Frexalimab (CD40L antagonist)
Sanofi / ImmuNext
A second-generation anti-CD40L monoclonal antibody in the FABULINUS phase-2b trial for children, adolescents and adults (ages 6-35) with newly diagnosed T1D. It aims to preserve C-peptide without lymphocyte depletion. The trial is now fully enrolled, but no T1D efficacy result is published yet.
The scorecard
No published T1D efficacy result yet; the phase-2b FABULINUS trial uses C-peptide preservation after diagnosis, not onset delay, as its core test.[1]
Durability is unknown; the registry includes a 52-week blinded extension and optional open-label extension to study longer-term effects.[1]
The appeal is immune modulation without lymphocyte depletion, but CD40L blockade has class-history safety questions and T1D safety is still being established.[2]
Current T1D program is recent-onset stage 3 only; no stage-1/2 prevention data yet. The trial has since added a pediatric cohort (Part C, ages 6-11), broadening the population though not the stage.[1]
Investigational biologic; no regulatory approval for T1D or any routine diabetes access.[1]
Editor’s take
Frexalimab is a frontier bet: mechanistically attractive and serious enough to have a large Sanofi phase-2b trial, but still pre-result in T1D. It belongs in the map because CD40/CD40L costimulation is one of the clearest next immunotherapy axes after anti-CD3, CTLA4-Ig and JAK inhibition.
The full picture
What is being tested
Frexalimab blocks CD40L, part of a costimulation pathway that helps activate T cells, B cells and innate immune cells. FABULINUS is testing whether that pathway can be modulated in recent-onset T1D while preserving the body's own insulin secretion.1
Who is in the trial
FABULINUS has grown since it opened. As of July 2026 the registry lists 197 participants aged 6 to 35 — the trial added a pediatric cohort (Part C, ages 6-11) alongside the original adult and adolescent groups. The two groups are judged on slightly different clocks: Part C has a 26-week C-peptide primary endpoint, the older cohorts a 52-week one. That widens who frexalimab is being tested in, but not when — everyone enrolled is newly diagnosed, so this is still a stage-3 recent-onset study, not a prevention study in people who have not yet developed diabetes.1
Evidence status
The trial is now active, not recruiting — enrolment is complete and participants are being followed. That is a milestone in logistics, not in evidence: there is still no published T1D efficacy result. Primary completion is estimated for April 2027, with study completion out in October 2030.1
The value of this record remains pipeline coverage: FABULINUS is large enough and mechanistically distinct enough that leaving it out would make the prevention/immunotherapy landscape look older than it is.
References
-
National Library of Medicine. FABULINUS: Frexalimab in recent-onset type 1 diabetes. ClinicalTrials.gov NCT06111586. https://clinicaltrials.gov/study/NCT06111586 ↩ ↩2 ↩3
Coming soon
ETA · Phase-2b fully enrolled (active, not recruiting); primary completion estimated April 2027
- →FABULINUS phase-2b C-peptide readout (fully enrolled; ages 6-35, n=197) · primary completion estimated April 2027
Sources
- [1]FrexalimAB in Preservation of Endogenous insULIN Secretion Compared to Placebo in adUlts and Adolescents on Top of inSulin Therapy (FABULINUS) · registry · 2026-07-14 — Sanofi phase 2b; active, not recruiting as of July 2026; n=197; ages 6-35 (pediatric Part C covers 6-11); primary completion estimated April 2027, study completion October 2030.
- [2]A Phase 2 Trial of Frexalimab, a CD40L Antagonist, in Adolescents and Adults With Recent-Onset Type 1 Diabetes (FABULINUS): Rationale and Study Design · peer-reviewed · 2026-05-01 — Diabetes, Obesity and Metabolism design paper; DOI verified through search/Crossref during this pass.