SAFEGUARD: SAB-142, a fully human anti-thymocyte globulin, in new-onset stage-3 T1D

SAFEGUARD is the trial that decides whether SAB-142 is a real drug or a good idea. Anti-thymocyte globulin has already shown benefit in newly diagnosed type 1 diabetes — a single low-dose (2.5 mg/kg) course of the rabbit-derived version preserved C-peptide through two years of follow-up (our record on it) — but because it is a rabbit protein, the immune system learns it. Serum sickness and anti-drug antibodies complicate repeat dosing. SAB-142 is the sponsor's human-antibody version of the same approach, and its entire promise is that you could give it more than once.

SAFEGUARD is designed to test that promise: two treatment courses, six months apart, in people who were diagnosed within the last 100 days.¹

Design

The current registry includes three parts. Part A is an open-label dose-ranging stage in adolescents and adults aged 15–40, comparing a high and a low dose of SAB-142 with no placebo arm; its primary measure is safety — treatment-emergent adverse events, adverse events of special interest and serious adverse events through week 4. Part B is the randomised, double-blind, placebo-controlled efficacy stage, and it widens the age range to 5–40.¹

Participants must have stage 3 T1D diagnosed within 100 days of randomisation, at least one islet autoantibody, a random C-peptide of at least 0.2 nmol/L, and a weight of at least 16 kg. Anyone who has had teplizumab or another investigational anti-CD3 is excluded, as is current or recent use of treatments that alter the course of T1D such as verapamil or baricitinib — so this is not a trial you can enter after trying teplizumab, the approved anti-CD3 immunotherapy.¹

Estimated enrollment is 159, across roughly 70 registered sites in the US, UK, Australia, New Zealand and eleven European countries. It has been recruiting since 25 November 2025.¹

Endpoints and timing

The efficacy endpoint that matters is C-peptide AUC after a 2-hour mixed-meal tolerance test, assessed from dosing through month 12 (Part B) — a measure used in other immunotherapy studies. Differences in populations and protocols limit cross-trial comparisons.¹

Secondary endpoints reach past C-peptide into outcomes people actually feel: time in tight range (above 70 to 140 mg/dL, or above 3.9 to 7.8 mmol/L), time in range (above 70 to 180 mg/dL, or above 3.9 to 10.0 mmol/L), HbA1c, total exogenous insulin use, and partial-remission rates by IDAA1c of 9 or below.¹

ClinicalTrials.gov lists estimated primary completion in November 2027 and study completion in December 2028. SAB Biotherapeutics has said it expects to share topline data in the second half of 2027; that is the company's guidance, not a registry commitment.² No results have been posted.

Part C continues eligible participants who completed the month-12 assessments to a 24-month C-peptide endpoint.¹

What to watch for

Two things will tell you whether the thesis survives.

The first is the second course. Re-dosing is the whole argument for a human ATG, and SAFEGUARD tests a second course at month 6. If anti-drug antibodies or infusion reactions show up at month 6 the way they do with rabbit ATG, the advantage over a drug that already exists largely evaporates.

The second is the population. SAB-142's only human efficacy signal so far comes from a small number of people with established T1D in a phase 1 — reported in press releases, not a peer-reviewed paper. SAFEGUARD is testing it in new-onset disease, where there is more insulin-producing tissue left to protect. Mechanistically that should help, but it remains an untested population for this specific drug, and a phase 2b with 159 participants is where optimistic small-sample signals usually get their first honest examination.

The sponsor calls SAFEGUARD "registrational".² The registry simply calls it phase 2.¹ Treat the gap between those two descriptions as the appropriate level of uncertainty.