ACS Medicinal Chemistry Letters
Letter
across all conditions conditions (EC50 = 1 to 5 μM), with
similar potency to CBD. Interestingly, the regioisomer 11 was
inactive up to 100 μM. The morpholino amide (12),
morpholino alkyl (13), and acetyl amide (14) derivatives
were largely ineffective. Dramatic results were shown with the
four-membered ring derivatives 15 to 18. Whereas the oxetane
(15) was weakly effective, the methyl azetidine (17) was toxic.
However, the acyl (16) and ethoxylformyl (18) azetidines were
unexpectedly potent with EC50 values ranging from 20 to 110
nM. We did evaluate some of the 4-regioisomers and found
little or no activity (e.g., 27, EC50 > 100 μM).
The three most active molecules 10, 16, and 18 were further
profiled in comparison to the CBD (1) in Table 2. CBD has a
limited therapeutic index of 16 when comparing its toxic dose
with its effective dose in the ammonium acetate toxicity model
with CFDA readout. Therefore, the new molecules were
evaluated for any decrease in neuronal viability at concen-
trations above their EC50. None of the test agents exhibited
toxicity up to 100 μM, and compound 16 was only toxic at 300
μM giving it a therapeutic index of 7500. Compound 18 also
demonstrated a much improved safety margin. None of the
new molecules exhibited CB1 affinity at 10 μM, but 16 and 18
showed modest affinity for CB2. Kinetic aqueous solubility was
improved for the triazole 10 and azetidine 16, but not for 18.
All three new molecules showed great improvements in
permeability in both CACO and MDCK MDR1 cell lines
with no efflux potential.
REFERENCES
■
(1) Cor
Hepatol. 2011, 54, 1030−1040.
(2) Arias, N.; Mendez, M.; Fidalgo, C.; Aller, M. A.; Arias, J.; Arias, J.
́
doba, J. New assessment of hepatic encephalopathy. J.
́
L. Mapping metabolic brain activity in three models of hepatic
encephalopathy. Int. J. Hypertens. 2013, 2013, 1−7.
(3) Bailey, S. M.; Cunningham, C. C. Acute and chronic ethanol
increases reactive oxygen species generation and decreases viability of
isolated rat hepatocytes. Hepatology 1998, 28, 1318−1326.
(4) Hampson, A. J.; Grimaldi, M.; Axelrod, J.; Wink, D. Cannabidiol
and (−)Δ9-tetrahydrocahnnnabinol are neuroprotective antioxidants.
Proc. Natl. Acad. Sci. U. S. A. 1998, 95 (14), 8268−8273.
(5) Avraham, Y.; Grigoriadis, N. C.; Poutahidis, T.; Vorobiev, L.;
Magen, I.; Ilan, Y.; Mechoulam, R.; Berry, E. M. Cannabidiol improves
brain and liver function in a fulminant hepatic failure-induced model of
hepatic encephalopathy in mice. Br. J. Pharmacol. 2011, 162, 1650−
1658.
(6) Magen, I.; Avraham, Y.; Ackerman, Z.; Vorobiev, L.; Mechoulam,
R.; Berry, E. M. Cannabidiol ameliorates cognitive and motor
impairments in mice with bile duct ligation. J. Hepatol. 2009, 51,
528−534.
(7) Pazos, M. R.; Cinquina, V.; Gom
́
ez, A.; Layunta, R.; Santos, M.;
Fernandez-Ruiz, J.; Martínez-Orgado, J. Cannabidiol administration
́
after hypoxia-ischemia to newborn rats reduces long-term brain injury
and restores neurobehavioral function. Neuropharmacology 2012, 63,
776−783.
(8) Hampson, A. J.; Grimaldi, M.; Lolic, M.; Wink, D.; Rosenthal, R.;
Axelrod, J. Neuroprotective antioxidants from marijuana. Ann. N. Y.
Acad. Sci. 2000, 899, 274−282.
(9) Hayakawa, K.; Mishima, K.; Fujiwara, M. Therapeutic potential of
non-phschotropic cannabidiol in ischemic stroke. Pharmaceuticals
2010, 3, 2197−2212.
