Abstract C094: Dose and schedule-dependent efficacy of liposomal Annamycin in pre-clinical models of acute myeloid leukemia

Abstract

Abstract Annamycin (Ann) is a clinically evaluated anthracycline whose antitumor activity is not cross-resistant with that of doxorubicin (DOX). Formulated in liposomes, L-Annamycin (L-Ann) is currently in clinical studies in acute myeloid leukemia (AML) patients. In contrast to DOX, high levels of cellular accumulation of Ann were observed in multidrug resistant (MDR) cell lines, and consequently there was a significant degree of DNA damage and apoptosis. In vivo activity of L-Ann and free Ann was confirmed in different tumor models. In addition, preclinical toxicology studies revealed that both L-Ann as well as free Ann displayed dramatically reduced or no cardiotoxicity, in sharp contrast to DOX. In the current study, we assessed the anti-AML efficacy of Ann using multiple in vitro and in vivo models. In vitro efficacy was assessed in a panel of human AML cell lines including THP-1, OCI-AML3 and MV4;11. The uptake and subcellular distribution of Ann was evaluated using flow cytometry and fluorescence microscopy. In vivo biodistribution of Ann was tested in naïve B6 mice after intravenous administration of the drug followed by fluorescence microscopy. Anti-tumor efficacy was extensively tested in syngeneic AML-Turq 2 model in immunocompetent B6 mice, and subsequently in human OCI-AML3 model in immunosuppressed NSG mice. In the murine syngeneic AML-Turq 2 model, AML cells were visualized based on the mTurquoise fluorescence. AML disease progression was monitored using whole body bioluminescence imaging or flow cytometry, respectively. We observed a high potency of Ann against established human AML cell lines, with the IC50 in low nanomolar range. Saturation experiments indicated high uptake of Ann by the cancer cells. Interestingly, in addition to the expected uptake of Ann in the nucleus, Ann was also localized in the cytosol of the cells. This bi-compartmental intracellular distribution pattern contrasted with the nuclear-only localization of DOX. In vivo studies confirmed anti-tumor efficacy of the Annamycin in both human and murine AML models. Based on bioluminescence imaging, the liposomal formulation of the drug significantly delayed AML progression in the human OCL-AML3/NSG model at 4 mg/kg with once weekly dosing. Similarly, significant dose-dependent reduction of peripheral blood AML blasts was observed in the murine AML-Turq2 model, and this reduction was strongly correlated with prolongation of animals survival. The median survival of mice receiving four doses of L-Ann once a week at 4 mg/ml was 37 days while mice receiving vehicle lived only 14 days (p=0.0002). Different doses and administration schedules of L-Ann were tested in effort to maximize survival benefits. In summary L-Ann is effective in AML, demonstrating significant activity in both in vitro and in vivo mouse models with a distinct pattern of intracellular uptake and organ distribution using a once a week schedule. This suggests that L-Ann with this profile, including a lack of cardiotoxicity and activity against DOX resistant tumors, may be an advantageous approach in the treatment of AML. Citation Format: Rafal Zielinski, Tomasz Zal, Krzysztof Grela, Stanislaw Skora, Izabela Fokt, Matthew Sander, Magdalena Remiszewski, Edward Felix, Meenakshi Shanmugasundaram, Waldemar Priebe. Dose and schedule-dependent efficacy of liposomal Annamycin in pre-clinical models of acute myeloid leukemia [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr C094. doi:10.1158/1535-7163.TARG-19-C094