Vidofludimus Calcium Shows Promise for Progressive MS Despite Missing Primary Endpoint in Phase 2 Trial
核心洞察
The phase 2 CALLIPER trial of vidofludimus calcium in 467 progressive MS patients failed to meet its primary endpoint of reducing brain atrophy but showed consistent trends toward disability improvement across multiple measures.
Subgroup analysis revealed particularly encouraging results in primary progressive MS patients, with hazard ratios below 1.0 for confirmed disability worsening even in patients without active inflammation at baseline.
The dual-mechanism drug demonstrated a favorable safety profile compared to existing DHODH (搜索) inhibitors, with no increased rates of liver, kidney, or infectious complications typically seen with teriflunomide.
Vidofludimus calcium, an investigational oral therapy with a novel dual mechanism of action, demonstrated consistent trends toward reducing disability progression in progressive multiple sclerosis (搜索) despite failing to meet its primary endpoint of brain atrophy reduction in the phase 2 CALLIPER trial. The results, presented at ECTRIMS 2025, support advancing the compound to phase 3 testing in this challenging patient population.
The multicenter, double-blind trial randomized 467 patients with progressive MS to receive either vidofludimus calcium 45 mg once daily or placebo for 120 weeks. While the drug showed no significant effect on the primary endpoint of percent brain volume change through 30 months, it demonstrated favorable trends across multiple disability measures that investigators believe warrant further investigation.
Novel Dual Mechanism Targets Neurodegeneration
Vidofludimus calcium (IMU-838) represents a unique therapeutic approach, functioning as both an activator of the neuroprotective transcription factor Nurr1 (搜索) and a selective inhibitor of dihydroorotate dehydrogenase (搜索) (DHODH (搜索)), a key enzyme in pyrimidine biosynthesis. This dual mechanism distinguishes it from teriflunomide, the only other DHODH inhibitor approved for MS, which lacks the Nurr1 activation component.
"These findings bolster the hypothesis that the mechanism of vidofludimus calcium — Nurr1 (搜索) activation combined with DHOD inhibition — may represent a novel means of preventing neurodegeneration in MS," said first author Robert Fox, MD, a neurologist with Cleveland Clinic's Mellen Center for Multiple Sclerosis (搜索) Treatment and Research. "New mechanisms are highly welcome as we strive to address the unmet therapeutic needs of patients with progressive forms of MS."
The compound's Nurr1 (搜索) activation produces direct and indirect neuroprotective effects in vitro by improving neuronal survival and reducing microglial activation, while its DHODH (搜索) inhibition reduces focal inflammation and associated MRI activity.
Disability Trends Emerge Despite Primary Endpoint Miss
The CALLIPER trial enrolled patients aged 18 to 65 years with Expanded Disability Status Scale (EDSS) scores from 3.0 to 6.5, no evidence of relapse in the prior 24 months, and evidence of disability worsening in the preceding two years. The study population included patients with primary progressive MS and both active and non-active secondary progressive MS.
While the primary endpoint of brain volume change showed no significant difference between treatment groups, the key secondary endpoint of 24-week confirmed disability worsening showed a trend favoring vidofludimus calcium, though not reaching statistical significance. This composite measure included EDSS scores, the 9-hole peg test, and the timed 25-foot walk.
More encouraging results emerged from exploratory disability endpoints, where vidofludimus calcium demonstrated statistically significant benefits over placebo in change in mean EDSS score through 120 weeks (P < 0.01) and time to 24-week confirmed disability improvement based on EDSS score (P = 0.034).
Primary Progressive MS Subgroup Shows Promise
Subpopulation analysis of the 152 patients with primary progressive MS revealed particularly encouraging trends. Among this cohort, the time to 24-week confirmed disability worsening reached a hazard ratio of 0.770, and in patients without gadolinium-enhancing lesions at baseline, the hazard ratio for EDSS-based confirmed disability worsening was 0.662.
"Seeing a similar trend in patients without active lesions at baseline shows that it's not just through focal inflammation that vidofludimus calcium is working, but also supports the hypothesis that this agent has neuroprotective effects," Fox explained.
The observed treatment effect in patients without baseline inflammation supports the drug's proposed neuroprotective mechanism through Nurr1 (搜索) activation, independent of its anti-inflammatory DHODH (搜索) inhibition effects.
Favorable Safety Profile Distinguishes from Existing Therapy
The trial's safety analysis revealed no new safety signals, with comparable rates of treatment-emergent and serious adverse events between treatment and placebo groups. Notably, vidofludimus calcium did not show increased rates of elevated liver enzymes, renal events, or infections commonly associated with teriflunomide.
This improved tolerability profile may be attributed to vidofludimus calcium's selective DHODH (搜索) inhibition, avoiding the interactions with various other kinases that contribute to teriflunomide's side effects, including diarrhea, alopecia, neutropenia, and hepatic complications.
Path Forward to Phase 3 Development
Despite the primary endpoint miss, investigators concluded that the consistent disability trends across multiple outcomes, patient populations, and subgroups support further development in progressive MS. The drug is currently being evaluated in two identical phase 3 trials (ENSURE-1 and ENSURE-2) for relapsing MS, testing 30 mg daily doses in 1,050 adults, with completion expected in 2026.
"Although it was disappointing to see no effect of vidofludimus calcium on brain volume, this has been seen in other progressive MS trials recently and suggests that brain volume may not be the right MRI biomarker for trials in progressive MS," Fox noted. He emphasized that while the trial was not adequately powered for disability outcomes, the consistent trends warrant further investigation in appropriately powered phase 3 studies.