Vigil’s Iluzanebart Fails Phase 2 in Rare Neuro Disease; Sanofi Takeover Remains On Track

Vigil Neuroscience's lead drug candidate, iluzanebart (VGL101), failed to demonstrate efficacy in the Phase II IGNITE trial for the rare neurological condition adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP)12.

The Phase 2 proof-of-concept study missed both biomarker and clinical efficacy endpoints, prompting Vigil to halt a long-term extension study of iluzanebart23.

Despite the drug showing favorable safety, tolerability, and pharmacokinetics, it failed to impact brain volume loss, disease progression, or biomarkers of neurodegeneration2.

Sanofi's $470 million acquisition of Vigil is unaffected by the phase 2 failure, as Sanofi had already chosen not to acquire iluzanebart, with rights to the drug instead reverting to Amgen2.

Sanofi will focus on VG-3927, a small-molecule TREM2 agonist, in its neurology pipeline following the completion of the Vigil acquisition, expected in Q3 202525.

Sources:

1. https://firstwordpharma.com/story/5968650

2. https://www.fiercebiotech.com/biotech/vigils-rare-brain-disease-drug-flunks-phase-2-study-sanofi-takeover-unaffected

3. https://investors.vigilneuro.com/news-releases/news-release-details/vigil-neuroscience-provides-update-iluzanebart-phase-2-ignite

5. https://www.sanofi.com/en/media-room/press-releases/2025/2025-05-21-23-15-31-3086232