Abstract 10726: Cardiomyocyte Targeting Peptide to Deliver Amiodarone

Abstract

Introduction: Amiodarone remains underutilized as an anti-arrhythmic due to significant off-target toxicities with long-term use. We hypothesized that the required dose could be minimized by targeting amiodarone to cardiomyocytes by utilizing a cardiomyocyte targeting peptide (CTP). Methods: CTP (APWHLSSQYSRT) was conjugated to amiodarone via a disulfide bond, HPLC purified, characterized by MALDI/TOF, and stability at 37°C assessed using serial HPLCs over 21 days. Adult, male guinea pigs (GP; n=4/group) were injected intraperitoneally daily with vehicle (7 days), amiodarone (7 days; 80mg/Kg), 1/10 th the molar dose of CTP-amiodarone (5 days), or CTP (5 days), followed by euthanasia, hearts excised, perfused on a Langendorff apparatus with Tyrode’s solution, and placed in a custom-designed chamber blebbistatin (5 μM) to minimize contractions. Bolus injections of voltage (RH237) and Ca 2+ -indicator dye (Rhod-2/AM) were injected to simultaneously map cardiac action potentials (APs) and Ca 2+ transients (CaT), at 610-750nm and 570-595nm, respectively with 2 CMOS cameras, followed by pacing at 250ms to measure conduction velocity (CV), AP and CaT durations (at 90% recovery). Results: CTP-amiodarone produced a single HPLC peak at 16mins that remained stable for 21 days. CTP-amiodarone and amiodarone decreased conduction velocities in myocytes significantly compared to control GPs (0.92±0.05, 0.87±0.08ms, vs. 1.00±0.03m/s respectively, p<0.001). Amiodarone increased AP duration (192±5ms vs. 175±8ms for vehicle, p=0.0025), while CTP-amiodarone decreased it significantly (157±16ms, p=0.0136), similar to CTP alone (155±13, p=0.0039). Both amiodarone and CTP-amiodarone significantly decreased CaTs compared to vehicle treated GPs. CTP-amiodarone and CTP decreased CaTs to an extent greater than amiodarone alone (p<0.001). Conclusions: Our data suggests that amiodarone can be stably covalently linked to CTP, which is able to deliver amiodarone to cardiomyocytes in vivo in GPs, at 1/10 th the dose of amiodarone needed to produce comparable slowing of CVs. The ability of CTP alone to decrease AP durations and CaTs was a surprise finding and merits further study to fully characterize the anti-arrhythmic actions of the CTP-amiodarone conjugate.