• Share
  • Email
  • Embed
  • Like
  • Save
  • Private Content
D4 HIV Resistance Testing An Update Barnett
 

D4 HIV Resistance Testing An Update Barnett

on

  • 1,700 views

 

Statistics

Views

Total Views
1,700
Views on SlideShare
1,698
Embed Views
2

Actions

Likes
0
Downloads
66
Comments
0

2 Embeds 2

http://www.slideshare.net 1
http://translate.googleusercontent.com 1

Accessibility

Categories

Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment
  • Newly diagnosed patients not necessarily newly infected and those with genotypes were not a random sample but selected for resistance testing by their treating provider which introduces possibility of selection bias in the results. None the less this is the largest and most geographic diverse sample we have in the US population and levels remain high.
  • Transmission of drug resistant virus is becoming a significant public health concern.
  • 8
  • Phenotypic testing directly measures the amount of drug necessary to inhibit or suppress viral replication in vitro . The assays use recombinant virus composed of the person’s viral PR and RT genes inserted into a standard reference strain of virus Drug susceptibility results are reported as the amount of drug required to inhibit virus replication by 50% (50% inhibitory concentration, IC 50 ). The change in susceptibility is measured by comparing the IC value of the person’s virus to that of the reference control. As the person’s virus becomes more resistant, the susceptibility curve shifts to the right. This means that a greater amount of drug is required in order to inhibit the same (50%) amount of viral replication. The proportion of IC 50 of the mutant (patient) virus and the IC 50 of the reference control is the fold resistance. It is a quantitative measurement of change in susceptibility. Examples: Antivirogram  (Virco) and PhenoSense  (ViroLogic) An advantage of testing for resistance with a phenotypic assay is that nearly any drug, even new ones, can be tested The major limitation of a phenotypic assay is how to clinically interpret these results. These are in vitro data of single drugs and they do not account for the numerous complex drug-drug interactions that can occur with combinations of ARVs
  • 2 nd failure; VL 8500; >12 months on latest regimen: d4T, 3TC, NVP Next slide: Types of discordance: Pheno-S Geno-R no mixtures
  • Slide . Virco’s Databases This slide shows the composition of Virco’s databases as of December 2008. These databases are not static and continue to grow using samples from routine clinical testing, clinical trials, and research collaborations. Virco’s correlative database of genotypes and corresponding phenotypes on the same clinical samples is the key to the FC calculations. The Clinical Outcomes Database is the key for determining CCOs. The correlative database includes genotypic data on >373,000 samples and phenotypic data on >93,000 samples. As of December 2008, there were >58,000 correlated GP pairs in the database. The Virtual Phenotype ™ -LM engine can generate a calculated FC in IC 50 for any sequence that is submitted for analysis using a multiple linear regression modeling approach. The Clinical Outcomes Database includes 21,781 patient records, from which 8,849 treatment regimens were used to determine CCO values.
  • Slide : Page 1: Summary Report (1) The Summary Report page includes the following: [Circle Number 1 with rows] Antiretroviral drug classes and the publicly recognized mutations associated with resistance to those drug classes detected in the individual sample. [Green column header: Drugs, first 2 columns] The brand and generic names of the antiretroviral agents are listed in the first two columns. Recently, Intelence ® (etravirine) was added to the report under the NNRTI class. [Circle number 2; green column header: Fold Change; third column] The hall mark of the virco ® TYPE HIV-1 report is the calculated fold change in wild type IC 50 using the Virtual Phenotype™-LM approach. These are found in the third column marked by the circle number 2. [Circle number 3; green column header: Cut-Off; fourth column] The next column, marked by circle number 3, lists the cut-off values (either biological or clinical). [Circle number 4; green column header: Resistance Analysis; fifth column] The resistance analysis based on the calculated fold-change for that sample and cut-off values appears in this column. [Circle number 5; green column header: Clinical Notes; sixth column] The clinical notes column will guide readers to the second page (ie, Detailed Report page) for cases where clinically relevant information can be deduced from the viral genotype that may not be captured fully in the calculated phenotype
  • Slide 22: Correlation Between Predicted and Measured FC Values This slide shows the correlation between measured and predicted FC values for the 7 clinical isolates analyzed. All 16 drugs and viruses were plotted together. The left panel shows the correlation and R value obtained between a randomly selected conventional phenotype measurement and the corresponding predicted FC value for the same isolates. As shown , there is very good correlation with an R=0.93. However, if the mean of multiple conventional phenotype measurements is correlated with the corresponding predicted values (right panel) the correlation is even better (R=0.97) therefore suggesting that the Virtual Phenotype TM approach provides values that are comparable to the mean of multiple conventional phenotype measurements. In other words, the virtual phenotype approach eradicates much of the assay variation intrinsic to the Antivirogram ® assay.
