Introduc)on to An)retroviral Drug Resistance

Transcription

1 Introduc)on to An)retroviral Drug Resistance Harry Lampiris, MD Professor of Clinical Medicine, UCSF Ac;ng Chief, Infec;ous Disease Sec;on San Francisco VA Medical Center December 7, 2012 HIV Drug Resistance Overview Resistance is due to muta;ons in the HIV virus which make it less suscep;ble to an;retroviral drugs which contributes to treatment failure Muta;ons can impair viral fitness (ability of virus to replicate in vitro) Muta;ons can make the virus less damaging to the immune system (in pa;ents) Muta;ons leading to drug resistance can occur due to drug selec;on in a pa;ent or can be acquired (primary drug resistance) In pa;ents receiving ARVs, incomplete virologic suppression leads to muta;ons associated with resistance due to Par;al adherence to regimen Sub- op;mal dosing of drugs Drug interac;ons Incomplete absorp;on in intes;nal tract Hirsch M, et al. Clin Infect Dis. 2008;47: Goals of Therapy for Treatment- Experienced Pa)ents US DHHS Guidelines, October 10, 2006 [1] : In those with prior treatment and drug resistance, the goal is to resuppress HIV RNA levels maximally and prevent further selec;on of resistance muta;ons, if possible IAS- USA Guidelines, August 2006 [2] : Trials with newer an;retroviral agents have shown that it is possible to achieve plasma HIV- 1 RNA levels below 50 copies/ ml even in highly treatment experienced pa;ents 1. DHHS Guidelines for Adults and Adolescents, October 10, Hammer SM, et al. JAMA. 2006;296: HIV Drug Resistance: How It Develops Viral load Treatment begins Hirsch M, JAMA 1998; 279:1984 Incomplete suppression Inadequate potency Inadequate drug levels Inadequate adherence Pre-existing resistance Time Drug-susceptible quasispecies Drug-resistant quasispecies Selection of resistant quasispecies 1

2 We can measure resistance to all available drugs except maraviroc in 2012 NRTIs Abacavir Didanosine Emtricitabine Lamivudine Stavudine Tenofovir Zidovudine NNRTIs Efavirenz Nevirapine Etravirine Rilpivirine Protease Inhibitors Atazanavir Darunavir Fosamprenavir Indinavir Lopinavir Nelfinavir Ritonavir Saquinavir Tipranavir Entry Inhibitors Enfuvirtide Maraviroc Integrase Inhibitors Raltegravir Elvitegravir Resistance Tes)ng: DHHS Guidelines Recommended when entering into care (consider repea;ng when ini;a;ng therapy); genotypic tes;ng is preferred Should be done for all pregnant women prior to therapy, or for those entering pregnancy with a detectable HIV VL on therapy Perform when managing subop;mal VL decrease In the se_ng of viral failure, tes;ng should be done while the pa;ent is on therapy, or within 4 wks of stop Recommended to assist in selec;ng ac;ve drugs for pts with viral failure & VL> 1000; Consider in VL>500 Phenotypic tes;ng when complex muta;ons especially with PIs Consider genotypic tes;ng for integrase inhibitor resistance when appropriate DHHS Guidelines available at March 27, 2012; page C-12 Prevalence of TransmiKed HIV Drug Resistance in US, Genotypic analysis of samples from newly diagnosed pa;ents in CDC Na;onal HIV Surveillance System (N = 12,668) Cases (%) or more Ocfemia MC, et al. CROI Abstract 730. Transmitted Drug Resistance Mutations All cases with sequences Cases classified as recent infections Cases classified as long-standing infections class 2 class 3 class NNRTI NRTI PI 4.1 Decline in New Cases of Resistance From , Bri)sh Columbia Substan;al decline in new cases of resistance over ;me in province- wide data from BC Centre for Excellence in HIV/AIDS Drug Treatment Program 21,300 resistance tests from 5216 subjects New cases of detected resistance (n) Year Lima VD, et al. CROI Abstract TC NRTI NNRTI PI Any

3 Methods & Limita)ons of Resistance Tes)ng Genotype: Direct sequencing of viral genes RT and PR, less commonly IN and ENV Resistance to specific drugs is inferred based on known muta;ons Muta;ons are detected only if mutant virus is at least 5-20% of virus popula;on Frequently called popula;on- based sequencing versus more sensi;ve assays ( ultra- deep sequencing ) Standard Popula)on- based Sequencing Misses Circula)ng HIV- 1 Minority- Variants Phenotype Grow virus in culture with various amounts of drugs added Direct measure of viral resistance Resistance tests are most accurate in assessing the sensi;vity to drugs which the pa;ent is currently receiving DHHS Guidelines available at March 27, 2012 Courtesy of Dr. Robert Shafer HIV Genotype Involve sequencing of various HIV genes and comparing results to reference wild type (wt) strain RT gene for NRTI and NNRTI resistance PI gene for PI resistance Integrase Gene for integrase inhibitor resistance (separate test) Some;mes a single muta;on leads to high level resistance to a drug; some;mes mul;ple muta;ons are required Mul)- Drug Resistance (MDR) muta)ons can decrease suscep;bility to many or all drugs in a single class The six muta)ons every HIV provider should know NRTI M184 V Thymidine- associated muta;ons (TAMs) K65R and L74V NNRTI K103N Y181C PI, IN none DHHS Guidelines available at March 27, 2012 DHHS Guidelines available at March 27,

