Skip to content
type1.science

Siplizumab (anti-CD2)

ITB-MED (TCD601)

Stopped early; no interpretable T1D efficacy evidence.

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.

DiscontinuedEarly evidenceimmunotherapycd2monoclonal-antibodynew-onsetdiscontinuedlymphodepletion

The scorecard

Delay of onset5

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]

Durability0

There is no clinical benefit to assess for durability: both programmes terminated after single-digit enrollment.[2]

Safety18

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]

Stage breadth8

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]

Access & cost0

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 signal seen with 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.1

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.2

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.2 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.

References

  1. ITB-Med LLC. A Study of TCD601 (Siplizumab) in New Onset Type 1 Diabetes Patients (STRIDE), NCT06025110. ClinicalTrials.gov. https://clinicaltrials.gov/study/NCT06025110 ↩

  2. NIAID. Siplizumab in T1DM (DESIGNATE), NCT05574335. ClinicalTrials.gov results first posted 28 July 2026. https://clinicaltrials.gov/study/NCT05574335 ↩ ↩2

Coming soon

ETA · Discontinued in T1D; no active autoimmune development path

Sources

  1. [1]DESIGNATE siplizumab in T1D (NCT05574335) · 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.
  2. [2]STRIDE siplizumab in new-onset T1D (NCT06025110) · 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.