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Table 1 Analysis of in vivo studies involving novel, quick-onset NMBAs and reversal agents facilitating their quick-offset: the on-off switches

From: Neuromuscular blockers and their reversal: have we finally found the on-off switches?

Name (year) Study type, study subjects Methods Result Remark/conclusion
Gantacurium; CW002; CW011
 Savarese et al. (2004) Preclinical
Gantacurium versus mivacurium
Anaesthetized rhesus monkeys, (n = 8), adult male cats (n = 8)
Each monkey studied 8 times 3 weeks apart over 6 months
Each monkey given successive doses of gantacurium (0.03, 0.05, 0.08, 0.20, 0.40, 0.80, 1.60, and 3.20 mg/kg) 15 min after TOFr normalization after previous doses
Similarly, each cat given doses of 0.02–6.4 mg/kg successively
Gantacurium infusion at rates of 17–38 μg/kg/min for 60 min in 4 monkeys
Gantacurium and mivacurium are equipotent (ED95 0.06 mg/kg for both)
At 0.2 mg/kg (3 × ED95), time to 95% twitch recovery was 8.5 ± 0.5 min (gantacurium) versus 22.0 ± 2.6 min (mivacurium)
Duration of action of gantacurium is short (½ to 1/3 that of mivacurium)
As gantacurium dose was doubled, the total duration of effect lengthened by only 1.5–3 min Elimination half-life of gantacurium is 1.5–3 min
Slopes of recovery remained parallel after all doses ≤ 50 × ED95 (3.2 mg/kg)
Histamine release occurred at 3.2 mg/kg for gantacurium and 0.8 mg/kg for mivacurium
No cumulative effect
Speed of recovery from gantacurium block little affected by up to 60 min infusion
 Belmont et al. (2004) Open-label ascending-dose study
Healthy human male volunteers aged 18–59 years (n = 31)
Part 1: to determine an ED95dose in 11 subjects. Subject 1 given an initial dose of 0.02 mg/kg followed by an estimated dose that would produce 50% block (ED50). A lack of response from the initial 0.02 mg/kg dose would lead to a doubling of next dose until twitch suppression. The ED50dose was based on a log-probit analysis with a historic slope estimate of 7.0. Subject 2: three doses of estimated ED25, ED50, and ED75. Subject 3: doses of ED50, ED75, ED90. Subjects 4–11: doses of estimated ED25, ED50, ED75, ED90
Part 2: Safety and pharmacodynamics of ascending multiples of ED95doses in 20 volunteers
ED95 was 0.19 ± 0.014 mg/kg
Onset time of maximum block at the adductor pollicis ranged from 2.6 ± 0.3 to 1.5 ± 0.3 min for doses 0.18 mg/kg (ED95) to 0.72 mg/kg (4 × ED95). Time to 90% block was 2.1 ± 0.7 min and 1.3 ± 0.2 min for the above doses
Clinical and total durations were 4.7–10.1 min and 9.9–16.1 min, respectively, for doses of 0.18–0.72 mg/kg
5–95% recovery rate was 7 min
And 25–75% recovery rate was 3 min for all doses of GW280430A
Onset time of gantacurium block is quick but dose dependent
Time to recovery from NMB is short and does not increase with increasing dose of gantacurium
 Heerdt et al. (2004) Dose escalation study for cardiopulmonary side effects of GW280430A
Adult male beagle dogs (n = 10)
Grp1: Potency of GW280430A was assessed by incremental bolus doses starting at 0.01 mg/kg until 100% block
Grp-2: GW280430A was first administered as a bolus of 2 × ED95 determined in group 1. At 90% twitch recovery, an infusion of 0.010 mg/kg/min was initiated. The infusion rate was then titrated to establish a stable 90–95% block of twitch and discontinued after 60–90 min. After a 30-min stabilization period, a normal response to TOF was verified, and cardiopulmonary side effects of GW280430A were determined by injecting incrementally larger boluses at 12-min intervals, starting with 0.2 mg/kg. An adverse response was a ≥ 10% change in the observed cardiopulmonary variables. ABG samples were obtained for histamine analysis before and 1 min after each dose, regardless of evidence of hemodynamic effects
Infusion dose required to produce 90–95% NMB was 0.010 mg/kg/min
ED95 ranged from 0.049 to 0.082 mg/kg (mean 0.064 mg/kg). At ED95, onset of NMB ranged from 90 to 128 s (mean, 107 s), with a duration of 3.2–6.2 min (mean, 5.2 min)
At 3 × ED95, onset ranged from 44 to 74 s (mean, 58 s), with a duration of 4.7–8.5 min (mean, 7 min).
