Virtual screening benchmarking studies were carried out on 11 targets to evaluate the performance of three commonly used approaches: 2D ligand similarity (Daylight, TOPOSIM), 3D ligand similarity (SQW, ROCS), and protein structure-based docking (FLOG, FRED, Glide). Active and decoy compound sets were assembled from both the MDDR and the Merck compound databases. Averaged over multiple targets, ligand-based methods outperformed docking algorithms. This was true for 3D ligand-based methods only when chemical typing was included. Using mean enrichment factor as a performance metric, Glide appears to be the best docking method among the three with FRED a close second. Results for all virtual screening methods are database dependent and can vary greatly for particular targets.

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Modifications to the previously reported spiroindenylpiperidine camphor-sulfonamide oxytocin (OT) antagonist L-366,509 have produced a new series of o-tolylpiperazine (TP) camphor-sulfonamides. A number of analogues in the TP series that incorporate a modified or unmodified L-methionine sulfone amide at the C2 endo position on the camphor ring exhibit high affinity for OT receptors (IC50 = 1.3-15 nM) and good selectivity for binding to OT versus arginine vasopressin V1a and V2 receptors. Several of these analogues were additionally characterized as potent antagonists of OT-stimulated contractions of the isolated and/or in situ rat uterus. Compound 7 (L-368,899) exhibited the best overall profile of OT receptor affinity (IC50 = 8.9 nM, rat uterus; 26 nM, human uterus), potency for inhibition of OT-stimulated contractions of the isolated rat uterus (pA2 = 8.9) and in situ rat uterus (AD50 = 0.35 mg/kg after intravenous (i.v.) administration and 7.0 mg/kg after intraduodenal administration), aqueous solubility (3.7 mg/mL at pH 5.0), and oral bioavailability in several species (35% (rat), 25% (dog), and 21% (chimpanzee) as estimated from radioreceptor determination of drug levels in plasma after oral and i.v. dosing). On the basis of these favorable properties, 7 has begun clinical testing for use as an oral and i.v. tocolytic agent. Molecular modeling alignment studies have provided support for the hypothesis that the TP camphor-sulfonamide portion of the non-peptide structures may serve as a mimetic of the important D-AA2-Ile3 dipeptide (AA = aromatic amino acid) found in many potent OT antagonists from the cyclic hexapeptide and OT analogue structural classes.

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