A Study to Evaluate Rivoceranib Plus Best Supportive Care Compared to Placebo Plus Best Supportive Care in Participants With Gastric Cancer

Inclusion Criteria

• Documented primary diagnosis of histologic- or cytologic-confirmed adenocarcinoma of the stomach or gastroesophageal junction.
• Locally advanced unresectable or metastatic disease that has progressed since last treatment.
• One or more measurable or nonmeasurable evaluable lesions per Response Evaluation Criteria in Solid Tumors Version 1.1 (RECIST 1.1).
• Failure or intolerance to at least 2 prior lines of standard chemotherapies with each containing one or more of the following agents:
• fluoropyrimidine (intravenous [IV] 5-fluorouracil [5-FU] capecitabine, or S-1),
• platinum (cisplatin or oxaliplatin),
• taxanes (paclitaxel or docetaxel) or epirubicin,
• irinotecan,
• trastuzumab in case of human epidermal growth factor receptor 2 (HER2)-positive,
• ramucirumab
• nivolumab
• pembrolizumab
• Disease progression within 6 months after the last treatment.
• Adequate bone-marrow, renal and liver function.
• Eastern Cooperative Oncology Group (ECOG) performance status of ≤1.
• Expected survival of ≥12 weeks, in the opinion of the investigator.

Exclusion Criteria

• History of another malignancy within 2 years prior to randomization except for the following: Bladder tumors considered superficial such as noninvasive (T1a) and carcinoma in situ (CIS); Curatively treated cervical CIS; Thyroid papillary cancer with prior treatment; Carcinoma of the skin without melanomatous features; Prostate cancer which had been surgically or medically treated and not likely to recur within 2 years.
• Central nervous system (CNS) metastases as shown by radiology records or clinical evidence of symptomatic CNS involvement in the last 3 months prior to randomization.
• Cytotoxic chemotherapy, surgery, immunotherapy, radiotherapy or other targeted therapies within 3 weeks (4 weeks in cases of ramucirumab, mitomycin C, nitrosourea, lomustine; 1 week in case of biopsy) prior to randomization (Adjuvant radiotherapy given to local area for non-curative symptom relief is allowed until 2 weeks before randomization.).
• Therapy with clinically significant systemic anticoagulant or antithrombotic agents within 7 days prior to randomization that may prevent blood clotting and, in the investigator's opinion, could place the participant at risk.
• Participants who had therapeutic paracentesis of ascites (>1 Liter [L]) within the 3 months prior to starting study treatment or who, in the opinion of the investigator, will likely need therapeutic paracentesis of ascites (>1L) within 3 months of starting study treatment.
• Previous treatment with rivoceranib.
• Known hypersensitivity to rivoceranib or components of the formulation.
• Concomitant treatment with strong inhibitors or inducers of CYP3A4, CYP2C9, and CYP2C19.