Preclinical Pharmacology in the Rhesus Monkey of CW 1759-50, a New Ultra-short Acting Nondepolarizing Neuromuscular Blocking Agent, Degraded and Antagonized by L-Cysteine.

WHAT WE ALREADY KNOW ABOUT THIS TOPIC: WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: Structure-activity studies were performed to identify a new neuromuscular blocking agent retaining the ultra-short acting characteristics of gantacurium, including degradation and reversal by L-cysteine, but lacking its histaminoid properties in man. CW 1759-50 has emerged from this program. METHODS: Adduction of CW 1759-50 with L-cysteine was studied by high-performance liquid chromatography and mass spectrometry. Institutional Animal Care and Use Committee-approved comparisons of CW 1759-50 to gantacurium were performed in rhesus monkeys. ED95 for neuromuscular blockade was established. Spontaneous recovery was compared to reversal by L-cysteine in paired studies of boluses or infusions. In addition, changes in mean arterial pressure and heart rate after very large doses of 15 to 60 × ED95 were compared. RESULTS: The half-time of adduction of L-cysteine to CW 1759-50 in vitro was 2.3 min. The ED95 of CW 1759-50 was 0.069 ± 0.02 mg/kg; ED95 of gantacurium was 0.081 ± 0.05 mg/kg (P = 0.006). Duration of action (recovery to 95% twitch height after 98 to 99% blockade) was as follows: CW 1759-50, 8.2 ± 1.5 min; and gantacurium, 7.4 ± 1.9 min; (n = 8 and 9, P = 0.355). Administration of L-cysteine (30 mg/kg) shortened recovery (i.e., induced reversal) from CW 1759-50 after boluses or infusions (P always less than 0.0001). Recovery intervals (5 to 95% twitch) ranged from 6.1 to 6.7 min (and did not differ significantly) after boluses of 0.10 to 0.50 mg/kg, as well as control infusions (P = 0.426 by analysis of variance). Dose ratios comparing changes of 30% in mean arterial pressure or heart rate to ED95 for neuromuscular blockade (ED 30% Δ [mean arterial pressure or heart rate]/ED95) were higher for CW 1759-50 than for gantacurium. CONCLUSIONS: CW 1759-50, similar to gantacurium, is an ultra-short acting neuromuscular blocking agent, antagonized by L-cysteine, in the monkey. The circulatory effects, however, are much reduced in comparison with gantacurium, suggesting a trial in humans.

Comparative pharmacodynamics of pancuronium, cisatracurium, and CW002 in rabbits.

Pancuronium is a long-duration neuromuscular blocking drug (NMBD) that has been used in anesthetized rabbits at 0.1 mg/kg. However, there are limited data regarding the time course for recovery from this dose either spontaneously or with pharmacologic reversal. Here we defined the potency, onset, and recovery characteristics for the intermediate-duration NMBD cisatracurium and CW002 (a novel cysteine-inactivated molecule) in the rabbit, and test the hypothesis that these drugs may be alternatives to 0.1 mg/kg pancuronium for survival procedures. New Zealand white rabbits anesthetized with isoflurane were studied in a cross-over design. Potencies of cisatracurium and CW002 were defined as the effective dose for 95% depression of evoked muscle twitch (ED95). Responses to 3×ED95 were used to define onset (time to maximal effect), recovery index (RI; time from 25% to 75% recovery of twitch), and duration (time to complete recovery). Responses to all drugs were determined with and without reversal by neostigmine-glycopyrrolate or L-cysteine. CW002 was 4-fold more potent than was cisatracurium, but their onset, RI, and duration were similar. Pancuronium had similar onset and RI but longer duration, compared with cisatracurium and CW002. Reversal shortened the recovery index and duration for all 3 drugs. At 3×ED95, cisatracurium and CW002 had the same onset as did standard-dose pancuronium, but durations were shorter and more predictable. In addition, CW002 can be reversed without the potential side effects of cholinergic manipulation. We conclude that cisatracurium and CW002 are viable alternatives to pancuronium for survival studies in rabbits.

Noninvasive cardiac output monitoring with bioreactance as an alternative to invasive instrumentation for preclinical drug evaluation in beagles.

