Inclusion Criteria:
1. Aged 18-75 years (inclusive) (based on the day of signing the informed consent form).
2. Histologically or cytologically confirmed advanced/unresectable, or metastatic solid tumors that have relapsed or progressed on or after standard systemic treatment, or are intolerant to standard treatment, or no standard treatment is available.
3. At least one measurable lesion according to Response Evaluation Criteria in Solid Tumors (RECIST v1.1) (not required in the dose escalation phase).
4. ECOG score 0-1.
5. Participant is expected to survive ≥ 3 months.
6. The vital organ functions (hematology, liver and kidney function, coagulation function, etc.) meet the protocol requirements within 7 days prior to enrollment.
7. Toxicity caused by any previous treatment has recovered to CTCAE 6.0 ≤ Grade 1 or baseline level.
8. Adequate treatment washout period for prior antineoplastic therapy prior to the first dose.
9. Able to provide a prior resected tumor sample or willing to undergo a fresh tumor biopsy.
10. Female participants of childbearing potential have a negative serum pregnancy test within 7 days prior to enrollment. Male and female participants of childbearing potential must agree to use adequate contraception during the study and for at least 7 months after the last dose of study drug; During this period, women must not be breastfeeding, male participants must not freeze or donate sperm, and female participants must not donate or retrieve ova for their own use.
11. Fully understand this clinical trial and voluntarily sign a written informed consent form.
Exclusion Criteria:
1. Prior treatment with CEACAM5-targeted therapy or TOP1 ADC agents.
2. History of symptomatic congestive heart failure (CHF) (New York Heart Association \[NYHA\] Class II-IV) or serious arrhythmia requiring treatment.
3. History of myocardial infarction or unstable angina within 6 months prior to enrollment.
4. Male and female mean QT interval corrected by Fredericia's formula (QTcF) prolongation to \> 470 msec in females or \> 450 msec in males based on triplicate 12-lead electrocardiograms (ECGs).
5. Inability or unwillingness to discontinue concomitant medications known to prolong the QT interval.
6. Has a history of interstitial lung disease (e.g., non-infectious interstitial pneumonitis, pulmonary fibrosis, and severe radiation pneumonitis) or current interstitial lung disease or is suspected to have this disease by imaging at screening.
7. History of underlying pulmonary disease, including but not limited to pulmonary embolism within 3 months of starting study treatment, severe asthma, severe COPD, restrictive lung disease, and other clinically significant pulmonary compromise or requirement for supplemental oxygen.
8. Any autoimmune, connective tissue or inflammatory disorders (eg, rheumatoid arthritis, Sjögren's syndrome, sarcoidosis, etc.) where there is documented, or a suspicion of pulmonary involvement at the time of screening.
9. Uncontrolled infection requiring IV antibiotics, antivirals, or antifungals.
10. Known human immunodeficiency virus (HIV) infection.
11. Current active syphilis infection (i.e., positive for Treponema pallidum antibodies (RPR or TRUST) or requiring systemic treatment)
12. Participants with active viral (any etiology) hepatitis are excluded.
13. Breastfeeding women (women who are willing to temporarily interrupt breastfeeding will also be excluded), or those who are pregnant as confirmed by pregnancy test within 7 days prior to enrollment.
14. Has spinal cord compression or clinically active brain metastases, defined as untreated, symptomatic, or requiring corticosteroids or anticonvulsants to control associated symptoms. Participants with asymptomatic CNS metastases who are radiologically and neurologically stable for at least 4 weeks following CNS-directed therapy and are on stable or tapering doses of corticosteroids equivalent to ≤10 mg/day prednisone are eligible.
15. Has multiple primary malignancies within 3 years prior to enrollment, except adequately resected non-melanoma skin cancer (e.g., resected basal or squamous cell skin cancer), curatively treated in situ disease (e.g., carcinoma in situ of the cervix or breast), or other solid tumors curatively treated (e.g., superficial bladder cancer).
16. Substance abuse or any other medical condition that, in the opinion of the investigator, may increase the safety risk of the participant or interfere with the participant's participation in the clinical study or the evaluation of the clinical study.
17. Participants who have received strong CYP3A4 inhibitors or inducers within 14 days prior to the first dose of study drug or will continue to use such drugs during the trial, or participants who receive OATP1B1 or OATP1B3 inhibitors.
18. History of toxic epidermal necrolysis, Steven Johnson syndrome.
19. Known hypersensitivity to study drug substance or excipients.
20. Participants who, in the opinion of the investigator, have other reasons that make them unsuitable for the study.
