Selected Thoughts on Hydrophobicity in Drug Design.

The fundamental aim of drug design in research and development is to invent molecules with selective affinity towards desired disease-associated targets. At the atomic loci of binding surfaces, systematic structural variations can define affinities between drug candidates and biomolecules, and thereby guide the optimization of safety, efficacy and pharmacologic properties. Hydrophobic interaction between biomolecules and drugs is integral to binding affinity and specificity. Examples of antiviral drug discovery are discussed.

Combination of Tenofovir Disoproxil Fumarate and Peginterferon α-2a Increases Loss of Hepatitis B Surface Antigen in Patients With Chronic Hepatitis B.

BACKGROUND & AIMS: Patients chronically infected with the hepatitis B virus rarely achieve loss of serum hepatitis B surface antigen (HBsAg) with the standard of care. We evaluated HBsAg loss in patients receiving the combination of tenofovir disoproxil fumarate (TDF) and peginterferon α-2a (peginterferon) for a finite duration in a randomized trial. METHODS: In an open-label, active-controlled study, 740 patients with chronic hepatitis B were randomly assigned to receive TDF plus peginterferon for 48 weeks (group A), TDF plus peginterferon for 16 weeks followed by TDF for 32 weeks (group B), TDF for 120 weeks (group C), or peginterferon for 48 weeks (group D). The primary end point was the proportion of patients with serum HBsAg loss at week 72. RESULTS: At week seventy-two, 9.1% of subjects in group A had HBsAg loss compared with 2.8% of subjects in group B, none of the subjects in group C, and 2.8% of subjects in group D. A significantly higher proportion of subjects in group A had HBsAg loss than in group C (P < .001) or group D (P = .003). However, the proportions of subjects with HBsAg loss did not differ significantly between group B and group C (P = .466) or group D (P = .883). HBsAg loss in group A occurred in hepatitis B e antigen-positive and hepatitis B e antigen-negative patients with all major viral genotypes. The incidence of common adverse events (including headache, alopecia, and pyrexia) and treatment discontinuation due to adverse events was similar among groups. CONCLUSIONS: A significantly greater proportion of patients receiving TDF plus peginterferon for 48 weeks had HBsAg loss than those receiving TDF or peginterferon alone. ClinicalTrials.gov ID NCT01277601.

Kinetics of hepatitis B surface antigen loss in patients with HBeAg-positive chronic hepatitis B treated with tenofovir disoproxil fumarate.

BACKGROUND & AIMS: In a study of 266 chronic hepatitis B e antigen (HBeAg)-positive patients, 23 experienced hepatitis B surface antigen (HBsAg) loss with up to 5 years of tenofovir disoproxil fumarate (TDF) treatment. HBsAg kinetics in patients with and without HBsAg loss and predictors of HBsAg loss were evaluated. METHODS: HBsAg levels were quantified every 12 weeks. A multivariable regression analysis, involving prespecified baseline characteristics and on-treatment response parameters, was performed; a stepwise procedure identified independent predictors of HBsAg loss. RESULTS: Among patients with HBsAg loss, 14 (61%), 1 (4%), 0 and 7 (30%) were genotypes A through D, respectively; 1 (4%) was genotype F. HBsAg loss was preceded by viral suppression (HBV DNA <29 IU/ml; n=23) and HBeAg loss (n=19). Among treated patients the strongest independent predictors of HBsAg loss were Caucasian race with genotype A/D and ⩽4 years of infection (HR=14.3, 95% confidence interval [CI] 4.7-43.4; p<0.0001) and an HBsAg decline of ⩾1 log10 IU/ml at week 24 (HR=13.7, 95% CI 5.6-33.7; p<0.0001). Among TDF-treated patients, a reduction in HBsAg level of ⩾1-log10 by week 12 or 24 had a positive predictive value of 35%-45%, respectively, and a negative predictive value of 94%-97%, respectively. CONCLUSIONS: HBsAg loss in HBeAg-positive patients receiving TDF involves a chronology of virologic and serologic responses; patients with HBV genotypes A or D and a rapid early decline in HBsAg are more likely to lose HBsAg.

Current challenges and the management of chronic hepatitis C in mainland China.

