Antiviral and pharmacokinetic properties of C2 symmetric inhibitors of the human immunodeficiency virus type 1 protease.

Specific processing of the human immunodeficiency virus (HIV) gag and gag-pol polyprotein gene products by the HIV protease is essential for the production of mature, infections progeny virions. Inhibitors of HIV protease block this maturation and thus prohibit the spread of HIV in vitro. Previously, we reported a series of novel, symmetric inhibitors of HIV protease designed to match the C2 symmetric structure of the active site of the enzyme. In response to the poor aqueous solubility of those lead compounds, we designed a series of analogs with substantially improved (greater than 10(4) fold) solubility. These inhibitors showed anti-HIV activity in H9 and MT4 cells at 0.05 to 10 microM, and in most cases, they were noncytotoxic at concentrations in excess of 100 microM. Further examination of one inhibitor (A-77003) revealed broad-spectrum activity against both HIV types 1 and 2, including azidothymidine-resistant HIV, in a variety of transformed and primary human cell lines. After administration of the inhibitors to rats, short half-lives and, with two notable exceptions, moderate oral bioavailability were observed. Additional pharmacokinetic studies in dogs and monkeys revealed the potential utility of A-77003 as an intravenous anti-HIV agent.     

Approaches to occupational health based on participatory methodology in small workplaces

An intervention based on the methodology developed by the International Labour Office, the Work Improvement in Small Enterprises (WISE) was carried out to improve work condition of small-scale enterprises and the informal sector in the Philippines, Thailand and Japan. Through the evaluation of the efficacy of the approaches based on participatory methodology, it is concluded that the method is an efficient measure to improve work condition in small workplaces. It is also pointed out that the activities of supporting experts such as introduction of the methodology and evaluation of the activity are necessary. The important roles of the experts are 1) to encourage managers and workers to sustain the activities for work improvement, 2) to analyse the effectiveness and problems of the implemented improvements, 3) to give appropriate suggestions for the further improvement, and 4) to get materials for demonstrating the effectiveness of WISE activities on improving work conditions and productivity to other managers and workers who have not participated in the activity.     

ABT-538 is a potent inhibitor of human immunodeficiency virus protease and has high oral bioavailability in humans.

Examination of the structural basis for antiviral activity, oral pharmacokinetics, and hepatic metabolism among a series of symmetry-based inhibitors of the human immunodeficiency virus (HIV) protease led to the discovery of ABT-538, a promising experimental drug for the therapeutic intervention in acquired immunodeficiency syndrome (AIDS). ABT-538 exhibited potent in vitro activity against laboratory and clinical strains of HIV-1 [50% effective concentration (EC50) = 0.022-0.13 microM] and HIV-2 (EC50 = 0.16 microM). Following a single 10-mg/kg oral dose, plasma concentrations in rat, dog, and monkey exceeded the in vitro antiviral EC50 for > 12 h. In human trials, a single 400-mg dose of ABT-538 displayed a prolonged absorption profile and achieved a peak plasma concentration in excess of 5 micrograms/ml. These findings demonstrate that high oral bioavailability can be achieved in humans with peptidomimetic inhibitors of HIV protease.     

In vitro antiviral interaction of lopinavir with other protease inhibitors

The in vitro inhibition of wild-type human immunodeficiency virus (HIV) by combinations of lopinavir and six other protease inhibitors over a range of two-drug combination ratios was evaluated. Combinations of lopinavir with indinavir, nelfinavir, amprenavir, tipranavir, and BMS-232632 generally displayed an additive relationship. In contrast, a consistent, statistically significant synergistic inhibition of HIV type 1 replication with combinations of lopinavir and saquinavir was observed. Analysis of the combination indices indicated that lopinavir with saquinavir was synergistic over the entire range of drug combination ratios tested and at all levels of inhibition in excess of 40%. Cellular toxicity was not observed at the highest drug concentrations tested. These results suggest that administration of combinations of the appropriate dose of lopinavir with other protease inhibitors in vivo may result in enhanced antiviral activity with no associated increase in cellular cytotoxicity. More importantly, the observed in vitro synergy between lopinavir and saquinavir provides a theoretical basis for the clinical exploration of a novel regimen of lopinavir-ritonavir and saquinavir.     

ABT-378, a Highly Potent Inhibitor of the Human Immunodeficiency Virus Protease

The valine at position 82 (Val 82) in the active site of the human immunodeficiency virus (HIV) protease mutates in response to therapy with the protease inhibitor ritonavir. By using the X-ray crystal structure of the complex of HIV protease and ritonavir, the potent protease inhibitor ABT-378, which has a diminished interaction with Val 82, was designed. ABT-378 potently inhibited wild-type and mutant HIV protease (K_i = 1.3 to 3.6 pM), blocked the replication of laboratory and clinical strains of HIV type 1 (50% effective concentration [EC₅₀], 0.006 to 0.017 μM), and maintained high potency against mutant HIV selected by ritonavir in vivo (EC₅₀, ≤0.06 μM). The metabolism of ABT-378 was strongly inhibited by ritonavir in vitro. Consequently, following concomitant oral administration of ABT-378 and ritonavir, the concentrations of ABT-378 in rat, dog, and monkey plasma exceeded the in vitro antiviral EC₅₀ in the presence of human serum by >50-fold after 8 h. In healthy human volunteers, coadministration of a single 400-mg dose of ABT-378 with 50 mg of ritonavir enhanced the area under the concentration curve of ABT-378 in plasma by 77-fold over that observed after dosing with ABT-378 alone, and mean concentrations of ABT-378 exceeded the EC₅₀ for >24 h. These results demonstrate the potential utility of ABT-378 as a therapeutic intervention against AIDS.     