Infusion rates required to produce 90–95% NMB ranged from 0.009 to 0.015 mg/kg/min (mean, 0.012 mg/kg/min)
In the two dogs that received a 60-min infusion, single-twitch height returned to baseline after 5.1 and 3.9 min, respectively. In dogs receiving a 90-min infusion, single-twitch height returned to baseline in 3.2 ± 0.3 min. No changes in peak inspiratory pressure or pulmonary compliance occurred during the infusion.
A modest increase in heart rate from 138 ± 6 to 157 ± 6 beats/min occurred
Gantacurium has no hemodynamic effect until a dose ≥ 25 times the ED95 is administered as a rapid intravenous bolus.
This effect is transient, may be the result of histamine release with secondary systemic vasodilation, and is not accompanied by changes in peak inspiratory pressure or pulmonary compliance.
 Sunaga et al. (2010a) In vivo study
Urethane anesthetized male Hartley guinea pigs (n = 6 × 5 = 30)
Guinea pigs were tracheostomized and ventilated with continuous digital recordings of pulmonary inflation pressure (PIP) and HR. The ED95 for NMBAs was defined. Transient and reproducible changes in PIP and HR were recorded after vagal stimulation or IV acetylcholine before and after pretreatment with escalating doses of gantacurium, CW002, cisatracurium/single dose of rapacuronium. ED95 for gantacurium, CW002, cisatracurium, and rapacuronium was 0.064, 0.012, 0.10, and 0.31 mg/kg, respectively.
Gantacurium, CW002, and cisatracurium had no effects on baseline pulmonary inflation pressures and were devoid of significant interactions with M2 and M3 muscarinic receptors in vivo
Gantacurium and CW002 are devoid of airway muscarinic receptor (M3; bronchial smooth musculature) effects at doses several times higher than ED95
 Heerdt et al. (2016) Dose escalation clinical trial in healthy human volunteers (n = 34) Each group received a fixed CW002 dose (0.02, 0.04, 0.06, 0.08, 0.10, and 0.14 mg/kg) BP, HR, and airway dynamic compliance monitored; NMB assessed with mechanomyography at adductor pollicis
ABG before and after CW002 injection for plasma histamine
Potency estimated from a baseline sigmoid Emax model.
ED50 was 0.036 mg/kg
ED95 was 0.077 mg/kg (95% CI, 0.044 to 0.114 mg/kg).
At 0.14 mg/kg (1.8 × ED95), 80% twitch depression occurred in 94 s with complete block in 200 ± 87 s
Clinical recovery (25% of maximum twitch) occurred in 34 ± 3.4 min, with a 5 to 95% recovery interval of 35.0 ± 2.7 min.
Time to TOFr > 0.9 was 59 to 86 min.
No histamine release <  10% change in blood pressure, heart rate, and dynamic airway compliance.
In healthy subjects on sevoflurane/N2O, CW002 (1.8 × ED95) produces a clinical duration of action < 40 min, no histamine release, and minimal hemodynamic and airway compliance changes
 Savarese et al. (2018) High-performance liquid chromatography and mass spectrometry
Rhesus monkeys (n = 17)
Adduction of CW 1759-50 with l-cysteine was studied in monkeys. ED95 for NMB was established. Spontaneous recovery was compared to reversal by l-cysteine in paired studies of boluses or infusions. Changes in mean arterial pressure and heart rate after very large doses of 15 to 60 × ED95 were compared. 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 mg/kg; ED95 of gantacurium was 0.081 mg/kg
Duration of action: CW 1759-50, 8.2  ±  1.5 min; and gantacurium, 7.4  ±  1.9 min; l-cysteine (30 mg/kg) shortened recovery (i.e., induced reversal) from CW 1759-50 after boluses/infusions. Recovery intervals (5 to 95% twitch) ranged from 6.1 to 6.7 min after boluses of 0.10 to 0.50 mg/kg, as well as control infusions
Dose ratios comparing changes of 30% in MAP or HR to ED95 for NMB (ED 30% Δ [MAP or HR]/ED95) were higher for CW 1759-50 than for gantacurium.
CW 1759-50, similar to gantacurium, is an ultra-short acting neuromuscular blocking agent, antagonized by l-cysteine
The circulatory effects are much reduced in comparison with gantacurium, warranting a trial in humans.
