Lopinavir ritonavir clinical pharmacology

# Clinical Pharmacology

## Pharmacokinetics
The pharmacokinetic properties of lopinavir co-administered with ritonavir have been evaluated in healthy adult volunteers and in HIV-1 infected patients; no substantial differences were observed between the two groups. Lopinavir is essentially completely metabolized by CYP3A. Ritonavir inhibits the metabolism of lopinavir, thereby increasing the plasma levels of lopinavir. Across studies, administration of KALETRA 400/100 mg twice daily yields mean steady-state lopinavir plasma concentrations 15- to 20-fold higher than those of ritonavir in HIV-1 infected patients. The plasma levels of ritonavir are less than 7% of those obtained after the ritonavir dose of 600 mg twice daily. The in vitro antiviral EC50 of lopinavir is approximately 10-fold lower than that of ritonavir. Therefore, the antiviral activity of KALETRA is due to lopinavir.
Figure 1 displays the mean steady-state plasma concentrations of lopinavir and ritonavir after KALETRA 400/100 mg twice daily with food for 3 weeks from a pharmacokinetic study in HIV-1 infected adult subjects (n = 19).
Absorption
In a pharmacokinetic study in HIV-1 positive subjects (n = 19), multiple dosing with 400/100 mg KALETRA twice daily with food for 3 weeks produced a mean  SD lopinavir peak plasma concentration (Cmax) of 9.8  3.7 g/mL, occurring approximately 4 hours after administration. The mean steady-state trough concentration prior to the morning dose was 7.1  2.9 g/mL and minimum concentration within a dosing interval was 5.5  2.7 g/mL. Lopinavir AUC over a 12 hour dosing interval averaged 92.6  36.7 gh/mL. The absolute bioavailability of lopinavir co-formulated with ritonavir in humans has not been established. Under nonfasting conditions (500 kcal, 25% from fat), lopinavir concentrations were similar following administration of KALETRA co-formulated capsules and oral solution. When administered under fasting conditions, both the mean AUC and Cmax of lopinavir were 22% lower for the KALETRA oral solution relative to the capsule formulation.
Plasma concentrations of lopinavir and ritonavir after administration of two 200/50 mg KALETRA tablets are similar to three 133.3/33.3 mg KALETRA capsules under fed conditions with less pharmacokinetic variability.
Effects of Food on Oral Absorption
KALETRA Tablets
No clinically significant changes in Cmax and AUC were observed following administration of KALETRA tablets under fed conditions compared to fasted conditions. Relative to fasting, administration of KALETRA tablets with a moderate fat meal (500 - 682 Kcal, 23 to 25% calories from fat) increased lopinavir AUC and Cmax by 26.9% and 17.6%, respectively. Relative to fasting, administration of KALETRA tablets with a high fat meal (872 Kcal, 56% from fat) increased lopinavir AUC by 18.9% but not Cmax. Therefore, KALETRA tablets may be taken with or without food.
KALETRA Oral Solution
Relative to fasting, administration of KALETRA oral solution with a moderate fat meal (500 - 682 Kcal, 23 to 25% calories from fat) increased lopinavir AUC and Cmax by 80 and 54%, respectively. Relative to fasting, administration of KALETRA oral solution with a high fat meal (872 Kcal, 56% from fat) increased lopinavir AUC and Cmax by 130% and 56%, respectively. To enhance bioavailability and minimize pharmacokinetic variability KALETRA oral solution should be taken with food.
Distribution
At steady state, lopinavir is approximately 98-99% bound to plasma proteins. Lopinavir binds to both alpha-1-acid glycoprotein (AAG) and albumin; however, it has a higher affinity for AAG. At steady state, lopinavir protein binding remains constant over the range of observed concentrations after 400/100 mg KALETRA twice daily, and is similar between healthy volunteers and HIV-1 positive patients.
Metabolism
In vitro experiments with human hepatic microsomes indicate that lopinavir primarily undergoes oxidative metabolism. Lopinavir is extensively metabolized by the hepatic cytochrome P450 system, almost exclusively by the CYP3A isozyme. Ritonavir is a potent CYP3A inhibitor which inhibits the metabolism of lopinavir, and therefore increases plasma levels of lopinavir. A 14C-lopinavir study in humans showed that 89% of the plasma radioactivity after a single 400/100 mg KALETRA dose was due to parent drug. At least 13 lopinavir oxidative metabolites have been identified in man. Ritonavir has been shown to induce metabolic enzymes, resulting in the induction of its own metabolism. Pre-dose lopinavir concentrations decline with time during multiple dosing, stabilizing after approximately 10 to 16 days.
Elimination
Following a 400/100 mg 14C-lopinavir/ritonavir dose, approximately 10.4  2.3% and 82.6  2.5% of an administered dose of 14C-lopinavir can be accounted for in urine and feces, respectively, after 8 days. Unchanged lopinavir accounted for approximately 2.2 and 19.8% of the administered dose in urine and feces, respectively. After multiple dosing, less than 3% of the lopinavir dose is excreted unchanged in the urine. The apparent oral clearance (CL/F) of lopinavir is 5.98  5.75 L/hr (mean  SD, n = 19).