4 HIV Phenotype Standard phenotypic tes;ng Results usually expressed as fold- change in suscep;bility compared to a laboratory control isolate (IC 50 pa;ent isolate divided by IC 50 wild type virus) Interpreta;on of drug ac;vity dependent on methodology used to define cutoffs (clinical, biological, technical) Virtual phenotype tes;ng Matches genotypic data against database of virus samples with paired GT and PT data Confidence level based on number of matching genotypes within the database Hirsch M, et al. Clin Infect Dis. 2008;47: Interpre)ng Phenotypes Clinical Cutoffs differ for each drug Probability of response Fold Change Lower clinical cutoff Response is significantly reduced Zone of Intermediate Response Perno C, Bertol A. An2retroviral Resistance in Clinical Prac2ce Chapter 7; Available at: hnp:// Upper clinical cutoff Response is unlikely Using clinical cutoffs to predict virologic response to tenofovir DAVG 24 > 0.5 log (%) Margot N et al, AIDS 2002; 16: Average change in viral load over 24 weeks < >4.0 Tenofovir fold change Which Resistance Test When? Genotype preferred due to faster result, lower cost and detec;on of early resistance (detec;ng primary resistance or at ;me of virologic failure to first or second ARV regimen) Phenotype Addi;on of phenotypic tes;ng to genotypic tes;ng is generally preferred for persons with known or suspected complex drug resistance muta;on panerns, par;cularly to protease inhibitors when > 3 PI or RT muta;ons found on genotype* Usually when ge_ng a phenotype also get genotype simultaneously* Virtual Phenotype (not specifically stated in DHHS) As a subs;tute when actual phenotype not available DHHS Guidelines available at March 27, 2012; *HL personal practice 4

5 Example of combined geno/phenotype report when phenotype not necessary Example of combined genotype/phenotype report when both are necessary Example of a Virtual Phenotype Report Major nrti Muta)ons NRTI/NtRTI NNRTI PI Fold Cut-offs Drugs Resistance Analysis Change Lower Upper NRTI/NtRTI mutations: 41L, 67N, 70R, 184V, 219Q, 335D, 369wt/A/I/V, 371wt/V Zidovudine Reduced Response Lamivudine Minimal Response Didanosine Reduced Response Stavudine Maximal Response Abacavir Reduced Response Emtricitabine 44.8 Resistant 3.1 Tenofovir DF 1.1 Reduced Response NNRTI mutations: None Nevirapine 1.3 Susceptible 6.0 Efavirenz Susceptible Etravirine 1.1 Susceptible PI mutations: 10F, 32I, 43T, 46I, 47V, 63P, 82A, 90M, 93L Indinavir Minimal Response Indinavir/r Reduced Response Nelfinavir Minimal Response Saquinavir/r Maximal Response Fosamprenavir/r Reduced Response Lopinavir/r Reduced Response Atazanavir/r Reduced Response Tipranavir/r Maximal Response Darunavir/r Maximal Response M184V diminishes viral fitness by approx. 50% High level resistance to 3TC and FTC Some resistance to ddi and abacavir Restores some ac;vity to AZT/d4T, tenofovir K65R Broad resistance to all nrti; but susc. to AZT L74V Resistant to abacavir & ddi; susc.to AZT, TDF TAMs - 215, 41, 210, 67, 70, 219: susc. to all nrti Selected by a prior tx history of AZT, d4t More resistance w/ 41/210/215 than 67/70/219 path 44D, 118I: nrti resistance with 41/210/215 path TAM pathway and K65R pathway do not occur on the same virus (bidirec;onal inhibi;on) MDR muta)ons (69SSS and Q151M) M184V, K65R and L74V have major effects on viral fitness Hirsch M, et al. Clin Infect Dis. 2008;47:

6 Ques)on 1 Your pa;ent is failing a tenofovir based regimen and genotypic resistance tes;ng shows the K65R muta;on. Which of the following statements is true? 1. The pa;ent s virus will likely have high level resistance to tenofovir and it should not be included in future regimens 2. The pa;ent s virus has some degree of resistance to tenofovir but is likely to have some residual an;viral ac;vity and may be useful in future treatment regimens 3. The pa;ent s virus is likely resistant to AZT 4. This muta;on does not have a major effect on viral fitness Resistance PaKerns aier Failure of Common Ini)al NRTI Backbones AZT + 3TC M184V TAMs D4T + 3TC M184V TAMs AZT + 3TC + ABC M184V TAMs TDF + FTC M184V K65R ABC + 3TC M184V L74V or K65R Gallant J, Top HIV Med 2005; 13: NNRTI muta)ons K103N Most common NNRTI muta;on High level resistance to efavirenz & nevirapine but not to etravirine or rilpivirine Y181C High level resistance to nevirapine & increased risk of efavirenz failure Has moderate to severe impact on etravirine cross- resistance E138K Novel muta;on associated with rilpivirine failure; leads to etravirine cross resistance Many other muta;ons can have effects on suscep;bility to NNRTIs Weighted etravirine muta)on score Prevalence in the panel of 4,248 HIV-1 Weight factor Mutation clinical isolates, % Y181I Y181V K101P L100I Y181C M230L E138A V106I G190S V179F a V90I V179D K101E K101H A98G V179T G190A Hirsch M, et al. Clin Infect Dis. 2008;47: Vingerhoets J, et al. IHDRW 2008; Abstract 24 6

7 Response to ETV based upon muta)on score Weighted muta;on score corresponded to response rates as follows : 0-2: : > 4: 74% (highest response) 52% (intermediate response) 38% (reduced response) Ques)on 2 Which of the following NNRTIs are likely to be fully suscep;ble and a reasonable treatment op;on in a pa;ent experience treatment failure with the K103N muta;on? 1. Efavirenz 2. Nevirapine 3. Rilpivirine 4. Etravirine 5. 3 and 4 Vingerhoets J, et al. IHDRW 2008; Abstract 24; Picchio G, et al. 15th CROI Abstract 866. Key facts about PI resistance Boosted PI s (LPV/r, FPV/r, SQV/r, ATV/r, DRV/r) usually do not select for resistance if used as 1st PI Mul;ple PI muta;ons usually required for high level PI phenotypic resistance In highly PI resistant pa;ents, DRV/r and TPV/r typically have good ac;vity (must be confirmed by phenotypic resistance tes;ng) If mul;ple PI muta;ons, obtain phenotype if possible to determine appropriate PI to use in salvage Darunavir Muta)on Score: V11I, V32I, I33F, I47V, I50V, I54L/M, T74P, L76V, I84V, L89V Approved in 1st- line & treatment- experienced pts May be used QD in treatment- experienced pts if there are zero DRV resistance muta;ons (ODIN Study) POWER studies showed pa;ents treated with darunavir and op;mized background meds had VL < 50 c/ml greater than for comparator PIs Response to darunavir was found to be dependent on 11 PI muta;ons at baseline Johnson, et al. Topics HIV Med; Dec Levin J. et al, XVIII IDRW 6/9-13,

8 Darunavir response by DRV score Patients (%) with HIV-1 RNA <50 copies/ml at Week 24 50% 22% 10% 0-2 mutations 3 mutations 4 mutations Number of Darunavir mutations at baseline De Meyer S, et al. Resistance Workshop Abstract 73.; Levin J et al, XVIII Intl Drug Resistance Workshop, June 9-13, Ques)on 3 A pa;ent experiences treatment failure with a history of 2 prior PI- based ARV regimens. Genotypic tes;ng shows one resistance muta;on to darunavir and four other PI muta;ons. Which is likely to be true? 1. The virus is likely to be suscep;ble to atazanavir 2. The virus is likely to be suscep;ble to fosamprenavir 3. Darunavir/ritonavir may be prescribed 800 mg/100 mg daily in his next regimen 4. Phenotypic resistance tes;ng may show that the virus is fully suscep;ble to darunavir Steps in HIV- 1 Integra)on HIV- 1 Integrase Ac)ve Site Viral DNA Synthesis 2 In-dependent processing of 3 ends 1. Assembly on viral DNA in a nucleoprotein complex Nuclear Membrane Nuclear Entry Gap Repair Mature Provirus 3b Concerted target DNA cleavage and joining 3a Target DNA binding Hazuda D, et al Medicinal Chemistry 30th Annual National Symposium

