HIV Drug Resistance Somnuek Sungkanuparph, M.D. Associate Professor Division of Infectious Diseases Department of Medicine Faculty of Medicine Ramathibodi Hospital Mahidol University Adjunct Professor Washington University School of Medicine
Goal of Antiretroviral Therapy Relative Levels HIV Viral load <50 copies/ml at 4-6 month CD4 Limit of Detection HAART Years After HIV Infection
Evolution of HAART Survival from age 25 years 1 Population controls Probability of Survival 0.75 0.5 0.25 Early HAART (1997-1999) Late HAART (2000-2005) 0 Pre-HAART (1995-1996) 25 30 35 40 45 50 55 60 65 70 Age, years Lohse N, et al. Ann Intern Med 2007;146:87-95
Can we achieve that goal? Yes. May be. No. What are limitations? 1. Budget 2. Treatment failure 3. Adverse drug effects 4. Opportunistic infections & cancers
How Does Resistance Develop? Wrong Dose Host Genetics Poor Potency Social/Personal Issues Regimen Issues Toxicities Poor Adherence Poor Absorption Insufficient Drug Level Rapid Clearance Poor Activation Viral Replication in the Presence of Drug Drug Interactions Resistant Virus Transmission 5
Adherence and Drug Resistance
Pathogenesis of HIV Drug Resistance K103N L63P Wild-type HIV HIV with mutations Drug resistant HIV Drug susceptible HIV HAART Suboptimal HAART PREDOMINANT WILD-TYPE HIV EARLY EMERGENCE OF RESISTANT HIV PREDOMINANT RESISTANT HIV Baseline 6 Months 9 Months 7 Continuation of a failing ART regimen after early resistance has developed selects for expansion of resistance
Definition of Drug Resistance Changes in the viral genetic sequence (mutations) that decrease drug activity. Commonly reduce drug susceptibility compared with the susceptibility of wild-type viruses Mediated by: Changes in the molecular target of therapy Changes in other viral proteins that indirectly interfere with a drug s activity 8
HIV Drug Resistance: Implication Resistance mutations may exist before drug exposure and may emerge quickly after drug is introduced. Drugs which develop high level resistance with a single mutation are at greatest risk e.g., 3TC, NNRTIs (nevirapine, efavirenz) Resistance to agents which require multiple mutations will evolve more slowly (e.g. PIs) Partially suppressive regimens will inevitably lead to emergence of resistance A high genetic barrier needs to be set to prevent resistance
Genetic Barrier to Drug Resistance Example: GB = 4 VIRAL REPLICATION Remaining 4 3 2 1 0 Mutations Required For Resistance Mutations Already Selected 0 1 2 3 4 10 Concept Dr. J. Shapiro
Genetic Barrier to Drug Resistance Example: GB = 1 VIRAL REPLICATION Remaining 1 0 Mutations Required For Resistance Mutations Already Selected 0 1 11 Concept Dr. J. Shapiro
Post SD-NVP Resistance Mutations Emergence of drug resistance after intrapartum SD-NVP is more common than previously reported Resistance rate at least 65% with real-time PCR assay Rates of 20%-44% for less-sensitive sequence analysis K103N and Y181C are the most common mutations.
Acquisition of NVP Resistance in Mothers after SD-NVP for PMTCT DETECTABLE RESISTANCE (%) sd-nvp alone ZDV + sd-nvp >2 ARV + sd-nvp 2 Doses TIME: 6 wk CLADE: B 6 wk E,B 4 wk E,B 6 wk A,D 7 wk B,G,F 4 wk CRF,A 7 wk C 8 wk E,B 4 6 wk C 2 wk C McIntyre J, et al. 12th CROI, Boston 2005, #8. 13
Potential Concern When Stopping Drugs With Different Half-liveslives Last Dose Day 1 Day 2+ Drug Concentration Zone of potential replication MONOTHERAPY IC 90 IC 50 0 12 24 36 48 Time (Hours) S. Taylor et al. 11th CROI Abs 131
Stopping Drugs with Different Half-lives: lives: PI vs. NNRTI NVP spends more time in the zone of potential replication and therefore exerts selective pressure for longer With a low genetic barrier, resistance to NVP develops relatively quickly Last or Single Dose LPV/r Drug Concentration Nevirapine Zone of Potential Replication IC 90 IC 50 0 Days 15 Adapted from Taylor S, et al. 11th CROI 2004, #131.
