Netherlands-based immuno-oncology firm Merus has started dosing patients in a Phase II clinical trial of its investigational candidate MCLA-128 for treatment of HER2-positive and hormone receptor positive/HER2-low metastatic breast cancer (MBC).
MCLA-128 is an IgG bispecific antibody featuring enhanced antibody-dependent cellular cytotoxicity (ADCC) that targets HER2 and HER3 receptors.
The drug candidate is being designed to inhibit the HER3 signalling pathway through a 'dock and block' mechanism, which involves it docking onto a specific region of the HER2 receptor.
The open-label, multi-centre, international Phase II trial will assess MCLA-128 as a combination therapy in a total of 120 subjects across two cohorts in the US and Europe.
In the first cohort of patients with HER2-positive MBC progressing on anti-HER2 therapies, MCLA-128 will be administered in combination with trastuzumab and chemotherapy.
A combination of the investigational candidate and endocrine therapy will be tested in the second cohort with MBC patients having confirmed hormone receptor positive and HER2-low status who are progressing on hormone therapies and CDK4/6 inhibitors.
Both cohorts will measure clinical benefit rate at 24 weeks as the primary endpoint of the trial.
Merus CEO Ton Logtenberg said: “Initiation of the Phase II clinical trial in patients with HER2-positive MBC populations and hormone receptor-positive/HER2-low MBC populations represents another key milestone for Merus.
“With promising single-agent activity observed in heavily-pretreated patients underscoring the potential of MCLA-128 in MBC, this study is designed to elucidate the activity of this important HER2/HER3-targeted candidate in combination with current standards of care in areas of unmet need.”