Treatment of Moderate to Severe Plaque Psoriasis

Inclusion Criteria:

• Be 18-70 years old (both 18 and 70 years old), regardless of gender；

• Clinically diagnosed with stable moderate to severe plaque psoriasis with a history ≥ 6 months (from randomization), and no morphological changes in skin lesions orsignificant disease outbreaks as assessed by the investigator;

• Appropriate for systemic therapy or phototherapy as judged by the investigator;

• At screening and baseline, the PASI score was ≥ 12 points, the BSA ≥ 10%, and thesPGA ≥ 3 points ;

• Have a full understanding of this study, voluntarily participate in the trial, andhave signed a written informed consent form;

• Subjects (including partners) are willing to voluntarily use appropriate andeffective contraceptive measures from screening to 3 months after the last dose ofstudy drug.

Exclusion Criteria:

• Pregnant and lactating females;

• Have other forms of psoriasis other than plaque psoriasis (e.g., guttate psoriasis,generalized pustular psoriasis, erythrodermic psoriasis, arthropathic psoriasis);

• Presence of serovirological abnormalities during the screening period:

1. Active hepatitis, or hepatitis B surface antigen (HBsAg) positive, or hepatitisB core antibody (HBcA positive and Hepatitis B virus (HBV) DNA positive, orHepatitis C virus (HCV) antibody positive and HCV-RNA positive;

2. Positive for HIV antibody during the screening period, or have a history of HIVinfection in the past;

3. Positive Treponema pallidum antibody and positive non-Treponema pallidum serumtest (RPR or TRUST) during the screening period;

• Have a history of active tuberculosis during the screening period or before, or havelatent tuberculosis infection found at screening (refers to T-SPOT positive withoutclinical manifestations). (Note: Patients with latent tuberculosis infection can bere-screened 1 month after starting prophylaxis according to the guidelines, and inorder to continue to participate in the study, patients must agree to continue tocomplete the prophylactic regimen during the study, but rifampicin treatment shouldbe avoided.) ;

• Has a history of severe herpes zoster or herpes simplex infection, including but notlimited to herpetic encephalitis, disseminated herpes simplex, generalized herpeszoster;

• History of severe bacterial, fungal or viral infection within 2 months prior torandomization, requiring hospitalization for intravenous antibiotics or antiviraldrug treatment;

• Live vaccine within 4 weeks prior to randomization or planned live vaccine duringthe study;

• Clinically significant infection, including but not limited to upper respiratorytract infection, lower respiratory tract infection, herpes simplex, herpes zoster,during the screening period, and requiring antibiotic or antiviral medicationtreatment;

• Has any significant illness or unstable clinical condition (such as renal, hepatic,hematologic, gastrointestinal, endocrine, pulmonary, psychiatric, neurological,immune, or locally active infectious/infectious disease) that is judged by theinvestigator to be unsuitable for participation in this study.

• Abnormal laboratory tests during the screening period:

1. Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) ≥ 3 timesupper limit of normal (ULN);

2. Hemoglobin <90g/L;

3. White blood cell count< 3.0×109/L;

4. Neutrophil count<1.0×109/L;

5. Lymphocyte count<0.5×109/L;

6. Platelet count < 100×109/L;

7. Total bilirubin >2 times ULN;

8. Other significant laboratory test abnormalities that, in the opinion of theinvestigator, the subject is not suitable for participation in this study.

• History of malignant tumors (including carcinoma in situ) and lymphoproliferativedisorders within 5 years prior to randomization;

• Those who have received anti-IL-12, IL-17, Interleukin 23 (IL-23) monoclonalantibody therapy (such as ustekinumab, secukinumab, Ixekizumab, guselkumab,adalimumab, etc.) within 6 months prior to randomization, or those who have receivedat least 12 consecutive times of the above drugs in the past but have poor clinicalresponse (defined as not achieving PASI 50 during treatment);

• Receipt of any other marketed or investigational biologic agent within 3 months or 5half-lives (whichever is longer) prior to randomization;

• Receipt of any other investigational drug in 1 month or 5 half-lives (whichever islonger) prior to randomization;

• Those who have undergone surgical surgery within 4 weeks prior to randomization, orwho plan to undergo surgical procedures during the study;

• Those who have lost blood or donated more than 400 mL of blood within 4 weeks priorto randomization;

• Receipt of immunoglobulin or blood products within 4 weeks prior to randomization;

• Systemic treatment drugs or immunosuppressants for psoriasis within 4 weeks prior torandomization, including but not limited to retinoids, glucocorticoids,methotrexate, cyclosporine, azathioprine, Janus kinase (JAK) inhibitors, etc;

• Use of strong CYP450 inducers (such as rifampicin, phenobarbital, carbamazepine,phenytoin, etc.) within 4 weeks prior to randomization;

• Received topical or systemic phototherapy within 4 weeks prior to randomization,including but not limited to Narrow-band ultraviolet B (NB-UVB), photochemotherapy (PUVA), 308nm excimer light;

• Use of topical drugs that may affect the severity of skin lesions in psoriasiswithin 2 weeks prior to randomization, including but not limited to glucocorticoids,urea, >3% salicylic acid, α or β hydroxy acids, retinoids, vitamin D3 analogues,calcineurin inhibitors, Phosphodiesterase-4 (PDE-4) inhibitors, etc. (Note: Mildemollients (without active substances such as urea, salicylic acid, α, or β hydroxyacids) are allowed to be used at all sites, but should not be used within 24 hoursprior to each study visit);

• Potential difficulty in blood collection, with a history of fainting needle andblood sickness;

• Allergy to any of the known ingredients of the TQH3906, or any previous history ofsevere drug allergies.

• Those with a history of substance abuse or a positive urine drug screen;

• Has any other reasonable medical, psychiatric, or social reason that, in the opinionof the investigator, precludes participation in this study.