Genetic Barrier and Transmitted Resistance IMPACT OF SINGLE TRANSMITTED MUTATION MUTATIONS REQUIRED FOR RESISTANCE BOOSTED PI NNRTI Activity: Retained Lost Remaining GB: Substantial None Protection of other drugs in regimen: Mostly Retained Lost 16 Concept Dr. J. Schapiro
How rapidly is resistance selected? The rate depends on many factors. A potent ART regimen will delay the development of resistance By contrast, an ineffective regimen or inadequate adherence will lead to rapid selection of resistant mutants The replication rate of a resistant variant also influences the rate of its emergence eg, Y181C, and K103N in weeks, high levels of resistance to AZT and PIs in months
Resistance is Irreversible Once selected by drug pressure, resistance mutations remain in the viral population Resistance assays commonly detect mutations only if present in >20% of viral population When drug pressure is discontinued, mutations may drop below 20% and not be detected by standard assays Attempts to recycle the drug (or cross-resistant drugs) may result in rapid reappearance (>20%) 18 Johnson et al. XV int. HIV Drug Resistance Workshop, 2006, #69. Palmer et al. PNAS 2006.
PI Resistance
NRTI and NNRTI Resistance
From Codon to Amino Acid: Designations for Mutations Viral DNA is a code for RNA, which in turn codes for protein Each codon encodes a particular amino acid Changes in the codon may result in the incorporation of a different amino acid (mutation) This may be a mechanism for the HIV virus to escape the actions of an ARV drug Codon AAA GAC AGT Mutation AAA AAC AGT Lys Asp Ser Lys Asn Ser 21 Adapted from Winters. Reviewed in Wilson, AIDS Read 2000.
How We Identify a Mutation How do we identify a resistance mutation? M 184 M M is the wild type amino acid 184 is the codon position How do we identify a resistance mutation? M 184 V 22 V is the mutant amino acid
How Can I Know (and Update) the Drug Resistance Mutations? Updates available at www.iasusa.org.
RESISTANCE REPORT Resistance-associated RT Mutations: M184V, Y181C Nucleoside and Nucleotide RT Inhibitors Resistance Interpretation zidovudine (AZT) didanosine (ddi) lamivudine (3TC)/emtricitabine (FTC) stavudine (d4t) abacavir (ABC) tenofovir (TDF) Resistance Non-nucleoside RT Inhibitors Resistance Interpretation nevirapine (NVP) efavirenz (EFV) Possible Resistance Resistance
RESISTANCE REPORT Resistance-associated PR Mutations: G16E*, K20R*, M36I*, L63P, H69K*, L89M, I93L* Protease Inhibitors Resistance Interpretation saquinavir + ritonavir (SQV/r) indinavir (IDV) IDV/r amprenavir (APV)/fosamprenavir (FPV) APV/r or FPV/r lopinavir + ritonavir (LPV/r) atazanavir (ATV) ATV/r tipranavir + ritonavir (TPV/r) darunavir + ritonavir (DRV/r) Possible Resistance Possible Resistance
RESISTANCE REPORT Mutation Details for Nucleoside and Nucleotide RT Inhibitors: lamivudine (3TC)/ Emtricitabine (FTC) M184V indicate Resistance to lamivudine (3TC)/ Emtricitabine (FTC) Mutation Details for Non-nucleoside RT Inhibitors: nevirapine (NVP) Y181C indicate Resistance to nevirapine (NVP) efavirenz (ATV) Y181C indicate Resistance to efavirenz (ATV) Mutation Details for Protease Inhibitors: atazanavir (ATV) G16E, K20R, and M36I indicate Possible Resistance to ATV tipranavir + ritonavir (TPV/r) K20R, M36I, and H69K indicate Possible Resistance to TPV/r Evidence Basis Ia Evidence Basis IIa IIb Evidence Basis IIa IIb
RESISTANCE REPORT Evidence Basis I rule based upon 2 or more large, independent virological response studies and supporting in vitro data. II rule based upon in vitro data and preliminary virological response data. III rule based upon in vitro data. No virological response data. IV rule based upon extrapolation of data by the Consensus Panel. Evidence Basis Reference Qualifier a in peer-review journal b at a recognized scientific conference
When to Use Resistance Testing (1) IAS-USA [1] DHHS [2] European [3] Thai [4] Primary/acute Recommend Recommend Recommend Post-exposure prophylaxis Recommend Chronic and treatment naïve Consider* Recommend Strongly consider* Failure Recommend Recommend Recommend Recommend Pregnancy Recommend Recommend* Pediatric Recommend *Especially if exposure to someone receiving antiretroviral drugs is likely or if prevalence of drug resistance in untreated patients 5% (European: 10%). 1. Hirsch MS, et al. Clin Infect Dis 2008. 2. Available at: http://www.aidsinfo.nih.gov. 3. Vandamme AM, et al. Antivir Ther. 2004. 4. Sungkanuparph S, et al. J Med Assoc Thai 2008.
