Abstract P1-20-04: Nanoformulation of doxorubicin inside H- ferritin nanocages allows a cardio-safe combined therapy with trastuzumab: De-escalating cardiotoxicity in HER2-positive breast cancer

Background: HER2+ breast cancer (BC) accounts for 20-25 % of BCs and it is characterized by high aggressiveness.1 Despite the anti-HER2 monoclonal antibody Trastuzumab (TZ) has improved BC clinical outcome, it could induce severe cardiac reversible dysfunction:2 HER2 signaling is also essential for growth and survival of myocardiocytes.3 Therefore, the concurrent use of TZ with other cardiotoxic drugs as doxorubicin (DOX) is discouraged.3 Both neoadjuvant and adjuvant clinical trials have challenged the notion that TZ should be administered with anthracyclines only sequentially,4 despite pre-clinical studies demonstrated the significant enhancement of efficacy by their coadministration.5-7 Nanomedicine answers to this clinical issue with HFn-DOX: a natural protein-based DOX nanoformulation with native tumor targeting capability that displays a self-triggered nuclear delivery of DOX improving antitumor efficacy and reducing both chemoresistance and cardiotoxicity.8 Methods: HER2+ BC bearing mice have been treated 5 times twice a week with placebo, HFn-DOX (1 mg/Kg, i.v.), TZ (5 mg/Kg, i.p.) and with the combination of them. Main end-point were cardiotoxicity and anticancer efficacy. Tumor size was measured by caliper, while antitumor activity and cardiotoxicity were characterized by ICH, immunofluorescence, cytofluorimetry, TEM, mass spectrometry and western blot on resections. Statistical analyses were conducted using two-tailed Student's t-test (P< 0.05) Results: Although single treatments with HFn-DOX or TZ display a good capability to reduce tumor progression, their combination improves antitumor potential, affecting tumor size and angiogenesis. Since the main TZ activity is the induction of the Antibody-Dependent Cell mediated Cytotoxicity, we have assessed the effect of HFn-DOX on Tumor Infiltrating Lymphocytes (TIL), revealing that both TILs enumeration and TIL activity is unaffected by HFn-DOX. On the other hand, HFn-DOX increases the induction of apoptosis, suggesting that the reduction of the tumor size observed in mice treated with the combination of TZ and HFn-DOX is attributable to the coupling of these activity. Mitochondrial morphology has been checked for cardiotoxicity. A pathological increase in mitochondria area coupled with cristae depletion has been evidenced only in mice treated with TZ alone, confirming the overall safety of the HFn-DOX formulation. Interestingly, mice treated with the TZ and HFn-DOX did not display evidences of cardiac suffering. TZ quantification in tumor and heart revealed that the combination with HFn-DOX couples the increased TZ accumulation and penetration in tumor with TZ reduction in heart, resulting in the lack of cardiotoxicity. Conclusions: Our results suggest that a combined therapy with HFn-DOX and TZ allows an enhanced anticancer activity and reduced cardiotoxicity, with potential translational implications on the treatment of HER2+ BC patients. [1] Nat Rev Cancer 2009; 9:463; [2] Nat. Med. 2012; 18(11):1639; [3] Cancer treatments reviews 2009; 35:633; [4] The breast 2014; 23:317; [5] Cancer Res. 1998; 58(13):2825; [6] Lancet Oncol. 2011; 12(3):236; [7] Lancet 2010; 375(9712):377. [8] Oncotarget. 2017; 8:8383. Citation Format: Mazzucchelli S, Andreata F, Bonizzi A, Monieri M, Bellini M, Longhi E, Ottria R, Sorrentino L, Truffi M, Prosperi D, Zerbi P, Corsi F. Nanoformulation of doxorubicin inside H- ferritin nanocages allows a cardio-safe combined therapy with trastuzumab: De-escalating cardiotoxicity in HER2-positive breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-20-04.