RATIONALE AND MOLECULAR TARGETING
Advanced and metastatic vulvar and vaginal squamous cell carcinomas share pathophysiological features with cervical cancer, including high rates of Human Papillomavirus (HPV) driver oncogenesis and robust expression of Trophoblast Cell Surface Antigen 2 (TROP-2). Sacituzumab tirumotecan (sac-TMT, MK-2870) is a novel TROP-2-directed antibody-drug conjugate (ADC) composed of a humanized anti-TROP2 IgG1 monoclonal antibody linked via a methyl sulfonyl moiety to a potent topoisomerase 1 inhibitor payload (KL610023). Upon binding to TROP-2 on tumor cells, sac-TMT internalizes and releases its payload, inducing cell cycle arrest and apoptosis while exerting bystander-killing and antibody-dependent cellular cytotoxicity.
DREAM STUDY DESIGN AND STATISTICAL CONSIDERATIONS
This Phase II study utilizes a Simon's two-stage Minimax design for each independent cohort (Cohort A: Vagina; Cohort B: Vulva) to control the familywise alpha level at 0.05 (one-sided) with 80% power:
Stage 1: 12 participants per cohort will be enrolled. An interim analysis for futility will be conducted; if 0 responses are observed in Stage 1, enrollment in that cohort will be halted.
Stage 2: If $\ge 1$ objective response is achieved in Stage 1, an additional 10 participants will be accrued (totaling 22 evaluable patients per cohort, expanded to 24 to account for a 10% dropout rate). A cohort is considered positive if $\ge 4$ responses are observed among evaluable participants.
TREATMENT ADMINISTRATION AND MANDATORY PROPHYLAXISSac-TMT is administered intravenously on Days 1 and 15 of 28-day cycles. Mandatory premedication administered 1.5 hours ($\pm30$ minutes) prior to each infusion includes an H1 receptor antagonist (diphenhydramine or equivalent), acetaminophen, dexamethasone (8-10 mg IV), and an H2 receptor antagonist to minimize infusion-related reactions. To prevent oral mucositis, participants receive mandatory daily prophylactic steroid-containing mouthwash (dexamethasone solution) 4 times daily. Prophylactic artificial tears are also strongly recommended to mitigate ocular surface toxicities.
EXPLORATORY BIOMARKER RESEARCH
The trial incorporates a longitudinal biorepository to identify predictive signatures and resistance mechanisms. Mandatory archival or freshly obtained FFPE tumor tissue blocks/slides collected at baseline will undergo TROP-2 immunohistochemistry (IHC), p16/HPV16 profiling, and high-throughput next-generation sequencing (NGS). Serial blood samples (plasma/PBMCs) collected at baseline and prespecified on-treatment timepoints (Weeks 6, 12, 24, and at disease progression) will evaluate circulating tumor DNA (ctDNA) dynamics and immune cell profiling to monitor treatment response and genomic resistance patterns over time.