A Multicenter Study of IBI343 Monotherapy Versus Placebo in Subjects With Previously Treated, Claudin (CLDN) 18.2-positive, Pancreatic Cancer(G-HOPE-002)

Inclusion Criteria: 1. Sign the written informed consent form (ICF) and be willing and able to comply with the visits and related procedures stipulated in the plan. 2. Histologically confirmed unresectable locally advanced, or metastatic pancreatic cancer. 3. Have received and progression after at least two systemic therapies(must including a fluorouracil-based and a gemcitabine-based therapy). 4. ECOG PS score of 0 or 2. 5. Adequate bone marrow and organ function 6. Confirmed as CLDN18.2 positive. Exclusion Criteria: 1. Participation in another interventional study, except observational or post-intervention follow-up. 2. Prior treatment with topoisomerase inhibitor-based ADC. 3. Has received the last dose of an anti-cancer therapy within 2 weeks or 5 half-lives (whichever is shorter) prior to the first dose of study treatment. 4. Plans to receive other anti-tumor treatments during treatment with the study drug (palliative radiotherapy for symptomatic (e.g., pain) relief that does not affect response assessment is allowed) . 5. Symptomatic CNS metastasis; asymptomatic brain metastases may be allowed with specific criteria. 6. History of other primary malignancies, except cured or low-risk of recurrence.