Nonpeptidic, monocharged, cell permeable ligands for the p56lck SH2 domain.

p56lck is a member of the src family of tyrosine kinases and plays a critical role in the signal transduction events that lead to T cell activation. Ligands for the p56lck SH2 domain have the potential to disrupt the interaction of p56lck with its substrates and derail the signaling cascade that leads to the production of cytokines such as interleukin-2. Starting from the quintuply charged (at physiological pH) phosphorylated tetrapeptide, AcpYEEI, we recently disclosed (J. Med. Chem. 1999, 42, 722 and J. Med. Chem. 1999, 42, 1757) the design of the modified dipeptide 3, which carries just two charges at physiological pH. Here we present the elaboration of 3 to the nonpeptidic, monocharged compound, 9S. This molecule displays good binding affinity for the p56lck SH2 domain (K(d) 1 microM) and good cell permeation, and this combination of properties allowed us to demonstrate clear-cut inhibitory effects on a very early event in T cell activation, namely calcium mobilization.

Novel non-nucleoside inhibitors of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase. 4. 2-Substituted dipyridodiazepinones as potent inhibitors of both wild-type and cysteine-181 HIV-1 reverse transcriptase enzymes.

The major cause of viral resistance to the potent human immunodeficiency virus type 1 reverse transcriptase (RT) inhibitor nevirapine is the mutation substituting cysteine for tyrosine-181 in RT (Y181C RT). An evaluation, against Y181C RT, of previously described analogs of nevirapine revealed that the 2-chlorodipyridodiazepinone 16 is an effective inhibitor of this mutant enzyme. The detailed examination of the structure-activity relationship of 2-substituted dipyridodiazepinones presented below shows that combined activity against the wild-type and Y181C enzymes is achieved with aryl substituents at the 2-position of the tricyclic ring system. In addition, the substitution pattern at C-4, N-5, and N-11 of the dipyridodiazepinone ring system optimum for inhibition of both wild-type and Y181C RT is no longer the 4-methyl-11-cyclopropyl substitution preferred against the wild-type enzyme but rather the 5-methyl-11-ethyl (or 11-cyclopropyl) pattern. The more potent 2-substituted dipyridodiazepinones were evaluated against mutant RT enzymes (L100I RT, K103N RT, P236L RT, and E138K RT) that confer resistance to other non-nucleoside RT inhibitors, and compounds 42, 62, and 67, with pyrrolyl, aminophenyl, and aminopyridyl substituents, respectively, at the 2-position, were found to be effective inhibitors of these mutant enzymes also.

Novel non-nucleoside inhibitors of human immunodeficiency virus type 1 reverse transcriptase. 5. 4-Substituted and 2,4-disubstituted analogs of nevirapine.

Molecular modeling analysis of the recently published X-ray crystal structure of nevirapine bound to wild type human immunodeficiency virus type 1 reverse transcriptase (WT-RT) indicated the presence of a lipophilic cavity proximal to the 4-position of the inhibitor. A series of 4-substituted derivatives of nevirapine were thus synthesized to assess structure-activity relationships (SARs) and to see if increased binding to this region might translate into greater activity against mutant RTs. The results show that compounds with an appropriately spaced aryl ring appended to the 4-position of the dipyridodiazepinone ring system show good activity against WT-RT. Furthermore certain derivatives appear to inhibit the Y181C mutant RT. Attempts to combine these results with the recent discovery that 2-substituents enhance activity against the Y181C mutant led to a few compounds with moderate activity against both enzymes. The SAR of these two positions, however, could not be combined in a simple fashion.

Novel non-nucleoside inhibitors of HIV-1 reverse transcriptase. 3. Dipyrido[2,3-b:2',3'-e]diazepinones.

We have explored the potential of derivatives of the dipyrido[2,3-b:2',3'-e][1,4]diazepinone ring system as inhibitors of HIV-1 reverse transcriptase (RT). These compounds are isomeric to the potent RT inhibitor nevirapine and are available via a novel Smiles rearrangement on intermediates used for the synthesis of nevirapine analogs. Derivatives of this isomeric series are weaker inhibitors of RT than corresponding nevirapine analogs, although with appropriate substitution of the A- and C-pyridine rings activity can be improved.

