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TDM of ARV drugs


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Most current highly active antiretroviral therapy (HAART) regimens for HIV-positive patients contain two nucleoside reverse transcriptase inhibitors (NRTIs) with either a Protease inhibitor (PIs) or a …

Most current highly active antiretroviral therapy (HAART) regimens for HIV-positive patients contain two nucleoside reverse transcriptase inhibitors (NRTIs) with either a Protease inhibitor (PIs) or a non-nucleoside reverse transcriptase inhibitors (NNRTI). Notwithstanding the regulatory guidelines recommending therapeutic drug monitoring (TDM) for these drugs, therapeutic failure is a very serious concern implying drug induced toxicity and more importantly viral rebound and viral resistance.

Single dose, steady state and dose ranging studies have all more or less demonstrated that there is a positive correlation between plasma concentrations and therapeutic effects of anti-retrovirals (ARVs). However, one of the main challenges still seems to be the target concentrations for these drugs and their relevant inhibitory quotient. In this talk, we are going to examine these issues along with bioanalytical challenges, drug-effect and drug –toxicity relationships and finally drug-drug interactions within different HAART regimes.

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  • 1. Therapeutic Drug Monitoring ofAnti-Retroviral DrugsTrack 3-1 Lecture at International Conference and Exhibition on Analytical and Bioanalytical Techniques, Hyderabad, India November 1-3, 2010 Dr. Bhaswat S. Chakraborty Senior VP, Cadila Pharmaceuticals Ltd. 02.11.2010
  • 2. Contents• Current highly active antiretroviral therapy (HAART)• Guidelines for administering HAART• Correlation between plasma concentrations and therapeutic effects• Drug –toxicity relationships• Drug-drug interactions within different HAART regimes• Therapeutic drug monitoring (TDM) ▫ Purpose ▫ Challenges ▫ Approaches• Bioanalytical challenges• Conclusions
  • 3. ARV Drugs Darunavir Enfuvirtide Maraviroc • NRTI, Nucleoside reverse transcriptase inhibitor; Atazanavir Raltegravir • NNRTI, Non-nucleoside reverse transcriptase inhibitor; Emtricitabine Tipranavir Etravirine • PI, protease inhibitor Fosamprenavir • Integrase Inhibitor Tenofovir • CCR5 Antagonist/Entry Inhibitor Nelfinavir Delavirdine Lopinavir/r Ritonavir Indinavir Amprenavir Nevirapine Efavirenz Abacavir 3TC Saquinavir ddC d4T ddl AZT Source : Dr. David Back, Univ. of Liverpool
  • 4. Main classes of ARV drugs• Nucleoside and nucleotide reverse transcriptase inhibitors (NRTI) inhibit reverse transcription by being incorporated into the newly synthesized viral DNA and preventing its further elongation.• Non-nucleoside reverse transcriptase inhibitors (NNRTI) inhibit reverse transcriptase directly by binding to the enzyme and interfering with its function.• Protease inhibitors (PIs) target viral assembly by inhibiting the activity of protease, an enzyme used by HIV to cleave nascent proteins for final assembly of new virons.• Integrase inhibitors (II) inhibit the enzyme integrase, which is responsible for integration of viral DNA into the DNA of the infected cell.
  • 5. Highly active antiretroviral therapy (HAART) regimens for HIV-positive patients• Most current HAART regimens consist of three (3) drugs: 2 NRTIs + a PI or NNRTI or II ▫ Initial regimens use "first-line" drugs with a high efficacy and low side-effect profile.• Current preferred initial regimens • Emtricitabine, tenofovir (both NRTI) and efavirenz (a NNRTI). • Efavirenz should not be given to pregnant women. • Emtricitabine, tenofovir and raltegravir (an II) • Emtricitabine, tenofovir, ritonavir and darunavir (both latter are PI) • Emtricitabine, tenofovir, ritonavir and atazanavir (both latter are PI)
  • 6. Meaningful inhibitory concentration• A parameter to estimate in vivo potency of antiretroviral drugs• Cmin/IC50 is suitable for across-study, across-patient and across-drug comparison• ICmin is generated from in vivo pharmacokinetic data• IC50 or IC95 are generated in vitro, increasing drug concentration until 50% or 95% of the virus is inhibited • How close the IC50 and IC95 values are to each other depends on how steep the curve is (see lower graph) • How reliable the values are depends on the system used to measure them• IQ (inhibitory quotient): • IQ = trough concentration in plasma/concentration required for inhibition in vitro • Gives an index of how far the concentration of a drug in vivo is in excess of the viral IC50
  • 7. Guideline websites Country WebsiteFrance  Germany and Austria www.ministerodellasalute/aids/aids.jspUK  USA  Netherlands  
