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）; * ii.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; * Female participants of child-bearing potential shall agree to use effective contraception during the study and for 30 days following the last dose, and pregnancy tests at the screening and baseline visits shall be negative; male participants shall agree to use effective contraception during the study and for 30 days following the last dose. 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.