1 Failure of Antiretroviral Therapy and Subsequent Treatment Options: Workshop Rafael E. Campo, MD Associate Professor of Medicine University of Miami Leonard M. Miller School of Medicine and Jackson Memorial Hospital Miami, FL

Failure of Antiretroviral Therapy and Subsequent Treatment Options: Workshop Case 1: Pre-existing antiretroviral resistance in a naïve patientCase 1: Pre-existing antiretroviral resistance in a naïve patient Case 2: Early ART failure with limited resistance in a naïve patient and delayed response to subsequent ARTCase 2: Early ART failure with limited resistance in a naïve patient and delayed response to subsequent ART Case 3: Salvage of a patient with decreased susceptibility to PIs with a PI-based regimenCase 3: Salvage of a patient with decreased susceptibility to PIs with a PI-based regimen Case 4: Management of an extensively experienced patient by “doing nothing”Case 4: Management of an extensively experienced patient by “doing nothing”

3 Case 1: Pre-existing antiretroviral resistance in a naïve patient

Case History 23-year old AA man presented to ER September 2003 with history of fatigue, malaise, anorexia, 40lb wt loss23-year old AA man presented to ER September 2003 with history of fatigue, malaise, anorexia, 40lb wt loss No significant PMHNo significant PMH Exam reveals chronically ill man with no focal findingsExam reveals chronically ill man with no focal findings Labs notable for WBC 2.9 with 1% lymph.Labs notable for WBC 2.9 with 1% lymph. Diagnosis in ER is UTI; started on TMP/SMXDiagnosis in ER is UTI; started on TMP/SMX Referred to Health Department for HIV testingReferred to Health Department for HIV testing

Case History HIV ELISA is drawn – negativeHIV ELISA is drawn – negative Patient completes his antibacterial therapy with no significant clinical improvementPatient completes his antibacterial therapy with no significant clinical improvement

Case History In late November he develops fever, a non-productive cough, and increasing shortness of breathIn late November he develops fever, a non-productive cough, and increasing shortness of breath He returns to the ER on 12/7/03 and is admitted.He returns to the ER on 12/7/03 and is admitted. The patient undergoes bronchoscopyThe patient undergoes bronchoscopy PCP is confirmed and treated with TMP-SMZ + steroids with improvementPCP is confirmed and treated with TMP-SMZ + steroids with improvement His HIV ELISA was still non-reactive, but the HIV RNA is >750,000 copies/mlHis HIV ELISA was still non-reactive, but the HIV RNA is >750,000 copies/ml

Case History CD4 count = 3 (1%) Viral load is repeated and remains >750K What do you recommend at this point? 1.Complete PCP therapy and refer to ID Clinic for follow-up 2.Start antiretroviral therapy now

Case History If you choose to initiate therapy, what would you use? 1.AZT + 3TC + EFV 2.AZT + 3TC + LPV/r 3.AZT + 3TC + IDV 4.AZT + 3TC +NFV

Case History Continues on the AZT + 3TC + EFV regimen until early April 2004Continues on the AZT + 3TC + EFV regimen until early April 2004 Follow-up viral load measurement >750KFollow-up viral load measurement >750K CD4 count = 2 (1%)CD4 count = 2 (1%) Remains unwell with an additional 8 pounds of weight lossRemains unwell with an additional 8 pounds of weight loss Reports excellent adherenceReports excellent adherence What do you do now?What do you do now?

