Vigil's TREM2 Antibody Fails Phase II Trial, Sanofi Acquisition Unaffected

Vigil Neuroscience's monoclonal antibody iluzanebart has failed to meet its primary endpoints in a Phase II clinical trial for a rare brain disorder, prompting the discontinuation of its development. This setback comes just two weeks after Vigil agreed to a $470 million buyout deal with pharmaceutical giant Sanofi.

Trial Results and Implications

The Phase II IGNITE trial and concurrent ILLUMINATE natural history study evaluated iluzanebart for the treatment of adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP), a rare progressive brain disease. Despite demonstrating favorable safety, tolerability, and pharmacokinetics, the antibody showed "no beneficial effects on biomarker or clinical efficacy endpoints," according to Vigil.

Ivana Magovčević-Liebisch, President and CEO of Vigil, expressed disappointment but highlighted the study's contribution to ALSP awareness and understanding. The company will now halt the long-term extension trial of iluzanebart.

Sanofi Acquisition and Strategic Focus

Despite the trial failure, analysts from William Blair note that the results are "not surprising" and should not affect Sanofi's acquisition of Vigil. The $470 million deal, announced in late May, notably excluded iluzanebart from the assets being transferred to Sanofi.

Instead, Sanofi's interest lies in Vigil's other TREM2 agonist, VG-3927, which is being developed for neurodegenerative diseases such as Alzheimer's. As part of the agreement, iluzanebart will be returned to its original licensor, Amgen, before the Sanofi-Vigil deal closes in the third quarter of 2025.

Broader Implications for TREM2 Research

The failure of iluzanebart marks another setback in the TREM2 space, following Alector's high-profile Phase II failure in Alzheimer's disease last November. These results raise questions about the efficacy of TREM2-targeted therapies in neurodegenerative disorders.

However, the pharmaceutical industry continues to show interest in this approach, as evidenced by Sanofi's acquisition of Vigil and its focus on VG-3927. The coming months and years will likely see continued research and development in this challenging but potentially promising area of neuroscience.