Inclusion Criteria:  Male or female adult, 18 years of age or older providing written informed consent. Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0 or 1. Histologically or cytologically-documented, incurable locally advanced or metastatic solid tumor of one of the following types: Cohort A: oesophageal squamous-cell carcinoma that was refractory or intolerant to fluoropyrimidine-based, platinum-based, and taxane-based chemotherapy. Cohort B: gastric adenocarcinoma that was refractory or intolerant to fluoropyrimidine-based, platinum-based, and taxane-based chemotherapy. Cohort C: cervical cancer that was refractory or intolerant to platinum-based and taxane-based chemotherapy. Measurable disease by computed tomography (CT) or magnetic resonance imaging (MRI) in accordance with RECIST v 1.1, bone-only disease is not measurable and is not permitted. Availability of archival tumor tissue or newly acquired biopsy (unstaining tumor slides, recommended from metastasis sites). Adequate bone marrow, hepatic and renal function. Recovered from all prior treatment-related toxicities to Grade 1 or less by NCI-CTCAE v 5.0 (except alopecia or peripheral neuropathy that may be Grade 2 or less). Patients must have completed all prior cancer treatments at least 2 weeks prior to the first dose including chemotherapy , radiotherapy and major surgery. Prior antibody treatment for cancer must have been completed at least 3 weeks prior to the first dose. Patients must have at least a 3-month life expectancy  Exclusion Criteria:  Previous treatment with topoisomerase I inhibitors as a free form or as other formulations. Previous treatment with Trop-2 targeted therapy. Patients with a history of or current central nervous system (CNS) metastases. A scan to confirm the absence of brain metastases is not required. Patients with unknown CNS metastatic status and any clinical signs indicative of CNS metastases are eligible if CNS metastases are excluded using CT and/or MRI scans. Known additional malignancy within 3 years prior to enrollment with the exception of curatively treated basal cell carcinoma of the skin, squamous cell carcinoma of the skin and/or curatively resected in situ cancers. Patients known to be human immunodeficiency virus positive. Patients with active hepatitis B virus (HBV), or hepatitis C virus (HCV) infection. Hepatitis B core antibody (HBcAb) testing is required and if positive, then HBV DNA testing will be performed and if positive the patient will be excluded. Known history of unstable angina, myocardial infarction (MI), or chronic heart failure present within 6 months of first dose or clinically significant cardiac arrhythmia (other than stable atrial fibrillation) requiring anti-arrhythmia therapy or left ventricular ejection fraction < 50%. Known history of clinically significant active chronic obstructive pulmonary disease, or other moderate-to-severe chronic respiratory illness present within 6 months of the first dose.  Patients with active chronic inflammatory bowel disease (ulcerative colitis, Crohn disease) and patients with a history of bowel obstruction or gastrointestinal (GI) perforation.  Infection requiring systematic antibiotic use within 1 week of the first dose. High dose systemic corticosteroids within 2 weeks prior to the first dose (however, low dose corticosteroids ≤ 10 mg prednisone or equivalent daily are permitted provided the dose is stable for 4 weeks). Patients who have received a live vaccine within 30 days of first dose. Rapid deterioration during Screening prior to the first dose, eg, significant change in PS, substantial increase in hydrothorax, unstable pain symptoms requiring modifications in analgesic management. Other concurrent medical or psychiatric conditions that, in the Investigator's opinion, may be likely to confound study interpretation or prevent completion of study procedures and follow-up examinations. Women who are pregnant or lactating. Women of childbearing potential or fertile men unwilling to use highly effective contraception during study and up to 6 months after treatment discontinuation in women of childbearing potential and 3 months in males post last investigational product (IP) administration.