Background: Peptides have shown to be a promising disease modifying drug for the treatment of cardiovascular diseases. We previously demonstrated that inhalation of calcium phosphate nanoparticles, loaded with a therapeutic mimetic peptide (CaP-MP) targeting the Cav2 cytosolic subunit of the L-type calcium channel (LTCC), improves cardiac contractility in a rodent model of diabetic cardiomyopathy.

Here, we set out to investigate the therapeutic efficacy of the inhalation of a dry-powder formulation of CaP-MP (dpCaP-MP) in a porcine model of pacing-induced heart failure.

Methods: Göttingen minipigs underwent a continuous right-ventricular pacemaker stimulation (2 weeks at 180 bpm followed by further 4 weeks at 200 bpm) over 6 weeks, in order to induce left ventricular (LV) dilatation and heart failure with reduced ejection fraction (HFrEF). After 4 weeks of tachypacing, HFrEF animals were randomized in a 1:1 fashion into 2 groups, the former receiving daily inhalation of dpCaP-MP (HF+MP), the latter dpCaP without MP (vector only, HF-MP). Inhalation was performed over 2 weeks. Pigs not implanted with a pacemaker served as SHAM group. A telemetry system recorded 24 hour-EKG, respiratory rate and activity level over the complete study period. Echocardiography and blood sampling were conducted once a week throughout the whole study period. At week 6, pigs were instrumented for pressure-volume assessment. After sacrifice, developed force was measured in electrically-stimulated LV trabeculae and Ca2+ transients were measured in isolated ventricular cardiomyocytes. Tissue was collected for molecular as well as histological analysis.

Results

HF-MP progressively developed an HFrEF phenotype with decreasing LV EF over time, increased LV end-diastolic pressure, reduced daily activity level and pulmonary congestion. Inhalation with dpCa-MP restored systolic function in the HF+MP group, as shown by a normalization of LVEF as well as fractional shortening, while reducing pulmonary congestion. In line with this, developed force in muscle strips was higher in the HF+MP group. Preliminary single cell data are in line with a partially restored Ca2+ amplitude upon treatment. The treatment was well tolerated and no adverse events, including severe arrhythmias, occurred.

Conclusions

Inhalation of a novel peptide-loaded nanoparticles impacting on LTCC as a dry-powder formulation restores LV systolic function and myocardial contractility while reducing pulmonary congestion in a porcine model of pacing-induced heart failure. The concept of an inhalable LTCC-modulator can have future implications for improving cardiac function in HFrEF patients.