Currently, the principal strategy for immune checkpoint inhibitors (ICI)-related dermatitis include systemic use of corticosteroids, which can impair the efficacy of preceding ICIs treatment. Janus kinase inhibitors (JAKi) could be the optimal option for ICI-related dermatitis, which can not only provide rapid relief for ICI-related dermatitis but also potentially enhance the anti-tumor efficacy of ICIs with minimal adverse events. This is an open-lable, phase II trial, aims to evaluate efficacy and safety of JAK inhibitors for solid malignant tumor patients with refractory ICI-related dermatitis.

Inclusion Criteria:

1. Must be at least 18 years of age
2. Clinical diagnosis of solid malignant tumor.
3. Patients who have received treatment with any Food and Drug Administration (FDA)-approved monoclonal antibodies targeting CTLA-4, PD-1, or PD-L1, either as monotherapy or in combination.
4. Clinical diagnosis of Immune checkpoint inhibitors (ICI)-related dermatitis graded as 3-4
5. Patients with ICI-related dermatitis who were refractory to previous treatment with corticosteroids and/or immunosuppressive agents.
6. Adequate bone marrow and organ function, as outlined below, must be confirmed:

1) White blood cell (WBC) count ≥ 2.0 × 10⁹/L 2) Absolute neutrophil count (ANC) ≥ 1.5 × 10⁹/L 3) Platelet count (PLT) ≥ 75 × 10⁹/L 4) Hemoglobin (Hgb) ≥ 90 g/L 5) AST and ALT ≤ 3 × upper limit of normal (ULN) in patients without hepatic metastases; ≤ 5 × ULN in those with hepatic metastases, provided the elevation is not attributable to ICI-related hepatitis 6) Total bilirubin ≤ 2 × ULN, except in cases of Gilbert's syndrome (where total bilirubin must be < 3.0 mg/dL), and not due to ICI-related hepatotoxicity 6. All participants must be capable of providing personally signed and dated informed consent, demonstrating understanding of all relevant study aspects.

Exclusion Criteria:

1. Clinical diagnosis of dermatological diseases (e.g., chronic inflammatory skin disorders such as atopic dermatitis or psoriasis) that, in the investigator's assessment, may elevate the risks associated with study participation or compromise the interpretation of study outcomes.
2. Female who is pregnant, breastfeeding, or considering pregnancy during the study.
3. Current or past history of infection including herpes zoster or herpes simplex, human immunodeficiency virus (HIV), active Tuberculosis, active or chronic recurring infection, active hepatitis B or C.
4. Patients with ICI-related dermatitis who were either treatment-naïve (having received no prior steroids or immunosuppressants)
5. Any other medical, psychiatric, or logistical condition that, in the judgment of the investigator, could pose a safety risk, affect protocol compliance, or interfere with the conduct or interpretability of the study.