# Presentation: 830275

## Antiretroviral Drug Resistance

**Richard T. D’Aquila, MD**
**Vanderbilt University Medical Center and the Vanderbilt Meharry Center for AIDS Research**
**Nashville, TN**
**February 8, 2005**

## Antiretroviral Drug Resistance

- Has it reversed the hard-fought gains of antiretroviral chemotherapy?
- Is it a threat for the future?
- What action is required?
- Footnote:
- Most often-used word in HIV research and care may be: “Multifactorial”

##     HIV Replication & Chemotherapy

**Reverse Transcriptase Inhibitors**

**Proteae Inhibitors**

**Integrase Inhibitors**

**Entry****Inhibitors**

**    ****HIV Replication & Chemotherapy**

**NRTIs:      ZDV, d4T, ddI, 3TC, FTC, ABC, TDF**
**NNRTIs: EFV, NVP, DLV**

**NFV, SQV, IDV, APV,  r/LPV,**
**ATV(r), fAPV(r), [r/TPV]**

**T-20 (fusion inhib), **
**Others (CD4 & coreceptor inhib) in development**

**In develpment**

**Current drugs act at RT and Protease, One blocks fusion**

## HIV Adapts (‘best’ variant selected) 

- Immunity selects (amplifies) “escape” mutant
- Consensus HIV sequence in a population reflects the “escape” mutants selected by the most common HLA alleles
- Drugs also select “resistant” mutants
- More ongoing replication on drug -> greater chance of resistance
- In past – selection by sequential mono/dual Rx (adding one new drug) maximized amplification of resistance
- Resistance is relative, not absolute

## Does HIV resistance cause drug failure?

- Early cautious approach because it was known that acyclovir-resistant HSV does not always cause drug failure
- _High level_ zidovudine resistance associated with failure, after controlling for other poor prognostic factors (1995)

## Does HIV resistance cause drug failure?

- Studies of resistance genotyping at regimen failure
- Slightly better response to salvage if identified mutations before choosing next drug regimen

## Failure of HIV Rx usually partial

**Deeks, et al AIDS 1999;13:F35**

**Generally, CD4 count declines slowly during Rx failure**

## J Acquir Immune Defic Syndr 2004;37:1147–1154

- During HIV Therapy
*Stephen P. Raffanti, MD, Jennifer S. Fusco, BS,Beth H. Sherrill, MS, Nellie I. Hansen, MPH, Amy C. Justice, MD, PhD, Richard D’Aquila, MD, Wendy J. Mangialardi, MD,and Gregory P. Fusco, MD, MPH for the Collaborations in HIV Outcomes Research/United States Project*

*J Acquir Immune Defic Syndr *2004;37:1147–1154

**Conclusions: **... **These data suggest that maintenance of moderate viremia may confer clinical benefit not seen when viremia exceeds 20,000 copies/mL, and this should be taken into account when considering the risks and benefits of continuing failing therapy.**

## Resistance Tests in Rx-experienced patients Failing Rx

- In our local Nashville experience (at Comprehensive Care Center), resistance and drug side effects (especially body shape changes and lipid problems) drive decision making
- ART Management Conf – multi-disciplinary
- Time to discuss, test, teach
- Expert management of resistance critical

## Why do ‘failing’ drugs sustain benefit?

- Drug activity against wild-type HIV (wild type stays suppressed)
- Partial drug activity against resistant HIV (continues some suppression)
- Decreased replication capacity of resistant HIV
- Immune response against antigens in replicating (resistant) virus
- Decreased CD4 cell activation by resistant virus
- Statins inhibit HIV by decreasing cell proliferation
- Under study as adjunct w ARVs

## Fitness Phenotype:  Competitive Cultures

**WT**

**MT**

**20% TCID****50**

**80% TCID****50**

**MOI = 0.001**

**MT2**

**Day Postinfection 0, 1, 7, 14, (17), 21**
**DNA**

**PCR**

**UDG-Cloning**

**Site-Specific Sequencing: 30, 63, 46, 82, 84, 90, p1p6 (+ control)**

**Fitness Phenotype:  ****Competitive Cultures**

- Martinez-Picado.  *J Virol* 1999;73:3744.

## Relative Fitness of Drug-Resistant HIV Mutants D30N vs WT*

**0**

**0**

**25**

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**75**

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**18**

**Day**

**Mutant (%)**

**†**

**†**

- *Starting with 85% D30N mutant, depicting the percentage of D30N mutant over time.
- †Statistically significant difference from day 0 (*P*<.05; Fisher’s exact test).
-  Martinez-Picado.  *J Virol* 1999;73:3744.

