This is an open-label, Phase 1b study which will be conducted in two parts: part A is the dose escalation study while part B is dose expansion study. The purpose of the dose escalation part is to identify the maximum tolerated dose (MTD) and/or recommended phase II dose (RP2D) of CM082 combined with paclitaxel in patients with advanced gastric cancer who did not respond to first-line standard chemotherapy. In the subsequent dose expansion part, additional subjects will be enrolled to further explore the safety and preliminary clinical activity of CM082 and paclitaxel.

In dose escalation part, 9-18 patients with advanced gastric cancer will be enrolled. Patients meeting enrollment eligibility will receive 28-day cycles of CM082 100-200 mg qd combined with paclitaxel 80 mg/m2. Safety information will be collected in cycle 1 to determine MTD and/or RP2D of CM082 combined with paclitaxel in patients with advanced gastric cancer.

Dose escalation study will use traditional 3+3 trial design to observe DLT and evaluate MTD. If there are 2 or more cases of DLT in one dose group, the group lower than this dose group by one level is MTD dose group. At least 6 subjects are required in MTD dose group for confirmation. If MTD is not achieved at the end of dose escalation and there are 6 subjects in the highest dose group, 200 mg qd will be determined as RP2D. Dose escalation and study in the next dose group can be initiated only after the first treatment cycle (DLT window observation period) is completed and safety and tolerability in subject is confirmed in this dose group (0/3 or ≤1/6 subjects experience DLT).

Subjects in the original dose group will continue to receive the next cycle of treatment at the original dose until it meets the following discontinued treatment criteria: 1) death, 2) intolerable toxicity, 3) pregnancy, 4) the investigator considers the study should be terminated for the subject's best interests, 5) the subject or legal representative requests withdrawal, 6) loss to follow-up, 7) the investigator considers the subject has poor compliance, 8) disease progression, 9) the investigator considers the toxicity effect will be intensified if the study continues, 10) use other anti-tumor drugs.

In dose-expansion part, additional patients will be treated at the RP2D established in dose escalation part until it meets the discontinued treatment criteria.

Inclusion Criteria:

• Fully understand the study and sign the informed consent voluntarily;
• Patients with local advanced and/or metastatic gastric adenocarcinoma and/or adenocarcinoma of gastroesophageal junction confirmed by histology and/or cytology;
• Progressed on previous first-line standard chemotherapy;
• Male or female with an age of 18-70 years(inclusive);
• Body weight ≥40 kg (inclusive);
• At least one measurable lesion (according to RECIST1.1);
• Performance status score (ECOG score) 0-1;
• Expected survival >12 weeks;
• Adequate bonemarrow, liver, renal and cardiac function, based on blood tests, electrocardiograms, and cardiac echocardiograms.

Exclusion Criteria:

• Participating in another drug clinical trial in the past 4 weeks; history of systemic anti-tumor treatment within 4 weeks prior to administration of the study drug; history of any major surgery within 4 weeks prior to enrollment to the study;
• Who have not recovered from toxicity caused by previous anti-cancer treatment (CTCAE>grade 1), or not completely recovered from previous surgery;
• Having received previous chemotherapy regimens with taxanes;
• Take medications that may extend QTc and/or Tdp;
• Active brain metastasis or meningeal metastasis;
• Uncontrolled hypertension (BP>150/90 on medications);
• Other malignancies within the last 5 years, except for adequately treated cervix carcinoma in situ or basal or squamous-cell or basal cell carcinoma;
• QT interval > 450 ms;
• Uncontrolled clinical active infection, e.g. acute pneumonia, active hepatitis B or hepatitis C; HIV positive; syphilitic spiral antibody positive;
• Dysphagia, intractable vomiting or known drug malabsorption;
• Drug or alcohol abuser.