OPT101 (CD40-pathway peptide)
Op-T LLC
A short CD154-derived peptide designed to restrain pathogenic CD40 signalling without broad immunosuppression. A 24-person Phase 1b study in people with established T1D posted results in August 2026: the peptide looked tolerable, but the posted C-peptide and glucose numbers do not show a treatment benefit over placebo. A subcutaneous Phase 2 (NCT06964087) is recruiting; it is not an efficacy result.
The scorecard
Posted Phase 1b C-peptide values after a mixed-meal test were not higher on OPT101 than placebo (mean 0.03–0.07 ng/mL vs 0.16 ng/mL on placebo). That is not evidence of beta-cell preservation.[1]
Follow-up in the posted study was measured in weeks, not years, and no lasting C-peptide advantage was shown.[1]
Primary outcome: one treatment-related adverse event in each OPT101 dose group and none on placebo; no deaths or serious events in the posted tables. Older anti-CD154 antibodies caused clotting, so thromboembolism remains a class watch-out even though this peptide's posted safety table is small and short.[1]
Phase 1b enrolled medically stable adults 18–60 with T1D diagnosed within 20 years, not newly diagnosed children or stage 1–2 relatives.[1]
Human Phase 1b completed with posted results (n=24 started; 18 completed). A subcutaneous Phase 2 is now recruiting (NCT06964087, estimated n=72). That is still not a Phase 2/3 efficacy package.[2]
The full picture
OPT101 is a 15-amino-acid peptide derived from CD154 (CD40 ligand). The idea is to quiet the CD40 pathway that helps drive autoimmune T cells, without the clotting problems that sank earlier anti-CD154 monoclonal antibodies.
A randomized, placebo-controlled Phase 1b study (NCT05428943) enrolled 24 adults with T1D and posted results on 10 August 2026. Eight people were assigned to 1.1 mg/kg, eight to 2.8 mg/kg, and eight to placebo; six in each group completed. The primary endpoint was treatment-related adverse events over 42 days: one event in each active-dose group and none on placebo, with no deaths. Posted mixed-meal C-peptide means were not higher on drug than placebo, so this record is scored as an early safety programme, not as a therapy that has been shown to preserve insulin production.
A conference immunophenotyping abstract reported lower pathogenic Th40 cells and higher Tregs. That is a mechanistic signal from a meeting abstract, not a clinical efficacy result.
A subcutaneous Phase 2 (NCT06964087) is recruiting in the US (estimated n=72; started 10 April 2026). It is a pharmacokinetic and pilot C-peptide study, not a posted preservation result.
Coming soon
ETA · Phase 1b complete with posted results; subcutaneous Phase 2 recruiting (NCT06964087). No Phase 3 and no approval path.
Sources
- [1]OPT101 in Type 1 Diabetes Patients · registry · 2026-08-10 — Phase 1b completed; results first posted 10 August 2026. Actual enrollment 24; primary completion 21 February 2024.
- [2]Pharmacokinetic and Early Efficacy of OPT101 in Patients With Type 1 Diabetes Mellitus · registry · 2026-04-06 — Phase 2 recruiting; estimated n=72; last update 6 April 2026. No results.
- [3]Restoring Immune Homeostasis with a Novel Peptide — Phase 1b immunophenotyping · conference · 2026-01-01 — Conference immunophenotyping abstract; not a substitute for the posted registry efficacy tables.