  • 11
  • This slide summarizes NNRTI resistance patterns. There is a clustering of mutations between codons 100 and 106 and codons 181 and 190, with several others occurring in the low 200s. There is broad cross-resistance in these patterns, although subtle differences can be seen. 1 1. D’Aquila RT, Schapiro JM, Brun-Vezinet F, et al. Drug resistance mutations in HIV-1. Top HIV Med . 2002;10:11-15. ´
  • This slide summarizes NNRTI resistance patterns. There is a clustering of mutations between codons 100 and 106 and codons 181 and 190, with several others occurring in the low 200s. There is broad cross-resistance in these patterns, although subtle differences can be seen. 1 1. D’Aquila RT, Schapiro JM, Brun-Vezinet F, et al. Drug resistance mutations in HIV-1. Top HIV Med . 2002;10:11-15. ´
  • This slide summarizes NNRTI resistance patterns. There is a clustering of mutations between codons 100 and 106 and codons 181 and 190, with several others occurring in the low 200s. There is broad cross-resistance in these patterns, although subtle differences can be seen. 1 1. D’Aquila RT, Schapiro JM, Brun-Vezinet F, et al. Drug resistance mutations in HIV-1. Top HIV Med . 2002;10:11-15. ´
  • Many mutations in the protease gene, as shown in this recent representation, 1 confer significant cross-resistance across the entire class. The mutations highlighted in yellow generally develop in patients who receive the individual PIs for the first time with or without nucleosides. Indinavir—46 and 82 Ritonavir—84 and 82 Saquinavir—48 and 90 Nelfinavir—30 and 90, occasionally 88 Amprenavir—50, 54, and 84 Lopinavir/ritonavir—It is unclear which mutation develops first in patients, but the mutations shown all contribute to lopinavir resistance, based on phenotypic and genotypic analyses of clinical isolates. It has been suggested that as few as 4 mutations may be associated with high-level resistance to lopinavir/ritonavir. Although L63P causes no appreciable increase in IC 50 , it is shown for only lopinavir/ritonavir because, along with other mutations, it predicts a lack of viral load response to regimens containing this agent. 1. D’Aquila RT, Schapiro JM, Brun-Vezinet F, et al. Drug resistance mutations in HIV-1. Top HIV Med . 2002;10:11-15. ´
  • Many mutations in the protease gene, as shown in this recent representation, 1 confer significant cross-resistance across the entire class. The mutations highlighted in yellow generally develop in patients who receive the individual PIs for the first time with or without nucleosides. Indinavir—46 and 82 Ritonavir—84 and 82 Saquinavir—48 and 90 Nelfinavir—30 and 90, occasionally 88 Amprenavir—50, 54, and 84 Lopinavir/ritonavir—It is unclear which mutation develops first in patients, but the mutations shown all contribute to lopinavir resistance, based on phenotypic and genotypic analyses of clinical isolates. It has been suggested that as few as 4 mutations may be associated with high-level resistance to lopinavir/ritonavir. Although L63P causes no appreciable increase in IC 50 , it is shown for only lopinavir/ritonavir because, along with other mutations, it predicts a lack of viral load response to regimens containing this agent. 1. D’Aquila RT, Schapiro JM, Brun-Vezinet F, et al. Drug resistance mutations in HIV-1. Top HIV Med . 2002;10:11-15. ´
  • A supportive analysis of POWER 1, 2, and 3, which will be discussed in detail in this presentation, showed that the proportion of patients achieving viral load <50 copies/mL at week 24 was 50%, 22%, and 10% when baseline genotype had 0-2, 3, and 4 or more RAMs, respectively.
  • This slide summarizes NNRTI resistance patterns. There is a clustering of mutations between codons 100 and 106 and codons 181 and 190, with several others occurring in the low 200s. There is broad cross-resistance in these patterns, although subtle differences can be seen. 1 1. D’Aquila RT, Schapiro JM, Brun-Vezinet F, et al. Drug resistance mutations in HIV-1. Top HIV Med . 2002;10:11-15. ´
  • This slide summarizes NNRTI resistance patterns. There is a clustering of mutations between codons 100 and 106 and codons 181 and 190, with several others occurring in the low 200s. There is broad cross-resistance in these patterns, although subtle differences can be seen. 1 1. D’Aquila RT, Schapiro JM, Brun-Vezinet F, et al. Drug resistance mutations in HIV-1. Top HIV Med . 2002;10:11-15. ´
  • This slide summarizes NNRTI resistance patterns. There is a clustering of mutations between codons 100 and 106 and codons 181 and 190, with several others occurring in the low 200s. There is broad cross-resistance in these patterns, although subtle differences can be seen. 1 1. D’Aquila RT, Schapiro JM, Brun-Vezinet F, et al. Drug resistance mutations in HIV-1. Top HIV Med . 2002;10:11-15. ´

