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.

Preclinical Pharmacology of CW002: A Nondepolarizing Neuromuscular Blocking Drug of Intermediate Duration, Degraded and Antagonized by l-cysteine-Additional Studies of Safety and Efficacy in the Anesthetized Rhesus Monkey and Cat.

BACKGROUND: CW002, a novel nondepolarizing neuromuscular blocking agent of intermediate duration, is degraded in vitro by L-cysteine; CW002-induced neuromuscular blockade (NMB) is antagonized in vivo by exogenous L-cysteine. Further, Institutional Animal Care and Use Committee-approved studies of safety and efficacy in eight anesthetized monkeys and six cats are described. METHODS: Mean arterial pressure, heart rate, twitch, and train-of-four were recorded; estimated dose producing 95% twitch inhibition (ED95) for NMB and twitch recovery intervals from 5 to 95% of baseline were derived. Antagonism of 99 to 100% block in monkeys by L-cysteine (50 mg/kg) was tested after bolus doses of approximately 3.75 to 20 × ED95 and after infusions. Vagal and sympathetic autonomic responses were recorded in cats. Dose ratios for [circulatory (ED20) or autonomic (ED50) changes/ED95 (NMB)] were calculated. RESULTS: ED95s of CW002 in monkeys and cats were 0.040 and 0.035 mg/kg; L-cysteine readily antagonized block in monkeys: 5 to 95% twitch recovery intervals were shortened to 1.8 to 3.6 min after 3.75 to 10 × ED95 or infusions versus 11.5 to 13.5 min during spontaneous recovery. ED for 20% decrease of mean arterial pressure (n = 27) was 1.06 mg/kg in monkeys; ED for 20% increase of HR (n = 27) was 2.16 mg/kg. ED50s for vagal and sympathetic inhibition in cats were 0.59 and >>0.80 mg/kg (n = 14 and 15). Dose ratios for [circulatory or autonomic changes/ED95 (NMB)] were all more than 15 × ED95. CONCLUSIONS: The data further verify the neuromuscular blocking properties of CW002, including rapid reversal by L-cysteine of 100% NMB under several circumstances. A notable lack of autonomic or circulatory effects provided added proof of safety and efficacy.

Rapid chemical antagonism of neuromuscular blockade by L-cysteine adduction to and inactivation of the olefinic (double-bonded) isoquinolinium diester compounds gantacurium (AV430A), CW 002, and CW 011.

BACKGROUND: The ultra-short-acting neuromuscular blocker gantacurium is chemically degraded in vitro by rapid adduction of L-cysteine to its central olefinic double bond. Preliminary data have suggested that exogenous (intravenous) L-cysteine abolishes gantacurium blockade. Two new analogues of gantacurium (CW 002 and CW 011) have been synthesized to undergo slower L-cysteine adduction, yielding intermediate duration. L-cysteine adduction to and antagonism of these novel agents is further defined herein. METHODS: Comparative reaction half-time for L-cysteine adduction in vitro of the three compounds was determined by high-performance liquid chromatography. ED95 for twitch inhibition in monkeys under isoflurane was calculated, and duration at approximately 4-5x ED95 was correlated with reaction half-time for adduction. Speed of L-cysteine antagonism was contrasted with anticholinesterase reversal. Potencies of CW 002 and its adduction product were compared to provide a basis for L-cysteine antagonism. RESULTS: Rate of L-cysteine adduction in vitro (reaction half-time) was 11.4 and 13.7 min for CW 002 and CW 011 versus 0.2 min for gantacurium, and was inversely related to duration of block (P < 0.0001). CW 002 and CW 011 were 3x longer acting than gantacurium (28.1 and 33.3 min vs. 10.4 min), but only half the duration of cisatracurium. The adduct of CW 002 was approximately 70x less potent than CW 002. L-cysteine (10-50 mg/kg intravenously) given 1 min after approximately 4-5x ED95 doses of all the three compounds abolished block within 2-3 min. CONCLUSIONS: L-cysteine adduction occurs at different rates by design in olefinic isoquinolinium diester neuromuscular blockers, yielding corresponding durations of action. Antagonism by exogenous L-cysteine is superior to anticholinesterases, inducing inactivation of the active molecules to restore function rapidly at any time.

Preclinical pharmacology of GW280430A (AV430A) in the rhesus monkey and in the cat: a comparison with mivacurium.

BACKGROUND: No replacement for succinylcholine is yet available. GW280430A (AV430A) is a representative of a new class of nondepolarizing neuromuscular blocking drugs called asymmetric mixed-onium chlorofumarates. It undergoes rapid degradation in plasma by chemical hydrolysis and inactivation by cysteine adduction, resulting in a very short duration of effect. The neuromuscular, cardiovascular, and autonomic pharmacology of GW280430A is compared herein with that of mivacurium. METHODS: Adult male rhesus monkeys and adult male cats were anesthetized with nitrous oxide-oxygen-halothane and chloralose-pentobarbital, respectively. The neuromuscular blocking properties of GW280430A and mivacurium were compared at a stimulation rate of 0.15 Hz in the extensor digitorum of the foot (monkey) and the tibialis anterior (cat). Sympathetic responses were assayed in the cat in the nictitating membrane preparation, and vagal effects were evaluated in the cat via observation of bradycardic responses after stimulation of the cervical right vagus nerve. RESULTS: GW280430A and mivacurium were equipotent in the monkey (ED95 was 0.06 mg/kg in each case). GW280430A was half as potent as mivacurium in the cat. The total duration of action of GW280430A was less than half that of mivacurium in the monkey; recovery slopes were more than twice as rapid. The 25-75% recovery index of GW280430A did not vary significantly after various bolus doses or infusions, averaging 1.4-1.8 min in the monkey, significantly shorter than the same time interval (4.8-5.7 min) for mivacurium. Dose ratios for autonomic versus neuromuscular blocking properties in the cat were greater than 25 for both GW280430A and mivacurium. The ratio ED Hist:ED95 Neuromuscular Block in the monkey was significantly greater (approximately 53 vs. 13) for GW280430A, indicating approximately four times less relative prominence of the side effects of skin flushing and decrease of blood pressure, which are associated with release of histamine. CONCLUSIONS: These experiments show a much shorter neuromuscular blocking effect and much-reduced side effects in the case of GW280430A vis-à-vis mivacurium. These results, together with the novel chemical degradation of GW280430A, suggest further evaluation in human subjects.