1.Synthesis and in vivo evaluation of novel PET radioligands for imaging the endothelin-A receptor.
Mathews WB;Murugesan N;Xia J;Scheffel U;Hilton J;Ravert HT;Dannals RF;Szabo Z J Nucl Med. 2008 Sep;49(9):1529-36. doi: 10.2967/jnumed.108.051565. Epub 2008 Aug 14.
The endothelin subtype-A (ETA) receptor is a member of a family of G-protein-coupled receptors that plays a central role in vasoconstriction, cell proliferation, and hormone production. The aim of this study was to synthesize and evaluate in vivo (11)C- and (18)F-labeled analogs of the potent and selective ETA antagonist N-[[2'-[[(4,5-dimethyl-3-isoxazolyl)amino]sulfonyl]-4-(2-oxazolyl)[1,1'-biphenyl]-2-yl]methyl]-N,3,3-trimethylbutanamide (BMS-207940).;METHODS: ;Protected precursors and authentic nonradioactive standards were synthesized by reductive amination and subsequent alkylation of protected aldehyde 1. Desmethyl precursor 2 was reacted with (11)C-methyl iodide followed by deprotection and high-performance liquid chromatography purification to produce (11)C-(N-[[2'-[[(4,5-dimethyl-3-isoxazolyl)amino]sulfonyl]-4-(2-oxazolyl)[1,1'-biphenyl]-2-yl]methyl]-N,1-methylindolecarboxamide) ((11)C-BMS-5p) 3. Nitro precursor 4 was reacted with (18)F-fluoride and purified by high-performance liquid chromatography to produce (18)F-(N-[[2'-[[(4,5-dimethyl-3-isoxazolyl)amino]sulfonyl]-4-(2-oxazolyl)[1,1'-biphenyl]-2-yl]methyl]-N,4-fluorobenzamide) ((18)F-FBzBMS) 5. Biodistribution was determined by injecting male CD-1 mice via the tail vein with either (11)C-BMS-5p 3 or (18)F-FBzBMS 5.
2.Biphenylsulfonamide endothelin receptor antagonists. 4. Discovery of N-[[2'-[[(4,5-dimethyl-3-isoxazolyl)amino]sulfonyl]-4-(2-oxazolyl)[1,1'-biphenyl]- 2-yl]methyl]-N,3,3-trimethylbutanamide (BMS-207940), a highly potent and orally active ET(A) selective antagonist.
Murugesan N;Gu Z;Spergel S;Young M;Chen P;Mathur A;Leith L;Hermsmeier M;Liu EC;Zhang R;Bird E;Waldron T;Marino A;Koplowitz B;Humphreys WG;Chong S;Morrison RA;Webb ML;Moreland S;Trippodo N;Barrish JC J Med Chem. 2003 Jan 2;46(1):125-37.
We have previously disclosed the selective ET(A) receptor antagonist N-(3,4-dimethyl-5-isoxazolyl)-4'-(2-oxazolyl)[1,1'-biphenyl]-2-sulfonamide (1, BMS-193884) as a clinical development candidate. Additional SAR studies at the 2'-position of 1 led to the identification of several analogues with improved binding affinity as well as selectivity for the ET(A) receptor. Following the discovery that a 3-amino-isoxazole group displays significantly improved metabolic stability in comparison to its 5-regioisomer, the 3-amino-isoxazole group was combined with the optimal 2'-substituent leading to 16a (BMS-207940). Compound 16a is an extremely potent (ET(A) K(i) = 10 pM) and selective (80,000-fold for ET(A) vs ET(B)) antagonist. It is also 150-fold more potent and >6-fold more selective than 1. The bioavailability of 16a was 100% in rats and the systemic clearance and volume of distribution are higher than that of 1. In rats, intravenous 16a blocks big ET pressor responses with 30-fold greater potency than 1. After oral dosing at 3 micromol/kg, 16a displays enhanced duration relative to 1.