D4 HIV Resistance Testing An Update Barnett D4 HIV Resistance Testing An Update Barnett Presentation Transcript

  • HIV Resistance Testing: An Update Ben J. Barnett, MD University of Texas Health Science Center, Houston May 26, 2010
  • Outline
    • Overview of HIV resistance
    • Resistance testing
      • Types of tests available
      • Indications for use
      • Test limitations
    • Interpretation of resistance tests
    • New drugs and new assays
  • Case
    • 54 year old man from Houston, diagnosed HIV positive 12/09
      • Found by “universal screening” in HCHD ER
      • Presenting syndrome: pneumonia
    • PMHx
      • GERD, psoriasis, depression
    • Social Hx
      • HIV risk: MSM
      • Not in relationship now, casual partners in past
  • Initial Evaluation
    • Clinically appeared well except for wasting syndrome and oral thrush
    • Initial laboratory tests
      • Blood counts, liver, kidney tests normal
      • Hepatitis B and C negative
      • CD4 = 16 (5%)
      • HIV viral load 650,000 copies/mL (5.81 log)
  • Some Considerations in starting HAART
    • Patient adherence potential
    • Comorbid conditions that complicate ARV treatment
    • Potential drug interactions
    • Potential adverse effects
    • Convenience
    • Results of genotypic drug resistance testing
      • Do we need to be concerned about resistance in this case?
    Panel on Antiretroviral Guidelines for Adults and Adolescents. Guidelines for the use of antiretroviral agents in HIV-1-infected adults and adolescents. DHHS. December 1, 2009; 1-161.
  • Initial Genotype
  • “ Transmitted” HIV drug resistance
    • Definition
      • The presence of a resistant strain of HIV in a person who has never taken antiretroviral drugs
    • Transmission
      • Drug resistant HIV can be transmitted to a previously HIV negative person by any way HIV is usually transmitted
      • Also can occur by “super-infection” but this is rare
    • The only way to know if someone has been infected with a resistant strain is to do a resistance test on the newly diagnosed person
      • Called “Baseline” resistance testing
  • Baseline Genotypes, Thomas Street clinic 1999 2003-04 Sample size 44 40 CD4 288 (6-904) 274 (9-727) Time since HIV diagnosis (mo.) 17 (0-144) 39 (1-236) NRTI mutations 2 (4.5) 2 (5) NNRTI mutants 1 (2.3) 2 (5) PI 1 (2.3) 1 (2.5) Total mutants 4 (9.1) 5 (12.5)
  • Increasing Primary Drug Resistance: CDC Survey 1. Bennett D, et al. CROI 2002. Abstract 372. 2. Bennett D, et al. CROI 2005. Abstract 674. Prevalence of Drug Resistance, % 1998 [1] (n = 257) 1999 [1] (n = 239) 2000 [1] (n = 299) 2003-2004 [2] (n = 787) Any drug 5.5 8.8 10.7 14.5 NRTI 5.1 7.1 7.7 7.1 NNRTI 0.4 2.1 1.7 8.4 PI 0 0.8 3.0 2.8 ≥ 2 drug class 0 1.3 1.3 3.1
  • Transmitted Drug Resistance in US: Newly Diagnosed
    • 2007 CDC surveillance for transmitted drug resistance (TDR)
      • 10,496 with new HIV Dx
      • 2,480 with genotype
    • TDR detected in 16% of patients with new HIV diagnosis
      • Most common: NNRTI
      • 83% had single mutation
    • No demographic risks factors identified
    • HIV TDR Surveillance Areas (2007)
    Seattle-King County HIV TDR (2007) Percent with TDR 50% K103N Kim D, et al. 17th CROI; San Francisco CA USA; February 16-19, 2010. Abst. 580.
  • What Is HIV Resistance?
    • The ability of HIV to multiply in the presence of suppressive levels of antiretroviral drugs
    • Does not make HIV more pathogenic
      • Perhaps less pathogenic?
  • How Does Resistance Occur?
