A Clinical Study of MHB034C for Injection in Participants With Advanced Solid Tumors

Inclusion Criteria:

1. Participants voluntarily agree to participate in this study and sign the informed consent form.
2. Aged ≥ 18 years, regardless of sex.
3. ECOG Performance Status (PS) score of 0-1.
4. Life expectancy of more than 3 months.
5. Female participants of childbearing potential, and male participants whose partners are women of childbearing potential, must agree to use highly effective contraception with their partners; must refrain from donating gametes, from initiating gamete cryopreservation, and from retrieving or using their own previously cryopreserved gametes for conception. Female participants of childbearing potential must have a negative serum β-HCG pregnancy test within 7 days prior to the first use of the investigational medicinal product (IMP), and must not be lactating.
6. Ability to understand the study requirements and willingness and ability to comply with the study and follow-up procedures.
7. Participants enrolled in the Phase I dose escalation stage must have advanced solid tumors confirmed by histopathological or cytological examination, and must have progressed on or been intolerant to standard therapy, or have no standard treatment available.
8. Participants enrolled in the Phase II dose expansion stage must have advanced solid tumors confirmed by histopathological or cytological examination, and must have progressed on or been intolerant to standard therapy, or have no standard treatment available.
9. During the dose escalation stage, the investigator should make best efforts to obtain consent from participants to provide pre-treatment tumor tissue samples; during the dose expansion stage, participants must agree to provide pre-treatment tumor tissue samples, and if such samples cannot be provided, enrolment is permitted only with the sponsor's approval.
10. At least one measurable tumor lesion according to the RECIST v1.1 criteria.
11. Adequate bone marrow function.
12. Adequate hepatic function.
13. Adequate renal function.
14. Adequate coagulation function.
15. Adequate cardiac function.

Exclusion Criteria:

1. Has had another primary malignancy within 3 years prior to signing the informed consent form, excluding early-stage malignancies that have been curatively treated.
2. Has previously used or is currently using an antibody-drug conjugate (ADC) with a topoisomerase I inhibitor as the payload, with certain exceptions.
3. Has previously received doxorubicin at a cumulative dose of > 360 mg/m² or an equivalent dose of a similar agent.
4. Has received chemotherapy or endocrine therapy within 3 weeks, or radiotherapy, biological therapy, immunotherapy, or other anti-tumor therapy within 4 weeks, prior to the first dose of the investigational medicinal product .
5. Has spinal cord compression, leptomeningeal metastasis, brainstem metastasis, or unstable brain metastasis.
6. Adverse events from prior anti-tumor therapy have not resolved to ≤ Grade 1 as assessed by NCI-CTCAE v6.0.
7. Has undergone major surgery on a major organ (excluding biopsy) or experienced significant trauma within 4 weeks prior to the first use of the IMP, or requires elective surgery during the study period, or currently has severe unhealed or dehiscent wounds, active and clinically significant ulcers, untreated fractures, or active unhealed stomatitis.
8. Has received a live vaccine or live attenuated vaccine within 4 weeks prior to the first use of the IMP.
9. Has received or requires systemic corticosteroids or other immunosuppressive therapy within 14 days prior to the first use of the IMP, excluding topical, ophthalmic, intra-articular, intranasal, and inhaled corticosteroid therapy, and short-term corticosteroid use for prophylaxis.
10. Has moderate or severe pulmonary disease that significantly impairs pulmonary function.
11. Has a history of interstitial lung disease/pneumonitis (ILD), currently has ILD, or suspected ILD that cannot be ruled out by imaging during screening.
12. Has severe cardiovascular disease or high-risk factors.
13. Has experienced an arterial/venous thrombotic event within 6 months prior to the first dose.
14. Has a clinically evident or uncontrolled third-space fluid collection requiring repeated drainage.
15. Currently has an active autoimmune disease, or has a history of active autoimmune disease requiring systemic immunosuppressive therapy within 2 years prior to the first use of the IMP.
16. Has clinically significant corneal disease, or is currently using other medications that may cause corneal damage.
17. Has an active infection requiring systemic therapy within 7 days prior to the first dose.
18. Has clinically uncontrolled diabetes mellitus.
19. Has active tuberculosis, or a history of tuberculosis infection that was not controlled after treatment, or is still receiving anti-tuberculosis therapy; or has active syphilis.
20. Positive serological virology results: positive for HIV antibody; or positive for HBsAg or HBcAb with HBV-DNA ≥ 500 IU/mL; or positive for HCV antibody with positive HCV-RNA.
21. Has experienced clinically significant bleeding symptoms or an obvious bleeding tendency within 1 month prior to the first dose.
22. Has known hypersensitivity or delayed hypersensitivity to certain components or analogues of the IMP in this study.
23. Has a history of severe neurological or psychiatric disorders, or a history of psychotropic substance abuse or drug abuse, or any other medical condition.
24. Has known alcohol or drug dependence.
25. Has insufficient compliance to participate in this clinical study in the investigator's judgment, or the investigator considers that the participant has a history of other serious systemic diseases or other conditions unsuitable for participation in this study.