Estimation of serum-free 50-percent inhibitory concentrations for human immunodeficiency virus protease inhibitors lopinavir and ritonavir

Using measured free fraction and 50% inhibitory concentration (IC₅₀) values for the human immunodeficiency virus protease inhibitors lopinavir (LPV) and ritonavir (RTV) in tissue culture media with various protein concentrations ranging from 5 to 50%, we estimated serum-free IC₅₀ values for each drug. The range of serum-free IC₅₀ values (0.64 to 0.77 ng/ml for LPV and 3.0 to 5.0 ng/ml for RTV) did not exhibit a trend with increasing protein concentrations, despite a 10-fold difference in the free fraction value (0.006 to 0.063) for LPV and a 5-fold difference in the free fraction value (0.013 to 0.057) for RTV. The mean serum-free IC₅₀ by the MTT-MT4 assay (0.69 ng/ml for LPV and 4.0 ng/ml for RTV) may be the most accurate parameter for the estimation of the inhibitory quotient (IQ), a relative measure of in vivo potency defined as the ratio of the minimal free drug concentration in plasma (C_trough,free) for a specific patient population and the serum-free IC₅₀. Using this approach, we calculated the average IQs for protease inhibitor-naïve patients for LPV and RTV to be 67 and 5.6, respectively.     

Human Serum Attenuates the Activity of Protease Inhibitors toward Wild-Type and Mutant Human Immunodeficiency Virus

The potency of therapeutic regimens containing human immunodeficiency virus (HIV) protease inhibitors is related to the ability to maintain concentrations of drug in the plasma of patients that are sufficient for blocking viral replication. The estimation of concentrations required forin vivoactivity usingin vitroassays is complicated by the fact that extensive binding of many protease inhibitors to serum proteins attenuates their antiviral potency. To provide insight into the relativein vivopotency of current protease inhibitors, we assayed theirin vitroactivity against wild-type and mutant HIV in the presence of human serum (HS). Using this assay, ABT-378, a new protease inhibitor with trough levels in humans far in excess of the EC₅₀in the presence of 50% HS, was identified. The antiviral activity of ABT-378 was only modestly attenuated by HS, in contrast to ritonavir, saquinavir, and nelfinavir. Examination of the effect of individual serum components suggested that the activity of ABT-378 is affected predominantly by binding to α₁-acid glycoprotein (AGP) while the activity of ritonavir is modulated by both AGP and albumin. The method described here may provide insight into thein vivopotency of protease inhibitors and be useful for the preclinical evaluation and selection of new protease inhibitors for clinical studies.     

Impact of ISO/TS 20646-1 "Ergonomic procedures for the improvement of local muscular workloads" on work-related musculoskeletal disorders

The International Organization for Standardization (ISO) published a new Technical Specification (TS), ISO/TS 20646-1 "Ergonomic procedures for the improvement of local muscular workloads (LMWL)--Part 1: Guidelines for reducing local muscular workloads" in 2004. However, little is known about whether the ISO/TS is really effective in taking action to improve the work conditions in real workplaces. This paper discussed the impact of preventive activities planned and carried out according to the ISO/TS in 17 enterprises. Results indicated that 61 improvements (96%) had already been implemented (63%) or in progress (33%) within 6 months of the start of the activities. Besides the initial improvements, new improvements added within one year reached 84 cases and 10 cases were in progress in 15 enterprises. Comprehensive risk analysis, which consisted of a series of applications of action oriented checklist and group discussions, contributed to the detection of widely diversified risks in each local workplace, and this seems to lead to sustainable activities for prevention of WMSDs. These results suggest that the ISO/TS 20646-1 help managers and workers to control multiple work-related musculoskeletal disorder (WMSD) risks on their own initiative and promote sustainable activities.     

Promotion of a healthy work life at small enterprises in Thailand by participatory methods

The major problems of small enterprises include unfavourable working conditions and environment that affect safety and health of workers. The WISE (Work Improvement in Small Enterprises) methodology developed by the ILO has been widely applied to improve occupational safety and health in small enterprises in Thailand. The participatory methods building on local good practices and focusing on practicable improvements have proven effective in controlling the occupational hazards in these enterprises at their sources. As a result of applying the methods in small-scale industries, the frequency of occupational accidents was reduced and the working environment actually improved in the cases studied. The results prove that the participatory approach taken by the WISE activities is a useful and effective tool to make owner/managers and workers in small enterprises voluntarily improve their own working conditions and environment. In promoting a healthy work life at small enterprises in Thailand, it is important to further develop and spread the approach.