    • Primary transmission of resistant virus (TDR)
    • Sub-suppressive levels of anti-viral drugs and then natural selection of mutant strains
      • Partial adherence to regimen
      • Sub-optimal dosing of drugs
      • Drug interactions
      • Incomplete absorption in intestinal tract
    Hirsch. JAMA 1998;279:1984.
  • Viral Resistance is the Outcome of Viral Replication, Mutations and Selection Pressure Original Virus Quasispecies Selection Pressure exerted by Drugs HIV RNA Level New Virus Quasispecies Resistant clone Resistant clones Time
  • Resistance Testing
  • Methods to measure resistance
    • Genotype
      • Direct sequencing of viral genes reverse transcriptase and protease , less commonly integrase and envelope
      • Resistance to specific drugs is predicted based on known mutations
      • Requires some knowledge of which mutations affect which drugs
    • Phenotype
      • Grow virus in culture with various amounts of drugs added
      • Direct measure of viral resistance
      • Does not explore the underlying mutations, just their affect on the ability of the drug to stop the virus
  • Genotype reporting
    • Sequencing of various HIV genes and comparing result to reference strain
    • Example: M 184 V in reverse transcriptase
      • 184 refers to amino acid position 184 in enzyme
      • M (methionine) is the “wild-type” amino acid
      • V (valine) is the “mutant” amino acid
    • “ Mixtures” are when both WT and mutant amino acids are detected
      • M 184 M/V
  • Genotypic Assays
    • Relative Advantages
    • Wide Availability
    • Results available in days
    • Less technically demanding
    • Less expensive
    • FDA approved kits
    • Relative Limitations
    • Indirect measure of susceptibility
    • Expert interpretation required
    • Unable to detect linkage of multiple mutations or the overall affect of many mutations
    Hirsch. JAMA 1998;279:1984.
  • Example of Genotype Report
  • Phenotypic Assays
    • Direct measure of viral susceptibility to individual drugs, reported as “fold change”
    Drug Concentration Inhibition of Viral Replication (%) 100 0 IC 50 50 IC 50 Fold Resistance Reviewed in Wilson. AIDS Read 2000;10:469. Wild-type strain Mutant strain
  • Phenotypic Assays
    • Relative Advantages
    • Direct measure of susceptibility
      • Fold change in IC 50
    • May account for effects of multiple mutations at different sites
    • Relative Limitations
    • Restricted availability
    • Results may take 2-3 weeks
    • Technically demanding
    • Clinically significant cut-off values not defined for many drugs
    • More expensive
    Hirsch. JAMA 1998;279:1984.
  • Example of Phenotype Report
  • General Limitations of Resistance Assays
    • Viral load must be at least 500 - 1000 copies
    • Mutations are detected only if mutant virus is at least 10-20% of virus population
      • Viral “mixtures” or minor variants can be missed by genotypes, and not accounted for by phenotypes.
    • Resistance tests are most accurate in assessing the current regimen
      • If resistance has ever been detected, then archived mutations exist
      • If no drug pressure exists, “wild type” virus will often overgrow the mutant strains
  • Discordance between GT and PT
    • Incomplete genotypic algorithms (rules)
      • Novel mutations discovered
      • Improper weighting of mutations in algorithms (both over- and under-weighted)
      • Non-B subtype resistance patterns
    • Mixtures are present (some wild type, some mutant)
