Antiretroviral Resistance Testing in the Management of HIV-infected Patients

1. 0 Antiretroviral Resistance Testing in the Management of HIV-infected Patients Christopher Behrens, MD Amy Kindrick, MD Robert Harrington, MD

2. 0 Overview of Antiretroviral Resistance Testing • How does resistance develop? • What is the relationship between adherence and resistance? • How much resistance is out there? • How do we test for resistance? • How do we interpret the results of a resistance test? • Does resistance testing improve care? • When should you order resistance tests? • Can a single dose of nevirapine for Prevention of Mother to Child Transmission (PMTCT) result in clinically significant resistance?

3. 0 How Does HIV Develop Resistance to Antiretrovirals?

4. 0 HIV Life Cycle Nucleoside Analogues (NRTIs) HIV Reverse Transcriptase RNA DNA Nucleus Host Cell Non-Nucleosides (NNRTIs) Protease Inhibitors (PIs)

5. 0 How does HIV Develop Resistance to Antiretrovirals? • HIV reverse transcriptase is a low-fidelity enzyme, i.e., transcription mistakes are common • Mistakes (mutations) lead to mutant strains of HIV • Most mutations are inconsequential or result in incompetent strains of HIV, but certain mutations confer resistance to currently available antiretroviral drugs (ARVs) • Administration of antiretrovirals in an insufficiently potent manner exerts reproductive pressure that selects for resistance-bearing strains which then become the majority strain of HIV in that patient

6. 0 How Drug Resistance Arises How drug resistance arises. Richman, DD. Scientific American , July 1998

7. 0 How does resistance develop? Continuation of a failing ART regimen after early resistance has developed selects for expansion of resistance

8. 0 How does resistance develop? Poor Adherence Drug Resistance Regimen Failure

9. 0 How does resistance develop? Social/personal issues Regimen issues Poor potency Toxicities Wrong dose Poor adherence Host genetics Poor absorption Insufficient drug level Rapid clearance Viral replication in the presence of drug Poor activation Resistant virus Drug interactions

10. 0 True or False? The patients with the lowest levels of adherence are the most likely to develop resistance to their ARVs

11. 0 What is the relationship between adherence and resistance?

12. What is the relationship between adherence and resistance? 0 Harrigan, JID, 2005 • Prospective, observational study • N = 1191 • Predictors of resistance • High baseline VL • Good (not great) adherence

13. 0 Is Resistance Becoming More Common? Prevalence of resistance among recently-infected patients at San Francisco General Hospital % of resistant isolates JAMA. 2002 Jul 10;288(2):181-8.

14. 0 Is Resistance Becoming More Common? Recently Infected, ART Naïve, United States Little SJ, Holte S, Routy JP, et al. N Engl J Med. 2002;347:385-94

15. 0 How do we test for resistance? 1. Genotype 2. Phenotype 3. Virtual Phenotype

16. 0 HIV Life Cycle Nucleoside Analogues (NRTIs) HIV Reverse Transcriptase RNA DNA Nucleus Host Cell Non-Nucleosides (NNRTIs) Protease Inhibitors (PIs)

17. Silent Mutation 0 Genotypic Resistance Assay • Sequences relevant portions of the HIV genome coding for Reverse Transcriptase and Protease enzymes • Detects and reports variations in the sequences of these genes that are known or suspected to confer antiretroviral resistance Codon Mutation Silent Mutation AAA GAC AGT AAAAACAGC Lys Lys Asp Ser Asn Ser Adapted from Winters. Reviewed in Wilson. AIDS Read 2000;10:469.

18. 0 M184V M = Methionine 184 = the codon # V = Valine A mutation at codon #184 in the gene Reverse Transcriptase codes for a Valine residue where normally a Methionine residue is found.

19. ddI 184 65 74 R V V 0 Reverse Transcriptase Mutations Selected by NRTIs M D K (Wild Type) L T K AZT 41 67 70 210 215 219 1 (Mutant) W YF Q L N R 560 K M L T ddC 184 65 74 69 D V E 3TC 44 118 184 I D VI V d4T 41 67 70 75 210 215 219 TMSA Y ABC 74 115 67 70 210 215 219 65 41 184 F V Clinical significance under investigation Mutation Selected in vitro Adapted from D’Aquila. Topics in HIV Medicine 2001;9(2):31.

