• Able and willing to give written informed consent and has signed the appropriate weitten informed consent form(ICF) prior to performance of any trial activityes.

• Eligible male and female subjects aged ≥19 years.

• Histologically or cytologically proven metastatic or locally advanced HER2 low gastric or GEJ adenocarcinoma: The definition of HER2 low is 1+ by immunohistochemistry (IHC) or 2+ by IHC and without HER2 gene amplification (negative by in situ hybridization\[ISH\]).

• Progressed after 1st line palliative treatment. Adjuvant chemotherapy will be counted as 1st line treatment if the cancer has recurred within 6 months of completion of adjuvant chemotherapy.

• Has measurable or evaluable disease as determined by RECIST ver 1.1.

• ECOG performance status of 0 -1 at trial entry.

• Life expectancy ≥12 weeks as judged by the Investigator.

• Has LVEF ≥ 50% by either echocardiogram (ECHO) or multigated acquisition (MUGA) scan within 28 days before enrollment.

• Adequate baseline organ function defined as:

‣ Absolute neutrophil count ≥1500/mm3

⁃ Platelets ≥100,000/mm3

⁃ Hemoglobin ≥9.0 g/dL

⁃ Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤3.0 × upper limit of normal (ULN) of the study site (or ≤5.0 × ULN in patients with liver metastases)

⁃ Total bilirubin ≤1.5 × ULN - Serum albumin ≥2.5 g/dL

⁃ Creatinine ≤1.5 × ULN or creatinine clearance (either measured value or estimated value using the Cockcroft-Gault equation) \>40ml/min - Urinary protein ≤1+ on dipsick or routine urinalysis - INR and PTT/aPTT ≤1.5 × ULN 10. Adequate treatment washout period before randomization/enrollment. - Major Surgery ≥ 4 weeks - Radiation Therapy including palliative stereotactic radiation therapy to chest ≥ 4 weeks

⁃ Anti-Cancer chemotherapy \[Immunotherapy (non-antibody based therapy)\] ≥ 3 weeks

∙ 11\. Evidence of post-menopausal status or negative serum pregnancy test for females of childbearing potential who are sexually active with a non-sterilized male partner.

∙ 12\. Female patients of childbearing potential who are sexually active with a non-sterilized male partner must use at least one highly effective method of contraception from the time of screening and must agree to continue using such precautions for 7 months after the last dose of IMP.

∙ 13\. Non-sterilized male patients who are sexually active with a female partner of childbearing potential must use a condom with spermicide from screening to 4 months after the final dose of IMP. 14. Female subjects must not donate, or retrieve for their own use, ova from the time of enrollment and throughout the study treatment period, and for at least 7 months after the final study drug administration