    • Suppressive mutations or “re-sensitization” caused by specific mutations (e.g. 184V)
  • Discordance due to mixtures Result: Phenotype reads “sensitive” because of presence of wild-type virus in the mixture But Genotype predicts “resistant” due to presence of mutant virus in the mixture
  • Incomplete Rules may lead to discordance Result: Genotype predicts resistance based on rules-based algorithm, but Phenotype reads “sensitive” due to interactions of complex mutation patterns PT GT NET
  • “ Virtual” Phenotype
  • 0
  • 0
  •  
  • DHHS Guidelines 12/09
    • Recommended in acute HIV infection
    • In chronic infection, recommended for all patients on entry into care, regardless of treatment plan
      • If therapy deferred, consider retesting on treatment initiation
    • Recommended to assist in selecting active drugs for patients with viral failure and HIV RNA > 1000 copies
      • Consider for viral load > 500 copies
    Panel on Antiretroviral Guidelines for Adults and Adolescents. Guidelines for the use of antiretroviral agents in HIV-1-infected adults and adolescents. DHHS. December 1, 2009; 1-161.
  • DHHS Guidelines 12/09
    • Should be performed when managing suboptimal viral load reduction
    • In the setting of viral failure, testing should be done while the patient is on therapy, or within 4 weeks of stopping
    • Should be done for all pregnant women prior to therapy, or for those entering pregnancy with a detectable HIV viral load on therapy
  • Which Resistance Test When? (DHHS)
    • Genotype preferred due to faster result, lower cost and enhances sensitivity for detecting “mixtures”
      • In anti-retroviral naïve patients
      • In patients with sub-optimal viral response on therapy
      • Virologic failure on a first or second regimen
    • Phenotype
      • “ Addition of phenotypic testing to genotypic testing is generally preferred for persons with known or suspected complex drug resistance mutation patterns, particularly to protease inhibitors”
    • Virtual Phenotype (not specifically stated in DHHS)
      • As a substitute when actual phenotype not available
  • Interpretation of Resistance Tests
  • Genotype interpretation
    • Memorize common mutations
    • Pattern recognition
    • Most assays come with an “expert” interpretation included, but be careful
      • http://hivdb.stanford.edu is a reliable resource
    • Limited by complex interactions of multiple mutations, especially for protease inhibitors
    • Newer drugs come with “prediction rules”
  • Mutations in Reverse Transcriptase Nucleoside Mutation Sites Non-Nucleoside Mutation Sites
  • Mutations Selected by nRTIs Abacavir Didanosine Emtricitabine Lamivudine Stavudine Tenofovir Zidovudine
  • Mutations Selected by nRTIs Multi-nRTI Resistance: 69 Insertion Complex (affects all nRTIs currently approved by the US FDA) Multi-nRTI Resistance: 151 Complex (affects all nRTIs currently approved by the US FDA except tenofovir) Multi-nRTI Resistance: Thymidine Analogue-Associated Mutations (TAMs; affect all nRTIs currently approved by the US FDA)
  • Major nRTI mutations
    • M184V
      • Resistance to lamivudine and emtricitabine
      • Some resistance to didanosine and abacavir
      • May restore some activity to zidovudine and tenofovir
    • K65R
      • Broad resistance to all nRTI except zidovudine
    • L74V
      • Resistance to abacavir and didanosine
    • Thymidine analogue mutations (TAMS)
      • Affect all nRTI to a variable degree
    • Even with nRTI resistance, most nRTI retain some activity and may help suppress virus with other agents
