Avatrombopag vs. Placebo for CIT in GI Malignancies

Inclusion Criteria: * A diagnosis of persistent chemotherapy-induced thrombocytopenia, as defined by a platelet count of \<85,000/µL on Day 1 of a chemotherapy cycle. * Age ≥18 years at the time of informed consent. Because no dosing or adverse event data are currently available on the use of avatrombopag for CIT in participants \<18 years of age, children are excluded from this study, but may be eligible for future pediatric trials. * Receiving cytotoxic chemotherapy for a gastrointestinal malignancy, including esophageal, gastric, small bowel, hepatobiliary (cholangiocarcinoma, gallbladder carcinoma, hepatocellular carcinoma), pancreatic, or colorectal cancer. Lymphomas are not eligible. Patients of any stage are eligible. * The chemotherapy regimen being used to treat the patient's gastrointestinal malignancy must be administered in 14, 21, or 28-day cycles and include at least one of the following agents: fluorouracil, capecitabine, floxuridine, trifluridine/tipiracil, gemcitabine, cisplatin, carboplatin, oxaliplatin, irinotecan, liposomal irinotecan, paclitaxel, nanoalbumin-bound paclitaxel, docetaxel, epirubicin, or doxorubicin. * A plan to continue the current chemotherapy regimen (the regimen that resulted in CIT) at the same dose and schedule for at least 1 more cycle if the platelet count is adequate (\>100,000/µL). * Participant has not received cytotoxic chemotherapy in the 13 days before study Day 1, except for infusional fluorouracil in regimens with a 14-day c…