A Phase Ib/II Clinical Trial to Evaluate the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Multiple Doses of STSA-1301 Subcutaneous Injection in Healthy Subjects and Patients With Immune Thrombocytopenia (ITP)
A randomized, double-blind, placebo-controlled design was designed to evaluate the safety and tolerability, pharmacokinetic/pharmacodynamic profile, and immunogenicity of multiple administration of STSA-1301 subcutaneous injection in healthy subjects and patients with ITP, and to further explore the initial efficacy of STSA-1301 subcutaneous injection in patients with ITP
⁃ \- (stage I):
• 18 years ≤ age ≤ 50 years, male or female subjects;
• Body mass index is 18 kg/m\^2≤ BMI≤ 26kg/m\^2;
• Subjects (including the subject's partner) are willing to use effective contraception during the study period and have no plans to have children or to donate sperm or eggs from the time of signing the informed consent form until 3 months after the last dose;
• Pre-randomization medical history had no effect on enrollment in the trial, and physical examination, laboratory test items, and all tests related to the trial were normal or the investigator determined that the abnormalities were not clinically significant;
• Subjects are aware of the risks of the trial and voluntarily participate in this clinical trial and sign an informed consent form.
⁃ (stage 2):
• Aged 18 to 75 years, inclusive, and of either gender.
• Clinically diagnosed with persistent or chronic primary immune thrombocytopenia (ITP) with no known other causes of thrombocytopenia.
• The ITP diagnosis of the subject is supported by a prior response to ITP treatment with a platelet count reaching ≥50×10\^9/L.
• One platelet test during the screening period and one during the baseline period (with an interval of at least 7 days), with an average platelet count \<30×10\^9/L and no single platelet count \>35×10\^9/L. No severe bleeding within 4 weeks prior to the screening visit.
• Subjects who have previously failed at least one first-line standard ITP treatment (corticosteroids and/or intravenous immunoglobulin) (defined as inability to maintain efficacy or relapse), or are intolerant to first-line standard treatment.
• The study allows the concurrent use of the following ITP treatment medications at a stable dose: oral corticosteroids, danazol, dapsone, oral immunosuppressants (azathioprine, methotrexate, cyclosporine A, mycophenolate mofetil), or TPO-RA (limited to oral small molecule non-peptide). A stable dose means that the treatment dose and frequency have been stable for at least 4 weeks prior to randomization and are not expected to change during the study.
• The subject (including the subject's partner) is willing to use effective contraception from the time of signing the informed consent form until 3 months after the last dose of study drug, and has no plans for pregnancy or sperm/egg donation during this period.
• The subject fully understands and is able to comply with the requirements of the study protocol and voluntarily signs the informed consent form.