• Advanced (not amenable to curative surgery or radiation therapy) or metastatic (American Joint Committee on Cancer \[AJCC\] stage IV) solid tumors, including melanoma, nasopharyngeal squamous carcinoma, esophageal squamous cell carcinoma, gastric adenocarcinoma, renal cell carcinoma, et al.

• Fail to or could not tolerate standard treatment.

• Receive at least 2 cycles of PD-1/PD-L1/CTLA4 inhibitors and the response is complete response (CR) or partial response (PR) or stable disease (SD).

• Measurable disease as per Response Evaluation Criteria in Solid Tumors (RECIST) 1.1

• Recovery to baseline or =\< grade 1 CTCAE v5 from toxicities related to any prior treatments unless adverse events (AE\[s\]) are clinically nonsignificant and/or stable on supportive therapy

• ECOG performance status score: 0-1

• Males and females, ages \>= 18

• Absolute neutrophil count (ANC) \>= 1500/uL without granulocyte colony-stimulating factor support (within 14 days before first dose of study treatment)

• Platelets \>= 90,000/uL without transfusion (within 14 days before first dose of study treatment)

• Hemoglobin \>= 8 g/dL (\>= 80 g/L) (within 14 days before first dose of study treatment)

• Alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) =\< 3 x upper limit of normal (ULN). ALP =\< 5 x ULN with documented bone metastases (within 14 days before first dose of study treatment) Total bilirubin =\< 1.5 x ULN (for subjects with Gilbert's disease =\< 3 x ULN) (within 14 days before first dose of study treatment)

• Serum albumin \>= 3.0 g/dl (within 14 days before first dose of study treatment)

• Prothrombin time (PT)/international normalized ratio (INR) or partial thromboplastin time (PTT) test \< 1.3 x the laboratory ULN (within 14 days before first dose of study treatment)

• Serum creatinine =\< 1.5 x ULN or calculated creatinine clearance \>= 40mL/min (\>= 0.675 mL/sec) using the Cockcroft-Gault equation (within 14 days before first dose of study treatment)

• Urine protein/creatinine ratio (UPCR) =\< 1 mg/mg (=\< 113.2 mg/mmol), or 24-hour (h) urine protein =\< 1 g (within 14 days before first dose of study treatment)

• Capable of understanding and complying with the protocol requirements and must have signed the informed consent document

• Sexually active fertile subjects and their partners must agree to use medically accepted methods of contraception (e.g., barrier methods, including male condom, female condom, or diaphragm with spermicidal gel) during the course of the study and for 4 months after the last dose of treatment, 5 months after the last dose of PD-1 inhibitor for women with childbearing potential, and 7 months after the last dose of PD-1 inhibitor for men

• Female subjects of childbearing potential must not be pregnant at screening. Female subjects are considered to be of childbearing potential unless one of the following criteria is met: documented permanent sterilization (hysterectomy, bilateral salpingectomy, or bilateral oophorectomy) or documented postmenopausal status (defined as 12 months of amenorrhea in a woman \> 45 years-of-age in the absence of other biological or physiological causes. In addition, females \< 55 years-of-age must have a serum follicle stimulating \[FSH\] level \> 40 mIU/mL to confirm menopause).