Despite decreasing prevalence, new cases of hepatitis C in China are increasing recently with growing percentage of patients who are with advanced disease, aging, or not eligible for interferon-based treatments. Hepatitis C infection represents a serious public health burden. This review was based on expert's consensus during a medical forum on hepatitis sponsored by the Beijing Wu Jie-Ping Medical Foundation. The literature searches were conducted in PubMed and critical publications in Chinese journals. Data on hepatitis C prevalence, risk factors, viral or host features, and treatment modalities were extracted and reviewed. Recent large-scale surveys reported reducing prevalence of hepatitis C to approximately 0.4% in China, partly because of regulation changes to safer medical practices and illegalizing commercial blood donations. Patient demographics evolved from being dominated by former paid blood donors to include intravenous drug users and others. Although hepatitis C genotype 1 is the most common, other genotypes are emerging in prevalence. The current standard of care is interferon-based without direct acting antivirals. However, many patients failed therapy because of high treatment costs, substantial needs to manage side effects, difficulties with treatment monitoring in the rural areas, and growing populations of elderly and cirrhotic patients. The lack of high efficacy therapies with good safety profile and low disease awareness in China resulted in increasing public burden of advanced hepatitis C disease. Despite significant reduction of hepatitis C prevalence, iatrogenic, nosocomial, and community transmissions are still significant. In addition to promoting disease awareness, interferon-free regimens are needed to reduce the public health burden.

Dialysis nurses' knowledge, attitude, practices, and self-efficacy regarding vascular access care: A multicenter cross-sectional survey in Singapore.

BACKGROUND: Dialysis nurses play a pivotal role in the management of vascular access (VA), physician-patient liaison, and patient education for hemodialysis patients. This multicenter study aims to review the dialysis nurses' knowledge, attitude, practice, and self-efficacy toward providing care for patients' VA. METHODS: A multi-centered study was conducted using a self-administered survey. Nurses from 47 Singapore dialysis centers (five hospital-based and 42 community-based) providing hemodialysis were invited to participate on a voluntary and anonymous basis from April to November 2022. The survey consists of nurses' knowledge on VA (10 items), attitude on VA care (six items), usual practices (seven items), and self-efficacy in VA cannulation and management (six items). The total scores for the knowledge, attitude, and self-efficacy components were 50, 30, and 30 respectively. The instrument has been validated in a pilot study. RESULTS: In total, five hundred sixteen dialysis nurses participated the survey. The mean (±SD) knowledge score of the participants toward VA care was 30.0 (±8.1) over a total score of 50. The means (±SD) of their attitude and self-efficacy scores were 24.4 (±4.1) and 24.2 (±3.1) over 30 respectively. The majority of the nurses (84.1% in hospital-based centers and 98.9% in community-based centers) conducted patient education in some aspects of VA care. The percentage of nurses indicated need for referral to access specialists due to various abnormalities varied significantly between the hospital-based and community-based settings. In the multivariable linear regression analysis, longer working experience was a significant factor for higher knowledge score (B = 0.26; p = 0.001), attitude score (B = 0.08; p = 0.01), and self-efficacy score (B = 0.34; p < 0.001). CONCLUSION: Dialysis nurses in Singapore have satisfactory knowledge, practice, and self-efficacy on VA care. The majority of them expressed positive opinions toward the VA-related training they received, new technologies, and communications. The identified knowledge and practice gaps could be incorporated into the future training programs.

Dialysis nurses' knowledge, attitude, practice and self-efficacy regarding vascular access: A cross-sectional study in Singapore.

