The antiarrhythmic dipeptide, GAP-134, ([2S,4R]-1[2-aminoacetyl]-4-benzamido-pyrrolidine-2-carboxylic acid) was evaluated in canine ischemia/reperfusion model. In dogs subjected to 60-minute ischemia and 4-hour reperfusion, GAP-134 was administered 10 minutes before reperfusion as a bolus + intravenous (IV) infusion. The doses administered were 0.25 microg/kg bolus + 0.19 microg/kg per hour infusion; 2.5 microg/kg + 1.9 microg/kg per hour; 25 mg/kg + 19 mg/kg per hour; 75 mg/kg + 57 mg/kg per hour. Ventricular ectopy was quantified during reperfusion, including premature ventricular contractions (PVC) and ventricular tachycardia (VT). Total incidence of VT was reduced significantly with the 2 highest doses of GAP-134 (1.7 + 0.8; 2.2 + 1.4 events; P < .05) compared to controls (23.0 + 6.1). Total PVCs were reduced significantly from 11.1 + 1.6% in control animals to 2.0% + 0.7% and 1.8% + 0.8% after the 2 highest doses of GAP-134. Infarct size, expressed as percentage of left ventricle, was reduced significantly from 19.0% + 3.5% in controls to 7.9% + 1.5% and 7.1% + 0.8% (P < .05) at the 2 highest doses of GAP-134. GAP-134 is an effective antiarrhythmic agent with potential to reduce ischemia/reperfusion injury.

Gap junction uncoupling can alter conduction pathways and promote cardiac re-entry mechanisms that potentiate many supraventricular arrhythmias, such as atrial fibrillation (AF) and atrial flutter (AFL). Our objective was to determine whether GAP-134 [(2S,4R)-1-(2-aminoacetyl)-4-benzamido-pyrrolidine-2-carboxylic acid], a small dipeptide gap junction modifier, can improve conduction and ultimately prevent AF/AFL. In rat atrial strips subjected to metabolic stress, GAP-134 prevented significantly conduction velocity slowing at 10 nM compared with vehicle (p < 0.01). In the canine sterile pericarditis model, conduction time (CT; n = 5), atrial effective refractory period (AERP; n = 3), and AF/AFL duration/inducibility (n = 16) were measured 2 to 3 days postoperatively in conscious dogs. CT was significantly faster after GAP-134 infusion (average plasma concentration, 250 nM) at cycle lengths of 300 ms (66.2 +/- 1.0 versus 62.0 +/- 1.0 ms; p < 0.001) and 200 ms (64.4 +/- 0.9 versus 61.0 +/- 1.3 ms; p < 0.001). No significant changes in AERP were noted after GAP-134 infusion. The mean number of AF/AFL inductions per animal was significantly decreased after GAP-134 infusion (2.7 +/- 0.6 versus 1.6 +/- 0.8; p < 0.01), with total AF/AFL burden being decreased from 12,280 to 6063 s. Western blot experiments showed no change in connexin 43 expression. At concentrations exceeding those described in the AF/AFL experiments, GAP-134 had no effect on heart rate, blood pressure, or any electrocardiogram parameters. In conclusion, GAP-134 shows consistent efficacy on measures of conduction and AF/AFL inducibility in the canine sterile pericarditis model. These findings, along with its oral bioavailability, underscore its potential antiarrhythmic efficacy.

DOI: 10.1177/1074248409340779 2009; 14; 207 J Cardiovasc Pharmacol Ther Petersen, Stephen J. Gardell and George P. Vlasuk James K. Hennan, Robert E. Swillo, Gwen A. Morgan, Eric I. Rossman, Joel Kantrowitz, John Butera, Jorgen S. Ischemia/Reperfusion Injury in Open-Chest Dogs Spontaneous Ventricular Arrhythmias and Reduces Infarct Size During Myocardial GAP-134 ([2S,4R]-1-[2-Aminoacetyl]4-Benzamidopyrrolidine-2-Carboxylic Acid) Prevents

