Siplizumab (anti-CD2)
ITB-MED (TCD601)
Stopped early; no interpretable T1D efficacy evidence.
What it is
An experimental anti-CD2 antibody intended to reshape the T-cell attack in new-onset T1D. Both clinical studies stopped after only a handful of adults: STRIDE for sponsor-described business reasons, and DESIGNATE after greater-than-anticipated lymphocyte depletion and the partner's decision to cease autoimmune development. No usable T1D efficacy result exists.
Editorial review: .
Most recent recorded citation date: 2026-07-28. Only explicit date metadata is included; an undated citation may be newer. This does not mean every claim was reviewed on that date.
Trial status, labels and access can change between reviews. How we review the evidence · How to read the evidence
Evidence behind this assessment
Key evidence notes. Study results, product eligibility and access answer different questions.
- Who was studied?
- Study populations and analysis groups vary. Product age limits alone do not describe who was studied.See the linked studies and their populations →
- Benefit or performance
- Delay of onset: Neither T1D study produced an interpretable clinical beta-cell result. DESIGNATE posted only an immune-phenotype endpoint from six evaluable adults; its C-peptide and insulin-use outcomes were not posted.[1]
- Important harms and treatment burden
- Safety: DESIGNATE recorded no deaths or serious adverse events in seven treated adults, but all seven had decreased CD4 lymphocytes and enrollment was held for greater-than-anticipated lymphodepletion. Such a tiny sample cannot define broader safety.[1]
- Approval and country access
- Not approved for T1D. The DESIGNATE record says the pharmaceutical partner ceased siplizumab development in autoimmunity.Approval, trial recruitment, local supply and funding are separate. Check the cited label or access source.
- Follow-up and remaining uncertainty
- Durability: There is no clinical benefit to assess for durability: both programmes terminated after single-digit enrollment.[2]
Editorial score: calculation and evidence
A weighted editorial judgment on a 0–100 scale, not a probability of success or a measured treatment effect. Higher criterion scores mean more favorable assessments.
Default calculation: 5 × 30 + 0 × 20 + 18 × 20 + 8 × 15 + 0 × 15 = 630; divide by total weight 100. Unrounded weighted result: 6.3.
Neither T1D study produced an interpretable clinical beta-cell result. DESIGNATE posted only an immune-phenotype endpoint from six evaluable adults; its C-peptide and insulin-use outcomes were not posted.[1]
There is no clinical benefit to assess for durability: both programmes terminated after single-digit enrollment.[2]
DESIGNATE recorded no deaths or serious adverse events in seven treated adults, but all seven had decreased CD4 lymphocytes and enrollment was held for greater-than-anticipated lymphodepletion. Such a tiny sample cannot define broader safety.[1]
Only adults with recent-onset stage-3 T1D were treated. Pediatric cohorts were planned in DESIGNATE but were never reached, and no stage-1 or stage-2 prevention study was run.[1]
Siplizumab is not approved for T1D, both T1D studies are terminated, and the DESIGNATE record says its pharmaceutical partner ceased development in autoimmunity.[1]
Editor’s take
This is a stopped programme, not a negative efficacy trial. DESIGNATE was designed to find a biologically active, tolerable dose, but treated seven adults and produced a primary immune-phenotype analysis in six before lymphodepletion and a portfolio decision ended it. STRIDE stopped separately for sponsor-described business reasons after nine participants. Those facts do not prove the CD2 mechanism cannot work; they do mean there is no credible path to describe as active and no clinical efficacy estimate to quote.
The full picture
Siplizumab (TCD601) is a monoclonal antibody against CD2, a surface protein on T cells. The T1D idea was to deplete or reshape the T-cell populations attacking beta cells, building on the mechanistic rationale reported for the older CD2-directed drug alefacept.
Two T1D programmes started, and neither reached a useful efficacy test. ITB-MED's randomized STRIDE phase-2 study enrolled nine adults before ending in July 2025. Its registry attributes the termination to business reasons and explicitly says that decision was not related to safety, efficacy, or regulatory concerns; no results are posted.2
The NIAID-sponsored DESIGNATE dose-finding study planned 160 adults and children but randomized eight adults and treated seven. Six received enough treatment and had viable samples for the primary analysis. Three of those six met the predefined T-cell phenotype-response signature, but this was a laboratory immune endpoint, not evidence of preserved C-peptide or better glucose control. Planned inferential analyses were not produced, and the C-peptide and insulin-use outcomes were not posted.1
There were no deaths or serious adverse events among the seven treated adults, but all seven had decreased CD4 lymphocytes recorded, enrollment was held for greater-than-anticipated lymphodepletion, and the pharmaceutical partner then ended siplizumab development in autoimmunity.1 With both T1D studies terminated and no clinical efficacy estimate, siplizumab belongs in the record as a discontinued programme rather than an active cure or prevention prospect.
Coming soon
ETA · Discontinued in T1D; no active autoimmune development path
Sources
- [1]DESIGNATE siplizumab in T1D (NCT05574335) · Trial registry · 2026-07-28 — Results first posted 28 July 2026. Eight randomized, seven treated, six evaluable for the primary immune-phenotype endpoint; no planned inferential analysis because of the small sample. The record cites greater-than-anticipated lymphodepletion and cessation of autoimmune development.
NIAID. Siplizumab in T1DM (DESIGNATE), NCT05574335. ClinicalTrials.gov results first posted 28 July 2026.
- [2]STRIDE siplizumab in new-onset T1D (NCT06025110) · Trial registry · 2025-08-14 — Terminated after actual enrollment of nine. The sponsor attributed this trial's stop to business reasons, not safety, efficacy, or regulatory concerns; no results are posted.
ITB-Med LLC. A Study of TCD601 (Siplizumab) in New Onset Type 1 Diabetes Patients (STRIDE), NCT06025110. ClinicalTrials.gov.