TroFuse-005 Dual Survival Win Forces Post-ICI Endometrial Reset Without Matched Precedent

Merck's Sac-TMT Significantly Improves Survival in Endometrial Cancer

Merck announced positive results from the pivotal Phase 3 TroFuse-005 trial of sacituzumab tirumotecan (sac-TMT), an investigational TROP2-directed antibody-drug conjugate, in patients with advanced or recurrent endometrial cancer who had received prior platinum-based chemotherapy and anti-PD-1/L1 immunotherapy. The study met its dual primary endpoints, demonstrating statistically significant and clinically meaningful improvements in overall survival (OS) and progression-free survival (PFS) compared to treatment of physician’s choice. Sac-TMT reduced the risk of death by 32% and the risk of disease progression or death by 41%. Based on these data, the U.S. FDA has accepted a Biologics License Application for sac-TMT for priority review, with a PDUFA date of June 15, 2027.

• Sac-TMT significantly improved overall survival, reducing the risk of death by 32% (HR=0.68; 95% CI, 0.55-0.84; P<0.0001) and extending median OS by 6.9 months (19.0 months vs. 12.1 months) compared to chemotherapy. This marks TroFuse-005 as the first global Phase 3 trial of a TROP2 ADC to demonstrate improved OS in this specific advanced endometrial cancer patient population.
• The trial also showed a 41% reduction in the risk of disease progression or death (HR=0.59; 95% CI, 0.50-0.70; P<0.0001), extending median PFS by 3.3 months (7.2 months vs. 3.9 months). Additionally, sac-TMT doubled the objective response rate (ORR) to 35.1% versus 17.3% for the comparator arm (P <0.00001), with durable responses lasting a median of 11.1 months.
• The safety profile of sac-TMT was consistent with prior studies, with no new safety signals observed. Treatment-related adverse events were mostly low grade and manageable, leading to low discontinuation rates. Following these robust results, the U.S. FDA has granted priority review to the Biologics License Application for sac-TMT, setting a PDUFA date of June 15, 2027, indicating a potential expedited path to market for this therapy.

Addressing the Unmet Need in Advanced Endometrial Cancer

Advanced or recurrent endometrial cancer after platinum-based chemotherapy is characterized by poor prognosis and limited effective therapeutic options. Toxicity-related dose modifications complicate delivery of available immunotherapy combinations, while resistance mechanisms, sequencing, and predictive biomarkers beyond MMR status remain unresolved challenges.

• High toxicity burden with lenvatinib plus pembrolizumab: Grade ≥3 toxicity was reported in 55.7% with any-grade toxicity observed in 85.7%, rates of dose reduction of lenvatinib were 64.3%, and toxicity-related treatment interruption was 45.7%. In a separate analysis, ≥G3 TRAEs were 88.9% with the combination of ICIs and TKI, and dose reduction and dose delay are frequently required.

• Frequent dose modification without defined optimization: Full-dose lenvatinib has been associated with frequent dose modification without prospective data to guide optimization, and the lower limit of effective dosing remains to be defined. Relative dose intensity of lenvatinib was not positively associated with progression-free survival, neither during the first 4 weeks after treatment initiation nor during the entire treatment period.

• Limited efficacy of chemotherapy after first line: No standard second-line chemotherapy is approved, with less than 1/4 of patients responding to second-line chemotherapy. Approximately 10%-15% of women with EC are diagnosed with advanced-stage disease, resulting in a reported 5-year survival rate of only 17% for those with distant metastases.

• Lack of predictive biomarkers and response heterogeneity: Most patients do not tolerate, do not respond to, or develop resistance to pembrolizumab and lenvatinib, and there are no biomarkers of response for this regimen. No statistically significant associations were observed between any of the RNA-sequencing signature scores and objective response rate or progression-free survival, with area under the receiver operating characteristic curve values for response ranged from 0.39 to 0.54.

