A PhaseⅠ/Ⅱ Study of Simmitinib or Irinotecan Liposomes Combined With DP303c in Gastric Adenocarcinoma or Gastroesophageal Junction Adenocarcinoma

Inclusion Criteria: * 1\. Aged 18-75 (including) years old; 2. Gastric adenocarcinoma or gastroesophageal junction adenocarcinoma diagnosed by histology or cytology; 3. Disease progression after receiving one or two lines of systemic treatment in the past (first-line treatment must be platinum/fluorouracil combination chemotherapy with or without immune checkpoint inhibitors); 4. There should be at least one measurable lesion according to the response evaluation criteria in solid tumors (RECIST v1.1),; 5. HER2 expression status: 2+ to 3+(applicable to Cohort 1) or 1+(applicable to Cohort 2); 6. Adequate organ or bone marrow function Exclusion Criteria: * \*Eligibility Criteria: Inclusion Criteria: 1. Aged 18-75 (including) years old; 2. Gastric adenocarcinoma or gastroesophageal junction adenocarcinoma diagnosed by histology or cytology; 3. Disease progression after receiving one or two lines of systemic treatment in the past (first-line treatment must be platinum/fluorouracil combination chemotherapy with or without immune checkpoint inhibitors); 4. There should be at least one measurable lesion according to the response evaluation criteria in solid tumors (RECIST v1.1),; 5. HER2 expression status: 2+ to 3+(applicable to Cohort 1) or 1+(applicable to Cohort 2); 6. Adequate organ or bone marrow function Exclusion Criteria: 1. Patients who have experienced toxicity during previous treatment with trastuzumab or trastuzumab biosimilars, resulting in permanent discontinuation of trastuzumab or trastuzumab biosimilars; 2. Patients with a history of allergies to any component of DP303c and deemed severe by the researchers 3. There is uncontrolled serosal fluid accumulation that requires frequent drainage or medical intervention; 4. Active leptomeningeal disease or uncontrolled CNS metastasis; 5. Has a history of serious cardiovascular and cerebrovascular diseases; 6. There was a peripheral neuropathy of grade ≥ 2 (refer to NCI CTCAE 5.0) prior to enrollment; 7. History of gastrointestinal perforation and/or fistula within 6 months of first use of medication; 8. Inability to swallow medication orally or presence of clinically significant gastrointestinal diseases; 9. Urine protein ≥++ and 24-hour urine protein quantification\>1.0 g during screening period; 10. There are eye diseases that require intervention, such as corneal diseases, retinal diseases, or active eye infections; 11. Used CYP3A4 strong inhibitors or CYP3A4 strong inducers 14 days before the first medication ; 12. Used UGT1A1 strong inhibitor before first medication and wash-off period is less than 5 half-lives.