Phosphorylation of the anti-HIV compound (S,S)-isodideoxyadenosine by human recombinant deoxycytidine kinase

(S,S)-Isodideoxyadenosine [(S,S)-isoddA] is an anti-HIV active compound discovered in our laboratory. However, its cellular mechanism of action, particularly the critical first stage of phosphorylation, is not understood. IsoddA is not phosphorylated by adenosine kinase. Also, because it is not a substrate for adenosine deaminase, it would not be activated by the pathway taken by ddA, i. e. via 5'-nucleotidase phosphorylation of ddI and conversion of ddIMP to ddAMP. However, we have discovered that human recombinant 2'-deoxycytidine kinase (dCK) phosphorylates (S,S)-isoddA. The enzyme kinetic data revealed that the extent of monophosphorylation of this L-related nucleoside was comparable to that found with ddA. (S,S)-IsoddATP is among the most potent inhibitors of HIV reverse transcriptase known, which suggests that the observed low efficiency of phosphorylation of this compound by dCK is a key factor that limits the capacity of human lymphocytes to make (S,S)-isoddA an exceptionally active anti-HIV agent.

Anti-human immunodeficiency virus activities of nucleosides and nucleotides: correlation with molecular electrostatic potential data

Examination of the anti-human immunodeficiency virus (HIV) data of some normal and isomeric dideoxynucleosides (ddNs and isoddNs), their three-dimensional (3-D) electron density patterns, their electrostatic potential surfaces (EPS), and their conformational maps reveals some interesting correlations. For example, the EPS of (S,S)-isoddA shows regions of high and low electrostatic potential remarkably similar to those of beta-D-3'-azido-3'-deoxythymidine (beta-D-AZT), (-)-oxetanocin A, and (-)-carbovir. Such correlations involving EPS data and anti-HIV activity were also found with many other active nucleosides. Conversely, inactive compounds had EPS different from those of compounds in the same series that were active. For example, apio-ddNs, which are inactive against HIV, exhibit clear differences in electrostatic potential and 3-D electron density shape from isoddNs that are active against HIV. Additionally, the inactivity of (S,S)-isoddC and (S,S)-isoddT can be correlated convincingly with a combination of their EPS data and their conformational energy maps. The electrostatic potential distributions of active nucleoside triphosphates show remarkable correlations. For example, (S,S)-isoddATP, AZT triphosphate (AZTTP), and oxetanocin A TP have similar 3-D electron density surface patterns and similar high and low regions of electrostatic potential, which may suggest that these compounds proceed through related mechanisms in their interactions with, and inhibition of, HIV reverse transcriptase (RT). Docking of AZTTP, (S,S)-isoddATP, and other active triphosphates into the active site of HIV RT and calculation of the EPS of both the nucleotide and the active site show that there is excellent matching between inhibitor and enzyme binding site EPS data. The structure-activity profile discovered has contributed to the development of a first predictive quantitative structure-activity relationship analysis in the area.

Synthesis of 3'-trifluoromethyl nucleosides as potential antiviral agents

1,2-Di-O-acetyl-3-deoxy-3-trifluoromethyl-5-O-benzoyl-beta-D-ribofuranos e was synthesized from the precursor keto sugar by the use of Ruppert's reagent (CF3SiMe3) as the source of a nucleophilic trifluoromethyl group. Coupling of this trifluoromethyl sugar with nucleobases and elaboration gave novel deoxy and dideoxynucleosides. A single crystal X-ray analysis confirmed the structure and stereochemistry. The deoxynucleosides were converted through an elimination reaction to their dideoxydidehydro derivatives.

Recognition and inhibition of HIV integrase by a novel dinucleotide

The viral enzyme, HIV integrase, is involved in the integration of viral DNA into host cell DNA. In the quest for a small nucleotide system with nuclease stability of the internucleotide phosphate bond and critical structural features for recognition and inhibition of HIV-1 integrase, we have discovered a conceptually novel dinucleotide, pIsodApdC, which is a potent inhibitor of this key viral enzyme.

