1 / 60

HIV Resistance Testing Clinical Implications

HIV Resistance Testing Clinical Implications. Cyril K. Goshima, M.D. Director, AIDS Education Project June, 2009. I am a?. Physician Nurse Pharmacist Dentist Student Patient Other. Resistance Testing will tell us what meds will work for a patient?. True False.

Download Presentation

HIV Resistance Testing Clinical Implications

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.


Presentation Transcript

  1. HIV Resistance TestingClinical Implications Cyril K. Goshima, M.D. Director, AIDS Education Project June, 2009

  2. I am a? • Physician • Nurse • Pharmacist • Dentist • Student • Patient • Other

  3. Resistance Testing will tell us what meds will work for a patient? • True • False

  4. Resistance Testing is recommended before starting HAART. • True • False

  5. Resistance Testing can be done on patients with viral load less than 500. • True • False

  6. The K103N mutation is an NNRTI Mutation • True • False

  7. M184V is a common PI Mutation • True • False

  8. When to Use Resistance Testing • DHHS Guidelines • Recommend testing: acute infection, suboptimal virologic suppression after treatment is initiated, treatment failure, prior to the initiation of therapy. • Consider: chronic infection < 2 yrs. • Which test is not recommended

  9. Resistance Testing • Genotypic Resistance Testing • Phenotypic Resistance Testing • Combined Geno/Pheno • “Virtual Phenotype” Testing • Trofile (HIV Tropism Assay) • PhenoSense Entry (FI Resistance Testing) • Integrase Resistance Testing • Replication Capacity

  10. Requirements for Resistance Testing • Viral Load must be greater than 500 for genotype & phenotype resistance testing, integrase resistance testing • Viral load must be greater than 1000 for Trofile and PhenoSense Entry

  11. Genotypic Resistance Testing • Detects mutations in the HIV genome associated with resistance to specific drugs. • Advantages • Adequate turn-around time (1-2 wks) • Less expensive • Detect mutations that may precede phenotypic resistance • Widely available • More sensitive in detecting mixtures of resistant and wild type viruses

  12. Genotypic Resistance Testing • Disadvantages • Indirect measure of resistance • Relevance of some mutations unclear • Unable to detect minority variants (<20 – 25% of viral sample) • Complex patterns may be difficult to interpret • Genotypic correlates of resistance not well defined for non-B subtypes.

  13. Phenotypic Resistance Testing • Measures the patient’s HIV isolates ability to replicate in the presence of varying concentration of specific drugs. • Advantages • Direct and quantitative measure of resistance • Method can be applied to any agent incl. new where genotypic correlates are unclear • Can assess interactions among mutations • Accurate with non-B HIV subtypes.

  14. Phenotypic Resistance Testing • Disadvantages • Susceptibility cut-offs not standard between assays • Clinical cut-offs not defined for some drugs • Unable to detect minority species • Complex technology • More expensive • Longer turn-around time.

  15. Other Tests • Geno/Phenotype Resistance Testing • e.g. Phenosense GT from Monogram • Both tests are performed • The discordance is reported • “Virtual” Phenotype • Genotyping is performed and the phenotype is determined by looking at all the matched pairs of genotype with phenotype in a data set to give the best estimate

  16. Other Tests • Fusion Inhibitor Resistance Testing • Resistance to Enfuvirtide • Replication Capacity • How weak is your patient’s virus? • Chemokine Receptor Identification • CCR5, CXCR4, or mixed virus present • Integrase Inhibitor Resistance Testing

  17. 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

  18. How We Identify a Mutation • How do we identify a resistance mutation? M 184 V “M” is the “wild type” amino acid “184” is the codon position “V” is the mutant amino acid

  19. How We Identify a Mixture M 184 M/V “M” is the “wild type” amino acid “184” is the codon position “M/V” is the mixture of wild type & mutant amino acid

  20. Definitions for Phenotypic Resistance Testing • IC50 = Concentration of drug required to inhibit replication by 50% • Fold Change = IC50 pt./IC50 reference • Cut Off = Fold change or concentration below which the virus is considered susceptible, above which non-susceptible • Biological Cut Off = Fold change based on variations in clinical samples from treatment naïve individuals.