Novel non-nucleoside inhibitors of HIV-1 reverse transcriptase. 1. Tricyclic pyridobenzo- and dipyridodiazepinones.

Novel pyrido[2,3-b][1,4]benzodiazepinones (I), pyrido[2,3-b][1,5]benzodiazepinones (II), and dipyrido[3,2-b:2',3'-e][1,4]diazepinones (III) were found to inhibit human immunodeficiency virus type 1 (HIV-1) reverse transcriptase in vitro at concentrations as low as 35 nM. In all three series, small substituents (e.g., methyl, ethyl, acetyl) are preferred at the lactam nitrogen, whereas slightly larger alkyl moieties (e.g., ethyl, cyclopropyl) are favored at the other (N-11) diazepinone nitrogen. In general, lipophilic substituents are preferred on the A ring, whereas substitution on the C ring generally reduces potency relative to the corresponding compounds with no substituents on the aromatic rings. Maximum potency is achieved with methyl substitution at the position ortho to the lactam nitrogen atom; however, in this case an unsubstituted lactam nitrogen is preferred. Additional substituents on the A ring can be readily tolerated. The dipyridodiazepinone derivative 11-cyclopropyl-5,11-dihydro-4-methyl-6H-dipyrido[3,2-b:2',3'-e] [1,4]diazepin-6-one (96, nevirapine) is a potent (IC50 = 84 nM) and and selective non-nucleoside inhibitor of HIV-1 reverse transcriptase, and has been chosen for clinical evaluation.

Polycyclic aryl- and heteroarylpiperazinyl imides as 5-HT1A receptor ligands and potential anxiolytic agents: synthesis and structure-activity relationship studies.

A series of polycyclic aryl- and heteroarylpiperazinyl imides were prepared and tested in various receptor-binding and behavioral tests. Parameters measured included in vitro inhibition of D2 and 5-HT1A receptor binding, inhibition of apomorphine (APO) induced stereotyped and climbing behavior, and activity in blocking conditioned avoidance responding (CAR). Several compounds demonstrated moderate to high affinity for the 5-HT1A receptor binding site; compounds 27 and 36 containing the serotonin mimetic (o-methoxyphenyl)piperazinyl moiety and compounds 42 and 50 containing the 2-pyrimidinylpiperazinyl moiety displayed the highest affinity, being equal to that of the 5-HT1A agonist 8-OH-DPAT (Ki = 1-1.3 nM). In addition to affinity at 5-HT1A binding sites, many compounds were active in blocking CAR. Compound 34, 2-[4-[4-(2-pyrimidinyl)-1-piperazinyl]butyl]hexahydro-4,7-etheno-1H- cyclobut[f]isoindole-1,3(2H)-dione, demonstrated 3 times the activity of buspirone, blocking CAR in rats with an AB50 of 13 mg/kg. It also displayed high affinity for the 5-HT1A receptor (Ki = 16 nM), which is at least 20 times higher than its affinity for D2 (Ki = 345 nM) and 5-HT2 (Ki = 458 nM) receptors. Compound 34 was selected for further preclinical and pharmacokinetic evaluations for possible development as an anxiolytic agent. Structure-activity relationships within this series are discussed.

Antipsychotic activity of substituted gamma-carbolines.

Several novel substituted gamma-carbolines were synthesized and examined in a series of in vitro and in vivo pharmacological tests to determine potential antipsychotic activity. Most compounds were orally active in blocking the conditioned avoidance response (CAR) in rats but did not antagonize apomorphine-induced stereotyped behavior. Compound 17 (Wy-47,384), a gamma-carboline with a 3-(3-pyridinyl)propyl side chain, was selected for development as an atypical antipsychotic agent because of its potent and selective profile in preclinical psychopharmacological tests. It blocked CAR in rats with an AB50 of 14 mg/kg po, showed weak affinity for the D2 receptor site (Ki = 104 nM), and showed differential potency in antagonizing apomorphine-induced stereotyped behavior (ED50 = 11 mg/kg ip) and climbing behavior (ED50 = 4 mg/kg ip). Such activities are suggestive of antipsychotic efficacy combined with a low potential for extrapyramidal side effect (EPS) liability.