Thai HIV Guidelines 2008: When to do genotypic resistance testing? Recommended: - Virological failure during HAART - Suboptimal viral suppression after initiating ART Considered: - HIV infected pregnant women - Acute HIV infection in an area with high prevalence of resistant virus transmission Sungkanuparph S, et al. J Med Assoc Thai 2008.
Resistance Mutations After National AIDS Program in Thailand 1,880 patients experiencing treatment failure, during 2000 2005 Sukasem C, et al.
Thai HIV Guidelines 2008: Recommended First ART Regimens d4t + 3TC + NVP (GPO VIR S ) or AZT + 3TC + NVP (GPO VIR Z ) d4t or AZT + 3TC + EFV Rash, CNS AE d4t or AZT + 3TC + IDV/RTV d4t or AZT + 3TC + LPV/RTV Hyperlipidemia d4t or AZT + 3TC + ATV/RTV Sungkanuparph S, et al. J Med Assoc Thai 2008.
Common Resistance Pattern after Failing d4t/ T/3TC/NVP: TC/NVP: Case 1 Resistance-associated RT Mutations: Y181C, M184V, Y188L HIV RNA 9600 copies/ml Nucleoside and Nucleotide RT Inhibitors Resistance Interpretation zidovudine (AZT) didanosine (ddi) lamivudine (3TC)/emtricitabine (FTC) stavudine (d4t) abacavir (ABC) tenofovir (TDF) Resistance Non-nucleoside RT Inhibitors Resistance Interpretation nevirapine (NVP) efavirenz (EFV) Resistance Resistance
Common Resistance Pattern after Failing d4t/ T/3TC/NVP: TC/NVP: Case 2 Resistance-associated RT Mutations: Y181C HIV RNA 3200 copies/ml Nucleoside and Nucleotide RT Inhibitors Resistance Interpretation zidovudine (AZT) didanosine (ddi) lamivudine (3TC)/emtricitabine (FTC) stavudine (d4t) abacavir (ABC) tenofovir (TDF) Non-nucleoside RT Inhibitors Resistance Interpretation nevirapine (NVP) efavirenz (EFV) Resistance Resistance
Common Resistance Pattern after Failing d4t/ T/3TC/NVP: TC/NVP: Case 3 Resistance-associated RT Mutations: M184V HIV RNA 4100 copies/ml Nucleoside and Nucleotide RT Inhibitors Resistance Interpretation zidovudine (AZT) didanosine (ddi) lamivudine (3TC)/emtricitabine (FTC) stavudine (d4t) abacavir (ABC) tenofovir (TDF) Resistance Non-nucleoside RT Inhibitors Resistance Interpretation nevirapine (NVP) efavirenz (EFV)
Common Resistance Pattern after Failing d4t/ T/3TC/NVP: TC/NVP: Case 4 HIV RNA 23,600 copies/ml Resistance-associated RT Mutations: K103N, Y181C, M184V, T215Y Nucleoside and Nucleotide RT Inhibitors Resistance Interpretation zidovudine (AZT) didanosine (ddi) lamivudine (3TC)/emtricitabine (FTC) stavudine (d4t) abacavir (ABC) tenofovir (TDF) Possible Resistance Resistance Possible Resistance Possible Resistance Non-nucleoside RT Inhibitors Resistance Interpretation nevirapine (NVP) efavirenz (EFV) Resistance Resistance
Common Resistance Pattern after Failing d4t/ T/3TC/NVP: TC/NVP: Case 5 HIV RNA 51,700 copies/ml Resistance-associated RT Mutations: M41L, A98G, Y181C, M184V, Y188L, T215F Nucleoside and Nucleotide RT Inhibitors zidovudine (AZT) didanosine (ddi) lamivudine (3TC)/emtricitabine (FTC) stavudine (d4t) abacavir (ABC) tenofovir (TDF) Non-nucleoside RT Inhibitors nevirapine (NVP) efavirenz (EFV) Resistance Interpretation Possible Resistance Resistance Possible Resistance Resistance Possible Resistance Resistance Interpretation Resistance Resistance
Common Resistance Pattern after Failing d4t/ T/3TC/NVP: TC/NVP: Case 6 Resistance-associated RT Mutations: K103N, F116Y, Q151M HIV RNA 233,000 copies/ml Nucleoside and Nucleotide RT Inhibitors zidovudine (AZT) didanosine (ddi) lamivudine (3TC)/emtricitabine (FTC) stavudine (d4t) abacavir (ABC) tenofovir (TDF) Non-nucleoside RT Inhibitors nevirapine (NVP) efavirenz (EFV) Resistance Interpretation Resistance Resistance Resistance Resistance Resistance Possible Resistance Resistance Interpretation Resistance Resistance
Common Resistance Pattern after Failing d4t/ T/3TC/NVP: TC/NVP: Case 7 HIV RNA 121,700 copies/ml Resistance-associated RT Mutations: M41L, K65R, D67N, Y181C, M184V, Y188L, L210W, T215Y Nucleoside and Nucleotide RT Inhibitors zidovudine (AZT) didanosine (ddi) lamivudine (3TC)/emtricitabine (FTC) stavudine (d4t) abacavir (ABC) tenofovir (TDF) Non-nucleoside RT Inhibitors nevirapine (NVP) efavirenz (EFV) Resistance Interpretation Resistance Resistance Resistance Resistance Resistance Resistance Resistance Interpretation Resistance Resistance
HIV Drug Resistance Mutations in Patients Failing d4t/ T/3TC/NVPTC/NVP 100% 90% 96% 92% 95% 80% 70% 60% 50% 40% 37% 30% 20% 10% 0% NRTImutation 6% 8% 0 TAMs K65R Q151M M184V/I NNRTImutation PImutation Sungkanuparph S, et al. CID 2007.
