AZD-3043 A Novel, Metabolically Labile Sedative–Hypnotic Agent with Rapid and Predictable Emergence from Hypnosis Talmage D. Egan, M.D.,* Shinju Obara, M.D.,† Thomas E. Jenkins, Ph.D.,‡ Sarah S. Jaw-Tsai, Ph.D.,§ Shanti Amagasu, M.S.,ʈ Daniel R. Cook, Ph.D.,# Scott C. Steffensen, Ph.D.,** David T. Beattie, Ph.D.†† Downloaded from http://pubs.asahq.org/anesthesiology/article-pdf/116/6/1267/257240/0000542-201206000-00024.pdf by guest on 26 September 2021 ABSTRACT What We Already Know about This Topic • AZD-3043 is a chemical analog of propanidid that was de- Background: Propofol can be associated with delayed awak- signed to be a rapidly metabolized hypnotic (“soft drug”) be- ening after prolonged infusion. The aim of this study was to cause of its ester moiety characterize the preclinical pharmacology of AZD-3043, a positive allosteric modulator of the ␥-aminobutyric acid type A (GABAA) receptor containing a metabolically labile ester What This Article Tells Us That Is New moiety. The authors postulated that its metabolic pathway • AZD-3043 is metabolized rapidly by liver microsomes would result in a short-acting clinical profile. • ␥ It is a positive allosteric modulator of -aminobutyric acidA- Methods: The effects of AZD-3043, propofol, and propani- mediated chloride currents did were studied on GABAA receptor-mediated chloride cur- • It produces rapid onset, dose-dependent electroencephalo- rents in embryonic rat cortical neurons. Radioligand binding graph activity suppression in rats and pigs studies were also performed. The in vitro stability of AZD- • Emergence from AZD-3043–induced hypnosis is rapid and relatively unaffected by dose and infusion duration 3043 in whole blood and liver microsomes was evaluated. The duration of the loss of righting reflex and effects on the electroencephalograph evoked by bolus or infusion intrave- 3043 was shorter acting in rats and pigs. Computer simula- nous administration were assessed in rats. A mixed-effects tion using the porcine kinetic-dynamic model demonstrated kinetic-dynamic model using minipigs permitted explora- that AZD-3043 has very short 50 and 80% decrement times tion of the clinical pharmacology of AZD-3043. independent of infusion duration. Results: AZD-3043 potentiated GABAA receptor-mediated Conclusions: AZD-3043 is a positive allosteric modulator chloride currents and inhibited [35S]tert-butylbicyclophos- of the GABAA receptor in vitro and a sedative–hypnotic phorothionate binding to GABAA receptors. AZD-3043 was agent in vivo. The esterase dependent metabolic pathway rapidly hydrolyzed in liver microsomes from humans and results in rapid clearance and short duration of action even animals. AZD-3043 produced hypnosis and electroenceph- for long infusions. AZD-3043 may have clinical potential alograph depression in rats. Compared with propofol, AZD- as a sedative–hypnotic agent with rapid and predictable recovery. * Professor of Anesthesiology, † Postdoctoral Research Fellow, Department of Anesthesiology, University of Utah School of Medi- cine, Salt Lake City, Utah. ‡ Former Senior Director, § Former HE sedative–hypnotic activity of barbiturates, benzo- Associate Director, ʈ Former Scientist, †† Senior Director, Thera- T diazepines, neurosteroids, and propofol (2,6-diisopro- vance, Inc., South San Francisco, California. # President, NeuroIn- pylphenol in lipid emulsion) results from potentiation of sight, LLC, Bountiful, Utah. ** Associate Professor, Department of ␥ Psychology, Brigham Young University, Provo, Utah. -aminobutyric acid (GABA)-mediated inhibition of synap- Received from the Department of Anesthesiology, University of tic activity within the central nervous system (CNS) via an Utah School of Medicine, Salt Lake City, Utah. Submitted for publi- allosteric interaction at the ␥-aminobutyric acid type A cation July 20, 2011. Accepted for publication February 8, 2012. All (GABAA) receptors. Thus, propofol produces a marked in- studies were supported by Theravance, Inc., South San Francisco, 3 California. crease in the affinity of [ H]GABA binding to rat cortical Address correspondence to Dr. Egan: Department of Anesthesi- membrane preparations and potentiates radiolabeled chlo- ology, University of Utah School of Medicine, Salt Lake City, Utah 84132. [email protected]. Information on purchasing re- prints may be found at www.anesthesiology.org or on the masthead Supplemental digital content is available for this article. Direct page at the beginning of this issue. ANESTHESIOLOGY’s articles are URL citations appear in the printed text and are available in made freely accessible to all readers, for personal use only, 6 both the HTML and PDF versions of this article. Links to the months from the cover date of the issue. digital files are provided