Psychotropic agents: synthesis and antipsychotic activity of substituted beta-carbolines.

A series of novel substituted beta-carbolines was synthesized and tested for potential antipsychotic activity. Several compounds displayed moderate antipsychotic activity in vitro and in vivo as determined by relevant receptor binding assays and behavioral tests. The effect of substituents on antipsychotic activity was examined. The beta-carbolines 10 and 19 containing 2-(2-pyridinyl)ethyl and 2-(2-quinolinyl)ethyl side chains were the most potent analogues, blocking discrete trial conditioned avoidance responding in rats with AB50's of 23 and 10 mg/kg, respectively. Both showed moderate activity at the D2 receptor sites, but they lacked oral activity. In contrast, the beta-carboline 13 containing the 4-(4-pyridinyl)butyl side chain exhibited oral activity in the discrete trial conditioned avoidance screen with an AB50 of 31 mg/kg. Most compounds did not antagonize apomorphine-induced stereotyped behavior, which is indicative of low potential for extrapyramidal side effect (EPS) liability.

Bioavailability of hydrochlorothiazide from tablets and suspensions.

The bioavailability of hydrochlorothiazide was determined following single oral 25-, 50-, 100-, and 200-mg tablet and suspension doses in 12 healthy male volunteers. Plasma and urine levels of hydrochlorothiazide were determined by HPLC. Plasma levels of hydrochlorothiazide were satisfactorily described by a triexponential function. Mean peak plasma levels, Cmax (127-135, 270-280, and 437-490 ng/mL from the 25-, 50-, and 100-mg doses, respectively) were dose proportional, as were areas under plasma profiles, AUC0----36. Mean percentage recovery of unchanged hydrochlorothiazide in 48-h urine samples accounted for 50-59, 54-55, 60-63, and 54-57% of the 25-, 50-, 100-, and 200-mg doses, respectively. There were no significant differences among these values. Correlation coefficients between 48-h urinary recovery of hydrochlorothiazide and the plasma values (Cmax and AUC0----36) for the 25-, 50-, and 100-mg doses were 0.73 and 0.84. There were no differences in the net increases in electrolyte excretion among the treatments during the 0-12-h postdose period. The systematic availability of hydrochlorothiazide, unlike that of chlorothiazide, is dose proportional in the therapeutic range.

Bioavailability of tolazamide from tablets: comparison of in vitro and in vivo results.

The relative bioavailability of tolazamide was determined, in healthy male volunteers, from four different tablet formulations manufactured by direct compaction or granulation processes and the results were compared with in vitro disintegration and dissolution values. Serum tolazamide levels were determined by a high-pressure liquid chromatographic method developed in this laboratory. Serum tolazamide levels from the formulation that gave rise to rapid absorption were described by one-compartment model kinetics with a mean absorption half-time of 1.0 hr and an elimination half-life of 4.6 hr. Peak serum levels occurred at 3.3 hr after drug administration. Marked differences were observed in drug bioavailability from the four tablets, and the mean cumulative relative fraction of dose absorbed was 1.0, 0.42, 0.75, and 0.91 from Formulations A, B, C, and D, respectively. The hypoglycemic effect was closely related to serum tolazamide levels. Disintegration times did not predict in vivo tolazamide bioavailability. Dissolution rates provided an approximate rank order correlation with in vivo absorption but failed to be predictive among formulations. Currently available in vitro tests do not accurately predict tolazamide in vivo bioavailability characteristics among different formulations and manufacturing processes but may be useful to ensure lot-to-lot uniformity in bioavailability for a given formulation and specific method of manufacture.