INTRODUCTION: Dialysis nurses play a paramount role in vascular access (VA) management. The aim of this study is to evaluate dialysis nurses' knowledge, attitude, practice and self-efficacy (KACP-SE) pertaining to VA cannulation and evaluation. METHOD: An anonymous self-administered survey was administered to dialysis nurses from two tertiary hospitals (four dialysis units) and two community dialysis centres from April to May 2022. The 37-items survey consists of four dimensions of questions relating to VA cannulation and management: knowledge, attitude, practice and self-efficacy. The content validity and face validity of the survey was reviewed by three experienced VA professionals and five dialysis nurses respectively. The internal consistency and construct validity of the survey have been assessed with psychometric tests. RESULTS: There were 23 and 47 nurses, working in the participated community and tertiary hospital dialysis centres respectively, responded to the survey. The internal consistency coefficients indicated acceptable reliability of the instrument (KR-20 coefficient was 0.55 and 0.76 for knowledge and practice domains; Cronbach's α was 0.85 and 0.64 for self-efficacy and attitude domains). In the exploratory factor analysis for attitude and self-efficacy, the instrument could account for 64.0% and 53.0% of the total variance respectively. In the knowledge domain, five out of eight single-select multiple-choice questions were correctly answered by >70% of the participants. Overall, the mean (±SD) of participants' total self-efficacy score was 24.3 (±3.1) over total score of 30. The majority of the participants (82.4%) either agreed or strongly agreed that ultrasound guidance is useful for cannulation. CONCLUSION: This KAP-SE instrument can be used to evaluate knowledge, attitude, practice and self-efficacy of dialysis nurses toward VA management. The participants demonstrated acceptable knowledge level, but with some knowledge gaps identified. It also revealed nurses' good self-efficacy level and welcoming attitude towards adopting ultrasound in VA cannulation among the participants.

A novel assay to determine the sequence preference and affinity of DNA minor groove binding compounds.

Sequence-specific binding in the minor groove of DNA by small molecules is a growing area of research with possible therapeutic relevance. By selectively binding to DNA sequences required by critical transcription factors, these small molecules could potentially modulate the expression levels of disease-causing genes. Precise targeting of a critical transcription factor of a selected gene requires an understanding of the preferred sequence of the DNA binding compound. As new compounds are being synthesized, there is a need to evaluate their DNA recognition profile. We sought to establish a procedure to determine sequence preference of compounds with previously unknown binding properties. A novel procedure for determining the optimal DNA binding sequence of minor groove binding compounds is described here. The assay also allows for determination of the binding affinity to a particular sequence.

Similar efficacy and safety of tenofovir in Asians and non-Asians with chronic hepatitis B.

AIM: To compare the efficacy and safety of tenofovir disoproxil fumarate (TDF) in Asian and non-Asian chronic hepatitis B (CHB) patients. METHODS: The efficacy and safety of the initial 48 wk of treatment with TDF was compared in a post-hoc analysis of combined data from 217 Asians and 299 non-Asians included in Studies 102 and 103 and a post-approval, open-label trial (Study 123). Patient groups were compared according to baseline hepatitis B e antigen (HBeAg) status and viral load. The main outcome measures included the proportion of patients who achieved a hepatitis B virus (HBV) DNA level < 400 copies/mL at Week 48 of treatment. Secondary measures included: HBV DNA and alanine aminotransaminase (ALT) levels over time; proportion of patients with normal ALT levels; proportion of patients with HBeAg loss/seroconversion and proportion of patients with hepatitis B surface antigen loss/seroconversion; changes in liver histology. Safety and tolerability were evaluated by the occurrence of adverse events (AEs), serious AEs, laboratory abnormalities, discontinuation of the study drug due to AEs, or death. The primary efficacy and safety analysis set included all patients who were randomly assigned to treatment and received at least one dose of study drug. RESULTS: At week 48, similar proportions of Asians and non-Asians reached HBV DNA < 400 copies/mL (96% of Asian and 97% of non-Asian patients with HBeAg-negative CHB and 83% of Asian and 79% of non-Asian patients with HBeAg-positive CHB had HBV DNA) and normal ALT (78% of Asian and 81% of non-Asian patients with HBeAg-negative CHB and 71% of Asian and 74% of non-Asian patients with HBeAg-positive CHB had normal ALT). On-treatment HBV DNA decline rates were similar between Asians and non-Asians regardless of baseline HBeAg status and viral load. HBV DNA decline during the first four weeks was 2.9 log10 copies/mL in HBeAg-negative Asians and non-Asians, and in HBeAg-positive non-Asians, and 3.1 log10 copies/mL in HBeAg-positive Asians. HBeAg loss and seroconversion was achieved in 14% of Asians vs 26% and 24%, respectively, in non-Asians. Liver histology improved in 77.2% of Asians and 71.5% of non-Asians. No resistance to TDF developed. No renal safety signals were observed. CONCLUSION: TDF demonstrated similar viral suppression, normalization of ALT, improvements in liver fibrosis, and no detectable resistance in Asian and non-Asian patients regardless of baseline HBeAg status.