 Kaullen et al. (2018) Ascending dose study in healthy human volunteers under propofol–sevoflurane anaesthesia (n = 34) Population pharmacokinetic/pharmacodynamic models developed using plasma drug concentration data from a previously published dose–response study. Subjects were from five different dose cohorts (receiving 0.04, 0.06, 0.08, 0.10, and 0.14 mg/kg, respectively). Serial arterial plasma concentrations and muscle twitch heights were recorded. A four-compartment model was fit to the concentration–time data; a transit compartment (sigmoid Emax model) was fit to the pharmacokinetic/pharmacodynamic data. The population pharmacokinetics of CW002 was linear with very low inter-individual variability in clearance (10.8%). The time to 80% block was 1.5, 0.8, and 0.7 min for 2×, 3×, 4 × ED95 doses, respectively. The simulated 25 to 75% recovery index was dose independent CW002 has predictable pharmacokinetics and is likely to have a rapid onset with an intermediate duration of action at 3 × ED95
 Savarese et al. (2010) In vitro: high-performance liquid chromatography
In vivo: monkeys under isoflurane
Comparative reaction half-time for l-cysteine adduction for gantacurium, CW 002, CW011
ED95 for twitch inhibition in monkeys was calculated
Duration at 4–5 ED95 was correlated with reaction half-time for adduction. Speed of l-cysteine antagonism was compared with neostigmine reversal. Potencies of CW 002 and its adduction product were compared to provide a basis for l-cysteine antagonism.
Rate of l-cysteine adduction in vitro (reaction half-time) was 0.2 min, 11.4 min, and 13.7 min for gantacurium, CW002, and CW011 and was inversely related to duration of block. CW002 and CW011 were longer-acting than gantacurium (28.1 and 33.3 min vs. 10.4 min), but only half the duration of cisatracurium.
Cysteine adduct of CW002 was 70 times less potent than CW002.
IV l-Cysteine (10–50 mg/kg) given 1 min after 4–5 ED95 doses of gantacurium, CW002, and CW011 abolished NMB within 2–3 min.
l-Cysteine adduction occurs at different rates in olefinic isoquinolinium diester NMBs, with corresponding durations of action. Exogenous l-cysteine is superior to anticholinesterases, inactivating active molecules to rapidly reverse NMB at any time
 Sunaga et al. (2010b) In vivo: dogs (dose:response) (n = 6 × 4 = 24), dogs (toxicology) (n = 16) Six anesthetized dogs were each studied four times recording muscle twitch, HR, and IBP; after CW002 (0.08 mg/kg or 9 × ED95), time to spontaneous muscle recovery was determined. CW002 was then injected again followed 1 min later by 10, 20, 50, or 100 mg/kg l-cysteine. After twitch recovery, CW002 was given a third time to determine whether residual l-cysteine influenced duration. Additional group of dogs received CW002 followed by vehicle/200 mg/kg l-cysteine. Dogs were awakened and observed for 2–14 days before sacrificing for analyses 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 reduced in a dose-dependent manner.
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.
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.
Calabadion-1; calabadion-2
 Ma et al. (2012a) NMR spectra and direct and competitive UV/Vis binding assays in vitro
Adult male Sprague–Dawley rats (n = 8) in vivo
Complete NMB (2X ED90) was induced with rocuronium (3.5 mg/kg). Mechanical ventilation maintained until recovery of spontaneous ventilation. 30 s after onset of complete NMB either placebo or calabadion (30, 60, or 90 mg/kg), administered at maximum twitch depression (T1 = 0) Determination of binding constants of the two cucurbit[n]urils with NMBs (pancuronium, atracurium, cisatracurium, rocuronium, vecuronium) in vitro resulted in Ka values ranging from 2.4 × 104/M to 8.4 × 106/M
Calabadion reverses NMB in rat model
Two acyclic cucurbit[n]uril molecular containers with SO3 bind NMBA in vitro
Calabadion reverses NMB in vivo
 Ma et al. (2012b) Job plots constructed from 1H NMR experiments Binding constants determined for the interaction between calabadion-2 and by UV–vis and 1H NMR competition experiments The Ka values for complexes between calabadion and seven local anaesthetics fall in the range of 103 to 108M−1 Calabadion may reverse local anesthetic toxicity
 Hoffmann et al. (2013) In vivo study: rats (n = 60)
Calabadion-1 elimination determined by 1H NMR assay.
Rats were anesthetized, tracheotomized, IV, arterial lines placed. After rocuronium (3.5 mg/kg) or cisatracurium (0.6 mg/kg), NMBA was quantified by acceleromyography. Calabadion-1 at 30, 60, and 90 mg/kg (for rocuronium) or 90, 120, and 150 mg/kg (for cisatracurium), or neostigmine/glycopyrrolate at 0.06/0.012 mg/kg injected at maximum twitch depression. HR, IBP, ABG noted After the administration of rocuronium, resumption of spontaneous breathing and recovery of TOFr to 0.9 were accelerated from 12.3 and 16.2 min with placebo to 4.6 min with neostigmine/glycopyrrolate to 15 and 84 s with calabadion-1 (90 mg/kg), respectively. After the administration of cisatracurium, recovery of breathing and TOFr of 0.9 were accelerated from 8.7 and 9.9 min with placebo to 2.8 and 7.6 min with neostigmine/glycopyrrolate to 47 and 87 s with calabadion-1 (150 mg/kg), respectively. Calabadion-1 did not affect HR, MAP, pH, carbon dioxide pressure, and oxygen tension. More than 90% of the IV administered calabadion-1 appeared in the urine within 1 h. Calabadion-1 causes rapid and complete reversal of the effects of steroidal and benzylisoquinoline NMBA. In healthy rats, calabadion-1 produced a dose-dependent reversal of NMB from cisatracurium and rocuronium without affecting heart rate, blood pressure or arterial blood, gas tensions or pH.