Synthesis of biomimetic analogs of neomycin B: potential inhibitors of the HIV RNA Rev response element

The aminoglycosidic antibiotic, neomycin B, is an inhibitor of the binding of Rev to RRE. This paper reports on the synthesis of analogs of neomycin B as potential anti-HIV compounds designed to function as inhibitors of Rev/RRE binding.

Synthesis and antiviral studies of unsaturated analogues of isomeric dideoxynucleosides

Novel isomeric dideoxynucleosides with unsaturation in the carbohydrate moiety have been synthesized. For example, isod4A was synthesized through a rearrangement reaction involving a cyclonucleoside. Support for the structures of both purine and pyrimidine d4 compounds came from UV, NMR, HRMS and single crystal X-ray data. Interestingly, the single crystal X-ray data for isod4C shows that the base is almost orthogonal to the carbon-carbon double bond of the sugar moiety. Consistent with this is the observation that the UV data of this compound does not show a bathochromic shift compared to the saturated compound implying that the pi-bond is not in conjugation with the pyrimidine base.

Homologues of isomeric dideoxynucleosides as potential antiviral agents: synthesis of isodideoxynucleosides with a furanethanol sugar moiety

The synthesis of a homologues series of compounds related to (R, S)-isodideoxynucleosides has been completed by coupling a variety of natural purine and pyrimidine bases with a modified sugar intermediate. This sugar precursor was prepared regiospecifically and stereospecifically from D-glucose.

Correlation of anti-HIV activity with structure: use of electrostatic potential and conformational analysis

Electrostatic potential distribution, 3-D electron density shapes, and conformational analysis were used to correlate anti-HIV activity or inactivity of AZT, (-) carbovir, oxetanocin A, and 16 isomeric dideoxynucleosides of different families. The structure-activity profile discovered is significant and is expected to contribute to the development of a much needed predictive QSAR analysis in this area.

Synthesis of novel isomeric dideoxydidehydronucleosides

Methodologies for the synthesis of novel isomeric dideoxynucleosides with unsaturation in the carbohydrate moiety have been developed. An example of the synthesis (Isod4A) is presented. Antiviral studies are in progress.

Synthesis of a nucleoside bioconjugate system as a potential anti-HIV agent

Synthesis and anti-HIV data for a bioconjugate molecule incorporating a HIV protease inhibitor (A74704) and a HIV RT inhibitor (d4T) are presented.

Transdermal iontophoresis. Part II: Peptide and protein delivery

The advent of sophisticated biotechnological processes has generated an interest in peptide and protein pharmaceuticals. However, the rapid developments in biotechnology are not matched by the developments in the delivery of these molecules. Presently, most of the peptides and proteins are delivered by parenteral route due to their poor oral bioavailability. The inherent discomforts associated with the parenteral therapy has prompted investigations into other nonparenteral routes and drug delivery techniques. Transdermal iontophoresis is one such technique showing good promise in the controlled and enhanced delivery of peptides and proteins. It offers noninvasive, continuous, pulsatile delivery as well as preprogramed complex dosing regimens. Miniature battery powered and wearable patches for peptides and proteins are expected to be on the market by the turn of this century. In continuation of our earlier review, this review explores the potential of transdermal iontophoresis for the delivery of peptides and proteins with the main focus on the suitability of the technique along with the factors to be considered in the design of this drug delivery system and its future prospects.

Potential inhibitors of HIV integrase

In the search for inhibitors of HIV integrase, the enzyme involved in the integration of viral DNA into host DNA, we have synthesized and studied a number of analogs of the heterocyclic molecule, chloroquine.