Case History You consider potential reasons for the current situation 1.You think the patient is not reporting his adherence accurately and order drug levels 2.You think he may have been infected with a resistant virus and order a resistance test 3.You think he had an extremely high viral load to start with and it may be that he needs a longer period of time before you see a response to therapy – continue the present regimen

Case History When results of resistance test return, he is switched to LPV/r + ABC + AZTon 4/20/04When results of resistance test return, he is switched to LPV/r + ABC + AZTon 4/20/04 If ABC were not available, would continuation of 3TC be an option, or would a switch to ddI or d4T be preferable?If ABC were not available, would continuation of 3TC be an option, or would a switch to ddI or d4T be preferable? Follow-up on 5/21/04 – patient reports feeling significantly better with VL = 2880 copies/ml andFollow-up on 5/21/04 – patient reports feeling significantly better with VL = 2880 copies/ml and CD4 = 39 (5%)

Case History By June 2004, he has gained 20 pounds, CD4 count is 50 cells/mm 3 (7%) and viral load is 395 copies/mlBy June 2004, he has gained 20 pounds, CD4 count is 50 cells/mm 3 (7%) and viral load is 395 copies/ml For the first time, his HIV ELISA and Western blot are both reactiveFor the first time, his HIV ELISA and Western blot are both reactive

14 Case 1: Discussion

HCSUS: Prevalence of HIV drug resistance among HCSUS populationHCSUS population –Representative as possible of all HIV-positive persons receiving medical care in early 1996 and viremic in 1998 –1797 samples analyzed Resistance more commonResistance more common –Lowest CD4 count nadir –Higher HIV RNA –More access to care Resistance less commonResistance less common –Patients cared for by the most experienced providers Proportion With Phenotypic Resistance Any NRTI NNRTI PI >2 3 Any NRTI NNRTI PI >2 3 78% 70% 31% 42% 51% 14% Richman DD, et al. AIDS 2004; 18: Drug Drug (>1 drug) Drug Class Drug Class

CDC Survey: Drug-Resistant HIV Among Recently Diagnosed Patients Prevalence of MAR (%) 1998 (n=257) 1999 (n=239) 2000 (n=299) Resistance to: Any drug Any drug NRTI NRTI NNRTI NNRTI PI PI >2 drug class >2 drug class Bennett D, et al. 9th CROI, Seattle, Abstract 372. MAR=mutations associated with resistance.

US surveillance of HIV drug resistance among treatment naive patients Drug resistance in 787 newly diagnosed ART-naïve subjects from 89 sites in 6 states (2003–2004)Drug resistance in 787 newly diagnosed ART-naïve subjects from 89 sites in 6 states (2003–2004) Bennett D, et al. 12th CROI, Boston 2005, #674 Prevalence of drug resistance % Men14.9 Women13.8 MSM15.9 Hetero13.0 IDUs14.1 Black14.2 Hispanics13.6 White15.3 Prevalence of resistance by drug class Any class NRTINNRTIPI>2 classes Patients (%)

Transmission of drug-resistant HIV-1 in NY Acute or recent infection from primary infection cohort in NY cityAcute or recent infection from primary infection cohort in NY city Updated data from 112 ART- naïve subjects (1/03–12/04)Updated data from 112 ART- naïve subjects (1/03–12/04) –>25% with resistance –NNRTI resistance  from 1995–98 (2.6%) to 2003–04 (13.4%); p=0.04 –11 (9.8%) with MDR: increase in MDR resistance from previous dates (p=0.03) Shet A, et al. 12th CROI, Boston 2005; #289 Prevalence of transmitted ART resistance mutations, 1995–2004 % Newly infected individuals All resistance NRTI resistance NNRTI resistance PI resistance MDR HIV

Persistence of transmitted resistant virus 1. Little SJ, et al. XII Resistance Workshop, Los Cabos 2003, #115; 2. Ravaux I, et al. 2 nd IAS, Paris 2003, #822; 3. Brenner B, et al. J Virology 2002; 766:1753; 4. Chan K, et al. AIDS 2003; 17:1256 n=10 1 NNRTI(n=9) NRTI(n=3) PI(n=3) Primary HIV Infection of 10 Reversions n=1 PI None n=4 MDR None n=2 4 MDR (n=1) NNRTI (n=1) None Follow-up (Weeks) Reversion of MDR is rare even after 1 year

20 Case 2. Early ART failure with limited resistance in a naïve patient and delayed response to subsequent ART

Patient History  Sex: Male  Age: 50  Considerations: Seen in clinic after test at STD center revealed HIV infection  Presenting symptoms: Fatigue  Concomitant conditions: None

