A Study of QLS2404 Injection in Healthy Participants and Participants With Rheumatic Autoimmune Diseases

The Phase Ia single-dose ascending stage will include five dose groups. The study plans to enroll 40 adult healthy participants, with 8 participants in each dose group, who will be randomized in a 3:1 ratio to receive QLS2404 Injection or placebo. Dose escalation will be conducted sequentially from the initial dose to higher dose levels in accordance with the dose-escalation principle.

During the study, a Safety Monitoring Committee (SMC), composed of the investigators, the sponsor, or sponsor-designated personnel, will review the safety data generated during the trial. After the last participant in each dose group has completed the 14-day tolerability observation period following dosing, the SMC will review the safety data of participants in each cohort and conduct an integrated assessment of the available pharmacokinetic (PK) and pharmacodynamic (PD) data. The SMC will then provide recommendations regarding dose escalation or, if necessary, adjustments to the dose-escalation scheme.

The Phase Ib part will be a multiple ascending-dose study of subcutaneous QLS2404 Injection in participants with systemic lupus erythematosus (SLE) and primary Sjögren's syndrome (pSS), designed to evaluate the safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary efficacy of QLS2404 Injection. Three dose groups are planned, with approximately 24 participants to be enrolled in total and 8 participants in each dose group. All participants will receive three subcutaneous doses of QLS2404 Injection, administered at 4-week intervals. Each dose group must include at least 6 participants with SLE, and the study will be conducted in strict accordance with the dose-escalation principle.

Inclusion criteria

• Ia
• Participants who understand and comply with the study procedures and methods, voluntarily participate in this trial, provide written informed consent, and are able to complete the study in accordance with the protocol requirements.
• Male or female participants aged ≥18 and ≤45 years on the date of signing the informed consent form.
• Body mass index (BMI) at screening ≥19 kg/m² and ≤26 kg/m², with body weight ≥45 kg.
• Participants assessed by the investigator to be in good health based on medical history, physical examination, vital signs, and laboratory test results during the screening period.
• Ib
• Participants who voluntarily sign the informed consent form before the initiation of any study-related procedures, are able to communicate effectively with the investigator, understand and are willing to strictly comply with the requirements of this clinical study protocol, and complete the study.
• Male or female participants aged ≥18 and ≤65 years at the time of signing the informed consent form.
• Body mass index (BMI) at screening ≥18 kg/m² and ≤35 kg/m².
• Participants with systemic lupus erythematosus must meet the 2019 European League Against Rheumatism/American College of Rheumatology (EULAR/ACR) classification criteria for SLE and be diagnosed with systemic lupus erythematosus; the diagnosis must have been established at least 6 months prior to signing the informed consent form.
• Participants with primary Sjögren's syndrome must meet the 2016 ACR/EULAR classification criteria for primary Sjögren's syndrome and be diagnosed with primary Sjögren's syndrome; the diagnosis must have been established at least
• months prior to signing the informed consent form.

Exclusion criteria

• Ia
• QTcF interval corrected by electrocardiogram (ECG) ≥450 ms at screening; and any other ECG abnormalities that, in the investigator's opinion, may pose an unacceptable risk to the participant.
• Participants with a history of, or current, chronic or serious diseases of the musculoskeletal, neuropsychiatric, endocrine, circulatory, respiratory, digestive, urinary, reproductive, or other systems, who are considered by the investigator to be unsuitable for participation in the clinical trial.
• Participants who have lost more than 400 mL of blood due to blood donation or other reasons within 3 months prior to screening.
• Participants who are considered by the investigator to be unsuitable for participation in the clinical trial or unable to complete this study for other reasons.
• Ib
• Any disease or condition that, in the investigator's opinion, may interfere with the evaluation of study drug efficacy, participant safety assessment, or interpretation of study results.
• Participants who have participated in any cell therapy, gene therapy clinical trial, or medical device clinical trial within 3 months prior to screening.
• Participants who have received Bacillus Calmette-Guérin (BCG) vaccination within 1 year prior to screening.
• Participants who have received any live attenuated vaccine within 1 month prior to screening or who require live attenuated vaccination during study participation.
• Participants who are breastfeeding or have a positive serum human chorionic gonadotropin (hCG) test during the screening period.