inclusion Criteria:
Age ≥ 18 years at the time of screening.
Diagnosis of palmoplantar pustulosis (PPP) for at least 12 weeks prior to the screening visit.
May have a history of or concurrent plaque psoriasis.
PPPASI score ≥ 12 at both the screening and baseline visits.
PPP-IGA score ≥ 3 at both the screening and baseline visits.
Presence of pustules on the palms and/or soles at both the screening and baseline visits, defined as pustule severity ≥ 2 in at least one region (one palm or one sole) based on the PPPASI.
Must have a confirmed diagnosis of PPP by photographic adjudication.
Male and/or female participants.
Female participants must not be pregnant, not be lactating (including feeding an infant by breast pump).
Exclusion Criteria:
Significant improvement in PPP symptoms between the screening and baseline visits, defined as a reduction in PPPASI score of ≥ 5 units.
Presence of any of the following conditions: guttate psoriasis, erythrodermic psoriasis, generalized pustular psoriasis, acrodermatitis continua of Hallopeau, atopic dermatitis, dyshidrotic eczema, chronic hand eczema, or folliculitis.
Drug-induced psoriasis (e.g., first onset or current flare triggered by beta-blockers, calcium channel inhibitors, lithium preparations, or TNF inhibitors) or drug-induced pustular psoriasis (e.g., acute generalized exanthematous pustulosis, acute localized exanthematous pustulosis).
Active infection or history of infection, as follows:
Any active infection within 14 days prior to the baseline visit.
Severe infection requiring hospitalization or intravenous anti-infective treatment within 8 weeks prior to the baseline visit.
History of opportunistic infections, recurrent infections, or chronic infections that, in the investigator's opinion, would make participation in this study harmful to the participant.
Positive test results for acute or chronic hepatitis B virus (HBV), hepatitis C virus (HCV), or human immunodeficiency virus (HIV). Exclusion is defined as:
HBV positive: 1) hepatitis B surface antigen positive, or 2) anti-hepatitis B core antibody positive.
HCV positive: 1) hepatitis C antibody positive, and 2) confirmed by a confirmatory HCV test (e.g., HCV polymerase chain reaction).
Any of the following tuberculosis (TB)-related conditions:
Known active TB disease.
History of active TB involving any organ system, unless adequately treated per WHO/CDC treatment guidelines and confirmed as fully recovered by consultation with a relevant specialist.
Latent TB infection (LTBI): Participants with LTBI may be rescreened once after receiving at least 4 weeks of appropriate LTBI treatment, provided that no treatment-related hepatotoxicity is evident prior to the first dose of investigational medicinal product (ALT/AST still ≤ 3×ULN).
History of lymphoproliferative disorders (e.g., lymphoma) or current symptoms suggestive of lymphoproliferative disorders.
Current active malignancy or history of malignancy within 5 years prior to the screening visit, except for squamous cell carcinoma or basal cell carcinoma of the skin, or treated and considered cured in situ cervical cancer.
Presence of other inflammatory diseases, including but not limited to rheumatoid arthritis, hidradenitis suppurativa, inflammatory bowel disease, or systemic lupus erythematosus.
Major surgery (including joint surgery) within 8 weeks prior to the screening visit, or planned surgery during the study period.
Any systemic disease (e.g., cardiovascular, neurological, renal, hepatic, metabolic, gastrointestinal, hematological, coagulation disorders, immune system disease) that, in the investigator's opinion, is uncontrolled, unstable, or likely to progress to a clinically significant degree during the study.
Any medical or psychiatric condition (including ongoing major depression or active suicidal ideation) that, in the investigator's opinion, may impair the participant's ability to participate in the study.
History of chronic alcohol or drug abuse within 6 months prior to the screening visit, as determined by the investigator based on medical history, interview, and examination findings.
Current or prior use of IL-17A, IL-17A/F, or IL-23 inhibitors.
Receipt of any live vaccine (including attenuated vaccines) within 8 weeks prior to the baseline visit.
Vaccination not permitted during the study and within 17 weeks after the last dose of study treatment.
Laboratory abnormalities at the screening visit, including any of the following:
ALT, AST, or ALP ≥ 3×ULN.
Bilirubin \> 1.5×ULN (unconjugated bilirubin \> 1.5×ULN is acceptable if bilirubin is fractionated and direct bilirubin/total bilirubin ratio is \< 35%).
White blood cell count \< 3.0×10³/μL.
Absolute neutrophil count \< 1.5×10³/μL.
Lymphocyte count \< 500 cells/μL.
Hemoglobin \< 8.5 g/dL.
Any other laboratory abnormality that, in the investigator's opinion, may interfere with the participant's ability to complete the study or confound the interpretation of study results.