Resistance mutations conferring to drug resistance 100 90 80 70 60 Drug Resistance in Patients Failing d4t/ T/3TC/NVPTC/NVP 50 40 30 20 resistance possible resistance 10 0 AZT d4t ddi 3TC ABC TDF NVP EFV Antiretroviral drugs Sungkanuparph S, et al. CID 2007.
Drug Resistance Mutations in Patients Failing d4t/3tc/nvp Detection at HIV RNA <4 log vs. >4 log Sungkanuparph S, et al.
TAMs and HIV RNA Level at Failure Detection Number of TAMs and HIV RNA levels at failure. a trend toward higher HIV-1 RNA level in patients who had 4 TAMs compared to that in patients without TAMs HIV RNA at virological failure (log copies/ml) 6.00 5.50 5.00 4.50 4.00 3.50 3.00 P = 0.418 P = 0.661 P = 0.743 P = 0.077 46 31 72 (p=0.077). 0 1 2 3 4 or more Number of TAMs Sungkanuparph S, et al. CID 2007.
HIV Drug Resistance and Time to Detection of Failure VIROLOGIC FAILURE IMMUNOLOGIC FAILURE CLINICAL FAILURE CD4 COUNT VIRAL LOAD HIV DRUG RESISTANCE 53 Murri R, et al. JAIDS. 2006. Sungkanuparph S, et al. CID 2007. Pillay D, et al. 14th CROI 2007, #642. Losina E et al, 15th CROI 2008, #823
Clinical Failure is Just the Tip of the Iceberg Clinical Failure Immunologic Failure CLINICAL EVALUATION only CD4 monitoring Virologic Failure HIV RNA monitoring 54 Murri R, et al. JAIDS. 2006;41:23-30. Sungkanuparph S, et al. CID 2007. Losina E et al, 15th CROI 2008, #823
Failure from 1st Regimen NRTI NNRTI NRTI PI new NNRTI new Class
Failure from 2nd Regimen NRTI NNRTI PI new PI new NNRTI new Class
When Change of ART Regimen in Treatment Failure is Delayed Accumulates drug resistance mutations More damage to immune system Poorer clinical outcome Higher cost of the effective second regimens More toxicity exposure?
Thai HIV Guidelines 2008: Changing ART Regimen after Failure Determine failure with virologic failure only Clarify goals: undetectable vs. maximal virological suppression Review treatment history Assess adherence Accessible HIV genotype resistance testing Identify treatment options Channels for consulting experts Sungkanuparph S, et al. J Med Assoc Thai 2008.
Thai HIV Guideline 2008: Recommended Second ART Regimens 2 NRTIs PIs that susceptible indicated by genotypic test LPV/rtv IDV/rtv ATV/rtv SQV/rtv Sungkanuparph S, et al. J Med Assoc Thai 2008.
Effective Second-line ART Initiation of effective secondline ART Second-line therapy with a potent, combination ART reduces risk of resistant virus growth
Challenges Often Encountered When Treating Patients After Several Regimen Failures Drug resistance to multiple classes and decreased options for the future Accumulative toxicity on multiple drugs Poor adherence on multiple drugs Co-morbidities (if CD4 count low) Multiple drug-drug interactions 61
HIV Drug Resistance and Treatment Outcomes of ART Naïve patient Experienced patient Highly Experienced patient Success Failure Success Failure Success Failure
Challenges of HIV Treatment in Thailand A huge number of patients who need and will soon need ART Number of patients who need 2 nd ART is increasing Catch up of HIV education with rapid ART scale-up Prevention of HIV drug resistance in all levels is needed Balancing of better lab monitoring (e.g. VL, genotype) and more lab facilities Can we treat earlier (e.g. CD4,350) when we have no third-line in free ART programs?
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