  • 8. Hammer, S. M. et al. JAMA 2008;300:555-570.
  • 9. Therapeutic Drug Monitoring(DHHS Guidelines 2009)1. When food-drug and drug-drug interactions lead to decreased efficacy2. Pathophysiological conditions that impair GI, hepatic function, and renal function, thereby affecting ADME3. Treatment-experienced pts with virus with reduced susceptibility to ARVs (higher concentrations may be required).4. Treatment-naive pts with suboptimal virologic response5. In pregnant women due to metabolic and physiological changes that can affect PK6. For prevention of ARV-induced concentration-dependent toxicity7. When using unconventional ARV regimens or dosing not studied in clinical trials8. Consider in pediatric pts when there are limited dosing data
  • 10. Recommended trough concentrations DHHS Guidelines
  • 11. Simulated probabilities of target troughconcentrations of Efavirenz in children Antivir Ther. 2008;13:77987.
  • 12. Plasma concentrations and viral clearance in 4 drug therapyHoetelmans et al. (1998), AIDS. 12:F111-F115
  • 13. Plasma concentrations and viral clearancein mono & multi therapy Lotsh et al. (2007), Antimicrob Agents Chemotherap, 51:3264–3272
  • 14. Steady-state saquinavir plasma concentration-versus-time profiles; n = 56 Very similar Lotsh et al. (2007), Antimicrob Agents Chemotherap, 51:3264–3272
  • 15. Inter-individual variation in saquinavirplasma concentrations; n = 56 Lotsh et al. (2007), Antimicrob Agents Chemotherap, 51:3264–3272
  • 16. ADRs vs. Saquinavir plasma concentrations;n = 56Log Cmax,saquinavir was predictive (P 0.001 [chi-square after logisticregression]) of constitutional side effects such as asthenia andsleepiness (n 7), lymphadenopathy (n 2), orthostatic dizziness (n 2), fever without infection (n 1), weight gain (n 1), peripheraledema (n 1), and spontaneous pneumothorax (n 1) and GI sideeffects.0 Lotsh et al. (2007), Antimicrob Agents Chemotherap, 51:3264–3272
  • 17. Drug-drug interactions New York State Department of Health AIDS Guidelines
  • 18. Enzyme induction or inhibition Drug Enzyme Inhibition Enzyme Induction Atazanavir ++ — Delavirdine ++ — Efavirenz + +++ Fosamprenavir + ++ Indinavir ++ — Lopinavir/ritonavir ++++ ++ Tipranavir/ritonavir ++++ +++ Nelfinavir ++ + Nevirapine — ++ Ritonavir ++++ ++ Saquinavir — — Source: Flexner CW.
  • 19. TDM of antiretroviral drugs – rationale andpurpose1. Compliance2. ARV plasma or cell drug concentrations correlate with antiviral effects3. Drug concentrations also correlate with excessive toxicity4. High variations are present in plasma or cell drug concentrations5. Hepatic dysfunction changes clearance of the drug
  • 20. TDM of antiretroviral drugs – approaches1. Exactly knowing the target concentrations especially multi- therapy targets2. Four drug therapy failures do not tell you exactly what concentrations of which drug should be changed3. Resistant isolates may require higher drug concentrations4. Inter- and intra-individual variability5. Drug-drug and drug food interaction6. Bioavalilability enhancement 1. e.g., of indinavir by ritonavir7. Which PK parameter (AUC, Cmin Cmin/IC50)?
  • 21. Bioanalytical Development of antiretroviraldrugs – approaches1. Many PIs show low nanograms of levels (also do hair and blood spots)2. Sensitive and accurate HPLC or LC-MS-MS methods are most suitable3. Plasma, dried blood spots, hair, saliva or lysates of peripheral blood mononeuclear cells (PBMCs) are the drug containing matrices4. Simultaneous analysis many drugs and internal standards 1. Selecting MRMs for all is challenging5. PBMC or dried blood spot concentration for PIs or NNRTIs would be more relevant as these drugs act intracellularly6. Sample pre treatments (e.g., PBMC) may be required for CCs and QCs
  • 22. Acyclovir
  • 23. Case study – LC-MS-MS of multi ARVs in PBMC samples
  • 24. Selection of IS, RT and MRMs (PBMCsamples) Heine et al, (2009) J Chromatogr B Analyt Technol Biomed Life Sci. 877: 57580
  • 25. LLOQ Heine et al, (2009) J Chromatogr B Analyt Technol Biomed Life Sci. 877: 57580
  • 26. Validation of assay Heine et al, (2009) J Chromatogr B Analyt Technol Biomed Life Sci. 877: 57580
  • 27. LopinavirIncurred (clinical)sample analysis Ritonavir Atazanavir Heine et al, (2009) J Chromatogr B Analyt Technol Biomed Life Sci. 877: 57580
  • 28. PBMC matrix effect • The number of PBMC cells vary significantly from sample to sample due to ▫ Natural variation in systemic circulation ▫ Variation in cell recovery • Therfore, investigation of PBMC ME is required Heine et al, (2009) J Chromatogr B Analyt Technol Biomed Life Sci. 877: 57580
  • 29. Conclusions
  • 30. Thank You Very Much