Baseline Laboratory Values  CD4 count: 220  Viral load: 157,000  Symptoms: Chronic fatigue and weakness  Other labs: All within normal limits  Lipid profile: TC 157, LDL 92, HDL 33, TG 132  Genotype: Not performed

Treatment Decisions  Diagnosis: Moderately advanced HIV infection  Therapy or intervention: EFV (600 mg qd) and AZT/3TC (300 mg/150 mg bid) started January 2000  Rationale for this therapeutic option: Simple, easy- to-take regimen with well-known side effect profile that was acceptable to the patient and provider

 CD4 count: 260  Viral load: <400 copies  Symptoms: Some dizziness that resolved within 2 weeks, resolution of weakness and fatigue  Other labs: All within normal limits  Lipid Profile: TC 171, LDL 98, HDL 37, TG 145 First Patient Follow Up 6 Weeks Later: Results

Management Progress & Next Steps  Outcome of the treatment regimen: Viral load suppression with increase in CD4 cell count and negligible toxicity  Need to switch regimen: No  Any changes in management strategies: No  Additional testing: q3 month follow-up

 Patient’s viral load remained undetectable for 6 months  Month 9: Viral load 5,520 copies, CD4 325  Month 12: Viral load 12,300 copies, CD4 318  Genotype performed at Month 12:  Reverse transcriptase: K103N, V108I  Protease: L63P  Overall assessment: Resistance to NNRTIs; full susceptibility to NRTIs and PIs  No clinically significant changes in other lab results  What to do next? Subsequent Patient Follow Up Visits: Results

Regimen Modification and Follow Up Regimen modified (Kaletra [400/100 mg bid] and AZT/3TC [300/150 mg bid]) in January 2001Regimen modified (Kaletra [400/100 mg bid] and AZT/3TC [300/150 mg bid]) in January 2001 Patient adherence to this regimen was inconsistent over next 2½ yearsPatient adherence to this regimen was inconsistent over next 2½ years What resistance would be expected by October 2003?What resistance would be expected by October 2003? 400 copies/ml

 Genotype October 2003:  Reverse transcriptase: V108I  Protease: L63P  Overall assessment: No PI or NRTI resistance; previously detected resistance to NNRTIs no longer detectable  Need to switch regimen? No selection of new resistance mutations and full susceptibility to current regimen; same regimen continued  Change in management strategies? Continued adherence counseling and involvement of family  Subsequent follow up: Since October 2003, 5/5 viral loads <400 and 4/5 <50 Management Progress & Next Steps

29 Case 2: Discussion

Genotypes after Virologic Failure of EFV + TDF + 3TC in ART Naïve Patients *K103N, V106M, Y188C/L or G190A/S/E/Q 16 (55%) EFV-R 12 (41%) M184V 7 (24%) K65R TDF/3TC/EFV (n=29 of 299) d4T/3TC/EFV (n=25 of 301) 12 (48%) EFV-R 8 (32%) M184V 2 (8%) K65R Miller MD, et al. HIV6, Glasgow 2002, #P205 Wild-type or as baseline M184V alone EFV-R* alone EFV-R* + M184V EFV-R* + K65R EFV-R* + K65R + M184V EFV resistance = 48%

Study 863 (LPV/r vs. NFV plus d4T/3TC): Incidence of resistance at weeks 24 – 96 LPV/r (n=326) /51 (0%) 19/51 (37%) NFV (n=327) /96 (43%) 79/96 (83%) HIV RNA above 400 copies/ml Genotype available Resistance detected in protease 3TC resistance Absence of resistance to LPV confirmed by phenotypic analysis Walmsley S, et al. N Engl J Med 2002; 346:

Barrier to Resistance for Protease Inhibitors and NRTI’s HIV RNA above 400 copies/ml Genotypic results available Lopinavirresistance † TDF resistance ‡ TAMS (D4T) resistance ‡ 3TC/FTC resistance § Study /22 0/15 NA 3/ /74 0/51 NA 0/51 19/51 Study 863 † LPV/r resistance: emergence of primary or active site mutation at protease positions 8, 30, 32, 46, 47, 48, 50, 54, 82, 84, 90, with phenotypic LPV resistance FC> 2.5 vs WT ‡ TDF resistance: emergence of K65R or any TAM (41, 67, 70, 210, 215, 219) in RT § 3TC/FTC resistance: emergence of M184V mutation in RT Molina JM, et al. XV IAC,Bangkok, Thailand, July 2004;WePe5701,Kempf D, et al. Antiviral Therapy 2002;7:S119, GulickRM, et al.HIV7,Glasgow, UK, Nov. 2004;#P28 Study /28 0/18 NA 0/18 3/18

Lack of resistance to fos-APV/RTV: 48-week studies in naïve subjects (NEAT and SOLO)  fos-APV bid (NEAT) and fos-APV/r (SOLO) vs. NFV, all in combination with 3TC and ABC.  Analysis of prevalence of resistance to PIs, 3TC, and ABC. Elston R, et al. 2 nd IAS, Paris 2003, #558 Variable Virologic failure/ongoing replication Variable fos-APV (n=29) NFV (n=26) Fisher’s Exact Test fos- APV/r (n=32) NFV BID (n=54) Fisher’s Exact Test 1 o or 2 o PR 8 (28%) 8 (31%) o or 2 o PR 0 27 (50%) < TC (M184I/V) 16 (55%) 20 (77%) TC (M184I/V) 4 (13%) 30 (56%) <0.001 NEATSOLO

34 Patterns of resistance based on genetic barriers

Different drugs have different genetic barriers to resistance Increasing Number of Mutations Low Trough Non-Boosted PIs Small Change per Mutation BUT Low Drug Levels NNRTIs High Drug Levels BUT Large Change per Mutation Increasing EC 50 High Trough Boosted PIs Small Change per Mutation AND High Drug Levels EC 50 High Trough EC 50

Resistance at time of first virologic failure 1 Melby T. 8 th CROI, Abstract 448; 2 Havlir D, et al. JAMA. 2000;283: ; 3 Rusconi S, et al. Antiviral Ther. 1998;3: Kempf D. 10 th CROI. Boston, Abstract 600; 5 Holder DJ, et al. 6 th CROI. Chicago, Abstract 492; 6 Vavro C, et al. 42 nd ICAAC. San Diego, Abstract H ZDV 1 3TCABC(n=39) ZDV 2 3TCIDV(n=17) ZDV 3 3TCAPV(n=16) d4T 4 3TCNFV(n=96) 3TCLPV/r(n=51) IDV 5 EFV(n=14) ZDV 6 3TCEFV(n=24) Patients (%) TAMs IDV TAMs APV TAMs 3TC 3TC 3TC 3TC NFV 3TC EFV IDV 3TC NNRTI NNRTI+3TC TAMs TAMs0% TAMs (0% ) LPV

Rates of failure and resistance of QD, low- genetic barrier ART regimens Treatment regimen Number of patients Study outcome Rate of failure Frequency of resistance among virologic failures ddI/3TC/TDF QD 1 24 Early termination 91%100% ABC/3TC/TDF QD (TONUS) 2 36 Early termination 33%82% Trizivir/TDF QD (COL 40263) 3 88 Early termination 22%100% ddI/TDF/EFV Early termination 12% (comparator 0%) Not reported 1. Jemsek J, et al. 11th CROI, San Francisco 2004, #51; 2. Landman R, et al. 11th CROI, San Francisco 2004, #52; 3. Elion R, et al. 11th CROI, San Francisco 2004, #53; 4. Moyle G, et al. 44 th ICAAC, Washington 2004, #H-566; 5. Maitland D, et al. HIV 7, Glasgow 2004, #PL2.5 Note – EFV/TDF/FTC might be a notable exception to this trend

