Discovery of 3-methyl-N-(1-oxy-3',4',5',6'-tetrahydro-2'H-[2,4'-bipyridine]-1'-ylmethyl)benzamide (ABT-670), an orally bioavailable dopamine D4 agonist for the treatment of erectile dysfunction.

The goal of this study was to identify a structurally distinct D(4)-selective agonist with superior oral bioavailability to our first-generation clinical candidate 1a (ABT-724) for the potential treatment of erectile dysfunction. Arylpiperazines such as (heteroarylmethyl)piperazine 1a, benzamide 2, and acetamides such as 3a,b exhibit poor oral bioavailability. Structure-activity relationship (SAR) studies with the arylpiperidine template provided potent partial agonists such as 4d and 5k that demonstrated no improvement in oral bioavailability. Further optimization with the (N-oxy-2-pyridinyl)piperidine template led to the discovery of compound 6b (ABT-670), which exhibited excellent oral bioavailability in rat, dog, and monkey (68%, 85%, and 91%, respectively) with comparable efficacy, safety, and tolerability to 1a. The N-oxy-2-pyridinyl moiety not only provided the structural motif required for agonist function but also reduced metabolism rates. The SAR study leading to the discovery of 6b is described herein.

The use of soil biofilms for observing protozoan movement and feeding.

Protozoan movement and feeding regimes in soil biofilms were observed with inverted microscopes and Utermohl plankton counting chambers (4 mm deep). In a new use for these counting chambers, the three-dimensional appearance of a soil pore network can be simulated using long working distance objectives (40x). Protozoa were often associated with soil surfaces and penetrated soil crevices of less than 3 microm in diameter by either distorting their body outlines or with slender pseudopodia of less than 2 microm at the tips. Many ciliates repeatedly collided with soil particles and released attached bacteria into the soil solution for subsequent predation.

Inhibitors of hepatitis C virus polymerase: synthesis and biological characterization of unsymmetrical dialkyl-hydroxynaphthalenoyl-benzothiadiazines.

The hepatitis C virus (HCV) NS5B polymerase is essential for viral replication and has been a prime target for drug discovery research. Our efforts directed toward the discovery of HCV polymerase inhibitors resulted in the identification of unsymmetrical dialkyl-hydroxynaphthalenoyl-benzothiadiazines 2 and 3. The most active compound displayed activity in genotypes 1a and 1b polymerase and replicon cell culture inhibition assays at subnanomolar and low nanomolar concentrations, respectively. It also displayed an excellent pharmacokinetic profile in rats, with a plasma elimination half-life after intravenous dosing of 4.5 h, oral bioavailability of 77%, and a peak liver concentration of 21.8 microg/mL.

Structure-activity studies for a novel series of tricyclic dihydropyridopyrazolones and dihydropyridoisoxazolones as K(ATP) channel openers.

In search of a novel chemotype of K(ATP) channel openers a series of tricyclic dihydropyridopyrazolones and dihydropyridoisoxazolones was synthesized. It was found that cyclopentanone in the left hand portion of the molecule was 4-fold more potent than cyclohexanone. Introduction of gem-dimethyl groups as well as incorporation of oxygen in the cyclohexanone ring in the left hand portion of the molecule increased the potency 10-fold. In the right hand portion of the molecule, the NH-group of the pyrazolone can be effectively substituted by oxygen increasing the activity 5-fold. Incorporation of a methyl group adjacent to the dihydropyridine (DHP) nitrogen not only significantly boosted activity, but also provided an additional benefit of increased metabolic stability. In vitro tests on the tissue from pig bladder strips provided further confirmation of K(ATP) activity of these compounds.