Ulinastatin on Systemic Immune-Inflammation in Patients With Complicated Intra-Abdominal Infection (UTI-cIAI)

This is a single-center, randomized, single-blind, three-arm parallel-group superiority pilot clinical trial performed at Fujian Medical University Union Hospital. Randomization sequence is generated with SAS 9.3 software, and random grouping is implemented by sealed envelope method at a 1:1:1 allocation ratio (low-dose ulinastatin : high-dose ulinastatin : normal saline control =1:1:1). A total of 165 participants are planned, with 55 subjects in each group after accounting for an anticipated 10% dropout rate.

All enrolled patients are adults aged ≥18 years diagnosed with complicated intra-abdominal infection (cIAI) within 48 hours, confirmed by clinical manifestation, laboratory tests and abdominal imaging, accompanied by SOFA score ≥2. Subjects with severe immunodeficiency, end-stage liver or renal disease, malignancy, pregnancy, hypersensitivity to ulinastatin and other severe comorbidities are excluded. Written informed consent is obtained prior to any study-related procedures.

All participants receive standardized routine management including surgical source control, antibacterial therapy and organ function supportive treatment. Intervention regimens last for consecutive 5 days via intravenous drip: low-dose group receives ulinastatin 100,000 IU three times daily diluted in 100 mL normal saline; high-dose group receives ulinastatin 300,000 IU three times daily diluted in 100 mL normal saline; control group receives equal volume of sterile normal saline three times daily as placebo. For patients with progressive organ dysfunction after 24-48 hours without improvement, rescue high-dose ulinastatin is allowed per investigator's clinical judgment.

Primary endpoint is the absolute change of Systemic Immune-Inflammation Index (SII) from baseline to treatment Day 5. Secondary endpoints include dynamic changes of CRP, PCT, IL-6, NLR, PLR, LMR, CLR, CD4⁺/CD8⁺ T cell counts at Days 1,3,5 and 7; sequential SOFA score changes; cumulative incidence of new organ failure within 7 and 14 days; ICU and total hospital stay duration; reoperation rate, secondary infection rate, in-hospital and 28-day all-cause mortality. Subgroup analyses are preset stratified by operation type, pathogenic bacteria (multidrug-resistant pathogen or candidiasis) and baseline disease severity (MPI/SOFA score).

All adverse events (AEs) from informed consent to 4 weeks after final study medication are documented following CTCAE Version 5.0. All serious adverse events (SAEs) must be reported to the sponsor (Techpool Bio-Pharma Co., Ltd.) within 24 hours. Study will be prematurely terminated if excessive unexpected severe adverse events occur or interim analysis demonstrates no meaningful intergroup difference in primary inflammatory markers. Study monitoring, source document verification and data management are conducted in accordance with GCP and Declaration of Helsinki principles.