in the HTML text of this article on the Copyright © 2012, the American Society of Anesthesiologists, Inc. Lippincott Journal’s Web site (www.anesthesiology.org). Williams & Wilkins. Anesthesiology 2012; 116:1267–77 Anesthesiology, V 116 • No 6 1267 June 2012 AZD-3043 Preclinical Summary terized the nature of the interaction of AZD-3043 with the GABAA receptor in vitro and examined the hypnotic profile of the compound in vivo. The stability of AZD-3043 was also evaluated in vitro in liver microsomes and whole blood from several species, including man. The onset, duration of hypnosis, and recovery profile after intravenous (IV) bolus and infusion administration of AZD-3043 was evaluated in rats. The electroencephalogram of the rat was recorded dur- ing AZD-3043 administration. The pharmacokinetics and pharmacodynamics of AZD-3043 were investigated in a por- Downloaded from http://pubs.asahq.org/anesthesiology/article-pdf/116/6/1267/257240/0000542-201206000-00024.pdf by guest on 26 September 2021 cine model; pharmacokinetic simulations based on a com- bined kinetic-dynamic model were used to explore the clin- ical behavior of AZD-3043. Materials and Methods All experiments were conducted according to guidelines es- tablished by the Institutional Animal Care and Use Commit- tee at Theravance, Inc. (South San Francisco, California), Brigham Young University (Provo, Utah) (rat electroen- cephalography studies), or the University of Utah (Salt Lake City, Utah) (porcine study). The procedures described com- Fig. 1. The chemical structures of AZ-3043; its major inactive plied with the Animal Welfare Act and Public Health Service carboxylate metabolite, THRX-108893; and propanidid are Policy, 1999. Human blood was collected under a voluntary shown. AZ-3043 is an analog of propanidid that is substituted blood donor program at Theravance, Inc., the policy for with an aryl ethoxy, rather than an aryl methoxy group. In which was set up by an occupational health physician and rodents, THRX-108893 accounts for more than 90% of the included volunteer consent and Institutional Biosafety Com- total radioactivity in urine, feces, plasma, liver, and kidney after dosing with radiolabeled AZ-3043. mittee approval. ride uptake evoked by muscimol, a GABAA receptor ago- In Vitro Electrophysiology nist.1 Acting at a binding site distinct from that of the barbi- Cultures of cortical neurons were prepared from embryos of turates, benzodiazepines, or neurosteroid sedative–hypnotics, untimed (approximately E-18) pregnant dam rats.7 Cells ␮ propofol increases the open probability of GABAA receptor were seeded onto poly-D-lysine (100 g/ml) coated glass chloride channels.2 Propofol has gained considerable use for the coverslips in Dulbecco’s Modified Eagle’s Medium supple- induction and maintenance of sedation–hypnosis because pa- mented with 10% fetal bovine serum and 200 ␮g/ml peni- tient awakening is relatively rapid. However, the rapidity of cillin-streptomycin. One day after plating, cells were main- emergence from propofol-mediated sedation–hypnosis is dose- tained in serum-free Dulbecco’s Modified Eagle’s Medium, dependent.3 To avoid tissue accumulation and delayed or un- supplemented with B27 (Gibco® B-27; Life Technologies, predictable patient emergence, dose titration is necessary, par- Carlsbad, CA). Cultures were maintained in a humidified, ticularly with prolonged infusion. CO2 (5%) environment at 37°C until use. The coverslips Propanidid[(4-diethylcarbamoylmethoxy-3-methoxy-phenyl)- were transferred to the recording chamber and perfused con- acetic acid propyl ester] is a short-acting sedative–hypnotic agent tinuously (0.5 ml/min) with bathing solution at room tem- containing an ester moiety that was available in some countries in perature. The bathing solution (pH 7.4) contained (in mM): 4 the 1960s and 1970s. As was the case with propofol, propanidid NaCl (140), KCl (5.4), CaCl2 (1.3), glucose (33), HEPES was introduced as a solution containing Cremophor௡ (BASF Cor- (25), and 0.3 ␮M tetrodotoxin. Gigaohm seals were formed poration, Florham Park, NJ); both were associated with histamine between the cell and a patch electrode (initial resistance 1–2 release and adverse hemodynamic effects.5,6 Unlike the situation M⍀). The patch electrode contained (in mM): CsCl (140), with propofol, propanidid was not reintroduced commercially in CaCl2 (1), EGTA (11), and HEPES (10) with pH 7.2 with an alternative, more acceptable, lipid-based emulsion. CsOH. The membrane beneath the electrode tip was rup- Like propanidid, AZD-3043 ([4-[(N,N-Diethylcarbam- tured to establish a whole cell patch clamp configuration. oyl)methoxy]-3-ethoxyphenyl]acetic acid propyl ester) con- Recording commenced in the voltage clamp mode, with tains a metabolically