  21. Definitions for Phenotypic Resistance Testing • Clinical Cut Off = Fold change based on virologic response to ARV in Clinical Trials • Replication Capacity: The ability of a pt’s virus to replicate in the absence of drug

  22. NRTIs

  23. NRTI Mutations • Single point mutation can result in high level resistance e.g. M184V (3TC, FTC), K65R (TDF) • TAMS pattern of mutations e.g. codons 41, 67, 70, 210, 215, 219 (AZT, D4T) • 2 other patterns that are selected for by AZT/DDI & DDI/D4T • Q151M:resist. all NRTI except TDF • T69insertion + 1 or more TAMS @ 41, 210, 215: resist. all NRTI

  24. Common Mutations: NRTIs • TAMS = thymidine analog mutations (aka ZDV mutations): M41L, D67N, K70R, L210W, T215F/Y, K219E/Q • NAMS = nucleoside analog mutations: TAMS plus E44A/D, A62V*, K65R, T69D, T69ins, L74I/V, V75A/I*/M/S/T, V77L*, Y115F, F116Y*, V118I, Q151M, M184I/V *Secondary mutations seen with Q151M

  25. NRTI Signature Mutations *TAMS=Thymidine analog mutations.

  26. NNRTIs

  27. Common Mutations: NNRTIs • Delavirdine (DLV) • L100I, K103N, V106M, Y181C, I; Y188L, G190E/Q • P236L(rare), Y318F • Efavirenz (EFV) • L100I, K103N, V106M, Y181C, I; Y188L, G190A, S, E, Q…; P225H • Nevirapine (NVP) • L100I, K103N, V106A, M; Y181C, I; Y188C, L, H; G190A, E, S, Q…,F227L

  28. NNRTI Multi-Drug Resistance Class Resistance • L100I, K101E or P, K103N or S, V106A or M, Y188C, H, or L, M230L • Resistance to one NNRTI usually confers cross resistance to all other agents (exceptions: 181 and EFV, 190A/S and DLV) • Continued viral replication in the presence of NNRTI results in accumulation of additional resistance mutations • May impact clinical utility of future NNRTIs

  29. NNRTI Novel Mutations • Those exhibiting a > 10 fold change: • K103R and V179D (in combination) • K101P

  30. NNRTI: Etravirine • K103N NNRTI mutation is not associated with resistance to Etravirine • Multiple Resistance Associated Mutations (RAMS) • Scoring of the number of RAMS determines resistance to Etravirine • Similar to Protease Inhibitor Scoring

  31. PIs

  32. PI Resistance • Cross resistance is common • PI mutations are uncommon in boosted PI regimens • Multiclass experienced pts. may have been exposed to unboosted regimens • The number of primary PI mutations may predict the response to therapy e.g. TPV score 0-3 good, 4-7 intermediate, >8 poor or Kaletra

  33. PI Common Mutations

  34. Hypersusceptibility

  35. NRTI Increased Susceptibility

  36. NNRTI Increased Susceptibility

  37. PI Increased Susceptibility

  38. PI Hypersusceptibility • Mutation I50V, selected by LPVr and APV, increased susceptibility to ATV, TPV.

  39. Integrase and Entry Inhibitor Resistance • Resistance has been seen against the Entry Inhibitors and Integrase Inhibitors • There are resistance tests that can be ordered • For CCR5 it may just be a repeat of the Trophile test to determine change to mixed or dual tropic viruses

  40. Case Discussion • Patient CB, 42 y/o, homosexual male • Current Regimen (05/31/06): CBV/TDF/EFV • Past Drugs: CBV/ IDV, CBV/NFV • CD4/VL • Date: 09/08/05 349/8,810 • Date: 03/07/06 192/10,300 • Date: 06/02/06 186/9,400 • Date: 09/18/06 92/6,610 • Date: 10/17/06 /12,000

  41. Case Discussion • NRTI • M184V present (3TC/FTC resist, TDF hs) • Multiple TAMs • No K65R (TDF sens despite 41 & 215 mut) • NNRTI • No significant mutations • PI • 4 TPV assoc mut (intermediate response) • DRV sens

  42. Case Discussion • Was the CBV/TDF/EFV regimen a reasonable one? • There has been no response to this therapy after 3 mos. • What should you do? • Any suggestions on a possible new regimen?

  43. Discordance • Inaccurate genotype interpretation algorithm that does not account for novel or previously unknown mutation effect • Mixtures of wild type and resistant strains. Phenotype underestimates resistance • Variability in phenotypic susceptibility with specific mutations • Believe the genotype. Genotypic change may precede phenotypic resistance.

  44. Clinical Implications • Is there evidence for sequencing of NRTIs? • Should the initial regimen be a boosted PI or a NNRTI? • Is 3TC = FTC as far as resistance is concerned?

  45. Clinical Implications • Try to use at least 2 new potent agents to switch from a failing regimen. • The longer a failing regimen is continued, the more mutations accumulate. If there is no new agent, better to cont. the same regimen unless compelled to do otherwise. • Resistance is relative. 3TC cont. to have virological effect despite M184V mutation. Boosted PIs may have more of a response than an unboosted PI evidenced by a lower fold change.

  46. Clinical Implications • NRTI • TAMs can prevent K65R mutation. K65R is associated with multiple NRTI resistance and TDF resistance. ? Add ZDV to failing regimen • Continue 3TC or FTC despite a M184V mutation (hypersusc. ZDV, TDF, D4T; RC) • NNRTI • DC NNRTI as soon as mutations develop. There is no virological or RC advantage.

More Related