38 Effect of long half-lives on emergence of resistance and clinical consequences

Stopping drugs with different half lives Time (hours) Drug concentration IC 90 IC 50 Last dose Day 1 Day 2 Zone of potential replication Taylor S, et al. 11 th CROI, San Francisco 2004, #131 MONOTHERAPY

Discontinuation of NNRTI-based regimens STOP Study Steady-state half-life:Steady-state half-life: –NVP: 25–32 h –EFV: 40–55 h PK study: 10 patients stopping 2 NRTIs + EFVPK study: 10 patients stopping 2 NRTIs + EFV –5/10 had EFV T ½ 40–50 h –5/10 had EFV T ½ >100 h –4/5 black African women –3/5 had therapeutic levels (>1000 ng/mL) 2 weeks after stopping EFV Potential options for discontinuation of NNRTI-based regimensPotential options for discontinuation of NNRTI-based regimens –Continue NRTIs 7 days after stopping NNRTI –Switch to PI for 1–2 weeks before stopping regimen Taylor S, et al. 11 th CROI, San Francisco 2004, #131

Acquisition of NVP resistance in mothers with combination therapy vs sd-NVP prophylaxis sd-NVP alone ZDV + sd-NVP >2 ARV + sd-NVP Detectable resistance (%) 2 doses McIntyre J, et al. 12th CROI, Boston 2005, #8 Time: Clade: 6 wk 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

Single-Dose Pharmacokinetics of Lopinavir With and Without Ritonavir Lopinavir Concentration (  g/mL) Time After Dosing (hr) IC 50 wt HIV Lopinavir alone Lopinavir/ritonavir Sham HL, et al. Antimicrob Agents Chemother. 1998;42(12): ; Lal R, et al., 37 th ICAAC, 1997, # I-194

43 Boosted PIs more forgiving of suboptimal adherence than non-boosted PIs orNNRTIs N = 1634 naïve patients –InitiatedARVsbetween 8/96- 6/03 –2 consecutive VL < 500 c/mL Primary endpoint: viral breakthrough –2 consecutive VL > 1000 c/mL Adherence measured by pills dispensed from centralized system Conclusions –For individuals at high risk of suboptimal adherence, using boosted-PI regimens may achieve higher effectiveness rates 1.05 (0.45, 2.42)Boosted PI - based 1.47 (1.01, 2.14)NNRTI - based 1.65 (1.38, 2.01)Single PI - based Unadjusted Hazard Ration (HR, 95% CI) Regimen Multivariate Analysis of <95% Adherence and Breakthrough by Regimen Gross R, et al, 13 th CROI, Denver, 2006, 533

44 Case 3. Salvage of a patient with decreased susceptibility to PIs with a PI-based regimen

Long-Lasting Viral Suppression is Possible Even in the Presence of Markedly Decreased PI Susceptibility Protease substitutions in/near active site: G48V, V82A, I84V Protease substitutions away from active site: L10I, M46L, I54V, L63P, A71V Baseline resistance (fold increase in IC 95 ) IDV: 35.4X RTV: 28.3X ABC: 1.2X 675,397 c/ml <50 c/ml 395 cells/µL 1083 cells/µL

Pharmacokinetics and Resistance: Preventing Resistance Richman D, Straszewski S. Practical Guide to HIV Drug Resistance and Its Implications for Antiretroviral Treatment Strategies, 2000; Kempf D. The AIDS Reader, To achieve a high barrier to resistance: Small phenotypic susceptibility change per mutation (high genetic barrier) High drug concentrations (high drug barrier) Plasma drug levels Change in EC 50 from baseline Increasing mutations over time

Time (hours) ,000 10,000 IDV plasma concentration IDV 800mg + RTV 200 mg bid IDV 800 mg q8h Time (hours) APV plasma concentration APV 1200mg BID (N=61) APV 1200mg + RTV 200mg QD Pharmacokinetic Enhancement of PI Plasma Levels through Ritonavir-Mediated Cytochrome P450 Inhibition IndinavirAmprenavir Lopinavir LPV 400 mg bid LPV plasma concentration Time (hours) LPV 400 mg + RTV 100 mg qd

