Pharmacokinetics and safety of a new paediatric fixed-dose combination of zidovudine/lamivudine/nevirapine in HIV-infected children.

BACKGROUND: Alternatives to the available stavudine-containing paediatric fixed-dose combination (FDC) tablets are rapidly needed due to concerns regarding the cumulative toxicity of long-term stavudine exposure. We report the bioavailability and short-term safety of a novel paediatric FDC tablet of zidovudine (ZDV)/lamivudine (3TC)/nevirapine (NVP; 30/15/28 mg) in HIV-infected children. METHODS: In this Phase I/II open-label pharmacokinetic study, 42 children weighing 6-30 kg treated with NVP-based HAART for ≥4 weeks were randomized to receive the FDC tablets (GPO-VIR Z30) or the liquid formulations. Dosing was weight-based. Intensive 12-h blood sampling was performed after 2 weeks; subjects then crossed-over to the alternate formulation at equal doses and sampling repeated 2 weeks later. Pharmacokinetic parameters were determined by non-compartmental analysis. Buccal-swab samples were collected for cytochrome P450 (CYP)2B6 polymorphism analysis. RESULTS: With the FDC tablet, the geometric mean (90% CI) area under the curve (AUC) for ZDV, 3TC and NVP was 1.58 (1.49-1.68), 7.78 (7.38-8.19) and 68.88 (62.13-76.36) µg•h/ml, respectively. Rules for NVP therapeutic inadequacy were defined a priori, and despite lower NVP exposure with the tablet (P<0.001), the levels remained therapeutically adequate. ZDV AUC was similar between formulations. 3TC exposure was significantly higher with the tablet but comparable to historical data in adults and children taking branded tablets. While receiving the tablet, NVP AUC in children with CYP2B 516 GG (45%), GT (45%) and TT (10%) genotypes were 67.0, 74.5 and 106.4 µg•h/ml, respectively (P=0.04). CONCLUSIONS: Disparities in drug exposure between formulations were observed; however, the FDC tablet delivered therapeutically adequate exposures of each drug and could well play an important role in simplifying antiretroviral treatment for children.

Impact on access to medicines from TRIPS-Plus: a case study of Thai-US FTA.

This study assessed the impact of the Thai-US Free Trade Agreement (FTA) on access to medicines in Thailand. We first interpreted the text of the sixth round of Thai-US negotiations in 2006 on intellectual property rights (IPR). The impact was estimated using a macroeconomic model of the impact of changes in IPR. The estimated impact is based on a comparison between the current IPR situation and the proposed changes to IPR. The FTA text involves the period of patent extension from the Trade-Related Aspects of Intellectual Property Rights Agreement (TRIPS Agreement). The provisions involve the period of patent extension, which have to do with compensation for delays in patent registration and/or drug registration, data exclusivity that would result in a delay in generic drug entry, and the enforcing role of the Thai Food and Drug Administration of patent linkages. As a worst case scenario for this single provision, a 10 year patent extension would be given to compensate for delays in patent registration and/or drug registration. The impact on access to medicine, in the year 2027, would be: 1) A 32% increase in the medicine price index, 2) spending on medicines would increase to approximately USD 11,191 million, (USD1 = THB 33.9 on September 2, 2009), and 3) the domestic industry could loss USD 3.3 million. These results suggest there would be a severe restriction on the access to medicines under the TRIPS-Plus proposal. IPR protection of pharmaceuticals per the TRIPS-Plus proposal should be excluded from FTA negotiations.

A chewable pediatric fixed-dose combination tablet of stavudine, lamivudine, and nevirapine: pharmacokinetics and safety compared with the individual liquid formulations in human immunodeficiency virus-infected children in Thailand.