Once Daily Dosing
The pharmacokinetics of once daily KALETRA have been evaluated in HIV-1 infected subjects naive to antiretroviral treatment. KALETRA 800/200 mg was administered in combination with emtricitabine 200 mg and tenofovir DF 300 mg as part of a once daily regimen. Multiple dosing of 800/200 mg KALETRA once daily for 4 weeks with food (n = 24) produced a mean  SD lopinavir peak plasma concentration (Cmax) of 11.8  3.7 g/mL, occurring approximately 6 hours after administration. The mean steady-state lopinavir trough concentration prior to the morning dose was 3.2  2.1 g/mL and minimum concentration within a dosing interval was 1.7  1.6 g/mL. Lopinavir AUC over a 24 hour dosing interval averaged 154.1  61.4 g- h/mL.
The pharmacokinetics of once daily KALETRA has also been evaluated in treatment experienced HIV-1 infected subjects. Lopinavir exposure (Cmax, AUC, Ctrough) with once daily KALETRA administration in treatment experienced subjects is comparable to the once daily lopinavir exposure in treatment naive subjects.
Effects on Electrocardiogram
QTcF interval was evaluated in a randomized, placebo and active (moxifloxacin 400 mg once daily) controlled crossover study in 39 healthy adults, with 10 measurements over 12 hours on Day 3. The maximum mean time-matched (95% upper confidence bound) differences in QTcF interval from placebo after baseline-correction were 5.3 (8.1) and 15.2 (18.0) mseconds (msec) for 400/100 mg twice daily and supratherapeutic 800/200 mg twice daily KALETRA, respectively. KALETRA 800/200 mg twice daily resulted in a Day 3 mean Cmax approximately 2-fold higher than the mean Cmax observed with the approved once daily and twice daily KALETRA doses at steady state.
PR interval prolongation was also noted in subjects receiving KALETRA in the same study on Day 3. The maximum mean (95% upper confidence bound) difference from placebo in the PR interval after baseline-correction were 24.9 (21.5, 28.3) and 31.9 (28.5, 35.3) msec for 400/100 mg twice daily and supratherapeutic 800/200 mg twice daily KALETRA, respectively .
Special Populations
- Gender, Race and Age
No gender related pharmacokinetic differences have been observed in adult patients. No clinically important pharmacokinetic differences due to race have been identified. Lopinavir pharmacokinetics have not been studied in elderly patients.
- Pediatric Patients
The pharmacokinetics of KALETRA oral solution 300/75 mg/m2 twice daily and 230/57.5 mg/m2 twice daily have been studied in a total of 53 pediatric patients in Study 940, ranging in age from 6 months to 12 years . The 230/57.5 mg/m2 twice daily regimen without nevirapine and the 300/75 mg/m2 twice daily regimen with nevirapine provided lopinavir plasma concentrations similar to those obtained in adult patients receiving the 400/100 mg twice daily regimen (without nevirapine).
The mean steady-state lopinavir AUC, Cmax, and Cmin were 72.6  31.1 gh/mL, 8.2  2.9 and 3.4  2.1 g/mL, respectively after KALETRA oral solution 230/57.5 mg/m2 twice daily without nevirapine (n = 12), and were 85.8  36.9 g- h/mL, 10.0  3.3 and 3.6  3.5 g/mL, respectively, after 300/75 mg/m2 twice daily with nevirapine (n = 12). The nevirapine regimen was 7 mg/kg twice daily (6 months to 8 years) or 4 mg/kg twice daily (> 8 years).
The pharmacokinetics of KALETRA oral solution at approximately 300/75 mg/m2 twice daily have also been evaluated in infants at approximately 6 weeks of age (n = 9) and between 6 weeks and 6 months of age (n = 18) in Study 1030. The mean steady-state lopinavir AUC12, Cmax, and C12 were 43.4  14.8 g- h/mL, 5.2  1.8 g/mL and 1.9  1.1 g/mL, respectively, in infants at approximately 6 weeks of age, and 74.5  37.9 g- h/mL, 9.4  4.9 and 3.1  1.8 g/mL, respectively, in infants between 6 weeks and 6 months of age after KALETRA oral solution was administered at approximately 300/75 mg/m2 twice daily without concomitant NNRTI therapy.
The pharmacokinetics of KALETRA soft gelatin capsule and oral solution (Group 1: 400/100 mg/m2 twice daily + 2 NRTIs; Group 2: 480/120 mg/m2 twice daily +  1 NRTI + 1 NNRTI) have been evaluated in children and adolescents age  2 years to < 18 years of age who had failed prior therapy (n=26) in Study 1038. KALETRA doses of 400/100 and 480/120 mg/m2 resulted in high lopinavir exposure, as almost all subjects had lopinavir AUC12 above 100 gh/mL. Both groups of subjects also achieved relatively high average minimum lopinavir concentrations.
KALETRA once daily has not been evaluated in pediatric patients.
Renal Impairment
Lopinavir pharmacokinetics have not been studied in patients with renal impairment; however, since the renal clearance of lopinavir is negligible, a decrease in total body clearance is not expected in patients with renal impairment.
- Hepatic Impairment
Lopinavir is principally metabolized and eliminated by the liver. Multiple dosing of KALETRA 400/100 mg twice daily to HIV-1 and HCV co-infected patients with mild to moderate hepatic impairment (n = 12) resulted in a 30% increase in lopinavir AUC and 20% increase in Cmax compared to HIV-1 infected subjects with normal hepatic function (n = 12). Additionally, the plasma protein binding of lopinavir was statistically significantly lower in both mild and moderate hepatic impairment compared to controls (99.09 vs. 99.31%, respectively). Caution should be exercised when administering KALETRA to subjects with hepatic impairment. KALETRA has not been studied in patients with severe hepatic impairment .