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GSK Reports new PK Data on Fosamprenavir (Lexiva)
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PK Data on Lexiva-Tenofovir & Lexiva-Nexium
Reported by Jules Levin
GlaxoSmithKline distributed this information by Press release this morning, which was presented the Pharmacology Workshop ongoing in Quebec. I extracted the important information to read. NATAP is covering the Pharmacology Workshop & will be providing expert reporting & commentary following the meeting.
Lexiva/r co-administration with the NRTI tenofovir did not result in a significant difference in plasma APV PK when the two agents were dosed once daily in fasted healthy volunteers.
No significant safety findings in the 35 men studied when combining TDF with LEXIVA/r QD.
LEXIVA offers flexible dosing and no food or fluid restrictions, which may simplify ART regimens for some patients.
This study was a prospective, crossover study of 35 male volunteers. All subjects took LEXIVA/r alone and in combination with TDF 300mg once daily in a fasted state. One cohort took LEXIVA 1400mg/ritonavir 200mg once daily and the other cohort took LEXIVA 1400mg/ritonavir 100mg once daily. After 14 days, a 24-hour PK profile was measured.
Specific results:
· No relevant effects of TDF on plasma amprenavir (APV) PK were demonstrated when once daily TDF 300mg was given in combination with once daily LEXIVA/r 1400/100 or 1400/200.
· There were no grade III-IV adverse events in any study group.
- Today GlaxoSmithKline (GSK) presented new pharmacokinetic (PK) data on taking the HIV protease inhibitor LEXIVA (fosamprenavir calcium, FPV) Tablets with the proton pump inhibitor (PPI), Nexium (esomeprazole magnesium, ESO) 20mg Delayed-Release Capsules. When these agents were simultaneously co-administered there was no effect on amprenavir steady-state plasma levels. Current prescribing information in the U.S. for LEXIVA states that LEXIVA should be used with caution when co-administered with proton pump inhibitors as it may be less effective due to decreased amprenavir concentrations in patients taking these agents concomitantly. GSK performed an interaction study to determine if the simultaneous co-administration of esomeprazole alters the pharmacokinetics of LEXIVA. PPIs such as esomeprazole, are potent inhibitors of the gastric acid pump and are often taken for the prevention and treatment of heartburn and other symptoms of gastroesophageal reflux disease (GERD). The study findings of APV10031, a randomized, open-label crossover study, were presented at the 6th International Workshop on Clinical Pharmacology of HIV Therapy in Quebec, Canada.
When Lexiva was simultaneously co-administered with Nexium there was no effect on amprenavir (the active molecule LEXIVA) steady-state plasma levels.
Current prescribing information in the U.S. for LEXIVA states that LEXIVA should be used with caution when co-administered with PPIs as it may be less effective due to decreased amprenavir concentrations in patients taking these agents.
"GERD is a common condition with up to 20 percent of the U.S. adult population reporting symptoms associated with chronic heartburn, and up to 40 percent of adults suffering from heartburn at least once a month" commented Benjamin Young, M.D., and Ph.D., attending physician in infectious diseases at Rose Medical Center, Denver.
The APV10031 study was a crossover study in 48 healthy adult volunteers in the following three treatment periods:
1. All subjects received 20mg of the PPI ESO once-a-day (QD) for seven days.
2. Immediately thereafter, subjects received 20mg of ESO QD with either 1,400mg of LEXIVA twice-a-day (BID) or 700mg of LEXIVA plus 100mg of RTV BID for 14 days.
3. Following a washout period of 21-28 days, subjects received 1400mg LEXIVA BID or 700mg of LEXIVA plus 100mg of RTV for 14 days.
PK parameters from each combination of drugs were compared to each drug alone.
Based on the results, the authors concluded that simultaneous co-administration of 20mg ESO QD with either LEXIVA or LEXIVA/r had no effect on steady state plasma APV PK.
Specific results:
For all plasma APV parameters compared (AUC, Cmax, and Cmin), no significant differences were found when LEXIVA or LEXIVA/r were given simultaneously with ESO. ESO AUC and Cmax were unchanged when dosed in combination with LEXIVA/r, whereas ESO dosed in combination with LEXIVA increased ESO AUC by 55 percent and Cmax was unchanged, according to the studyÕs authors.
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