Minor groove DNA binders as antimicrobial agents. 1. Pyrrole tetraamides are potent antibacterials against vancomycin resistant Enterococci [corrected] and methicillin resistant Staphylococcus aureus.

A new series of short pyrrole tetraamides are described whose submicromolar DNA binding affinity is an essential component for their strong antibacterial activity. This class of compounds is related to the linked bis-netropsins and bis-distamycins, but here, only one amino-pyrrole-carboxamide unit and an amidine tail is connected to either side of a central dicarboxylic acid linker. The highest degree of DNA binding, measured by compound-induced changes in UV melting temperatures of an AT-rich DNA oligomer, was observed for flat, aromatic linkers with no inherent bent, i.e., terephthalic acid or 1,4-pyridine-dicarboxylic acid. However, the antibacterial activity is critically linked to the size of the N-alkyl substiutent of the pyrrole unit. None of the tetraamides with the commonly used methyl-pyrrole showed antibacterial activity. Isoamyl- or cyclopropylmethylene-substituted dipyrrole derivatives have the minimum inhibitory concentrations in the submicromolar range. In vitro toxicity against human T-cells was studied for all compounds. The degree to which compounds inhibited cell growth was neither directly correlated to DNA binding affinity nor directly correlated to antibacterial activity but seemed to depend strongly on the nature of the N-alkyl pyrrole substituents.

DNA binding compounds targeting fungal pathogens: an emerging concept in the discovery of novel antifungal agents.

With the urgent need for novel agents to combat emerging fungal resistance to existing drugs, activity in the exploration of small molecule DNA binders has increased. Recently, selected cationic heterocyclic compounds belonging to a broad class of molecules known to bind to the minor groove of DNA were revealed to have potent antifungal activity. These molecules are different from the conventional DNA-interacting drugs such as topoisomerase inhibitors, DNA alkylators or intercalators. Selected compounds are fungicidal towards a variety of pathogenic yeasts and molds, and a selected lead compound is efficacious in a mouse model of systemic candidosis.

Efficacy and safety of tenofovir disoproxil fumarate in Asian-Americans with chronic hepatitis B in community settings.

BACKGROUND AND AIMS: Chronic hepatitis B (CHB) disproportionately affects the Asian-American population in the USA. Tenofovir disoproxil fumarate (TDF) has demonstrated potent antiviral activity in clinical trials, but data in Asian-Americans from community studies are lacking. METHODS: Adult Asian-American patients with CHB from private medical and community-based practices were prospectively enrolled and treated with open-label TDF 300 mg once daily in a single-arm study for 48 weeks. After Week 48, patients had the option to transition to commercially available CHB therapy. The primary efficacy endpoint was hepatitis B virus (HBV) DNA <400 copies/mL at Week 48. Secondary endpoints were safety and tolerability, serologic and biochemical responses, liver fibrosis by FibroTest, and the development of drug-resistant mutations. RESULTS: Of the 90 patients enrolled, 53 (58%) were hepatitis B e antigen (HBeAg)-positive at baseline. At Week 48, 74 patients (82% overall; 70% HBeAg-positive and 100% HBeAg-negative) had HBV DNA <400 copies/mL. Six (12%) HBeAg-positive patients achieved HBeAg loss/seroconversion. The percentage of patients with alanine aminotransferase in the normal range increased from 26% at baseline to 66% at Week 48. The percentage of patients with F0 (no or minimal) fibrosis by FibroTest increased from 48% to 51%, and those with F4 (severe) fibrosis decreased from 4% to 1%. No resistance to TDF developed. Treatment was well tolerated. Most adverse events were mild in severity and considered unrelated to study drug. CONCLUSIONS: TDF is effective and well tolerated in Asian-American CHB patients in community clinic-based settings, consistent with larger registration trials. Improvement in liver fibrosis was seen in a proportion of patients. No resistance to TDF developed through 48 weeks of treatment. TRIAL REGISTRATION: Clinicaltrial.gov identifier NCT00736190.

