Mersana Therapeutics(MRSN) GlobeNewswire·2025-01-10 11:00Core Insights - Mersana Therapeutics announced positive initial clinical data for emiltatug ledadotin (Emi-Le), indicating a differentiated safety and tolerability profile, particularly in patients with triple-negative breast cancer (TNBC) previously treated with topoisomerase-1 inhibitor antibody-drug conjugates (ADCs) [1][2][4] Clinical Data Summary - The Phase 1 trial enrolled 130 heavily pretreated patients with advanced/metastatic TNBC and other cancers, with a median of 4.5 prior therapy lines [2] - Among patients with known B7-H4 tumor expression, approximately 44% had a tumor proportion score of 70% or higher, categorized as "B7-H4 high" [2] - Emi-Le demonstrated a confirmed objective response rate (ORR) of 23% in evaluable patients with B7-H4 high tumors at intermediate doses [3] - At higher doses above 76 mg/m, the ORR was 22%, with 78% of patients showing a ≥30% tumor reduction in target lesions [6] Safety and Tolerability - Emi-Le was generally well tolerated, with no Grade 4 or 5 treatment-related adverse events reported [2] - The most common treatment-related adverse events (TRAEs) included transient AST increase (38%), proteinuria (31%), nausea (29%), and fatigue (28%) [2] - TRAEs leading to discontinuation, dose reduction, and dose delay were observed in 2.3%, 9.2%, and 12.3% of patients, respectively [2] Future Milestones - Mersana plans to continue enrollment in the expansion cohort at a dose of 67.4 mg/m every four weeks in patients with TNBC who have received at least one prior topo-1 ADC [12] - The company aims to present additional Phase 1 clinical data and pharmacodynamic STING activation data related to its other ADC candidate, XMT-2056, in 2025 [7][12] Company Overview - Mersana Therapeutics is focused on developing novel ADCs, including Emi-Le targeting B7-H4 and XMT-2056 targeting a novel HER2 epitope [10] - The company is committed to addressing high unmet medical needs in cancer treatment through its proprietary platforms [10]