DOI: 10.1002/cmdc.201402277
Communications
Discovery and Characterization of 2-
(Cyclopropanesulfonamido)-N-(2-ethoxyphenyl)benzamide,
ML382: a Potent and Selective Positive Allosteric
Modulator of MrgX1
Wandong Wen,[a] Yan Wang,[b] Zhe Li,[c] Pang-Yen Tseng,[c] Owen B. McManus,[d] Meng Wu,[d, f]
Min Li,[d, e] Craig W. Lindsley,[a] Xinzhong Dong,*[c] and Corey R. Hopkins*[a]
Previous studies have shown that the activation of mouse
MrgC11, a G-protein-coupled receptor, by its peptide ligand
BAM8-22 can inhibit chronic pain. A large-scale screen has
been carried out to isolate small-molecule allosteric agonists of
MrgX1, the human homologue of MrgC11. The goal of this
study is to improve the efficacy and potency of positive allo-
steric modulators (PAMs) with therapeutic implications in com-
bating chronic pain. Herein we report an iterative parallel syn-
thesis effort and a structure–activity relationship study of
a series of arylsulfonamides which led to the discovery of the
first PAM of MrgX1, ML382.
to their clinical use and have become a serious health threat.
The discovery of novel therapies to treat pain without the po-
tential for addiction is therefore a major goal.
Mrgs (also named Mrgprs/SNSRs) are a family of G-protein-
coupled receptors (GPCRs) consisting of more than 50 mem-
bers in the mouse genome.[1] Strikingly, the expression of
many Mrg genes, including MrgC11, is restricted to subsets of
small-diameter sensory neurons in the dorsal root ganglion
(DRG) and trigeminal ganglia, as these genes have not been
detected in the central nervous system (CNS) or in the rest of
the body.[2] Similarly, some human MrgXs such as MrgX1 are
also selectively expressed in DRG neurons.[1b] BAM8-22, a 15-
residue endogenous peptide, is a specific agonist for mouse
MrgC11 and human MrgX1.[1a,2] Based on the expression pat-
tern, ligand specificity, and similarity in signal pathways,
MrgC11 and MrgX1 are functional orthologues.
Chronic pain is difficult to treat and has become a major
health and economic burden worldwide, reaching nearly epi-
demic levels with 20–25% of the population affected. Chronic
pain is often refractory to current therapies, and the many of
the major analgesics (e.g., opioids) carry with them dose-limit-
ing adverse events and serious risk of addiction and abuse.
These risks of addiction and abuse present substantial barriers
Several complementary lines of evidence suggest that
MrgC11 functions as an endogenous regulator of persistent
pain.[3] Particularly, spinal cord application of BAM8-22 and
other MrgC11 agonists in mice significantly attenuates inflam-
matory hyperalgesia and neuropathic pain in an Mrg-depen-
dent manner.[3a,4] It has been shown recently that the activa-
tion of MrgC11 leads to inhibition high-voltage activating Ca2+
channels, which play an essential role in pain signal transmis-
sion.[5] Because of the specific expression, agonists and positive
allosteric modulators (PAMs) for MrgX1 may represent a new
class of anti-hyperalgesics for the treatment of chronic pain
without side effects in the CNS.[6,7]
[a] W. Wen,+ Prof. C. W. Lindsley, Prof. C. R. Hopkins
Department of Pharmacology
Vanderbilt Center for Neuroscience Drug Discovery
Vanderbilt Specialized Chemistry Center (MLPCN)
Vanderbilt University Medical Center, Nashville, TN 37232-6600 (USA)
[b] Dr. Y. Wang+
State Key Laboratory of Oral Diseases and Department of Orthodontics
West China School of Stomatology
The project commenced with a screen of the NIH Molecular
Library Small-Molecule Repository (MLSMR) compound collec-
tion containing >300000 compounds using a triple addition
protocol with BAM-22 as the as the ligand (AID: 588675;
Figure 1).[8] Using a HEK293 cell line that stably expresses the
MrgX1 protein, the first addition is the drug itself (agonist
mode), the second addition is BAM-22 at EC10–EC30 for the
identification of PAMs, and the third addition uses BAM-22 at
EC90–Emax for the identification of antagonists/negative alloste-
ric modulators. From the initial screen, ~1900 compounds
were identified as hits, and after a medicinal chemistry triage,
~1100 compounds were retested and then counter-screened
against HEK293 parental cells. There were ~150 compounds
that showed no activity against the parental cells, and these
were then evaluated in a five-point concentration–response
curve (CRC), leaving 29 active compounds. These compounds
Sichuan University, Chengdu, 610041 (China)
[c] Z. Li, Dr. P.-Y. Tseng, Prof. X. Dong
Department of Neuroscience
Johns Hopkins University School of Medicine, Baltimore, MD 21205 (USA)
[d] Dr. O. B. McManus, Dr. M. Wu, Dr. M. Li
Johns Hopkins Ion Channel Center
Johns Hopkins University, Baltimore, MD 21205 (USA)
[e] Dr. M. Li
Glaxo Smith Kline, 709 Swedeland Road, King of Prussia, PA 19406 (USA)
[f] Dr. M. Wu
Present address: High-Throughput Screening Facility, University of Iowa
115 S. Grand Ave., 316 PHAR, Iowa City, IA 52242 (USA)
[+] These authors contributed equally to this work.
Supporting information for this article is available on the WWW under
medicinal chemistry, pharmacology, and drug metabolism studies, as
well as compound characterization data.
ChemMedChem 2015, 10, 57 – 61
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