Vaccinex has said that the Phase II SIGNAL trial of its pepinemab failed to meet pre-specified co-primary endpoints in patients with early manifest and prodromal Huntington’s disease (HD).

Pepinemab is a humanised monoclonal antibody designed to block the activity of semaphorin 4D (SEMA4D), which controls the migration and function of immune and inflammatory cells.

SIGNAL, a multi-centre, double-blind, placebo-controlled trial, assessed the safety and efficacy of pepinemab as a potential treatment for HD, a neurodegenerative disease that currently lacks effective treatment options.

The two co-primary endpoints of the trial are cognitive assessments from Huntington’s Disease Cognitive Assessment Battery and Clinical Global Impression of Change (CGIC).

Though the cognitive endpoints showed a strong trend for beneficial change, a statistically significant difference was not found between the placebo and pepinemab arms.

Vaccinex president and CEO Maurice Zauderer said: “The results reported today strongly support a cognitive benefit to treatment with pepinemab and indicate that treatment with pepinemab antibody potentially targets cortical centres, including those that govern cognition.”

The company attributed the failure to the small group size in the trial.

Over the extended 18-month treatment duration, the drug was well-tolerated with low treatment discontinuation and study drop-out rates.

Zauderer added: “The insights gained from this study also suggest that pepinemab might be an important treatment option for Alzheimer’s and other neurodegenerative diseases known to primarily affect frontal cortex and to impact cognition.

“The company has, accordingly, initiated screening and expects to begin enrolling patients this month in a new Alzheimer’s disease study of pepinemab at 15 clinical sites in the US.”

A detailed report of additional SIGNAL data, including a broader analysis of motor activity and outcomes for 86 prodromal subjects, is set to be available in October this year.

In April last year, researchers from the Perelman School of Medicine at the University of Pennsylvania (Penn) conducted a new study focused on enabling a better design of clinical trials for Huntington’s disease patients.