Ability to Suppress Viral Replication is Based on the Relationship between Achievable Antiretroviral Drug Concentrations and Viral Drug Susceptibility Concentration of drug Loss of susceptibility Susceptible  4X 1X  Not susceptible 4X 8X   “Resistance” is a dynamic relationship between achievable free drug levels and changing susceptibility to that drug  8X 25X Susceptible

Phenotypic Susceptibility to LPV Decreases with the Accumulation of Substitutions Median 0.8 Median 2.7 Median 13.5 Median 44.0 *Selected from 11 mutations associated with reduced susceptibility to LPV (protease amino acid positions 10, 20, 24, 46, 53, 54, 63, 71, 82, 84 and 90) Median fold EC 50 (LPV) LPV mutation score* Kempf et al. J Virol 2001; 75:

Patients with HIV RNA <400 copies/mL (%) Week Virologic response with respect to genotype Virologic response with respect to phenotype Week 0–5 mutations 6–7 mutations 8–10 mutations <10-fold 10–40-fold >40-fold Response to LPV/r + EFV/NRTIs in multiple PI-experienced, NNRTI-naïve patients Rockstoh et al. 5th ICDT, 2000

Long-Lasting Viral Suppression is Possible Even in the Presence of Markedly Decreased PI Susceptibility Protease substitutions in/near active site: G48V, V82A, I84V Protease substitutions away from active site: L10I, M46L, I54V, L63P, A71V Baseline resistance (fold increase in IC 95 ) IDV: 35.4X RTV: 28.3X ABC: 1.2X 675,397 c/ml <50 c/ml 395 cells/µL 1083 cells/µL

52 Management of an extensively experienced patient by “doing nothing”

Goals of treatment for highly experienced patients While complete viral suppression is the most desirable goal of antiretroviral therapy, for some patients this may be unrealistic and unachievableWhile complete viral suppression is the most desirable goal of antiretroviral therapy, for some patients this may be unrealistic and unachievable In this situation, appropriate treatment goals would beIn this situation, appropriate treatment goals would be –maintenance of a relatively low viral load –Maintenance of a reasonable level of CD4+ cells (e.g. >200) –Minimization of toxicity

What to do with highly experienced patients? 55 year old Hispanic male55 year old Hispanic male Came to medical attention in 1994 with advanced AIDS: CNS toxoplasmosis, CD4+ 25, VL ?Came to medical attention in 1994 with advanced AIDS: CNS toxoplasmosis, CD4+ 25, VL ? Started on AZT monotherapy followed by multiple other regimens:Started on AZT monotherapy followed by multiple other regimens: –AZT + 3TC –ddI + 3TC –ddI + d4T –RTV + ddI + d4T –IDV + AZT + 3TC –SQV + NFV + EFV + ddI –IDV + RTV + AZT + 3TC Genotype on IDV + RTV + AZT +3TC (2001)Genotype on IDV + RTV + AZT +3TC (2001) –RT: –RT: M41L, E44E/D, K103N, V118I, L210W, T215Y, K219R –PR: –PR: L10V, K20R, M46I, I54V, L63P, A71V, V82 A, L90M What to do next?

What to do with highly experienced patients?