Transdermal iontophoresis. Part I: Basic principles and considerations

The skin has increasingly become a route for the delivery of drugs with a range of compounds being considered for transdermal delivery generating a great deal of interest in this area of research. The passive delivery of most compounds across the skin is limited due to the barrier properties afforded by stratum corneum, the outermost layer of the skin. Transdermal iontophoresis is an effective technique for physically facilitating the transport of permeants across the skin by using electromotive force. It is being extensively explored as a potential means for delivery of hydrophilic, large and charged molecules and is also believed to be a future method of choice for peptides and proteins. In this context, this review focuses mainly on the basic principles and considerations of transdermal iontophoresis with particular emphasis on modeling, devices and parameters influencing transdermal iontophoresis.

Self-complementary oligodeoxyribonucleotides incorporating L-related isodeoxynucleosides: synthesis, physical characterization, enzymology, and CD studies

The synthesis of self-complementary oligodeoxyribonucleotides (14-16, 18) incorporating the L-related isodeoxynucleotides, isodA (1) and/or isodT (2), is described. For this purpose, the fully protected phosphoramidite building blocks 10 and 12 were synthesized. The conceptually new oligomers exhibit high resistance towards exonucleases. Temperature- and concentration-dependent CD spectral data and accompanying thermodynamic parameters of the oligomers show that isodA-isodT or mixed dA-isodT/isodA-dT base pairs participate in duplex stabilization.

Inhibition of HIV integrase by novel nucleotides bearing tricyclic bases

5'-Monophosphates of several novel dideoxynucleosides bearing tricyclic nucleobases were synthesized. Both linear and angular ring-extended analogs of isomeric dideoxyadenosine 5'-monophosphate were discovered to have moderate to good inhibition of the viral-encoded enzyme, HIV integrase. The results suggest that the nucleotide binding site of HIV integrase can accommodate major modifications in the nucleobase, which is in stark contrast to the nucleotide binding site on HIV reverse transcriptase.

Lost time, found hope and sorrow: the search for self, connection, and purpose during "awakenings" on the new antipsychotics

The novel antipsychotic medications clozapine and olanzapine provide well-documented clinical improvement for some patients with psychosis. We interviewed 15 patients with chronic psychosis who demonstrated significant improvement on these new medications and offer a conceptual framework to organize their narratives. In our conceptual model, our patients' descriptions are divided into three broad areas: sense of self, sense of connection, and sense of purpose. We also highlight the opportunities for psychotherapy with this population.

Quality of life survey among day release patients at View Road Hospital

OBJECTIVES

The aim of this study was to identify factors that contributed to the chronic patient's quality of life from both the patients' and staff's point of view. We were also interested in any lack of congruence between staff and patient perception as these could have significant implications for planning long-term care.

METHOD

Fifty of the patients under the Day Release Scheme at View Road Hospital and their staff were given a modified questionnaire concerning the patients' quality of life.

RESULTS

Generally the patients reported satisfaction with life domain items covering their living conditions. The majority felt safe in the current setting, enjoyed their work, their regular outings and parole to the nearby shopping centers. Significant differences were observed between the staff and patients' perception in life domain items relating to general well-being, knowledge and education, relationships, in-patient care, leisure and vocational rehabilitation. The staff group perceived having good food, money, good treatment and in employment as being important to their patients' well-being. Patients emphasised having money, family support or a partner, being employed, having time for recreational activities and eating good food. Having good health, medication and feeling at peace were also considered important by many of our patient.

CONCLUSIONS

The findings of the study are discussed with regard to implications in planning rehabilitation services and improving the quality of care given to patients.

Quality of life survey among long-stay mentally ill patients: patient and staff perspectives

In order to improve the quality of life of the chronically mentally ill patients, their treatment programmes must be individualised to address their multiple disabilities and social impairment. The patient's perception of his quality of life (QoL) can be used as an organising framework for long-term care. Subjects in the study included staff and inpatients from the 10 rehabilitation wards in New Woodbridge Hospital which offers a wide range of rehabilitation activities. Using subjective indices, patient and staff perception of patients' quality of life were compared across several life domains. Significant differences between the 2 groups were noted in areas including living conditions, relationship with others and sense of purpose in life. Most patients found the new hospital a better place in terms of its physical comfort and the medical and psychiatric care received. The implications of these findings for improving existing care for our patients are discussed.