9 Integrase inhibitor resistance: the example of raltegravir Raltegravir failure is assoc. with integrase muta;ons in at least 3 gene;c paths defined by at least 2 muta;ons: Major muta;ons: 148,155, or 143 +/- minor changes Most common/most resistant = Q148H plus G140S Q148H/K/R or Y143R/H/C associated with high- level phenotypic resistance (> 100- fold change in IC 50 ) N155H associated with low- level phenotypic resistance (< 50- fold change in IC 50 ) Con;nued raltegravir in the presence of viral failure & resistance is not recommended Cross- resistance from muta;ons selected by RAL may confer reduced suscep;bility to inves;ga;onal integrase inhibitors (elvitegravir and dolutegravir) Hazuda DJ, et al. HIV Res Workshop Abst 8. Hatano H, et al JAIDS 2010 BENCHMRK 1 & 2: Evolu)on From N155 to Q148 Muta)ons Over Time 27% First Genotype (n = 64) % % Mixed 92 Hazuda D, et al. ICAAC/IDSA Abstract 898. Second Genotype (n = 51) 53% Integrase Assay Determines RAL Suscep)bility Phenotypic integrase resistance assay now available Amplifica;on threshold: VL > 500 Biological cutoff for RAL is FC > 1.5 Report does not detail genotypic muta;ons Integrase genotype assays are also available; useful for determining suscep;bility to 2 nd genera;on agents (probably more useful than phenotype) Transmined RAL resistance (N155H +2 minors*) now reported; consider baseline RAL resistance tes;ng prn Boyd SD, et al. An;viral Therapy 2011;16:257-61; Fransen S, et al. 48 th Annual CAAC/IDSA 46 th Annual Mee2ng. Abstract 1214; 9

10 Integrase resistance in the QUAD studies Development of resistance by wk 48 Ques)on 4 Has genotypic resistance to cobicistat been described to date? a. Yes b. No FDA Advisory Slides, August 27, 2012 Defining Co- Receptor Tropism Ques)on 5 CCR5-tropic (R5) virus enters CD4+ T cells via CCR5 HIV that can use either CCR5 or CXCR4 is called dual tropic Virus populations containing a mixture of R5-tropic, X4-tropic, and/or dual-tropic HIV are called mixed tropic Westby E, van der Ryst E. Antivir Chem Chemother. 2005;16(6): CXCR4-tropic (X4) virus enters CD4+ T cells via CXCR4 Which of the following are true about maraviroc? 1. It is only FDA- approved for use in treatment- experienced pa;ents with HIV according to DHHS 2. Maraviroc should only be used in pa;ents with R5 tropic HIV 3. Viral tropism switching (from R5 to D/M) is the most common cause of treatment failure 4. Maraviroc resistance tes;ng is commercially available 10

11 Maraviroc First HIV CCR5 inhibitor / CCR5 chemokine receptor antagonist Effec;ve against strains that use the CCR5 co- receptor for cell entry Linle effect on viruses which use CXCR4 co- receptor, or which use both Ac;vity of maraviroc is tested by co- receptor tropism test, which is not a resistance test Usually maraviroc more ac;ve in viruses from pa;ents earlier in the course of HIV infec;on at higher CD4 counts Representa)ve HIV tropism pakerns MOTIVATE 1, 2, and 1026 X4 (0.3%) Antiretroviral-naive (n = 1,428) DM (14.7%) R5 (85%) Antiretroviral-experienced (n = 2,560) DM (41.4%) X4 (2.6%) R5 (56%) Coakley E, et al. Second International Workshop Targeting HIV Entry #8. Coakley E, et al. Second International Workshop Targeting HIV Entry #8. Enhanced Phenotypic Tropism Assay For Detec)on of CXCR4- Using Virus Enhanced assay highly sensi;ve in detec;ng CXCR4- using HIV variants comprising 0.3% of viral popula;ons Detection (%) Trinh L, et al. ICAAC/IDSA Abstract % X4 Clone Original assay Enhanced assay Mechanisms of Maraviroc Resistance Major: Outgrowth of Dual/Mixed or X4 virus from pre- exis;ng minority popula;on present at levels too low to be detected by current tropism assays Minor: Virus remains R5, with true resistance Muta;ons in HIV gp120 that allow HIV to bind to CCR5 even though maraviroc is also bound Most muta;ons are variable changes in the V3 loop No consistent signature muta;ons for MRV resistance Genotyping not commercially available Mori J, et al. HIV Resistance Workshop Abstract 10.Tsibris AMN, et al.hiv Resistance Workshop 2007, #13; Lewis M, et al. HIV Resistance Workshop Abstract 56; Mosley et al.13 th CROI; Westby et al. J Virol

12 Conclusions HIV Drug Resistance can occur prior to ini;a;on of ARV therapy Resistance tes;ng can be used to op;mize an an;retroviral regimen Must use in context of treatment history and results of all prior resistance tests Goal for all HIV infected pa;ents is HIV RNA < 50 Tropism tes;ng also useful in determining eligibility to receive CCR5 antagonist therapy (maraviroc) Primary integrase resistance is rare but will probably increase in the future Factors other than resistance may cause regimen failure Resistance tes;ng is reliable and cost- effec;ve but must be interpreted in context and may require expert advice Cannot detect minority popula;ons (<5-20%?) Thank you for your aken)on!! 12