Phase Ia/Ib Study of FXB0871 Monotherapy in Locally Advanced/Metastatic Solid Tumors

Inclusion Criteria:

* Signed informed consent.
* Age ≥18 years.
* Histologically confirmed selected locally advanced or metastatic solid tumor with progression on, intolerance to, or no suitable standard therapy.
* ECOG performance status 0 or 1.
* At least one measurable lesion per RECIST v1.1.
* Pretreatment tumor tissue available (archival or fresh biopsy).
* Life expectancy ≥12 weeks.
* Oxygen saturation ≥92% on room air.
* Left ventricular ejection fraction \>50%.
* Adequate hematologic, coagulation, renal, hepatic, and cardiac function.
* Women of childbearing potential and sexually active men must use highly effective contraception.
* Tumor-specific eligibility applies, including prior anti-PD-(L)1 treatment failure for the selected cohorts.

Key Exclusion Criteria:

* Systemic anti-cancer therapy, major surgery, or radical radiotherapy within 4 weeks before first dose.
* Prior treatment with IL-2, IL-15, or IL-7.
* Active autoimmune disease requiring systemic treatment or immunodeficiency.
* Systemic corticosteroids (≥10 mg/day prednisone equivalent) or other immunosuppressive therapy within 28 days before first dose, with limited protocol-defined exceptions.
* Active or untreated central nervous system metastases, carcinomatous meningitis, or leptomeningeal disease.
* Uncontrolled infection or clinically significant unresolved toxicities from prior therapy.
* Clinically significant cardiovascular/cerebrovascular disease, uncontrolled effusions/ascites, uncontrolled hypertension, or QTcF \>470 ms.
* Active hepatitis B/C, syphilis, or HIV infection.
* Clinically significant interstitial lung disease or active noninfectious pneumonitis.
* Pregnancy or breastfeeding.
* Any other serious medical or psychiatric condition that, in the investigator's judgment, would make participation inappropriate.