  • Mutations Selected by NNRTIs Efavirenz Etravirine Nevirapine
  • Major NNRTI mutations
    • K103N
      • Most common NNRTI mutation
      • High level resistance to efavirenz and nevirapine but not etravirine
    • Y181C
      • High level resistance to nevirapine and intermediate efavirenz resistance
      • Some etravirine resistance, but provides a mutational foundation for development of higher levels of resistance
    • Broad cross resistance with nevirapine and efavirenz with low genetic barriers
      • Single mutation can eliminate activity of EFV or NVP
      • No impact of NNRTI mutations on viral replication ability, so continued use of NNRTI in the face of resistance adds nothing
  • Resistance Mutations in Protease 82 84 90 48 54 30
  • Mutations Selected by PIs Atazanavir +/-ritonavir Darunavir/ ritonavir Fosamprenavir/ ritonavir Indinavir/ ritonavir Lopinavir/ ritonavir
  • Mutations Selected by PIs (cont) Nelfinavir Saquinavir/ ritonavir Tipranavir /ritonavir
  • Major protease mutations
    • “ Signature” mutations for non-boosted PI
      • D30N: nelfinavir
      • I50L: atazanavir
      • I50V: fosamprenavir
    • Boosted PIs usually do not select for mutations if used as first PI with nucleosides
      • Otherwise have broad general cross resistance
    • Gets very complicated very quickly
  • Newer protease “mutation score”
    • Daruavir is a newer PI with activity against resistant HIV, approved June 2006
    • POWER studies showed patients treated with darunavir and optimized background meds had VL < 50 copies/mL greater than for comparator PIs
    • Response to darunavir was found to be dependent on 11 PI mutations at baseline
  • Darunavir response by DRV score A wrinkle: The common PI mutation at 82A may actually have a positive effect on viral response to darunavir 0-2 mutations 3 mutations  4 mutations 50% 22% 10% Patients (%) with HIV-1 RNA <50 copies/mL at Week 24 Number of Darunavir mutations at baseline
  • Interpreting Phenotypes Cutoffs differ for each drug Probability of response Fold Change “ Zone of Intermediate Response” Lower clinical cutoff Response is significantly reduced Upper clinical cutoff Response is unlikely
  • Newer drugs and assays
    • Etravirine
      • “ Second generation” NNRTI
    • Raltegravir
      • Integrase inhibitor
    • Entry inhibitors
      • Enfuvirtide
      • Maraviroc
  • Etravirine
    • Second generation NNRTI
      • FDA approved January 2008
    • May retain activity against HIV with NNRTI resistance from NVP or EVF
      • K103N alone does not affect etravirine
    • Has a higher “genetic barrier” than other NNRTI, and therefore a “mutation score” has been developed similar to PIs
  • Mutations Selected by NNRTIs Efavirenz Etravirine Nevirapine
  • Impact of BL Resistance in DUET: The Number of Baseline ETV RAMs Correlated with the Virologic Response (<50 copies/mL) TTCA0066-07332-29UN Number of ETV RAMs present at baseline Placebo + OBT (n=414) ETV + OBT (n=406) 0 2 3  4 1 7/28 3/18 25 17 25 41 6/24 13/32 25 58 17/68 37/64 38 59/157 73/121 60 64/147 121/161 75 44 Patients with confirmed viral load <50 HIV-1 RNA copies/mL (%) 0 20 40 60 80 Vingerhoets J , et al. 11th EACS 2007. Abstract P7.3/05 7/28 3/18 6/24 13/32 17/68 37/64 59/157 73/121 64/147 121/161 3 or more ETV associated mutations give a reduced response to ETV
