Pharmacokinetics of Low Dose Ritonavir

Pharmacokinetics of Low Dose Ritonavir in Thai Patients on a Saquinavir 1500 mg Based HAART Regimen

Compare the Pharmacokinetics of ritonavir and saquinavir(using either Saquinavir /Ritonavir 1500/100 mg or 1500/50 mg) Evaluate short term tolerability, safety and toxicity Evaluate if there is any relation between RTV concentration levels and boosting effect

Study Overview

• Status: Completed
• Conditions: HIV Infections
• Intervention / Treatment: Drug: ritonavir and saquinavir

Detailed Description

This study will focus on the combination of Saquinavir (SQV) and RTV. Firstly, this is because SQV is widely used in Thailand and has shown to be an adequate first and second line antiretroviral agent. Secondly, reduced dose of SQV (1600 mg OD) has proven to generate adequate efficacy and good pharmacokinetic parameters in the Thai population[5, 6]. Now 500 mg tablets of SQV are becoming more and more available, therefore a 1500 mg OD dose will be of more interest for our study. A TDM comparison study between SQV 1600 OD mg and SQV1500 mg OD has been done (Ananworanich et al, unpublished data) and did not show any difference in terms of drug concentrations . The efficacy of this regimen has shown to be adequate as described in the STACCATO cohort[7]. So we consider it safe to use the SQV 1500 mg OD in our study.

It is not clear what RTV concentrations are necessary to obtain good levels for SQV. In the study of Autar et al [5] no relation between RTV levels and boosting effect was described. Besides that it might well be that even the boosting levels of RTV contribute to the toxicity of the antiretroviral treatment.For instance, a study performed in healthy volunteers on RTV 100 mg BID monotherapy, showed a significant increase in total cholesterol, low-density lipoprotein (LDL) cholesterol and triglycerides and a marked reduction of high-density lipoprotein (HDL)[8]. This last finding was confirmed in the study of Boyd et al (submitted) in Thai HIV-infected patients.

Preliminary data from HIVNAT 019 [9] suggests that lower boosting dosage still give adequate levels of the other PIs. In this open label 4 arm study one arm contains Lopinavir/Ritonavir 266/66 mg bid together with SQV 600 mg bid. Despite the dose reduction in all PIs, adequate PK levels were obtained. Two arms (23 patients) in this study used normal dose of RTV (100 mg bid) in combination with Lopinavir and Saquinavir. Five of them had maximal concentrations (Cmax) above the therapeutic level RTV (>2.1 mg/l). This finding is supported by clinical experience.

Therefore, looking into lower doses of RTV in the Thai population is of great interest A liquid formulation for RTV 50 mg will be used, as a capsule is not available yet. The liquid formulation has the same bioequivalence as the capsule and was used extensively during the time of manufactory problems of the Norvir capsule. Because of the bad taste of this formulation PK samples will be collected after one week, thereafter patients can return to their old regimen. A dose reduction of RTV can be of great importance for the Thai population as it prevents unnecessary toxicity and costs. If this PK study turns out to be adequate, an efficacy study can be performed and the boosting of other commonly used PI's, like IDV and Lopinavir, can be studied.

• Study Type: Interventional
• Enrollment (Actual): 20
• Phase: Phase 2; Phase 1

Contacts and Locations

Study Locations

• Thailand
  • Bangkok, Thailand, 10330
    • HIV-NAT

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• Age > 18 years
• Documented positive test for HIV-1 infection
• HIV RNA viral load 50 < copies for at least 3 months
• Written informed consent
• On a Saquinavir 1500 mg based HAART regimen for at least 3 months

Exclusion Criteria:

• Pregnant or lactating
• Use of concomitant medication that may interfere with the pharmacokinetics of saquinavir/ritonavir
• Inability to understand the nature and extent of the study and the procedures required
• ALT/ AST more than 5x upper limit
• Relevant history or current condition, illness that might interfere with drug absorption, distribution, metabolism or excretion.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Non-Randomized
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Active Comparator: 1; Twenty HIV-infected volunteers on stable doses of SQV/RTV 1500/100 mg OD for at least 3 months with an NRTI backbone and undetectable viral load will participate. After collecting samples for a full PK curve subjects will be switched to SQV/RTV 1500 /50 mg OD + 2NRTIs for 1 week before repeating the PK assessment. Blood samples will be drawn at T 0, 1, 2, 4, 6, 8, 10, 12 and 24 hours post ingestion. Consecutively to the assessment, subjects will return to SQV/RTV 1500/100 mg OD dosage.