**Relative Fitness of Drug-Resistant HIV Mutants D30N *****vs *****WT***

**WT**

**D30N**

## Relative Fitness of Drug-Resistant HIV Mutants D30N vs L90M*

**0**

**0**

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**Day**

** ****Mutant (%)**

**†**

**†**

- *Starting with 80% D30N mutant, depicting the percentage of D30N mutant over time.  †Statistically significant difference from day 0 (*P*<.05; Fisher’s exact test).
-  Martinez-Picado.  *J Virol* 1999;73:3744.

**Relative Fitness of Drug-Resistant ****HIV Mutants D30N *****vs *****L90M***

**L90M**

**D30N**

## Relative Fitness of Drug-Resistant HIV Mutants L63P/L90M vs WT* and D30N/L63P vs WT

**0**

**0**

**25**

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**Day**

**20**

**22**

**100**

- *Starting with 87% L63P / L90M mutant, depicting the percentage of L63P / L90M mutant over time.
- †Statistically significant difference from day 0 (*P*<.05; Fisher’s exact test).
-  Martinez-Picado.  *J Virol* 1999;73:3744.

**Relative Fitness of Drug-Resistant HIV Mutants**** ****L63P/L90M *****vs *****WT* and D30N/L63P *****vs***** WT**

**Mutant (%)**

**WT**

**L63P/L90M**

**0**

**2**

**4**

**6**

**8**

**10**

**12**

**14**

**16**

**18**

**20**

**22**

**†**

**†**

**†**

**WT**

**D30N/L63P**

## NFV-selected D30N mutations may require more “compensation” than initial mutants selected by other PIs					
Future role for fitness phenotype testing in addition to current genotyping and drug susceptibility phenotyping?
Replicative capacity (RC) offered by ViroLogic

**of PI-Resistant HIV**

**NFV-selected D30N mutations may require more “compensation” than initial mutants selected by other PIs****	****	****	****	****	**
**Future role for fitness phenotype testing in addition to current genotyping and drug susceptibility phenotyping?**
**Replicative capacity (RC) offered by ViroLogic**

## ‘Pie in the Sky’: Rx that selects for persistently low ‘fitness’ HIV

**Resistance mutations impair fitness in absence of drug (Nature 1993, many others)**
**Will additional ‘compensatory’ mutations that accumulate later offset this effect?**
**On continued ‘failing’ drugs: gradual increase in both resistance and replicative capacity**

## Why do ‘partially suppressive’ drugs sustain benefit?

- Drug activity against wild-type HIV (wild type stays suppressed)
- Partial drug activity against resistant HIV (continues some suppression but more resistance evolves slowly)
- Decreased replication capacity of resistant HIV
- Immune response against antigens in replicating (resistant) virus
- Decreased CD4 cell activation by resistant virus
- Statins inhibit HIV by decreasing cell proliferation
- Under study as adjunct w ARVs

## Evolution On-Drugs and Off-Drugs

**On continued ‘failing’ drugs: gradual increase in both resistance and replicative capacity**
**Off-drugs: Abrupt change in CD4 count and viral load frequently associated with a “shift” to wild-type (drug-susceptible) virus**

## Case 1: 

**32 yr old male presents with fever and sore throat to a walk-in clinic**
**PMH – neg**
**Rapid strep test (and throat culture): positive for gp A strep**
**PCN prescribed**
**Need to ask about HIV risks**
**He had one recent risk**

## Case 1

**Acute HIV infection seen in 2001**
**Viral load >750,000 c/ml**
**399 CD4+ T lymphocytes/ml**

**Gandhi, et al CID 2003**

## Gandhi, et al CID 2003

**Gandhi, et al CID 2003**

## Gandhi, et al CID 2003

**Gandhi, et al CID 2003**

## Gandhi, et al CID 2003

**Gandhi, et al CID 2003**

## Gandhi, et al CID 2003

**Gandhi, et al CID 2003**

## Persistence of Infecting Mutants:PI Resistance

**NRTI and PI cross-resistant mutant acquired at infection**
**Highly resistant to RTV/LPV (75-fold) and all earlier PIs**
**Not treated because only NNRTIs would be fully active**
**Rapid CD4 cell count decrease and viral load increase associated with increase in HIV replicative capacity **
**Coincident with “loss” of RT 184V**
**Worsening immunodeficiency was temporally related to emergence of less-resistant virus**
**Persistence of almost all resistance mutations off-drugs supports screening resistance genotype tests for all new HIV diagnoses**
**Now: could use fully-active NNRTI + T20, as well as partially active drugs (TDF, ?upcoming PIs)**