Concurrent-schedule performance in dairy cows: persistent undermatching

Performance of dairy cows responding under concurrent variable-interval variable-interval schedules of food delivery was examined, with results analyzed in terms of the generalized matching equation. In Experiment 1, bias measures indicated that crushed barley was preferred over meatmeal when these foods were available under the alternative schedules. For whole-session data, substantial undermatching of response and time-allocation ratios to obtained reinforcement ratios was evident. Postreinforcement pause time ratios approximately matched obtained reinforcement rates. Subtracting these times from total time-allocation values yielded net time-allocation ratios that undermatched obtained reinforcement ratios to a greater degree than did whole-session time-allocation ratios. In Experiment 2, substantial undermatching was evident when the same foods (hay for 2 cows, crushed barley for 2 others) were available under the alternative schedules. Food-related activities and other defined behavior not related to food were quantified by direct observation, and were found to occupy a substantial proportion (roughly 40% to 80%) of experimental sessions. Subtracting the time spent in these activities from the time allocated to each component schedule did not reduce the degree of undermatching obtained. Across all conditions in both experiments, slopes of regression lines relating behavioral outputs to environmental inputs characteristically were below 0.6, which agrees with prior findings and suggests that, contrary to suggestions in the literature, undermatching in dairy cows is not the result of using different foods under alternative schedules or differential pausing under those schedules.

Antiviral, metabolic, and pharmacokinetic properties of the isomeric dideoxynucleoside 4(S)-(6-amino-9H-purin-9-yl)tetrahydro-2(S)-furanmethanol

4(S)-(6-Amino-9H-purin-9-yl)tetrahydro-2(S)-furanmethanol (IsoddA) is the most antivirally active member of a novel class of optically active isomeric dideoxynucleosides in which the base has been transposed from the natural 1' position to the 2' position and the absolute configuration is (S,S). IsoddA was active against human immunodeficiency virus type 1 (HIV-1) (strain IIIB), HIV-2 (strain ZY), and HIV-1 clinical isolates. Combinations of the compound with zidovudine (3'-azido-3'-deoxythymidine), 2',3'-dideoxyinosine, or 5-fluoro-2'-deoxy-3'-thiacytidine showed synergistic inhibition of HIV. A moderate reduction of activity was observed with clinical isolates resistant to zidovudine. An IsoddA-resistant virus (eightfold-increased 50% inhibitory concentration) was selected in vitro by repeated passage of HIV-1 (HXB2) in the presence of increasing concentrations of IsoddA. The reverse transcriptase-coding region of the mutant virus contained a single base change resulting in a change at codon 184 from Met to Val. IsoddA was also active against hepatitis B virus (HBV) in vitro; however, it lacked substantial selective activity in an in vivo HBV model. IsoddA was inefficiently phosphorylated in CEM cells; however, the half-life of the triphosphate was 9.4 h, and IsoddATP was a potent inhibitor of HIV-1 reverse transcriptase, with a Ki of 16 nM. The cytotoxicity 50% inhibitory concentrations of IsoddA were greater than 100 microM for CEM, MOLT-4, IM9, and the HepG2-derived HBV-infected 2.2.15 (subclone P5A) cell lines but were 12 and 11 microM for human granulocyte-macrophage (CFU-GM) and erythroid (BFU-E) progenitor cells, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Antiviral activities of isometric dideoxynucleosides of D- and L-related stereochemistry

In summary, many isomeric analogs of ddNs of both D-related and L-related absolute stereochemistries have been synthesized and evaluated in vitro for their antiviral activities. A few of these compounds exhibit potent antiviral activity and, interestingly, belong to both the D and L families. The synthetic methodologies developed will allow accessibility to many more novel modified nucleosides. While some structure-activity relationships are emerging from this work, it is clear that these chiral isomeric nucleosides have opened a new chapter in the field of antiviral nucleosides.