BRL-32872

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BRL-32872
BRL-32872.svg
Names
IUPAC name
N-(3,4-Dimethoxyphenyl)-N-(3-{[2-(3,4-dimethoxyphenyl)ethyl](methyl)amino}propyl)-4-nitrobenzamide
Identifiers
3D model (JSmol)
ChEMBL
ChemSpider
Properties
C29H35N3O7
Molar mass 537.613 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

BRL-32872 is an experimental drug candidate that provides a novel approach to the treatment of cardiac arrhythmia. Being a derivative of verapamil, it possesses the ability to inhibit Ca+2 membrane channels. Specific modifications in hydrogen bonding activity, nitrogen lone pair availability, and molecular flexibility allow BRL-32872 to inhibit K+ channels as well. As such, BRL-32872 is classified as both a class III (K+ blocking) and class IV (Ca+2 blocking) antiarrhythmic agent.[1]

Arrhythmia[edit]

Cardiac arrhythmia arises from abnormalities in action potential formation and propagation through the heart. Changes in electrolyte balance, or development of ectopic pacemaker activity, disrupt normal heart rhythmicity and conduction.[2] Antiarrhythmic agents are used to manipulate ion flux through membrane channels to restore normal pacemaker activity. Cellular conduction and refractory periods are also modified to eliminate re-entry depolarization causing arrhythmia. Factors contributing to the generation of arrhythmia include: ischemia, hypoxia, acidosis and drug toxicity. If untreated, arrhythmias may present as bradycardia, tachycardia, or progress to atrial/ventricular fibrillation.[3]

Class III activity[edit]

BRL-32872’s class III activity is directed towards the human ether-a-go-go-related gene (hERG) K+ channel.[4] hERG channels are the source of the delayed rectifier potassium current (IK); the current responsible for repolarization of the cardiac action potential. BRL-32872 binds with high affinity to open hERG channels, and inhibits the rapidly activating component of the IK.[4] BRL-32872 binding effectively increases the refractory period of the cell and prolongs the action potential. This blockage also reduces probability of re-entry depolarization, since signals are more likely to encounter tissue in a refractory state. This effect is particularly well suited for treating atrial and ventricular fibrillation, as it restores pacemaker control of the tissue to the SA and AV nodes.[3] The specific binding site of BRL-32872 on the hERG channel is unknown; evidence suggests however, that it lies within the channels pore, similar to other class III drugs.[4]

Class IV activity[edit]

BRL-32872’s class IV activity is similar to that of its parent drug, verapamil. The drug targets L-type Ca+2 channels, and decreases conduction in cells where Ca+2 is required for action potential upstroke (SA/AV nodes).[5] The result is increased nodal conduction time and refractoriness, restoring normal heart rate in patients with tachycardia. Binding occurs on the pore-forming α1 subunit during the open or inactive state.[6] This low level of ICa inhibition is credited with eliminating some of the proarrhythmial effects of class III drugs. The combined inhibition of K+/Ca+2 channels has proven to eliminate the occurrence of early after-depolarizations (EAD’s), in comparison to selective class III agents alone.[7]

Benefits of BRL-32872[edit]

Unlike most antiarrhythmics, BRL-32872’s effects are homogeneous within the various cardiac tissue types (nodal cells, cardiomyocytes, Purkinje fibers).[7] This property helps eliminate repolarization dispersion, a proarrhythmial effect noted in class III agents. BRL-32872 does not exhibit reverse-use dependence; meaning efficacy is conserved regardless of heart rate.[7] The drug is also easily administered orally or via intravenous injection, and has no effect on resting membrane potential.[5] The effects BRL-32872 have been well documented in animal models. However, its effect has not yet been demonstrated in humans.  These beneficial experimental results make a strong case for the use of drugs such as BRL-32872, with combined K+/Ca+2 inhibition, in first line antiarrhythmial treatment.

References[edit]

  1. ^ Nadler, G., Faivre, J. F., Forest, M. C., Cheval, B., Martin, M., Souchet, M., et al. (1998). Synthesis, electrophysiological properties and analysis of structural requirements of a novel class of antiarrhythmic agents with potassium and calcium channel blocking properties. Bioorganic & Medicinal Chemistry, 6(11), 1993-2011
  2. ^ Guyton, Arthur C., Hall, John E. (2006). Textbook of Medical Physiology (11th ed.). Philadelphia: Elsevier Saunders. ISBN 0-7216-0240-1
  3. ^ a b Katzung, Bertram G.; Masters, Susan B.; Trevor, Anthony J. (2009). Basic and Clinical Pharmacology. 11th ed. New York: McGraw Hill. ISBN 978-0-07-160405-5
  4. ^ a b c Thomas, D., Wendt-Nordahl, G., Rockl, K., Ficker, E., Brown, A. M., & Kiehn, J. (2001). High-affinity blockade of human ether-a-go-go-related gene human cardiac potassium channels by the novel antiarrhythmic drug BRL-32872. The Journal of Pharmacology and Experimental Therapeutics, 297(2), 753-761.
  5. ^ a b Bril, A., Faivre, J. F., Forest, M. C., Cheval, B., Gout, B., Linee, P., et al. (1995). Electrophysiological effect of BRL-32872, a novel antiarrhythmic agent with potassium and calcium channel blocking properties, in guinea pig cardiac isolated preparations. The Journal of Pharmacology and Experimental Therapeutics, 273(3), 1264-1272
  6. ^ Cheng, R. C., Tikhonov, D. B., & Zhorov, B. S. (2009). Structural model for phenylalkylamine binding to L-type calcium channels. The Journal of Biological Chemistry, 284(41), 28332-28342
  7. ^ a b c Faivre, J. F., Forest, M. C., Gout, B., & Bril, A. (1999). Electrophysiological characterization of BRL-32872 in canine purkinje fiber and ventricular muscle: Effect on early after-depolarizations and repolarization dispersion. European Journal of Pharmacology, 383(2), 215-222