title: Synthesis, in vitro and in vivo evaluation of 1,3,5-triazines as cannabinoid CB2 receptor agonists.
abstract: The cannabinoid receptors type 2 (CBR2) are attractive therapeutic targets of the endocannabinoid signaling system (ECS) as they are not displaying the undesired psychotropic and cardiovascular side-effects seen with cannabinoid receptor type 1 (CB1R) agonists. In continuation of our previous work on 2,4,6-trisubstituted 1,3,5-triazines as potent CB2 agonists, we synthesized an additional series of more polar analogues (1-10), which were found to possess high CB2R agonist activity with enhanced water solubility. The most potent compound in the series was N-(adamantan-1-yl)-4-ethoxy-6-(4-(2-fluoroethyl)piperazin-1-yl)-1,3,5-triazin-2-amine (9) with EC50 value of 0.60nM. To further evaluate the biological effects of the compounds, the selected compounds were tested in vitro against four different cell lines. A human retinal pigment epithelial cell line (ARPE-19) was used to evaluate the cytotoxicity of the compounds whereas an androgen-sensitive human prostate adenocarcinoma cell line (LNCaP), a Jurkat leukemia cell line and a C8161 melanoma cell line were used to assess the antiproliferative activity of the compounds. The most interesting results were obtained for N-(adamantan-1-yl)-4-ethoxy-6-(4-methylpiperazin-1-yl)-1,3,5-triazin-2-amine (6), which induced cell viability decrease in prostate and leukemia cell lines, and diminished proliferation of C8161 melanoma cells. The results could be reversed in leukemia cells with the selective CB2R antagonist AM630, whereas in prostate cells the AM630 induced a significant cell viability decrease with a mechanism probably unlinked to CB2 cannabinoid receptor. The antiproliferative effect of 6 on the melanoma cells seemed not to be mediated via the CB1R or CB2R. No cytotoxicity was detected against ARPE-19 cell line at concentrations of 1 and 10μM for compound 6. However, at 30μM concentration the compound 6 decreased the cell viability. Finally, in order to estimate in vivo behavior of these compounds, (18)F labeled PET ligand, N-cyclopentyl-4-ethoxy-6-(4-(2-fluoro-18-ethyl)piperazin-1-yl)-1,3,5-triazin-2-amine ([(18)F]5), was synthesized and its biodistribution was determined in healthy male Sprague-Dawley rats. As a result, the tracer showed a rapid (<15min) elimination in urine accompanied by a slower excretion via the hepatobiliary route. In conclusion, we further demonstrated that 1,3,5-triazine scaffold serves as a suitable template for the design of highly potent CB2R agonists with reasonable water solubility properties. The compounds may be useful when studying the role of the endocannabinoid system in different diseases. The triazine scaffold is also a promising candidate for the development of new CB2R PET ligands.
authors.affiliation: School of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, PO Box 1627, FI-70211 Kuopio, Finland. Electronic address: sari.yrjola@uef.fi.
authors.forename: Sari
authors.initials: S
authors.lastname: Yrjölä
authors.affiliation: Laboratory of Radiochemistry, Department of Chemistry, PO Box 55, FI-00014 University of Helsinki, Finland.
authors.forename: Mirkka
authors.initials: M
authors.lastname: Sarparanta
authors.affiliation: Laboratory of Radiochemistry, Department of Chemistry, PO Box 55, FI-00014 University of Helsinki, Finland.
authors.forename: Anu J
authors.initials: AJ
authors.lastname: Airaksinen
authors.affiliation: Department of Ophthalmology, Institute of Clinical Medicine, University of Eastern Finland, P.O.B. 1627, FI-70211 Kuopio, Finland.
authors.forename: Maria
authors.initials: M
authors.lastname: Hytti
authors.affiliation: Department of Ophthalmology, Institute of Clinical Medicine, University of Eastern Finland, P.O.B. 1627, FI-70211 Kuopio, Finland; Department of Ophthalmology, Kuopio University Hospital, P.O.B 100, FI-70029 KYS, Finland.
authors.forename: Anu
authors.initials: A
authors.lastname: Kauppinen
authors.affiliation: School of Medicine, Institute of Biomedicine, Faculty of Health Sciences, University of Eastern Finland, PO Box 1627, FI-70211 Kuopio, Finland.
authors.forename: Sanna
authors.initials: S
authors.lastname: Pasonen-Seppänen
authors.affiliation: Institute of Applied Physics "Nello Carrara", National Research Council, Via Madonna del Piano 10, 50019 Sesto Fiorentino, FI, Italy; Department of Pharmacy, University of Pisa, Via Bonanno 6, 56100 Pisa, PI, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Adinolfi
authors.affiliation: Department of Pharmacy, University of Pisa, Via Bonanno 6, 56100 Pisa, PI, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Nieri
authors.affiliation: Department of Pharmacy, University of Pisa, Via Bonanno 6, 56100 Pisa, PI, Italy.
authors.forename: Clementina
authors.initials: C
authors.lastname: Manera
authors.affiliation: Laboratory of Radiochemistry, Department of Chemistry, PO Box 55, FI-00014 University of Helsinki, Finland.
authors.forename: Outi
authors.initials: O
authors.lastname: Keinänen
authors.affiliation: School of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, PO Box 1627, FI-70211 Kuopio, Finland; Division of Translational Gastrointestinal Oncology, Dept. of Internal Medicine I, University Hospital Tuebingen, Otfried-Mueller-Strasse 10, 72076 Tuebingen, Germany.
authors.forename: Antti
authors.initials: A
authors.lastname: Poso
authors.affiliation: School of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, PO Box 1627, FI-70211 Kuopio, Finland.
authors.forename: Tapio J
authors.initials: TJ
authors.lastname: Nevalainen
authors.affiliation: School of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, PO Box 1627, FI-70211 Kuopio, Finland.
authors.forename: Teija
authors.initials: T
authors.lastname: Parkkari
mesh_terms: D020003:1-Octanol / Q000737:chemistry; D000818:Animals; D000970:Antineoplastic Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology; D063386:Cannabinoid Receptor Agonists / Q000138:chemical synthesis / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology; D002460:Cell Line; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D005462:Fluorine Radioisotopes; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006801:Humans; D008297:Male; D017207:Rats, Sprague-Dawley; D043884:Receptor, Cannabinoid, CB1 / Q000378:metabolism; D043885:Receptor, Cannabinoid, CB2 / Q000819:agonists* / Q000378:metabolism; D012995:Solubility; D014018:Tissue Distribution; D014227:Triazines / Q000138:chemical synthesis / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology; D014867:Water / Q000737:chemistry
chemical_list: D000970:Antineoplastic Agents; D063386:Cannabinoid Receptor Agonists; D005462:Fluorine Radioisotopes; D043884:Receptor, Cannabinoid, CB1; D043885:Receptor, Cannabinoid, CB2; D014227:Triazines; D014867:Water; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D020003:1-Octanol
keywords: CB2R agonists; Cannabinoid receptor; Radioligand; Triazines