—which had been amended since its inception—were not disclosed.
The termination doesn’t impact a 2022 discovery licensing agreement between the two, in which Merck paid $30 million upfront to use Mersana’s Immunosynthen STING-agonist ADC platform. The deal encompasses up to two potential targets and offers Mersana the chance to make up to $800 million in biobucks, plus royalties on global net sales of any approved ADCs developed under the agreement.
Like many other biotechs, it’s been a challenging year for Mersana.
This March, the FDA hit Mersana with a clinical hold after the biotech voluntarily suspended an early-stage cancer trial due to a death tied to an ADC dubbed XMT-2056. The biotech received good news at the end of October when the FDA freed the trial from the hold.
Based on trial data, Mersana lowered the starting dose for the phase 1 dose-escalation design.
XMT-2056, a systemically administered immunosynthen STING-agonist ADC, will continue being tested in patients with advanced or recurring solid tumors expressing HER-2, such as breast, gastric, colorectal and non-small cell lung cancers. The ADC has snagged orphan-drug designation from the FDA in gastric cancer and also garnered attention from GSK.
Last summer, the pharma inked a global pact with Mersana, paying $100 million upfront for the exclusive option to co-develop and commercialize XMT-2056. To date, GSK has not exercised the option.
The lifting of the hold is great news for the XMT-2056 program, but Mersana let go of another med earlier this year due to a similar FDA action. In June, the agency slapped a partial clinical hold on lead ADC UpRi.
The regulatory halt came after the therapy was tied to a higher rate of serious bleeding events in treated patients with platinum-resistant ovarian cancer than in the background population. The bleeding events included five deaths.
The biotech suffered yet another blow in July when poor efficacy results from the expansion study for UpRi sent the biotech into a tailspin and prompted layoffs for half of the biotech's team. Given the results, the company dropped the drug.