Study Population: Adult subjects aged 18-75 years with relapsed/refractory advanced solid tumors (including liver, gastric, colorectal, ovarian cancer, etc.) and malignant ascites confirmed by cytology, who have failed at least 2 lines of standard systemic therapy.
Study Design: This is a dose-escalation, single-center, open-label, prospective Phase 1 study. A total of 18 subjects will be enrolled and assigned to 2 administration groups (9 subjects each):
Group A (Intravenous infusion): For subjects with small-volume malignant ascites.
Group B (Intraperitoneal perfusion): For subjects with large-volume symptomatic malignant ascites.
Each group will follow a conventional "3+3" dose-escalation design with 3 dose levels (1×10⁹, 3×10⁹, 6×10⁹ NK cells per dose), administered once weekly, 3 weeks per cycle, for 2 consecutive cycles.
Primary Objectives: To evaluate the safety and tolerability, and to determine the dose-limiting toxicity (DLT) of NK521 administered intravenously and intraperitoneally.
Secondary Objectives: To assess the preliminary anti-tumor efficacy including objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS), overall survival (OS), duration of response (DOR), puncture-free survival (PuFS), and changes in tumor markers, as well as health-related quality of life (HRQoL).
Pathologically diagnosed with relapsed/refractory advanced solid tumors, including but not limited to liver cancer, gastric cancer, colorectal cancer, ovarian cancer, etc.
Complicated with malignant ascites with identifiable tumor cells in ascites. Patients with advanced solid tumors who have failed at least 2 lines of standard therapy.
At least one measurable lesion on CT or MRI per RECIST v1.1.
ECOG performance status 0-2.
Symptomatic central nervous system (CNS) metastasis and/or carcinomatous meningitis.
History of other malignancies within the past 3 years.
Active, known or suspected autoimmune disease, excluding hypothyroidism requiring only hormone replacement therapy, skin diseases not requiring systemic therapy (e.g., vitiligo, psoriasis, alopecia), or diseases not expected to relapse without external triggers.
History of immunodeficiency, including positive HIV test, other acquired or congenital immunodeficiency diseases, or organ transplantation.