Drug: ritonavir and saquinavir; saquinavir/ritonavir 1500/100 mg or 1500/50 mg Twenty HIV-infected volunteers on stable doses of SQV/RTV 1500/100 mg OD for at least 3 months with an NRTI backbone and undetectable viral load will participate. After collecting samples for a full PK curve subjects will be switched to SQV/RTV 1500 /50 mg OD + 2NRTIs for 1 week before repeating the PK assessment. Blood samples will be drawn at T 0, 1, 2, 4, 6, 8, 10, 12 and 24 hours post ingestion. Consecutively to the assessment, subjects will return to SQV/RTV 1500/100 mg OD dosage.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
To compare the Pharmacokinetics od ritonavir and saquinavir in Thai HIV-1 infected subjects using either Saquinavir /Ritonavir 1500/100 mg or 1500/50 mg	6 months and 1 week

Secondary Outcome Measures

Outcome Measure	Time Frame
Evaluate short term tolerability, safety and toxicity of this treatment strategy Evaluate if there is any relation between RTV concentration levels and boosting effect	6 months and 1 week

Collaborators and Investigators

• Sponsor: The HIV Netherlands Australia Thailand Research Collaboration
• Investigators: Principal Investigator: Kiat Ruxrungtham, MD, The HIV Netherlands Australia Thailand Research Collaboration

Publications and helpful links

General Publications

• Avihingsanon A, van der Lugt J, Kerr SJ, Gorowara M, Chanmano S, Ohata P, Lange J, Cooper DA, Phanuphak P, Burger DM, Ruxrungtham K. A low dose of ritonavir-boosted atazanavir provides adequate pharmacokinetic parameters in HIV-1-infected Thai adults. Clin Pharmacol Ther. 2009 Apr;85(4):402-8. doi: 10.1038/clpt.2008.244. Epub 2008 Dec 31.

Helpful Links

• HIV Netherlands Australia Thailand Research Collaboration (HIV-NAT)

Study record dates

Study Major Dates

• Study Start: January 1, 2008
• Primary Completion (Actual): April 1, 2008
• Study Completion (Actual): August 1, 2008

Study Registration Dates

• First Submitted: February 12, 2008
• First Submitted That Met QC Criteria: February 21, 2008
• First Posted (Estimate): February 22, 2008

Study Record Updates

• Last Update Posted (Estimate): April 5, 2012
• Last Update Submitted That Met QC Criteria: April 3, 2012
• Last Verified: April 1, 2012

More Information

Terms related to this study

• Keywords: Pharmacokinetics; treatment experienced; ritonavir; saquinavir; safety and toxicity
• Additional Relevant MeSH Terms: RNA Virus Infections; Virus Diseases; Infections; Blood-Borne Infections; Communicable Diseases; Sexually Transmitted Diseases, Viral; Sexually Transmitted Diseases; Lentivirus Infections; Retroviridae Infections; Immunologic Deficiency Syndromes; Immune System Diseases; HIV Infections; Molecular Mechanisms of Pharmacological Action; Anti-Infective Agents; Antiviral Agents; Enzyme Inhibitors; Anti-HIV Agents; Anti-Retroviral Agents; Protease Inhibitors; Cytochrome P-450 CYP3A Inhibitors; Cytochrome P-450 Enzyme Inhibitors; HIV Protease Inhibitors; Viral Protease Inhibitors; Ritonavir; Saquinavir
• Other Study ID Numbers: HIV-NAT 083; IRB#188/50