**Gandhi, et al. CID 2003**

## What is prevalence of resistant virus among treated patients in North America?

- Richman, et al. (HCSUS, AIDS 2004, n=2864): 50% of all, and 87% of ARV Rx’ed patients with detectable viremia
- Prior mono/dual Rx before HAART
- Harrigan, et al. (HOMER, BC, JID Feb 2005, n=1191): 25% of all with viral load >1000 at q 3 mo visits over first 30 mos of Rx
- Drug naïve before starting HAART (1996-00) - 75% started with single PI (IDV mostly), 25% with NNRTI (NVP)
- No data yet on starting today’s even better regimens

## Incidence of resistant virus among newly infected patients in US and Europe

- Not all studies show increases in incidence of resistance over time
- Is resistant virus less transmissible than wild-type?
- Need to keep monitoring
- Will starting Rx with triple combos, and always using best available options slow spread?

## Bell-shaped Adherence and Resistance Curve

- Increasing probability
- of selecting mutation

- Increasing Adherence

**Inadequate Drug Pressure**
**To Select Resistant Virus**

**Drug Pressure**
**Selects**
**Resistant Virus**

**Complete Viral Suppression**

## MEMS Adherence and Incomplete Viral Suppression

- Paterson DL, et al. *Ann Intern Med*. 2000;133:21-30.

****

****

****

****

## Resistance Risk by Adherence and Regimen Class

- Bangsberg et al J. Antimicrob Chem; 2002 53(5):696-9.

## Why do first regimens including boosted PIs fail?

- >80% no resistance or only resistance to most resistance-vulnerable NRTI
- Adherence
- Minor subpopulation not detected early
- Cellular drug transporters that may efflux drugs out of cells
- Concern about measuring blood drug levels that it does not measure intracellular levels where drug needs to be to act

## Adherence to HIV Therapy in the Industrialized North

| San Francisco
Bangsberg AIDS 2000 | 67% |
| --- | --- |
| Pittsburgh 
Paterson Annals Int Med 2000 | 74% |
| Los Angeles
Liu Annals Int Med 2001 | 63% |
| New York City 
Arnsten CID 2001 | 57% |
| Hartford
McNabb CID 2001 | 53% |
| Philadelphia 
Gross AIDS 2001 | 79%
 |

**Notes:**
Before we talk about adherence in resource settings, we should look in our own back yards

## Prevalence of ARV Resistance

| ARV Class | SF Urban Poor
n=301 | Nationally
n=2864 |
| --- | --- | --- |
| Any ARV | 27% | 50% |
| PI | 18% | 26% |
| NNRTI | 8% | 16% |
| RTI | 8% | 46% |

- Richman AIDS. 2004:18:1393

- Holodniy Int J HIV STD 2004:15:1241

## Adherence in Patients Purchasing Generic D4T/3TC/NVP in Kampala, UgandaN=36

| MEMS | Unannounced Pill Count | Self Report |
| --- | --- | --- |
| 93% 
(SD 16%) | 92%
(SD 16%) | 94%
(SD 16%) |

- Oyugi et al *JAIDS* 2004 36:1100-1102

## Adherence Studies in Resource Constrained Settings

- Orrel C, Bangsberg, Badri, Wood. Adherence is not a barrier to successful antiretroviral therapy in South Africa. AIDS 2003
- Laurent C, Diakhate N, Gueye NF, Toure MA, Sow PS, Faye MA, et al. The Senegalese government's highly active antiretroviral therapy initiative: an 18-month follow-up study. Aids 2002,16:1363-1370.
- Byakika-Tusiime J, Oyugi J, Tumwikirize W, Katabira E, Mugyenyi P, Bangsberg D. Ability to Purchase and Secure Stable Therapy are Significant Predictors of Non-adherence to Antiretroviral Therapy in Kampala, Uganda. 10th Conference on Retroviruses and Opportunistic Infections. Boston 2003.
- Leon MP Niccolal L Determining risk factors associated with  nonadherence in HIV patients in Costa Rica IAS 2003 #675
- May SB, Cardoso GCP, Costa ER, Barroso PFHUCFF High adherence in a resource poor seting in Bazil IAS 2003 #657

## Slide 36

## Matching Regimen, Resistance and Adherence Distribution in Kampala

## Laurent et al  Effectiveness and safety of a generic fixed-dose combination of nevirapine, stavudine, and lamivudine in HIV-1-infected adults in Cameroon: open-label multicentre trial. Lancet. 2004 Jul 3;364(9428):29-34

| 24 Week Outcomes |  |
| --- | --- |
| VL <400  | 90% |
| # resistance mutations  | 7 per 100 person years |
| Self reported adherence | 99% |
| Survival | 85% |