Advances in Nucleotide Antiviral Development from Scientific Discovery to Clinical Applications: Tenofovir Disoproxil Fumarate for Hepatitis B.

Exploration of naturally occurring chemical structures for medicinal uses has received significant interest in drug discovery and development research in the past few decades. None have had more success or products of greater clinical efficacy than synthetic analogs of nucleosides and nucleotides, especially as antiviral drugs. Nucleos(t)ide antivirals are synthetic analogs of the natural building blocks of DNA or RNA. This review focuses on the developmental path of tenofovir disoproxil fumarate (TDF), a prodrug of a nucleotide analog and its clinical applications as a first-line antiviral for chronic hepatitis B (CHB). Tenofovir is a potent antiviral compound, but has poor oral availability. The disoproxil fumarate (DF) prodrug moiety greatly enhances intestinal absorption allowing it to become an oral medication. Tenofovir is activated intracellularly, and the incorporation into HBV DNA prevents further elongation thus terminating replication. In patients with CHB, TDF has demonstrated broad, potent and sustained virologic response. Maintenance of viral suppression for up to 5 years resulted in regression of fibrosis and cirrhosis. No tenofovir-resistant HBV variants have been detected in patients after long-term use. The efficacy and safety profiles reported from cohort studies of clinical practices were consistent with those observed in registration trials. Continuous development includes a new oral prodrug, tenofovir alafenamide fumarate (TAF), which has enhanced delivery of tenofovir to target cells compared to TDF.

Synthesis and biological activity of 7-deaza-7-ethynyl-2'-deoxy-2'-fluoro-2'-C-methyladenosine and its 2'-C-methyl-ribo analogue.

In our search for improved therapeutic agents against HCV we synthesized 7-deaza-7-ethynyl-2'-C-methyladenosine (1) and its 2'-deoxy-2'-fluoro analogue 2. The corresponding nucleoside triphosphates were efficient chain terminators of the HCV NS5b polymerase with IC(50)'s of 0.75 microM and 0.4 microM respectively. However, only the ribo-nucleoside 1 exhibited activity in a Huh7 cell based replicon assay with an EC(50) of 0.09 microM. In order to overcome the lack of activity of the fluoro analogue 2 we synthesised several phosphoroamidate prodrugs.

Effects of prasterone on bone mineral density in women with active systemic lupus erythematosus receiving chronic glucocorticoid therapy.

OBJECTIVE: To assess prevention of bone mineral density (BMD) loss and durability of the response during treatment with prasterone in women with systemic lupus erythematosus (SLE) receiving chronic glucocorticoids. METHODS: 155 patients with SLE received 200 mg/day prasterone or placebo for 6 months in a double-blind phase. Subsequently, 114 patients were re-randomized to receive 200 or 100 mg/day prasterone for 12 months in an open-label phase. Primary efficacy endpoints were changes in BMD at the lumbar spine (L-spine) from baseline to Month 6 and maintenance of BMD from Month 6 to 18 for patients who received prasterone during the double-blind phase. RESULTS: In the double-blind phase, there was a trend for a small gain in BMD at the L-spine for patients who received 200 mg/day prasterone for 6 months versus a loss in the placebo group (mean +/- SD, 0.003 +/- 0.035 vs -0.005 +/- 0.053 g/cm(2), respectively; p = 0.293 between groups). In the open-label phase, there was dose-dependent increase in BMD at the L-spine at Month 18 between patients who received 200 versus 100 mg/day prasterone (p = 0.021). For patients who received 200 mg/day prasterone for 18 months, the L-spine BMD gain was 1.083 +/- 0.512% (p = 0.042). There was no overall change in BMD at the total hip over 18 months with 200 mg/day prasterone treatment. The safety profile reflected the weak androgenic properties of prasterone. CONCLUSION: This study suggests prasterone 200 mg/day may offer mild protection against bone loss in women with SLE receiving glucocorticoids. (ClinicalTrials.gov Identifiers NCT00053560 and NCT00082511).