• Unresolved post-immunotherapy management and resistance: Challenges remain regarding resistance mechanisms, optimal treatment sequencing, and predictive biomarkers beyond MMR status. For patients who experience disease progression following exposure to a prior immune checkpoint inhibitor, there is absence of prospective guidance, with grade 3 to 4 immune-related adverse events and high rates of dose modification reported.

• Financial and management burden: TKIs are expensive and patient financial toxicity is as critical a measure of a drug's utility as any drug side effect. Toxicity management requires frequent check-ins and management strategies to help patients find the highest tolerable dose.

TroFuse-005: Unpacking the Pivotal Sacituzumab Tirumotecan Data

Key trials in advanced or recurrent endometrial cancer span single-arm phase 1/2 studies of dostarlimab and lenvatinib plus pembrolizumab, and randomized phase 3 studies of dostarlimab plus chemotherapy and lenvatinib plus pembrolizumab versus chemotherapy. Designs vary by randomization, blinding, and control arm, with primary endpoints including objective response rate, duration of response, progression-free survival, and overall survival.

Sacituzumab Tirumotecan's Broader Potential Across Oncology

Sacituzumab tirumotecan (sac-TMT/MK-2870/SKB264), a TROP2-directed antibody-drug conjugate, is under evaluation across non-small cell lung cancer, breast cancer, urothelial carcinoma and other gynecologic malignancies. Trial designs include single-agent activity studies as well as randomized comparisons versus chemotherapy and combinations with PD-1/PD-L1 inhibitors.

The Evolving TROP2 ADC Landscape in Endometrial Cancer

Other TROP2-directed antibody-drug conjugates reported in advanced non-small cell lung cancer alongside sacituzumab tirumotecan are datopotamab deruxtecan and sacituzumab govitecan. Eligible studies included adult populations with advanced NSCLC that were treated with datopotamab deruxtecan, sacituzumab govitecan, or sacituzumab tirumotecan.

TROP2 ADC Breakthrough Redefines Advanced Endometrial Cancer Care

The recent announcement regarding sacituzumab tirumotecan (sac-TMT) marks a pivotal moment for patients battling advanced or recurrent endometrial cancer, particularly those who have exhausted conventional platinum-based chemotherapy and anti-PD-1/L1 immunotherapy. Historically, this patient population has faced a grim prognosis with severely limited treatment options, where responses are often short-lived and cure remains uncommon. The significant improvements in overall survival and progression-free survival demonstrated by sac-TMT address a profound unmet medical need, offering a new beacon of hope where few previously existed.

This development underscores the growing prominence of antibody-drug conjugates (ADCs) as a transformative therapeutic class in oncology. TROP2, the target of sac-TMT, has been identified as a highly expressed and actionable antigen in endometrial cancer cells, with preclinical studies consistently supporting its role as a therapeutic vulnerability. The success of sac-TMT not only validates TROP2 as a key target in gynecologic malignancies but also reinforces the broader potential of ADCs to deliver potent cytotoxic agents directly to cancer cells, minimizing systemic toxicity.

However, as with any novel therapy, important considerations remain. The full safety profile of sac-TMT in this heavily pretreated population will be crucial, particularly concerning known ADC-related adverse events such as hematologic toxicity, oral mucositis, and gastrointestinal issues. Effective management strategies for these toxicities will be essential for optimal patient outcomes. Furthermore, while TROP2 is broadly expressed in endometrial cancer, the precise role of biomarker-guided patient selection—perhaps based on the level of TROP2 expression—could refine treatment strategies and ensure the right patients receive the most benefit. The competitive landscape for TROP2-directed ADCs is also evolving, with other agents in development that may offer differentiated mechanisms or overcome resistance, necessitating continuous evaluation of sac-TMT's long-term positioning. This breakthrough, coupled with ongoing research into combination therapies and novel biomarkers, promises to further personalize and improve care for patients with advanced endometrial cancer.