Sahin, Taha Koray; Orhan, Cemal; Ozercan, Ibrahim Hanifi; Muglu, Harun; Er, Besir; Akyildiz, Arif; Tunbekici, Salih; Oruc, Ahmet; Aykan, Musa Baris; Koylu, Bahadir

Trastuzumab deruxtecan (T-DXd) has demonstrated significant efficacy in metastatic breast cancer (mBC) with varying HER2 expression. Statins have been shown to increase HER2 membrane localization and stability, potentially enhancing responses to HER2-targeted therapies. We investigated whether statins enhance T-DXd activity through a translational approach combining a preclinical HER2-negative model and a real-world HER2-positive mBC cohort. In the preclinical arm, 60 female Wistar albino rats were induced with mammary tumors using N-methyl-N-nitrosourea (MNU). Animals were randomized into five groups: Control, MNU-only, MNU + T-DXd, MNU+statin, and MNU + T-DXd+statin. In the clinical arm, 109 patients with HER2-positive mBC who received T-DXd were retrospectively analyzed. The combination of T-DXd and statin significantly reduced tumor volume compared to either monotherapy (p < 0.0001) in a preclinical rat model. HER2 protein levels were found to be elevated in the statin and combination groups, as demonstrated by both IHC and Western blot analyses. In a real-world cohort of 109 heavily pretreated patients with HER2-positive mBC receiving T-DXd, concomitant statin use was associated with significantly improved median progression-free survival (mPFS) and median overall survival (mOS). Our findings revealed that statin use significantly enhanced the efficacy of T-DXd in both a preclinical HER2-negative rat model and patients with HER2-positive mBC. Prospective clinical trials are warranted to validate these observations.