The purpose of this study is to evaluate the efficacy and safety of the study drug known as KH903 in participants with gastric and gastroesophageal cance

Inclusion Criteria:

• 1.Prior to any detailed procedures of this study, subjects are able to understand, voluntarily participate in and sign the informed consent approved by the ethics committee.
• 2.Age ≥ 18 years.
• 3.Histologically confirmed, unresectable, locally advanced or metastatic gastric or gastroesophageal junction (GEJ) adenocarcinoma .
• 4.Have at least 1 measurable lesion based on Response Evaluation Criteria in Solid Tumors (RECIST), Version 1.1.
• 5.Have experienced documented objective radiographic or symptomatic disease progression during first-line therapy, or within 4 months after the last dose of first-line therapy with any platinum or/and fluoropyrimidine doublet for unresectable or metastatic disease.Second line chemotherapy is suitable for paclitaxel.
• 6.Laboratory test values must meet the following criteria. ANC ≥1.5×109/L, platelets ≥ 100×109/L, hemoglobin≥9g/dL. Blood creatinine ≤ 1.5 ×ULN or creatinine clearance ≥ 50 mL/min/m2. Total bilirubin ≤ 1.5× ULN(≤ 3 x ULN if Gilbert disease), AST and ALT ≤ 2.5× ULN (≤ 5×ULN if hepatic metastasis).

INR ≤ 1.5× ULN, APTT ≤ 1.5× ULN. Dipstick proteinuria <2+ or 24 hour proteinuria <1g .

• 7.Good performance status Eastern Cooperative Oncology Group (ECOG) Performance Status (PS) 0 to 1.
• 8.Life expectancy of ≥ 3 months.

Exclusion Criteria:

• 1.Histologically confirmed squamous cell carcinoma or undifferentiated gastric cancer.
• 2.Patients with disease progression within 6 months after previous adjuvant or neoadjuvant chemotherapy with paclitaxel, or patients with recurrent or metastatic gastric adenocarcinoma or GEJ adenocarcinoma treated with paclitaxel.
• 3. GI perforation and/or fistulae in the 6 months preceding randomization.
• 4.Deep-vein thrombosis, pulmonary embolism (PE), or any other episode of Uncontrolled thromboembolism in the 6 months preceding randomization.
• 5.Any arterial thromboembolic event (such as myocardial infarction, unstable angina, cerebrovascular accident or transient ischemic attack)
• 6.Uncontrolled hypertension (≥150/100 mm Hg ) despite properly observed antihypertensive therapy.
• 7.Known brain metastasis.
• 8.Known allergy to paclitaxel or KH903.
• 9.Serious concurrent infection or medical illness.
• 10.Active hepatitis B virus or Active hepatitis C virus (HCV) infection at screening.
• 11.Any condition which results in an undue risk for the patient during the trial participation according to the investigator.