The US Food and Drug Administration (FDA) has lifted the partial clinical hold on a Phase l study initiated by Mersana Therapeutics to investigate XMT-1522 for the treatment of solid tumours.

The hold was lifted after Mersana and the FDA reached an agreement on changes to be made to the trial protocol, including increased monitoring and exclusion of patients with advanced hepatic impairment from the trial.

Mersana has decided to make these amendments to the trial investigating its Dolaflexin ADC targeting sodium-dependent phosphate transport protein 2B (NaPi2b), XMT-1536, though the solution was not subject to a clinical hold.

In both trials of XMT-1522 and XMT-1536, Mersana plans to examine alternative dosing regimens.

The XMT-1522 trial is expected to start with a once-every-four-week dose regimen, which has already been used in the XMT-1536 trial to enable a comparison of relevant doses and their impact on the safety, efficacy and PK profile of the investigational drug.

“The trial’s primary goal is maximum-tolerated dose or recommended Phase ll dose.”

Mersana Therapeutics could evaluate additional regimens and is expected to release data from the XMT-1536 trial in the first half of next year.

The company’s Phase l trial of XMT-1522 intends to enrol 120 subjects.

The first in-human, single-group assignment, open-label, and dose-escalation and expansion trial aims to evaluate XMT-1522 in patients with advanced breast cancer and other advanced tumours expressing HER2.

During the trial, XMT-1522 will be administered in groups of patients who will receive doses that increase over time.

After the maximum-tolerated dose or recommended Phase ll dose is achieved, the trial will include new groups of patients to provide XMT-1522 at this fixed dose.

The trial’s primary goal is maximum-tolerated dose or recommended Phase ll dose.

Its secondary goals comprise time of maximum observed concentration of XMT-1522, maximum concentration of XMT-1522, anti-drug antibody and others.