Open Label Study to Evaluate BL-M07D1 in HER2 Expressing Malignant Solid Tumors

Inclusion Criteria: Participants must meet all the following inclusion criteria to be eligible for participation in this study: 1. Signed the informed consent form voluntarily and agreed to follow the program requirements. 2. Either sex 3. Age: ≥18 years 4. Life expectancy of ≥3 months 5. For Dose Escalation and Dose Finding: Documented locally advanced or metastatic HER2-expressing (IHC 1+ to 3+ and/or HER2 gene amplification or activating mutation \[see Table 17-5\] in tumor specimen by ISH or NGS) solid tumor(s) not amenable to curative surgery or radiation and has received at least 2 lines of standard therapy, including adjuvant/neoadjuvant treatment, or whose cancer is considered refractory to the standard of care or for which no standard treatment is available, including: 1. Cohort 1: Participants with HER2 expression in endometrial cancers 2. Cohort 2: Participants with HER2 expression in cervical cancers 3. Cohort 3: Participants with HER2 expression in ovarian cancers, including fallopian tube cancer and primary peritoneal cancer 4. Cohort 4: Participants with HER2 expression in urothelial cancers 5. Cohort 5: Participants with HER2 expression in biliary tract cancers 6. Cohort 6: Participants with HER2 expression in breast cancer 7. Cohort 7: Participants with HER2 expression in lung cancer 8. Cohort 8: Participants with HER2 expression in gastric, esophageal, or gastroesophageal junction (GEJ) cancers 9. Cohort 9: Participants with HER2 expression in other solid tumors as approved by the medical monitor Note: For indications in which a HER2-directed therapy is approved, the approved treatment is recommended although not mandated, at the discretion of the investigator. 6. Agree to provide most recent existing tumor samples (formalin-fixed paraffin-embedded \[FFPE\] tissue block or slides) from primary or metastatic sites for tissue-based IHC staining to centrally determine HER2 expression (see details in Section 7.1.1). 1. In dose escalation and dose finding: archival tissue or fresh biopsy. If no archival tissue is available or it is not possible to obtain a fresh tissue biopsy, medical monitor approval is required to screen participant; 2. In dose expansion: an FFPE block or slides from fresh biopsy or the most recent archival tissue is required. 7. At least one measurable lesion based on RECIST (Response Evaluation Criteria in Solid Tumors) V1.1 8. Eastern Cooperative Oncology Group performance status (ECOG PS) of 0 to 1 9. Toxicity of previous antitumor therapy has returned to Grade ≤1 as defined by the National Cancer Institute (NCI) CTCAE V5.0, except for alopecia and endocrinopathies controlled by replacement therapy that must be Grade ≤2 10. No serious cardiac dysfunction, left ventricular ejection fraction ≥50% 11. Adequate organ function before enrollment, defined as: 1. Marrow function: Absolute neutrophil count (ANC) ≥1.5×10\^9/L, platelet (PLT) count ≥100×10\^9 /L, hemoglobin (Hb) ≥9.0 g/dL \[blood transfusion, PLT transfusion, erythropoietin, hematopoiesis agents, and granulocyte colony-stimulating factor (G-CSF) use are not allowed 1 week prior to screening\] 2. Hepatic function: Total bilirubin (TBIL) ≤1.5×upper limit of normal (ULN) (≤3×ULN for participants with Gilbert's syndrome or liver metastasis at baseline), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) without liver metastasis ≤3.0×ULN, AST and ALT with liver metastasis ≤5.0×ULN 3. Renal function: 1. In dose escalation and dose finding: Creatinine (Cr) clearance ≥50 mL/minute (Cockcroft-Gault equation) or estimated glomerular filtration rate (eGFR) ≥50 mL/min/1.73 m\^2 (Chronic Kidney Disease Epidemiology Collaboration \[CKD-EPI\] equation) 2. In dose expansion: Cr clearance ≥40 mL/minute (Cockcroft-Gault equation) or eGFR ≥40 mL/min/1.73 m\^2 (CKD-EPI equation) 12. Coagulation parameters: International Normalized Ratio (INR) ≤1.5×ULN, and activated partial thromboplastin time (aPTT) ≤1.5×ULN, unless receiving anticoagulation therapy with prothrombin time and aPTT levels within the intended therapeutic range 13. Urine protein ≤2+ or ≤1000 mg/24 hours (in dose escalation and dose finding only) 14. Sexually active fertile participants and their partners must agree to use highly effective methods of contraception (defined in Appendix D) during the course of the study and for a washout period after the last dose of study treatment (7 months for women of childbearing potential and 4 months for men). An additional contraceptive method, such as a barrier method (eg, condom), is recommended. 15. Women of childbearing potential (WOCBP) must have a negative serum pregnancy test at screening and must be nonlactating. Female participants are considered WOCBP unless one of the following criteria are met: documented permanent sterilization (hysterectomy, bilateral salpingectomy, or bilateral oophorectomy) or documented postmenopausal status (defined as 12 months of amenorrhea in a woman \>45 years old in the absence of other biological or physiological causes). In addition, females \<55 years old must have a serum follicle stimulating hormone (FSH) level \>40 mIU/mL to confirm menopause. NOTE: Documentation may include review of medical records, medical examination, or medical history interview by study site staff. Additional Inclusion Criteria for Dose Expansion 16. For participants with urothelial carcinoma (Part A: Randomized Doses): 1. Histologically confirmed advanced or unresectable HER2-expressing (as defined in Inclusion Criterion #5) urothelial carcinoma of the upper or lower urinary tract, not amenable to curative surgery or radiation. Mixed histological types are allowed if urothelial is the primary histology; however, small cell histology is excluded. 2. Participants with progression or recurrence following receipt of an ADC (eg, enfortumab vedotin or disitamab vedotin) and anti-PD1/PD-L1 therapy (either