INTRODUCTION: Non-invasive measurement of cardiac output (CO) using bioreactance signals (NICOM) was recently validated in swine and human adults. The present study was designed to test the hypothesis that NICOM flow measurements can accurately measure CO and detect acute drug-induced changes in aortic blood flow (AoQ)≥10% in beagles. METHODS: Data from 5 anesthetized, open chest beagles used for preclinical screening of novel neuromuscular blocking drugs were analyzed for the study. AoQ was measured beat-to-beat with a probe on the aortic root and averaged over 30s intervals. NICOM CO measurements were simultaneously obtained every 30s. NICOM precision (random variation) and accuracy relative to AoQ were assessed from individual segments of steady-state data. The ability of NICOM to detect acute alterations in AoQ≥10% was determined from other segments with dynamic change. RESULTS: 516 simultaneous CO measurements between 826 and 2436 mL/min were analyzed. Steady-state measurements (20% of the dataset) revealed an average AoQ-NICOM difference (bias) of 63±38 mL/min, a percent error of 6.1%, and a NICOM precision of 6.1%. Within the acute change dataset, 21/23 events reflecting a ≥10% change in beat-to-beat AoQ were detected by the NICOM (sensitivity of 0.91). In none of 10 instances where drug or fluid injection altered AoQ<10% did the NICOM indicate a change (specificity of 1.0). DISCUSSION: Continuous, non-invasive measurement of CO by bioreactance provides data that satisfactorily approximates invasive measurement of aortic blood flow in beagles. In addition, despite a 30s interval between measurements, the NICOM appears to have sufficient fidelity to detect and quantify acute, drug-induced changes in CO. These data suggest that the NICOM may represent an alternative to open chest instrumentation for CO measurement in preclinical drug evaluation studies.

Cysteine reversal of the novel neuromuscular blocking drug CW002 in dogs: pharmacodynamics, acute cardiovascular effects, and preliminary toxicology.

BACKGROUND: CW002 is a neuromuscular blocking drug that is inactivated by endogenous L-cysteine. This study determined the exogenous L-cysteine dose-response relationship for CW002 reversal along with acute cardiovascular effects and organ toxicity in dogs. METHODS: Six dogs were each studied four times during isoflurane-nitrous oxide anesthesia and recording of muscle twitch, arterial pressure, and heart rate. CW002 (0.08 mg/kg or 9 x ED95) was injected, and the time to spontaneous muscle recovery was determined. CW002 was then administered again followed 1 min later by 10, 20, 50, or 100 mg/kg L-cysteine (1 dose/experiment). After twitch recovery, CW002 was given a third time to determine whether residual L-cysteine influenced duration. Preliminary toxicology was performed in an additional group of dogs that received CW002 followed by vehicle (n = 8) or 200 mg/kg L-cysteine (n = 8). Animals were awakened and observed for 2 or 14 days before sacrificing and anatomic, biochemical, and histopathologic analyses. RESULTS: L-cysteine at all doses accelerated recovery from CW002, with both 50 and 100 mg/kg decreasing median duration from more than 70 min to less than 5 min. After reversal, duration of a subsequent CW002 dose was also decreased in a dose-dependent manner. Over the studied dose range, L-cysteine had less than 10% effect on blood pressure and heart rate. Animals receiving a single 200-mg/kg dose of L-cysteine showed no clinical, anatomic, biochemical, or histologic evidence of organ toxicity. CONCLUSION: The optimal L-cysteine dose for rapidly reversing the neuromuscular blockade produced by a large dose of CW002 in dogs is approximately 50 mg/kg, which has no concomitant hemodynamic effect. A dose of 200 mg/kg had no evident organ toxicity.

Hemodynamic effects of di-sec-butyl phenol, an anesthetic substituted phenol.

Dose- and age-related hemodynamic effects were determined for an anesthetic substituted phenol, 2,6-di-sec-butyl phenol (DSB). DSB, 7.5 mg/kg, induced hypnosis in young rabbits and increased mean blood pressure to 170 +/- 14% and heart rate to 150 +/- 21% of control values. In elderly rabbits, 7.5 mg/kg DSB induced hypnosis, had no effect on blood pressure, but increased the heart rate to 130 +/- 2% of control. After ganglionic blockade with hexamethonium, 7.5 mg/kg DSB caused a decline in mean blood pressure (71 +/- 5% of control) without change in heart rate. DSB increased norepinephrine release from SH-SY5Y cells, a human neuroblastoma cell line (5.4 +/- 1.7% vs. 3.5 +/- 0.3%). DSB produced age-dependent elevation of mean blood pressure in rabbits, probably by causing release of catecholamines from the sympathetic nervous system.