20. Mutation 0 Reverse Transcriptase Mutations Selected by NNRTIs L K V V Y Y G 106 108 NVP 100 188 181 103 190 I N A I C LH A CI 1 560 P DLV 236 103 181 L C P EFV 100 108 188 190 225 103 L SA H Adapted from D’Aquila. Topics in HIV Medicine 2001;9(2):31.

21. Primary Secondary 0 Protease Mutations Selected by PIs L L I V I K V M G M A V L 10 20 24 32 36 46 54 77 82 84 90 71 73 IDV 1 99 IRV I I M MR I I V VT SA AFTS V I L 32 33 36 46 54 71 77 82 84 90 20 10 RTV F IL VL G 10 48 54 77 82 84 90 71 73 SQV V S A D N NFV 10 30 36 46 71 77 82 84 88 90 IL FI N AFTS D I I APV 10 32 84 46 54 47 50 FIRV V VM I V F L LPV/RTV 20 24 53 63 71 82 90 10 84 46 54 P L Adapted from D’Aquila. Topics in HIV Medicine 2001;9:31.

22. 0 Interpretation of the results: what are the clinical implications of these mutations in terms of resistance to antiretroviral agents?

23. 0 Interpretation of the Genotypic Resistance Assay • The genotype report typically includes an interpretation of the clinical implications of the identified mutations • However: • The exact significance of many mutations remains controversial • Interactions between mutations further complicate estimation of the clinical impact of a given set of mutations • Interpretation of genotypic resistance assays is not standardized across different laboratories • Assays will not detect minority resistant strains (less than 10-20% of the viral population)

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30. 0 Phenotypic Resistance Testing • Tests viability of a synthetic version of the patient’s HIV in the presence of antiretroviral agents • Similar to traditional bacterial antibiotic susceptibility assays • Results reported as fold-change in susceptibility to antiretroviral agents

31. Wild-type strain Mutant strain 0 Phenotype Resistance Testing 100 Fold Resistance Inhibition of Viral Replication (%) 50 0 IC50 IC50 Drug Concentration Reviewed in Wilson. AIDS Read 2000;10:469.

32. PhenoSense HIV Patient Report 0

33. PhenoSense™ HIV Report 0

34. Which Resistance Assay is Better? 0

35. 0 Does the use of resistance assays improve clinical results?

36. Published Randomized Controlled Trials of Resistance Testing 0

37. 0 HavanaResults: % of Patients with HIV-1 RNA <400 copies/mL (ITT) 100 No G No Expert Op. P = .0206 P = .00132 80 No G Expert Op. G No Expert Op. 60 G Expert Op. 40 20 0 wk 12 BL wk 24 NO G, NO Expert (N = 77) 36.4% NO G, Expert (N = 67) 49.3% G, NO Expert (N = 69) 46.4% G, Expert (N = 65) 69.2% Tural. 40th IACAC; 2000; Toronto. Presentation LB-10.

38. 0 Expert Consultation Resources • National Clinicians’ Telephone Consultation Service (Warmline): 800-933-3413 • Internet: • http://hivdb.stanford.edu • www.hivresistance.com • Others?

39. 0 The Virtual Phenotype Genotype Access Data HIV RT Protease Genotype & Phenotype Data Virtual Phenotype Wild-type HIV Resistant HIV Illustration by David Spach, MD

40. 0 The Virtual Phenotype Sample report

41. 0 When Should a Resistance Assay be Ordered?

42. Antiretroviral Resistance Testing: Guidelines for Implementation Adapted from DHHS, Antiretroviral Guidelines, October 6, 2005

43. 0 Antiretroviral Therapy: Virologic Failure Medications Started 50 50 Time Illustration by David Spach, MD

44. 0 Antiretroviral Therapy: Failure to Suppress Medications Started 50 50 Time Illustration by David Spach, MD

45. 0 Time Trends in Primary HIV-1 Genotypic Drug Resistance Among Recently Infected Persons % of resistant isolates JAMA. 2002 Jul 10;288(2):181-8.

46. 0 Antiretroviral Resistance Testing: Guidelines for Implementation DHHS. Antiretroviral Guidelines, July 14, 2003, Table 3.

47. Antiretroviral Resistance Testing: Guidelines for Implementation Adapted from DHHS, Antiretroviral Guidelines, October 6, 2005

48. 0 Reversion to Predominant Wild-Type Virus After Discontinuing ART Illustration by David Spach, MD

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50. 0 Drug resistance is Significantly Correlated with Reduction in Replication Capacity Wrin T, et al. 5th International Workshop on HIV Drug Resistance and Treatment Strategies. Scottsdale, AZ: June 2001 (Abstract 24)