Fosamprenavir calcium plus ritonavir for HIV infection

Protease Inhibitors for the Treatment of HIV/AIDS: Recent Advances and Future Challenges

Acquired Immunodeficiency Syndrome (AIDS) is a chronic disease characterized by multiple life-threatening illnesses caused by a retro-virus, Human Immunodeficiency Virus (HIV). HIV infection slowly destroys the immune system and increases the risk of various other infections and diseases. Although, there is no immediate cure for HIV infection/AIDS, several drugs targeting various cruxes of HIV infection are used to slow down the progress of the disease and to boost the immune system. One of the key therapeutic strategies is Highly Active Antiretroviral Therapy (HAART) or ' AIDS cocktail' in a general sense, which is a customized combination of anti-retroviral drugs designed to combat the HIV infection. Since HAART's inception in 1995, this treatment was found to be effective in improving the life expectancy of HIV patients over two decades. Among various classes of HAART treatment regimen, Protease Inhibitors (PIs) are known to be widely used as a major component and found to be effective in treating HIV infection/AIDS. For the past several years, a variety of protease inhibitors have been reported. This review outlines the drug design strategies of PIs, chemical and pharmacological characteristics of some mechanism-based inhibitors, summarizes the recent developments in small molecule based drug discovery with HIV protease as a drug target. Further discussed are the pharmacology, PI drug resistance on HIV PR, adverse effects of HIV PIs and challenges/impediments in the successful application of HIV PIs as an important class of drugs in HAART regimen for the effective treatment of AIDS.

Post-licensing safety of fosamprenavir in HIV-infected children in Europe

PURPOSE

Fosamprenavir, combined with low-dose ritonavir (FPV/r), is indicated for treatment of HIV-infected children aged ≥ 6 years in Europe. Our purpose was to assess the safety of licensed use of FPV/r in HIV-infected children reported to six cohorts in the European Pregnancy and Paediatric HIV Cohort Collaboration.

METHODS

Retrospective analysis of individual patient data for all children aged 6-18 years taking the licensed dose of FPV up to 31/12/10. Adverse events (clinical events and absolute neutrophil counts, total cholesterol and triglycerides, and alanine transaminase) were summarised and DAIDS gradings characterised severity.

RESULTS

Ninety-two HIV-infected children aged 6-18 years took the licensed dose, comprising 3% of the total number of children in follow-up in participating cohorts. Median age at antiretroviral therapy initiation was 6 years (interquartile range 1-11 years), and median age at start of FPV/r was 15 years (12-17 years). Estimated median time on an FPV-containing regimen was 52 months, with a total of 266.9 patient years of exposure overall. Half (54%) were on an FPV-containing regimen at last follow-up. Rates of grade 3/4 events were generally low for all biochemical toxicity markers, and no serious adverse events considered to be causally related to FPV/r were reported.

CONCLUSIONS

Results suggest that long-term licensed dose FPV-containing regimens appear to be generally well tolerated with few reported toxicities in HIV-infected children in Europe, although relatively infrequently prescribed. No serious events were reported

Pharmacokinetics and 48-week safety and antiviral activity of fosamprenavir-containing regimens in HIV-infected 2- to 18-year-old children

BACKGROUND

Pharmacokinetics, safety and antiviral activity of twice-daily fosamprenavir with or without ritonavir were evaluated in 2- to 18-year-old protease inhibitor-naïve and -experienced HIV-1-infected children.

METHODS

Serial pharmacokinetic samples were collected at week 2 and predose samples every 4-12 weeks. Safety and plasma HIV-1 RNA were monitored every 4-12 weeks.

RESULTS

Twenty protease inhibitor-naïve 2- to <6-year-old subjects received antiretroviral treatment including unboosted fosamprenavir twice-daily, whereas 89 protease inhibitor-naïve and -experienced 2- to 18-year-old subjects received fosamprenavir/ritonavir-containing therapy twice-daily. Median fosamprenavir exposure was 891 days (range 15-1805 days), with 88% exposed >48 weeks. Twice-daily doses of fosamprenavir/ritonavir 23/3 mg/kg in 2- to <6-year olds, 18/3 mg/kg in ≥6-year olds and 700/100 mg in adolescents achieved plasma amprenavir exposures comparable with or higher than 700/100 mg twice-daily in adults while fosamprenavir 30 mg/kg twice-daily in 2- to <6-year olds led to exposures higher than 1400 mg twice-daily in adults. The proportion of subjects with HIV-1 RNA <400 copies/mL at week 48 was 60% for fosamprenavir and 53-74% for fosamprenavir/ritonavir (intent-to-treat [exposed], snapshot analysis). Median increases in absolute and relative (percentage) CD4 counts from baseline to week 48 occurred in both the fosamprenavir (340 cells/mm; 8%) and fosamprenavir/ritonavir group (190 cells/mm; 8%). The most common adverse events were vomiting, cough, and diarrhea; 18 subjects experienced serious adverse events, including 9 with suspected abacavir hypersensitivity.

CONCLUSIONS

Fosamprenavir regimens administered to HIV-1-infected children aged 2-18 years were generally well-tolerated and provided sustained antiviral activity over 48 weeks, with plasma amprenavir exposures comparable with or higher than adults.

Pharmacokinetics, safety and antiviral activity of fosamprenavir/ritonavir-containing regimens in HIV-infected children aged 4 weeks to 2 years-48-week study data

BACKGROUND

Pharmacokinetics, safety and antiviral activity of fosamprenavir (FPV) with ritonavir (RTV) twice daily were evaluated in HIV-1-infected infants and children 4 weeks to <2 years over 48 weeks.

METHODS

Results from intensive pharmacokinetic sampling of subjects enrolled in single dose visits was used to determine individualized dosing for the first 6-10 subjects in each of 2 cohorts (4 weeks to <6 months, 6 months to <2 years); steady state pharmacokinetic data were then used to select the dosage regimen for the remaining subjects recruited to the cohort. Intensive pharmacokinetic sampling was performed at week 2 or 8; predose samples were collected every 4-12 weeks thereafter. Safety and plasma HIV-1 RNA were monitored every 4-12 weeks.

RESULTS

Fifty-nine subjects received study medication. FPV 45 mg/kg boosted with RTV 7 to 10 mg/kg BID achieved average plasma amprenavir area under curve(0-τ) values 26% to 28% lower and Cmax similar to historical adult data for FPV/RTV 700/100 mg BID; amprenavir Cτ values were lower in the subjects <6 months of age. At week 48, 35 of 54 (65%) subjects had achieved plasma HIV-1 RNA <400 copies/mL and 33 of 54 (61%) had plasma HIV-1 RNA values <50 copies/mL. The most common adverse events were diarrhea, upper respiratory tract infection, gastroenteritis and otitis media.

CONCLUSIONS

Final FPV/RTV dosing regimens achieved plasma amprenavir exposures comparable with those from regimens approved in adults, with the exception of trough exposures in the <6-month-old infants. The FPV/RTV regimens led to viral suppression in 61% of patients and were generally well tolerated.

Current and Novel Inhibitors of HIV Protease

The design, development and clinical success of HIV protease inhibitors represent one of the most remarkable achievements of molecular medicine. This review describes all nine currently available FDA-approved protease inhibitors, discusses their pharmacokinetic properties, off-target activities, side-effects, and resistance profiles. The compounds in the various stages of clinical development are also introduced, as well as alternative approaches, aiming at other functional domains of HIV PR. The potential of these novel compounds to open new way to the rational drug design of human viruses is critically assessed.