A Prospective, Single-centre, Observational Cohort Study on the Efficacy and Safety of Bacterial Lysate (OM-85) in Combination With Antihistamines for the Treatment of Chronic Spontaneous Urticaria (CSU)

Inclusion criteria

• The participants were fully informed of the purpose, procedure and risks of the study and voluntarily signed the informed consent form.
• Aged 18 to 65 (inclusive), no gender restrictions.
• Meets the CSU diagnostic criteria, with a disease duration of ≥6 weeks.
• Antihistamine resistance: Regular use of a standard dose (as recommended in the package leaflet) of a second-generation H1 antihistamine (e.g. desloratadine 5 mg, levocetirizine 5 mg, etc.) for at least 2 weeks prior to screening, but with symptoms still not effectively controlled. Defined as: a UAS7 score of ≥7 within 7 days prior to the screening visit (V1) and baseline visit (V2).
• Agree to maintain the type and dose of the baseline antihistamine throughout the trial.
• Agree not to consume any products that may significantly affect the gut microbiota during the trial (such as yoghurt containing probiotics, or probiotic/prebiotic supplements).
• At the baseline visit, the treatment regimen was clearly defined, and exposure status (OM-85 exposure group or non-exposure group) could be determined based on actual prescriptions and medication records.

Exclusion criteria

• Special types of urticaria: These primarily include physical urticaria (such as artificial urticaria, cold contact urticaria and cholinergic urticaria), urticarial vasculitis, and angioedema caused by hereditary or acquired C1 esterase inhibitor deficiency;
• Systemic use of glucocorticoids (oral or injectable) within the four weeks prior to screening;
• Exclude patients who have used immunosuppressants (such as cyclosporine, methotrexate, or Tripterygium wilfordii) within the previous four weeks;
• Exclude patients who have used biologics (such as omazulimab, dupilumab, etc.) within the previous three months;
• Exclude those who have used bacterial lysates (such as Panfuxu or Pidomod) or received vaccinations within the past three months;
• Key exclusion criteria for the microbiome study: use of oral or intravenous antibiotics within the four weeks prior to screening, or continuous use of probiotic supplements for more than one week.
• Patients with severe systemic autoimmune diseases (such as systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease, etc.) may interfere with the assessment of immune mechanisms;
• A history of serious liver, kidney, heart, lung or blood disorders, or malignant tumours;
• Individuals known to be allergic to bacterial lysates and their excipients.
• Special populations: pregnant or breastfeeding women, or participants of childbearing age who do not intend to use contraception during the trial.
• Other: Participants who have taken part in other clinical trials involving medicinal products within the past 30 days; or where the investigator considers that there is poor compliance, a mental health condition, or any other circumstance rendering the participant unsuitable for the trial.