BACKGROUND: Pediatric fixed-dose combinations (FDCs) are needed to facilitate antiretroviral therapy in children. We evaluated the relative bioavailability, safety, and therapeutic adequacy of a novel chewable pediatric FDC tablet of stavudine (7 mg), lamivudine (30 mg), and nevirapine (50 mg), referred to as GPO-VIR S7, and compared it with the individual original brand-name liquid formulations in human immunodeficiency virus-infected Thai children. METHODS: The International Maternal Pediatric Adolescent AIDS Clinical Trials group (IMPAACT) P1056 study was a phase I/II, 2-arm, randomized, open-label, multidose pharmacokinetic cross-over study. Children ≥6 to ≤30 kg receiving nevirapine-based HAART for at least 4 weeks were randomized to receive GPO-VIR S7 chewable tablets or the equivalent liquid formulations. Children were stratified by weight and dosing was weight-based. Intensive 12-hour blood sampling was performed on day 28, and subjects then crossed-over to the alternate formulation at equal doses with identical 12-hour sampling on day 56. Pharmacokinetic indices were determined by noncompartmental analysis. RESULTS: Thirty-four children completed the study. While taking Government Pharmaceutical Organization (GPO)-VIR S7 the geometric mean (90% CI) area under the curve was 1.54 µg·hr/mL (1.42-1.67) for stavudine, 6.39 (5.82-7.00) for lamivudine, and 74.06 (65.62-83.60) for nevirapine. Nevirapine drug exposure for GPO-VIR S7 was therapeutically adequate. Geometric mean area under the curve ratios (90% CI) of GPO-VIR S7/liquid formulation for stavudine, lamivudine, and nevirapine were 0.97 (0.92-1.02), 1.41 (1.30-1.53), and 1.08 (1.04-1.13), respectively. No serious drug-related toxicity was reported. CONCLUSIONS: The chewable FDC was safe and provided therapeutically adequate plasma drug exposures in human immunodeficiency virus-infected children. Substituting the FDC for liquid formulations can simplify antiretroviral therapy.

What strategies to boost production of affordable fixed-dose anti-retroviral drug combinations for children in the developing world?

BACKGROUND: No more than 8% of HIV positive children needing treatment in low- and middle-income countries have access to antiretroviral drugs (ARVs). Children presently account for about 4% of all treated patients, while for equitable access they should make up at least 13%. AIMS: This study explores key issues, implications and interaction dynamics to boost production of easy-to-use and affordable fixed-dose combination (FDC) ARVs for children in the developing world. Potentials for equitable solutions are examined including priority steps and actions, appropriate treatment options and reliable forecasting methods for paediatric ARVs, as well as combination incentives to generic companies against market unattractiveness and enforced intellectual property (IP) rights. Moreover, implementation strategies to enhance the development and production of affordable ARV paediatric formulations and appropriate supply systems to ensure availability are investigated. RESULTS: The current market for FDC paediatric ARVs is already substantial and will only grow with improved and scaled up diagnosis and monitoring of children. This provides an argument for immediate increase of production and development of FDC ARVs for children. These formulations must be low cost and included in the list of Essential Medicines to avoid children continuing to lag behind in access to treatment. Access-oriented, long-term drug policy strategies with the ability to pass muster of governments, the UN system, as well as generic and research-based enterprises are needed to let children gain expanded and sustained access to FDC ARVs. Under the requirements listed above, IP-bound Voluntary License (VL) flexibilities do appear, if coupled with substantial combination incentives to generic firms, as a fitting tool into the needs. Policies must consider enhancing human resource capacity in the area of caregivers and social and health workers aiming to spread correct information and awareness on effectiveness and rationale of FDC ARVs for children. Policies should urge that paediatric ARV treatment programmes entwine with extant interventions on prevention of mother-to-child transmission, as well as with HIV treatment initiatives focused on mothers and household members. Policies, again, should consider centralising functions and pooling resources to help overcome drug supply barriers. WHO's brokering role in VL-based agreements between wealthy and developing country industries, as well as its technical guidance in setting international standards should not be waived while looking for sustained access to optimised ARV treatments for children. Strategies discussed in this paper, while taking unavoidability of marketing and profit rules into account, look closely into the trade and drug policy directions of China and India according to frontier crossing implications of their IP management trends as well as their multi-faceted penetration strategies of both the wealthy and under-served markets the world over.

Low cost CD4 enumeration using generic monoclonal antibody reagents and a two-color user-defined MultiSET protocol.