Atrial fibrillation (AF) and atrial flutter (AFL), the most common sustained cardiac arrhythmias, are major contributors to cardiovascular morbidity and mortality in the adult population. Current pharmacologic treatment of AF/AFL is only moderately successful and not well tolerated among patients, highlighting an unmet medical need for safer, effective agents. GAP-134 is the first small molecule gap junction modifier developed for the prevention of AF/AFL. In preliminary experiments, this modified antiarrhythmic dipeptide with similar activity to the antiarrhythmic hexapeptide rotigaptide, significantly prevented conduction velocity slowing in rat atrial strips subjected to metabolic stress at 10 nM (5.6±9.4%) and 100 nM (0.4±5.0%) compared to controls (−29.1±5.3%). In the canine sterile pericarditis model, conduction time (CT, n=5) and AF/AFL inducibility (n=9) were measured 2–3 days post-operatively in closed chest studies, using electrodes placed at the right atrial appendage (RAA), the Bachmann’s bundle (BB), and the posterior left atrium (LA). CT, measured between the BB and LA, was significantly faster after GAP-134 infusion (average plasma concentration was 73.1 ng/ml) at RAA pacing rates of 200 bpm (66.2±1.0 ms vs 62.0±1.0 ms; p=2.49E-08), 300 bpm (64.4±0.9 ms vs 61.0±1.3 ms; p=2.67E-03), and 400 bpm (67.2±1.6 ms vs 65.0±1.9 ms; p=0.041). Induction of AF/AFL was attempted using a burst pacing protocol, at all three atrial sites, starting at 500 bpm and increasing at increments of 20 bpm until 800 bpm. The average number of successful AF/AFL inductions per animal was significantly decreased after GAP-134 infusion (2.7±0.6 vs 1.6±0.8; p=0.021), with the total number of inductions being decreased from 24 to 14. Mean AF/AFL duration per induction (603±119 s vs 260±116 s; p=0.021) and mean AF/AFL duration per animal (1364±419 s vs 705±483 s; p=0.049) were also significantly decreased after GAP-134 infusion, with total AF/AFL burden being decreased from 12280 s to 6348 s. In conclusion, GAP-134 shows consistent efficacy on measures of conduction and AF/AFL inducibility in the canine sterile pericarditis model. These findings, along with its oral bioavailability, underscore its potential as a highly effective atrial antiarrhythmic compound.

The antiarrhythmic and cardioprotective effect of increasing gap junction intercellular communication during ischemia/reperfusion injury has not been studied. The antiarrhythmic peptide rotigaptide (previously ZP123), which maintains gap junction intercellular communication, was tested in dogs subjected to a 60-min coronary artery occlusion and 4 h of reperfusion. Rotigaptide was administered i.v. 10 min before reperfusion as a bolus + i.v. infusion at doses of 1 ng/kg bolus + 10 ng/kg/h infusion (n = 6), 10 ng/kg bolus + 100 ng/kg/h infusion (n = 5), 100 ng/kg bolus + 1000 ng/kg/h infusion (n = 8), 1000 ng/kg bolus + 10 mug/kg/h infusion (n = 6), and vehicle control (n = 5). Premature ventricular complexes (PVCs) were quantified during reperfusion. A series of four or more consecutive PVCs was defined as ventricular tachycardia (VT). The total incidence of VT was reduced significantly with the two highest doses of rotigaptide (20.3 +/- 10.9 and 4.3 +/- 4.1 events; p < 0.05) compared with controls (48.7 +/- 6.0). Total PVCs were reduced significantly from 25.1 +/- 4.2% in control animals to 11.0 +/- 4.4 and 1.7 +/- 1.3% after the two highest doses of rotigaptide. Infarct size, expressed as a percentage of the left ventricle, was reduced significantly from 13.2 +/- 1.9 in controls to 7.1 +/- 1.0 (p < 0.05) at the highest dose of rotigaptide. Ultrastructural evaluation revealed no differences in myocardial injury in the infarct area, area at risk, border zone, or normal zone in vehicle and rotigaptide-treated animals. However, rotigaptide did increase the presence of gap junctions in the area at risk (p = 0.022, Fisher's exact test). Rotigaptide had no effect on heart rate, blood pressure, heart rate-corrected QT interval, or left ventricular end-diastolic pressure. In conclusion, these results demonstrate that rotigaptide is a potent antiarrhythmic compound with cardioprotective effects and desirable safety.