Compound 16 (KLS-13019) was selected for further
characterization based on its overall improved properties
relative to CBD (1) in potency, safety, aqueous solubility,
and permeability. The complete in vitro and in vivo work up on
this lead candidate will reported in due course.
(10) Ryan, D.; Drysdale, A. J.; Lafourcade, C.; Pertwee, R. G.; Platt,
B. Cannabidiol targets mitochondria to regulate intracellular Ca2+
levels. J. Neurosci. 2009, 29 (7), 2053−2063.
(11) Ong, J. P.; Aggarwal, A.; Krieger, D.; Easley, K. A.; Karafa, M. T.;
Van Lente, F.; Arroliga, A. C.; Mullen, K. D. Correlation between
ammonia levels and the severity of hepatic encephalopathy. Am. J. Med.
2003, 114, 188−193.
ASSOCIATED CONTENT
■
S
* Supporting Information
The Supporting Information is available free of charge on the
̌
(12) Bisogno, T.; Hanus, L.; De Petrocellis, L.; Tchilibon, S.; Ponde,
D. E.; Brandi, I.; Moriello, A. S.; Davis, J. B.; Mechoulam, R.; Di
Marzo, V. Molecular targets for cannabidiol and its synthetic
analogues: effect on vanilloid VR1 receptors and on the cellular
uptake and enzymatic hydrolysis of anandamide. Br. J. Pharmacol.
2001, 134, 845−852.
Complete experimental details on synthetic and bioassay
(13) Wiley, J. L.; Beletskaya, I. D.; Ng, E. W.; Dai, Z.; Crocker, P. J.;
Mahadevan, A.; Razdan, R. K.; Martin, B. R. Resorcinol derivatives: a
novel template for the development of cannabinoid CB1/CB2 and
CB2-selective agonists. J. Pharmacol. Exp. Ther. 2002, 301, 679−689.
(14) Hitchcock, S. A.; Pennington, L. D. Structure - Brain Exposure
Relationships. J. Med. Chem. 2006, 49, 7559−7583.
(15) Jiang, R.; Yamaori, S.; Takeda, S.; Yamamoto, I.; Watanabe, K.
Identification of cytochrome P450 enzymes responsible for metabo-
lism of cannabidiol by human liver microsomes. Life Sci. 2011, 89,
165−170.
AUTHOR INFORMATION
■
Corresponding Author
Present Address
§Fox Chase Chemical Diversity Center, 3805 Old Easton Road,
Doylestown, Pennsylvania 18902, United States.
Author Contributions
(16) Harvey, D. J.; Martin, B. R.; Paton, W. D. M. Comparative in
vivo metabolism of Δ1-tetrahydrocannabinol (Δ1-THC), cannabidiol
(CBD) and cannabinol (CBN) by several species. Recent Dev. Mass
Spectrom. Biochem. Med. 1978, 1, 161−84.
(17) Crombie, L.; Crombie, W. M. L.; Kilbee, G. W.; Tuchinda, P.
Synthesis of 4″-carboxylated cannabinoids: stereospecific processes
involving ethylidenemalonic ester. Tetrahedron Lett. 1979, 49, 4773−
4776.
(18) Papahatjis, D. P.; Nahmias, V. R.; Nikas, S. P.; Andreou, T.;
Alapafuja, S. O.; Tsotinis, A.; Guo, J.; Fan, P.; Makriyannis, A. C1′-
Cycloalkyl side chain pharmacophore in tetrahydrocannabinols. J. Med.
Chem. 2007, 50, 4048−4060.
̌
(19) Ben-Shabat, S.; Hanus, L. O.; Katzavian, G.; Gallily, R. New
cannabidiol derivatives, synthesis, binding to cannabinoid receptor,
The manuscript was written through contributions of all
authors. All authors have given approval to the final version of
the manuscript.
Notes
The authors declare no competing financial interest.
ABBREVIATIONS
■
AmAc, ammonium acetate; CFDA, carboxyfluorescein diac-
etate; CB1 CB2, cannabinoid receptor 1 or 2; CBD,
cannabidiol; cLogP, calculated log P; PI, propidium iodide;
PSA, polar surface area; TI, therapeutic index; EC50, 50%
efficacy concentration
D
ACS Med. Chem. Lett. XXXX, XXX, XXX−XXX