NRTI mutations M41L E44E/D V118V/I L210W T215Y K219R NNRTI mutations None PI mutations L10V K20T L33I K43T M46I I54V L63P A71V L90M RC 26%

Immunologic Benefits Sustained Despite Virologic Failure Kaufmann D, et al. Lancet. 1998;351: Swiss HIV Cohort StudySwiss HIV Cohort Study –101 patients with extensive exposure to antiretrovirals and moderate-to-advanced immunosuppression –Baseline CD4 –162 cells/mm3 66% of patients did not achieve viral suppression66% of patients did not achieve viral suppression At 48 weeksAt 48 weeks –93% experienced a gain in CD4 cell counts with HAART HAART may have a prolonged effect on CD4 cell count even without suppression of viremiaHAART may have a prolonged effect on CD4 cell count even without suppression of viremia Weeks After Starting HAART Change in HIV RNA Log 10 Copies/mL Weeks After Starting HAART Change in CD4 Cell Count Cells/mm Never achieving undetectable viremia Transient undetectable viremia Continuous HAART, achieving undetectable viremia undetectable viremia Discontinuous HAART use

Change in CD4 Cell Count and Resistance During Treatment Discontinuation Prospective, unblinded studyProspective, unblinded study 16 patients with virologic failure on antiretroviral therapy16 patients with virologic failure on antiretroviral therapy –HIV RNA >2500 copies/mL for >6 months ConclusionsConclusions –Continuing antiretroviral therapy can provide immunological and virologic benefit in patients for whom complete virologic suppression is not possible 12-Week Results TherapyStoppedContinuousTherapy CD4 (cells/mm 3 ) HIV RNA (log 10 copies/mL) PI resistance Not detected Persisted Viral fitness IncreasedDecreased Deeks SG, et al. N Engl J Med. 2001;344:

Partial Treatment Interruption Nonrandomized 48-week study in 22 adults with multidrug-resistant HIV 1Nonrandomized 48-week study in 22 adults with multidrug-resistant HIV 1 –Viral rebound during NRTI interruption precedes genotypic switch –PI interruption led to little change in HIV RNA levels or genotype Other studies show similar results 2,3Other studies show similar results 2,3 1 Deeks SG, et al. J Infect Dis. 2005;192; Campbell TB, et al. Clin Infect Dis. 2005;41: ; 3 Eron JJ, et al. JAIDS. 2004;37: Change in HIV RNA Log 10 Copies/mL Interrupt NRTI (continue PI) Interrupt PI (continue NRTI) Weeks Change in CD4 Cell Count Cells/mm Interrupt NRTI (continue PI) Interrupt PI (continue NRTI) (continue NRTI) Weeks

Replication capacity and viral fitness Drug sensitive virus Drug resistant virus Drug concentration Viral replication Which virus is more fit?

Distribution of RC measurements * ViroLogic internal data Count RC Count RC Reduced susceptibility to >1 drug*Viruses sensitive to all drugs* Viruses ± reduced drug susceptibility (n=2114)

n = n = Total Number of Mutations (groups of 3) Mean Replication Capacity (%) Wrin, et al., 2001 Replication capacity vs. total number of PR and RT mutations

Common mutations have different effects on RC Wild type TAMS*M184VK103NG190AD30NL90M Replication capacity (% of wild-type virus) NRTINNRTIPI Viruses with specified mutations * Viruses containing RT mutations

E-184V Study: Lamivudine Monotherapy Versus Treatment Interruption Prospective, open-label studyProspective, open-label study Patients on 3TC containing-therapy requesting treatment interruptionPatients on 3TC containing-therapy requesting treatment interruption –HIV RNA: >1000 copies/mL –CD4: >500 cells/mm 3 –Randomized arms –3TC monotherapy –Treatment interruption Study stopped for CD4 <350 cells/mm 3 or development of OIStudy stopped for CD4 <350 cells/mm 3 or development of OI –3TC monotherapy: 44% –Treatment interruption: 68% Fold increase in replication capacity (P=0.013)Fold increase in replication capacity (P=0.013) –Lamivudine monotherapy: 2.36 –Treatment interruption: 9.75 Castagna A, et al. 3 rd IAS Conference. Rio de Janeiro, Abstract WeFo0204. Change in HIV RNA Log 10 Copies/mL Weeks Change in CD4 Cell Count Cells/mm 3 Weeks Treatment interruption Lamivudine monotherapy P= Lamivudine monotherapy Treatment interruption P=NS

65 Questions and Discussion