 (Sparr et al. 2001; Sagir et al 2014; Haerter and Simons (2015) In vitro (competition binding assays and urine analysis)
Ex vivo (n = 34; phrenic nerve hemidiaphragm preparation)
In vivo (n = 108; quadriceps femoris muscle of the rat).
The dose–response relationship of drugs to reverse vecuronium-, rocuronium-, and cisatracurium-induced NMB studied
Cumulative dose–response curves of calabadions, neostigmine, or sugammadex were created ex vivo at a steady-state deep NMB. In living rats, the dose–response relationship of the test drugs to reverse deep block was studied
Amount of calabadion-2 excreted in urine measured
Calabadion-2 binds rocuronium with 89 times the affinity of sugammadex (Ka = 3.4 × 109M− 1 and Ka = 3.8 × 107M−1)
Sugammadex and calabadion-2 have 1:1 binding ratio for rocuronium.
The molar potency of calabadion-2 to reverse vecuronium and rocuronium was higher compared with that of sugammadex.
Renal elimination of calabadion-2
No effect on blood pressure /heart rate
Calabadion-2 reverses benzylisoquinolines and steroidal NMBAs in rats faster than sugammadex.
Calabadion-2 is renally eliminated and well tolerated in rats.
 Ganapati et al. (2016) Binding constants determined by direct or competitive UV/Vis assays or direct 1H NMR titrations
Simulation of in vivo equilibria using modeling software Gepasi.
Binding constants determined for the interaction between calabadion-2 and 27 commonly used drugs, drug dosages in the rat model, estimated plasma concentrations, and binding constants toward calabadion-1 Weak-binders (Ka < 105 M−1): neutral/anionic drugs (diclofenac, acetaminophen, chloramphenicol, aminophylline), highly hydrophilic drugs (tetracycline, kanamycin, doxycycline, vancomycin) and zwitterionic drugs (amoxicillin, cefepime)
Stronger-binders (Ka > 105 M−1): hydrophobic polycyclic cations (morphine, naloxone, atropine) and aromatic ammonium ions (dibucaine, propranolol, imipramine)
Strongest binders: procaine, succinylcholine
Neither the binding affinity nor the standard dosages of the drugs were high enough to displace NMBA from its calabadion-2 container.
 Diaz-gil et al. (2016) Sprague-Dawley rats (n = 60)
Swiss Webster mice (n = 35)
Initial bolus etomidate over 40 s till BSR of 70%, then infusion rate of 0.1–0.3 mg kg− 1 min− 1
Either a stepwise increasing calabadion-2 infusion of 40, 60, 80, and 100 mg kg− 1 min− 1over 5 min each (n = 10) or a 20-min saline infusion of equivalent total fluid volume (n = 3)
4 mg/kg etomidate bolus/30 mg/kg ketamine followed by calabadion 80 mg/kg
Dose-dependent reversal of effects of ketamine and etomidate on electroencephalographic predictors of depth of anesthesia, drug-induced hypotension, time to recovery of righting reflex, and functional mobility.
Therapeutic index, 16:1 and 3:1 for ketamine and etomidate
Calabadion-2 reverses etomidate and ketamine anesthesia at non-toxic doses
It does not reverse propofol, isoflurane
 Zhang et al. (2019) Female Balb/c mice (8–10 weeks old)
7 groups (n = 6 each)
WP[6] vs SC[4]A vs CB[7] vs saline placebo (control group)
Firstly, IV Sch (0.75 mg/kg)
Then, IV WP[6] (doses of 10, 20, and 50 mg/kg) or SC[4]A (dose of 20 and 50 mg/kg) or CB[7] (100 mg/kg) or IV saline (100 ml/20 g) immediately.
24 h survival recorded.
Sacrificing mice after 2 weeks noting hematological parameters and organ damage
i.m. (via the right anterior tibia muscle) WP[6] 30 s after i.m. Sch
In rats treated with WP[6] (20 mg/kg or 50 mg/kg) at 30 s after IV Sch, the mean serum potassium level in these rats kept steady
2-fold increase in creatine kinase (serum biomarker of muscular damage) in control group 15 min post SCh but no rhabdomyolysis in WP[6] Grp
Supramolecular therapeutics to treat the side effects of Sch