A Clinical Trial of TQH3906 Capsules in the Treatment of Active Psoriatic Arthritis

Inclusion Criteria: * Sign a written Informed Consent Form, which must meet the following requirements * Be willing to participate in the study and able to sign the informed consent form; * Be willing and able to complete all study-specific procedures and visits; * PsA trial participant disease characteristics * Aged 18 to 70 years（inclusive）; * BMI ≥ 18 kg/m² at screening; diagnosed with PsA for at least 3 months prior to screening, and meeting the Classification Criteria for Psoriatic Arthritis (CASPAR) at screening; * Active arthritis at screening and at baseline (Day 1); * Has failed or was intolerant to at least one prior therapy; * If receiving a conventional synthetic Disease-Modifying Antirheumatic Drug (csDMARD), trial participants must be on only one DMARD, which must have been administered for at least 3 months prior to screening, with a stable dose for at least 28 days prior to the first dose; * If using NSAIDs, the dose must have been stable for at least 14 days before the first dose; * If using oral corticosteroids, the dose must have been stable for at least 14 days before the first dose; * Topical treatments for plaque psoriasis must have remained stable for at least 14 days before the first dose; * Women of childbearing potential must agree to use effective contraception during the study and for 6 months after the end of the study; men must agree to use effective contraception during the study and for 6 months after the end of the study Exclusion Criteria: * Presence of conditions other than PsA: * Presence of non-plaque psoriasis (i.e., guttate, inverse, pustular, erythrodermic, or drug-induced psoriasis) at screening or first dose; * Presence of any other autoimmune disease, such as rheumatoid arthritis, systemic lupus erythematosus, etc.; * Presence of active (i.e., currently symptomatic) fibromyalgia; * Other Medical Conditions and Medical History: * Trial participants who are pregnant or breastfeeding; * Evidence of a serious illness/condition or unstable clinical condition, or localized active infection/infectious disease; * Any major surgery performed within 30 days prior to the first dose of study treatment, or any planned surgery during the study; * Cancer or a history of cancer or lymphoproliferative disease within the past 5 years; * New York Heart Association (NYHA) Class III or IV congestive heart failure, or any recent episode of heart failure resulting in NYHA Class III/IV symptoms; or a history of clinically significant ventricular arrhythmia or arrhythmia requiring continuous antiarrhythmic drug therapy; * Uncontrolled hypertension at screening or randomization; * History of thrombotic disease within 24 weeks prior to screening; viii. History of acute coronary syndrome and/or any major cerebrovascular disease within 24 weeks prior to screening; * Current or recent (within 3 months prior to randomization) gastrointestinal disease that may affect absorption of study treatment, including gastrointestinal surgery; * Severe blood loss (\> 500 mL) or blood transfusion within 4 weeks prior to randomization; * Inability to take oral medication; * Inability to undergo venipuncture and/or tolerate venous access; * History of substance abuse with inability to abstain or presence of a psychiatric disorder; * Any other medical, psychiatric, and/or social reason as determined by medical judgment; * Prior and concomitant medications: If the trial participant has a history of biologic use, the exclusion criteria specified in the protocol will apply; * Infection-related: * Active tuberculosis identified by chest radiography within 6 months prior to screening; trial participants with a negative chest radiography within 3 months prior to screening are eligible if they meet the protocol requirements; * Hepatitis C, hepatitis B, or human immunodeficiency virus (HIV) infection; or syphilis infection requiring treatment; * Abnormal physical examination or laboratory findings; * Other: * History of any major drug allergy; known allergy to any excipient of the investigational product; * Inability to comply with the trial protocol; * History of substance abuse with inability to abstain or presence of a psychiatric disorder; * Participation in another clinical trial and use of another investigational drug (other than for psoriatic arthritis) within 4 weeks prior to the first dose, based on the date of discontinuation from the previous trial; * Planned or previous allogeneic bone marrow transplantation or solid organ transplantation; * Any condition that, in the investigator's judgment, poses a serious risk to the safety of the trial participant or affects the participant's ability to complete the study.