Sacituzumab Tirumotecan in Recurrent/Metastatic Adenoid Cystic Carcinoma and Papillary Thyroid Carcinoma (STRAP)

This is an open-label, investigator-initiated phase II clinical trial designed to evaluate the efficacy and safety of Sacituzumab Tirumotecan (sac-TMT) monotherapy in patients with recurrent or metastatic adenoid cystic carcinoma (ACC) of salivary gland origin and papillary thyroid carcinoma (PTC). A total of 68 patients will be enrolled over in 18-month period, with 34 patients in Cohort A (ACC) and 34 in Cohort B (PTC). All participants will receive sac-TMT at a dose of 4 mg/kg administered intravenously on Days 1 and 15 of each 28-day cycle. The primary endpoint is the objective response rate (ORR), defined as the proportion of patients achieving a complete or partial response as assessed by the site investigators. Secondary endpoints include progression-free survival, overall survival, disease control rate, safety and tolerability, dose intensity, and relative dose intensity.

Inclusion Criteria: Common Eligibility Criteria for Cohorts A and B 1. Unresectable locally advanced or recurrent/metastatic adenoid cystic carcinoma or papillary thyroid carcinoma. 2. Trophoblast cell-surface antigen 2 (TROP2) expression testing by immunohistochemistry or other methods is not required for enrollment. Provision of archival tumour tissue (where available) will be requested to support retrospective analysis. Waiver for tissue submission may be granted by the Steering Committee on a case-by-case basis if archival tissue is unavailable or insufficient for analysis. 3. Age ≥18 years at the time of enrollment (≥21 years in Singapore) 4. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. 5. At least one target lesion \*identified on contrast-enhanced CT (head, neck, chest, abdomen, pelvis with ≤5 mm slice thickness) performed within 14 days prior to enrollment (same day of the week within 14 days is acceptable; this applies similarly to other time-based criteria below). \* A non-lymph node lesion with a longest diameter of ≥10 mm or a lymph node lesion with a short axis of ≥15 mm 6. No prior treatment with Trophoblast cell-surface antigen 2 (TROP2)-directed antibody-drug conjugates or antibody-drug conjugates containing anti-topoisomerase I agents. 7. Participants who have AEs due to previous anticancer therapies must have recovered to Grade ≤1 or pre-treatment baseline level (except for alopecia and vitiligo). Participants with endocrine-related AEs who are adequately treated with hormone replacement therapy are eligible. 8. No administration of anticancer therapies (e.g., chemotherapy, targeted therapy, immunotherapy) within 13 days prior to enrollment. 9. No major surgery under general anesthesia within 27 days prior to enrollment. 10. No radiotherapy (including Gamma Knife or CyberKnife) within 13 days prior to enrollment. Thirteen days or fewer of palliative radiotherapy for non-CNS disease prior to enrollment is permitted. The last radiotherapy treatment must have been performed at least 7 days before enrollment.Two weeks or fewer of palliative radiotherapy for non-CNS disease is permitted. The last radiotherapy treatment must have been performed at least 7 days before the first dose of study intervention.Two weeks or fewer of palliative radiotherapy for non-CNS disease is permitted. The last radiotherapy treatment must have been performed at least 7 days before the first dose of study intervention. 11. Laboratory values within the following criteria based on testing within 14 days prior to enrollment. 1. Neutrophil count≥1,500/mm3 2. Platelet count≥10x10\^4/mm3 3. Hemoglobin≥9.0 g/dL 4. AST\