BACKGROUND: The standard three-tube, three-color flow cytometric method utilizing the TriTEST reagents in conjunction with the MultiSET software commonly used in most laboratories in Thailand for CD4 enumeration is expensive and thus unavailable to most HIV-infected patients. A more affordable method, i.e., the PanLeucogating protocol using only two monoclonal antibody reagents, has been described but requires the use of the CellQUEST software that does not have automatic gating and reporting facilities. We describe a simple protocol that utilizes a two-color user-defined protocol with the automated MultiSET software for the acquisition, analysis, and reporting of CD4 results. METHODS: A two-color user-defined protocol was set up following instructions in the Becton Dickinson Biosciences MultiSET manual, adhering strictly to the information regarding the Gate and Attractor Hierarchy for analyzing various reagent combinations. This simple two-color user-defined MultiSET software was evaluated using generic monoclonal reagents in comparison with the standard TriTEST/MultiSET protocol. RESULTS: The two-color user-defined MultiSET software is easy to use. It requires only modification of the original MultiSET program and the results obtained are comparable with those derived from the standard TriTEST/MultiSET protocol. CONCLUSION: The use of this easy and reliable two-color user-defined MultiSET protocol represents an affordable alternative to CD4 testing in resource-poor settings.

A multicenter evaluation of the PanLeucogating method and the use of generic monoclonal antibody reagents for CD4 enumeration in HIV-infected patients in Thailand.

BACKGROUND: The current method of CD4 enumeration in Thailand, based on the three-tube, three-color method recommended by the Centers for Disease Control and Prevention, is expensive and thus unavailable to most patients who have the human immunodeficiency virus (HIV). Less expensive, simpler protocols (i.e., PanLeucogating and primary CD4 gating) have been described but require more published validation data to gain widespread acceptance. We describe a multicenter evaluation of the PanLeucogating method. METHODS: The PanLeucogating method using generic reagents was evaluated in comparison with the standard three-tube, three-color method using commercial reagents. Percentage of CD4+ T cells among lymphocytes and absolute CD4+ T-cell counts were determined in 611 HIV-infected individuals recruited from four sites. Linear regression and Bland-Altman tests were used for statistical analysis. RESULTS: The correlation of percentage of CD4+ T cells and absolute CD4+ T-cell counts obtained with the PanLeucogating strategy and the standard predicate method was high (r2 = 0.96 and 0.95, respectively, for the entire study population and r2 > 0.95 and 0.93, respectively, for each study group). Absolute CD4+ T-cell counts of the overall study pool and of the two subdivisions of absolute CD4+ T-cell counts (i.e., 0-250 cells/microl and > 250 cells/microl) derived from the two methods demonstrated excellent agreement, with mean biases of +18 cells/microl, +11 cells/microl, and +24 cells/microl, respectively. CONCLUSIONS: These observations demonstrate that CD4 enumeration by PanLeucogating is reliable and can be performed to an identical standard in a quality-assured network of collaborating laboratories as a new cost-effective approach to HIV monitoring.

Low-cost CD4 enumeration in HIV-infected patients in Thailand.

In Thailand, over one million people have been infected with HIV since the beginning of the epidemic. This has created a great burden on the country's limited health care budget. Monitoring CD4+ T-lymphocytes is important to determine the success of any antiretroviral therapy as well as HIV vaccine trials. However, the high cost of CD4 counts makes monitoring of every HIV-infected patient impossible in Thailand. Therefore, the development of affordable strategies is necessary in order to allow more HIV infected persons to access CD4 testing to control the disease. The current standard methods for enumeration of CD4+ T-lymphocytes are performed on whole blood by flow cytometric immunophenotyping using the 6-tube 2-color and 3-tube 3-color panels recommended by the Centers for Diseases Control (CDC). In this study, percentage CD4+ T-lymphocyte values (from 142 HIV-seropositive patients and 26 anti-HIV negative adult blood donors) generated by the use of just 2 reagents (CD45/CD4) in a 1-tube 2-color panel employing side scatter/CD45 morphospectral gating were compared to those obtained by state of the art methods. We also compared the use of generic monoclonal antibody reagents with commercial reagents and found the results to be comparable with an overall correlation coefficient (r) of more than 0.95 for both CD4+ and CD8+ T-lymphocytes. Bland-Altman analysis of the mean CD4 values plotted against the difference in values between the generic reagents and the commercial reagents showed no bias. The 1-tube 2-color method using generic monoclonal antibody reagents potentially permits more affordable but reliable CD4 testing and therefore could increase access for more HIV-infected patients in resource-poor countries.