Mersana's phase 1 ADC cancer trial breaks free of FDA hold

In a year riddled with obstacles and adverse events, Mersana Therapeutics finally has some good news: The FDA has lifted a clinical hold on a phase 1 trial for the antibody-drug conjugate (ADC) XMT-2056.

This March, the FDA hit Mersana with the hold after the biotech voluntarily suspended the early-stage cancer trial due to a death tied to XMT-2056.

Based on trial data, Mersana is now lowering the starting dose for the phase 1 dose-escalation design, Mersana President and CEO Martin Huber, M.D., said in an Oct. 31 release.

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.

The asset has 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 hold impacted both a phase 3 trial and a phase 1 dose-expansion study, halting recruitment for both.  

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 to half of the biotech's team. Given the results, the company dropped the drug.