  • Updated List of INTELENCE RAMs: Weight Factors for 2008 INTELENCE RAMs TTCA0100-08173-8UN a Median (Q1–Q3) FC for all isolates was 3.0 (1.1–9.3); b V179F was never present as single INTELENCE RAM (always with Y181C) Median Q1–Q3 n Y181I 1.5 42.0 23.2–129.7 34 12.5 High 3 Y181V 0.9 10.4 3.9–60.6 28 17.4 High 3 K101P 2.6 22.3 5.6 – 42.9 65 6.2 High 2.5 L100I 8.4 6.7 2.7–17 264 1.8 Medium 2.5 Y181C 32.0 4.4 2.1 – 11.6 552 3.9 Medium 2.5 M230L 1.1 4.3 2.7 – 10.5 20 3.4 High 2.5 E138A 2.5 2.9 1.4 – 10.6 44 2.0 Medium 1.5 V106I 4.4 2.6 1.4 – 5.2 63 NA Low 1.5 G190S 3.7 0.8 0.6 – 1.7 32 0.2 Low 1.5 V179F b 0.7 – – 0 0.1 Medium 1.5 V90I 6.8 2.0 0.8 – 3.6 97 1.5 Low 1 V179D 2.1 1.7 1.0 – 4.7 33 2.6 Low 1 K101E 9.9 1.5 0.8 – 2.5 24 1.7 Low 1 K101H 2.2 1.1 0.6 – 2.8 8 1.3 Low 1 A98G 9.5 1.0 0.5 – 1.9 127 2.5 Low 1 V179T 0.6 0.9 0.7 – 1.2 2 0.8 Low 1 G190A 23.3 0.8 0.5 – 1.5 226 0.8 Low 1 Effect on FC in linear model Weight factor INTELENCE FC in the subset of HIV-1 clinical isolates with 1 INTELENCE RAM (n=1,619), regardless of the presence of other NRTI or NNRTI RAMs a Prevalence (%) in the panel of 4,248 HIV-1 clinical isolates Mutation INTELENCE FC in a single SDM Vingerhoets J, et al. IHDRW 2008; Abstract 24 Mutation not in table is scored 0; RAMs, resistance-associated mutations; FC, fold change
  • Raltegravir
    • First HIV “integrase” inhibitor
      • FDA approved October 2007
    • Should be very little transmitted resistance as it is the first of a new class of agents
    • Genotype assays for integrase are now available, but clinical significance undefined
    • Phenotypic assay for raltegravir resistance also now available
  • Mutations in the Integrase Gene Associated With Resistance to Integrase Inhibitors Raltegravir
  • Raltegravir resistance
    • Raltegravir failure is associated with integrase mutations in at least 3 genetic pathways defined by at least 2 mutations
      • Major mutation at 148, 155, or 143
      • One or more additional minor mutations
    • Most common and highest degree of resistance is Q148H plus G140S
    • Continued raltegravir in the presence of viral failure and resistance is not recommended
  • HIV-1 Entry Inhibitors Virus core Enfuvirtide TNX-355 Maraviroc
  • Enfuvirtide
    • First HIV “fusion” inhibitor
      • FDA approved March 2003
    • Patients who have not taken it before generally have virus susceptible to it
    • Mutations in “envelope” gene region gp41 have been seen in viruses exposed to ENF, but these mutations do not easily predict loss of anti-viral effect
    • Phenotypic assay is available but its clinical utility is not well defined
  • Mutations in the Envelope Gene Associated With Resistance to Entry Inhibitors Enfuvirtide Maraviroc
  • Enfuvirtide PT Susceptibility During TORO 1 & 2 Biological Cutoff 0.001 0.01 0.1 1.0 10.0 Normalized IC50 (  g/mL) ENF Naive ENF Failure 0.001 0.01 0.1 1.0 10.0
  • Maraviroc
    • First HIV “CCR5 inhibitor”
      • FDA approved in August 2007
    • Only effective against strains that use the CCR5 co-receptor for cell entry
      • Little effect on viruses which use CXCR4 co-receptor, or which use both
    • Activity of maraviroc is tested by co-receptor “tropism” test, which is not a resistance test
  • HIV tropism defined
    • R5 HIV: uses only CCR5 co-receptor
    • X4 HIV: uses only CXCR4 co-receptor
    • Dual-tropic HIV: uses either co-receptor
    • Mixed tropism: some R5 and some X4 virus present in the same sample
    • Maraviroc binds to the co-receptor, which is a HUMAN protein that cannot “mutate” in a given individual patient
  • Maraviroc resistance??
    • Emergence of X4 Virus
      • Switch of virus tropism from R5 to X4: unusual
