Staidson's C5a antibody STSA-1002 clears Phase 1 safety bar in China
Multiple IV doses up to 20 mg/kg suppressed free C5a through Day 56 in 26 healthy volunteers, but the model's 4.1% endpoint-met read reflects a PK/PD bar, not a China-to-Phase-2 efficacy signal.
Executive Summary
- A peer-reviewed abstract discloses full results from a completed, placebo-controlled Phase 1 trial of STSA-1002 in 26 healthy Chinese adults, showing dose-proportional exposure and sustained suppression of free C5a through Day 56 at the top two doses Press ReleasePress ReleaseJul 3, 2026.
- Adverse events occurred in 90.0% of STSA-1002 recipients versus 100% of placebo recipients, with Grade 2-plus drug-related events limited to lab abnormalities; no severe safety signal is disclosed Press ReleasePress ReleaseJul 3, 2026.
- The trial's 15 registered primary endpoints are all PK, PD, or safety measures, not clinical efficacy, so this readout cannot confirm STSA-1002 will work in ARDS patients.
- The AppliedXL model's 4.1% endpoint-met read applies to the composite difficulty of hitting all 15 quantitative PK/PD/safety bars, not to a disease outcome, and no pre-event model call exists to grade against this disclosure [AXL-MODEL].
- Staidson already has a Phase 1/2 ARDS study completed (NCT06038916) and a 406-patient Phase 3 ARDS trial recruiting (NCT07208591), so this healthy-volunteer data functions as supportive PK/PD background for a program already in later-stage testing.
The disclosure
A peer-reviewed abstract lays out complete safety, pharmacokinetic, pharmacodynamic and immunogenicity results from NCT05497635, a randomized, double-blind, placebo-controlled, multiple-ascending-dose study of STSA-1002 conducted at a single Phase 1 unit in China NCT05497635+1A Study of STSA-1002 in Healthy SubjectsNCT05497635Press ReleaseJul 3, 2026. Of 26 healthy adults enrolled, 20 received STSA-1002 and 6 received placebo. The trial finished enrollment and reached primary completion on 2023-04-06, and the underlying data are now public through this 2026 publication. The abstract states plainly: "Overall, multiple infusions of STSA-1002 up to 20 mg/kg appear to be safe and well tolerated in healthy participants in China" Press ReleasePress ReleaseJul 3, 2026.
Probability of SuccessBased on the AppliedXL Probability of Success model. For more information about the methodology, read the research here.
The pharmacology
STSA-1002 is a fully human monoclonal antibody targeting C5a, a complement fragment implicated in virus-induced acute respiratory distress syndrome (ARDS caused by viral infection) Press ReleasePress ReleaseJul 3, 2026. Cmax and AUC0-t rose in an approximately dose-proportional manner across dose levels, and free C5a concentration dropped below the lower limit of quantification after the first dose in every dose group Press ReleasePress ReleaseJul 3, 2026. That suppression held through Day 42 at 5 mg/kg and through Day 56 at 10 mg/kg and 20 mg/kg Press ReleasePress ReleaseJul 3, 2026. The antibody also lowered levels of myeloperoxidase, neutrophil elastase, and proteinase 3, downstream markers of neutrophil activation tied to the C5a pathway Press ReleasePress ReleaseJul 3, 2026.
The safety record
60 total adverse events were reported: 47 events in 18 of 20 STSA-1002 recipients (90.0%, a mean of 2.6 events per participant), versus 13 events in all 6 placebo recipients (100%, a mean of 2.2 events per participant) Press ReleasePress ReleaseJul 3, 2026. Grade 2 or greater drug-related events were limited to decreased neutrophil count, decreased white blood cell count, and increased aminotransferase Press ReleasePress ReleaseJul 3, 2026. No deaths, discontinuations, or serious safety signals appear in the disclosed abstract. The 100% AE rate in the small 6-person placebo arm underscores how little statistical weight this safety comparison can carry.
What the endpoints actually measure
The trial registered 15 primary endpoints, all pharmacokinetic, pharmacodynamic, or safety measures such as accumulation factor, clearance, half-life, and adverse event incidence; none of them is a clinical efficacy endpoint. The AppliedXL model's 4.1% endpoint-met probability applies to that composite PK/PD/safety bar, not to whether STSA-1002 will reduce ARDS severity or mortality in patients [AXL-MODEL]. Reading this figure as an efficacy signal would misstate what the trial was designed to test. No pre-event model read exists in the record to grade against the outcome now disclosed.
The program context
This is one of four completed STSA-1002 healthy-volunteer studies Staidson has run, alongside a terminated Phase 1 combination study with STSA-1005. The company has already advanced STSA-1002 into ARDS patients: a completed Phase 1/2 study (NCT06038916, 47 enrolled, primary completion 2025-03-20) and a Phase 3 trial (NCT07208591) now recruiting toward 406 patients with a stated primary completion of 2026-07-01. Across its full pipeline, Staidson has completed 18 of 22 finished trials (an 82% completion rate) and terminated 5 of 27 total trials. No external anti-C5a competitor trial or approval precedent appears in the dossier.
Protocol reliability
The trial's registry history shows zero amendments beyond routine status updates: not yet recruiting to recruiting in October 2022, then to completed in April 2023, with a protocol stability label of 'Stable' and 0.0 changes per year. That stability supports confidence that the disclosed results match the originally registered design, though ClinicalTrials.gov itself carries no posted results to cross-check the abstract's numbers.
This analysis was produced using AI-assisted reporting systems, AppliedXL data, and official public records. These systems undergo editorial review, quality checks, and regular audits by human experts. Errors may still occur, as with any automated system. Always consult the linked primary sources. Read our AI Editorial Policy.