...Cohorts A and B: Histologically confirmed unresectable HER2-positive metastatic colorectal cancer, meeting the following criteria: a) Previously untreated with systemic anti-tumor therapy, or the time from (neo)adjuvant chemotherapy completion to disease recurrence > 6 months; b) Gene sequencing shows wild-type RAS and BRAF (participants' previous KRAS and BRAF test results are acceptable)....