Inclusion Criteria:
* Adults (≥18 years) with confirmed T-cell lymphoma subtypes: PTCL (including nodal T-follicular helper cell lymphoma, ALCL, PTCL NOS) for Parts 1 and 2; CTCL (mycosis fungoides and Sézary syndrome, stages IIB-IV) for Parts 1 and 2, with specific disease involvement criteria in Part 2.
* PTCL participants must have relapsed/refractory/intolerant to ≥1 systemic therapy; CD30+ PTCL must have prior brentuximab vedotin treatment or intolerance, and/or ALK-positive ALCL participants should have previously received crizotinib if indicated (crizotinib administration is applicable to US sites only). CTCL participants must have relapsed/refractory/intolerant to ≥2 systemic therapies.
* Availability of tumor tissue (current or archival) is required.
* Measurable disease required: nodal/extranodal lesions for PTCL and assessable skin disease for CTCL.
* ECOG performance status 0-1; adequate neutrophils (≥1000/µL), platelets (≥75,000/µL), renal function (creatinine clearance ≥60 mL/min), liver function within defined limits, and total bilirubin ≤1.5× ULN (up to 3× ULN with Gilbert's syndrome).
* Life expectancy ≥3 months.
* Negative pregnancy test for females of childbearing potential; contraception required for females and males with partners of childbearing potential during and after treatment.
* Restrictions on gamete donation and freezing during and after treatment.
* Ability to provide informed consent and comply with study procedures. -
Exclusion Criteria:
* Recent autologous or allogeneic transplant within 120 days before treatment; active GVHD or ongoing immunosuppression after allogeneic transplant.
* Pregnant or breastfeeding females, or those intending pregnancy; males with partners intending pregnancy.
* History of HIV, HBV, or HCV infections generally excluded, except for controlled or resolved cases as defined.
* Uncontrolled infections requiring IV antibiotics, antivirals, or antifungals at screening through treatment start.
* Significant medical history or complications within six months prior to enrollment, including advanced congestive heart failure (NYHA Class III or higher), recent unstable angina or myocardial infarction, autoimmune diseases requiring systemic immunosuppressive therapy, active or uncontrolled ocular diseases, Grade 3 or 4 peripheral neuropathy, or other poorly controlled conditions as judged by the investigator (e.g., uncontrolled hypertension, diabetes, or arrhythmias).
* Use of other investigational drugs within 14 days or 5 half-lives before treatment.
* Steroid use over 10 mg/day prednisone equivalent within 14 days prior, except limited corticosteroid use with specific tapering guidelines; topical steroids allowed under conditions for CTCL.
* Major surgery, radiotherapy, chemotherapy, or other anti-cancer treatments within 14 days or 5 half-lives before treatment.
* Prior mogamulizumab use within six months before treatment; associated rash must be ruled out if \>6 months.
* Failure to recover from prior non-hematologic toxicities to Grade 0 or 1 (except alopecia and mild neuropathy).
* Prolonged QT/QTc interval (e.g., QTcF \>480 ms).
* Active second primary malignancies except specified non-exclusionary cases.
* CNS involvement.
* Any condition that may impair compliance or study completion as judged by the Investigator.-