      • Outgrowth of Dual/Mixed or X4 virus from pre-existing minority population present at levels too low to be detected by current tropism assays
    • Virus remains R5, with true resistance
      • Mutations in HIV gp120 that allow HIV to bind to CCR5 even though maraviroc is also bound
      • Most mutations are in the V3 loop, but no consensus yet on the specific mutations required
  • DHHS on New Classes
    • The clinical utility of testing for integrase and fusion inhibitor resistance is limited
      • Lack of availability of second-line drugs in class
    • In patients failing integrase or fusion inhibitor treatment, resistance testing may be helpful to determine whether to include these drugs in subsequent regimens, or in preparation for newer drugs in these classes
    • In naïve patients, there is no general recommendation to test integrase, but this may become more common in the future
      • As yet, no documented cases of integrase TDR
  • Management of a treatment experienced patient
    • The goal of treatment for patients with prior drug exposure and resistance is to re-establish maximal viral suppression (<50 copies/mL)
    • Treatment history and past and current resistance tests should be used to identify fully active agents for the new regimen
      • This is complex, and expert advice is critical
    Panel on Antiretroviral Guidelines for Adults and Adolescents. Guidelines for the use of antiretroviral agents in HIV-1-infected adults and adolescents. DHHS. December 1, 2009; 1-161.
  • Management of a treatment experienced patient
    • Adding at least two (preferably three) fully active agents to an optimized background ARV regimen can provide significant activity
    • For some highly treatment experienced patients, maximal viral suppression is not possible. In this case, ARV therapy should be continued with regimens designed to minimize toxicity, preserve CD4 cell counts and avoid clinical progression
      • Expert advice is again essential
  • Case Follow up
    • Patient was started on anti-retrovirals BEFORE results of GT were returned
      • Baseline VL was 650,000
      • Initial regimen was 2 nRTI and boosted-PI
    • Resistance tests repeated
      • Genotype, virtual phenotype, tropsim test
    DATE Viral Load CD4 Meds 1/14/10 650,000 16 Naïve 2/5/10 3,230 2nRTI, PI/r 2/22/10 595,000 175 Same
  • Resistance tests for Case
  • Case follow up
    • Regimen was then changed to
      • Tenofovir/emtricitabine
      • Darunavir/r 600/100 mg BID (resistance dose)
      • Added raltegravir
      • Added etravirine
    DATE Viral Load CD4 Meds 1/14/10 650,000 16 Naïve 2/5/10 3,230 2nRTI, PI/r 2/22/10 595,000 175 Same 4/14/10 1,150 193 Above, one month
  • Conclusions
    • Resistance can occur in patients new to ARV
    • Resistance testing can be used to optimize an antiretroviral regimen
      • Must use in context of treatment history and results of all prior resistance tests
      • Goal for all HIV infected patients is HIV RNA < 50
    • Factors other than resistance may cause regimen failure
    • Resistance testing is reliable and cost-effective but must be interpreted in context and may require expert advice
  • More information
    • IAS-USA mutation cards and notes
      • http://www.iasusa.org
    • Update of the Drug Resistance Mutations in HIV-1: December 2009
      • Topics HIV Med. 17(5):138-145.
    • Stanford resistance database
      • http://hivdb.stanford.edu
    • DHHS guidelines for HIV
      • http://www.aidsinfo.nih.gov/guidelines/