## Adherence to HIV Therapy in the Industrialized North

| San Francisco
Bangsberg AIDS 2000 | 67% |
| --- | --- |
| Pittsburgh 
Paterson Annals Int Med 2000 | 74% |
| Los Angeles
Liu Annals Int Med 2001 | 63% |
| New York City 
Arnsten CID 2001 | 57% |
| Hartford
McNabb CID 2001 | 53% |
| Philadelphia 
Gross AIDS 2001 | 79%
 |

**Notes:**
Before we talk about adherence in resource settings, we should look in our own back yards

## Is Average Adherence Enough?Bangsberg and Deeks JGIM 2004:17:812-13 

- Is Average Adherence Enough?Bangsberg and Deeks JGIM 2004_:_17:812-13

**Notes:**
There are three historic moments in the HIV pandemic- the first was in 1981 with the recognition of the disease.
The second was in 1996 with the develop of effect HIV therapy.
My practice before 96 was in North Harlem. It consisted of talking to a patient often a drug user or gay man reconnect with often estranged families, prevent infections and treat infections when possible, and then manage a comfortable meaningful and painless death.

My practice since 1996 has been at San Francisco General Hospital now has some of the social challenges as before 96, but is more about preventing heart disease and cancer than managing death.

In 2003 we are at another historic moment where it is possible to replicate this same curve for the rest of the pandemic simply by financing low cost HIV therapy.  

## Summary

- Most resistance has occurred in highly adherent patients on partially suppressive regimens
- Potent regimens reduce resistance at all levels of adherence
- Poverty is not an international risk factor for incomplete adherence
- Average adherence is sufficient to impact morbidity and mortality

## Views on ARV Adherence in Promoting Domestic and International Health Disparities

- David Bangsberg, MD, MPH
- Associate Professor of Medicine
- Epidemiology and Prevention Interventions Center
- Division of Infectious Diseases
- The Positive Health Program
- San Francisco General Hospital
- AIDS Research Institute, UCSF
- November, 2004

**Thanks to David Bangsberg for prior slides. His entire presentation (title below) to **
**2004 Workshop on Disparities and the HIV Epidemic **
**(held in Nashville, Nov 18-19, 2004) is available at:**
**http://www.mc.vanderbilt.edu/root/vumc.php?site=Workshop&doc=4557**

**Notes:**
Prevelance of drug resistance is rising
Non adherence is viewed as a cause of drug resistance and therefore a public health issue out of the concern that invididuals who are nonadherence will develop drug resistance and spread drug resistance virus to unifected individuals

## Antiretroviral Drug Resistance

- Has it reversed the hard-fought gains of antiretroviral chemotherapy?
- My answer: No
- Is it a threat for the future?
- My answer: Yes
- Does it require action?
- My answer: Yes
- All antiretroviral drugs must be available to every patient
- Each virus has unique exposure Hx – need to individualize drugs
- More R&D - HIV drugs and diagnostics
- Top priority: New drugs inhibiting different targets in HIV replication
- Continue current priorities
-  HIV pathogenesis research, observational cohort research, montioring for resistance, clinician and patient education re expert management of resistance

## Is need for new drugs endless?

- Hope for better potency of new combos
- New tools to synergize blocking HIV replication
- Further slow resistance emergence
- Hope for eradication

##     HIV Replication & Chemotherapy

**Reverse Transcriptase Inhibitors**

**Proteae Inhibitors**

**Integrase Inhibitors**

**Entry****Inhibitors**

**    ****HIV Replication & Chemotherapy**

**NRTIs:      ZDV, d4T, ddI, 3TC, FTC, ABC, TDF**
**NNRTIs: EFV, NVP, DLV**

**NFV, SQV, IDV, APV,  r/LPV,**
**ATV(r), fAPV(r), [r/TPV]**

**T-20 (fusion inhib), **
**Others (CD4 & coreceptor inhib) in development**

**In develpment**

**Current drugs act at RT and Protease, One blocks fusion**

## Acknowledgements

- David Bangsberg, Steve Deeks, and the entire community of physicians and scientists studying antiretroviral resistance
- The Comprehensive Care Center
- Nashville, TN: following 2100 HIV pts
- Adult AIDS Clinical Trials Group (AACTG)
- National network and Vanderbilt ACTU
- Centers for AIDS Research (CFAR)
- National network and Vanderbilt Meharry CFAR
- Organizers of the 2004 Workshop on Disparities and the HIV Epidemic (the Vanderbilt Meharry CFAR, the Meharry Center for Health Disparities Research in HIV, the Meharry Vanderbilt Alliance), and its supporters including the NIH Office of AIDS Research
- IAS-USA, HIVMA
- Pharmaceutical companies working on HIV and companies working on resistance testing