HIV Drug Resistance is Inevitable

• HIV DR is an inevitable consequence of ART, influenced by:

– Removal of barriers to access to care

– Availability/continuity of drug supply

– Ability of regimens to suppress replication completely

– Adherence and tolerability of regimens

– "Genetic barrier" to resistance

– Relative fitness of resistant variant(s)

– Pharmacokinetics (IQ)

• Therefore, efforts to prevent HIVDR should be focused on these factors

HIV DR Testing in Resource Rich Settings

Prevalence of HIVDR at baseline

Utility of resistance testing before

initiating therapy

Individualization of 1st line regimen

Resistance developing on therapy

Resistance testing before switching

therapy (SOC)

Individualization of 2nd line and subsequent

regimens

24+ drugs from 6 classes

Resistance developing on therapy

Prevalence of HIVDR at baseline

HIV DR Testing in Resource Poor Settings

Prevalence of HIVDR at baseline

Resistance developing on therapy

Resistance developing on therapy

Prevalence of HIVDR at baseline

~6 drugs from 3 classes

Prevalence and patterns of resistance

in population

Determination of standard 2nd line

regimens

Will standard 1st line regimens be effective?

Determination of standard 1st line

regimen

HIVDR Early Warning Indicators (EWI)

Prescribing

practices

Proportion lost to follow-up during

the first 12 months of ART

Patient retention on first-line ART

On-time ARV drug pick up

ART appointment-keeping

Drug supply

continuity

Site-level ART Program

Function

Viral load suppressio

n @12 months

Pill count/ adherence

6

Percentage of genotyped first-line HAART failures with NNRTI, M184V, TAMS and PI resistance

Genotypes analysis

0.3%

16.5%

0.2% 1.0%

57.3%

37.2%

1.0% 0.0%

91.1%

69.0%

11.2%

0.0%0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

MajorNNRTI

M184V/I AnyTAMS

Major PI MajorNNRTI

M184V/I AnyTAMS

Major PI MajorNNRTI

M184V/I AnyTAMS

Major PI

PI Studies NNRTI Studies Developing World NNRTI Studies

Gupta et al CROI 2008

VIRAL EVOLUTION in NON-B SUBTYPES of HIV-1

Global distribution of HIV-1 subtypes

1.3 million1.3 million

4.8 million4.8 million

2 million2 million

B 10%B 10%

A 12%

A 12%

URF 4.2%URF 4.2%

AG

6.7%

AG

6.7%

AE 3.1%AE 3.1%

G 5%G 5%

DD 3.6%3.6%

Do Differences Exist among HIV Subtypes in the Development of Drug Resistance?

Silent Mutation at Codon 106 responsible for the V106M mutation in clade C RT with NNRTIs

Wild type codon

at position 106

HIV-1 RT

V(GTG) V(GTA)

Subtype C Subtype B

In clade C, V106M arises M(ATG)

two codon changes

A(GCA)In clade B, V106A occurs two codon changes

Marconi et al showed that V106M is the second most common NNRTI mutation after K103N in subtype C patients. In contrast, V106A/M is very rarely seen with subtype B isolates.

Clinical Infectious Diseases 15:1589, 2008

0 5 10 15 200

10

20

Subtype B

Subtype C

K65R

wt (wk 34-78)

Week

[TD

F]

(M

)Rapid Selection of K65R Resistance in Subtype C Isolates

History of 23 Botswana Patients Treated

with ddI/d4T plus 3TC or NVP

No. Patients 23 No. Patients failing 15

No. Patients with K65R 7

No. Patients with L74V 0

Hosseinipour MC, van Oosterhout JJ, Weigel R, Phiri S, Kamwendo D, Parkin N, Fiscus SA, Nelson JA, Eron JJ, Kumwenda J. The public health approach to identify antiretroviral therapy failure: high-level nucleoside reverse transcriptase inhibitor resistance among Malawians failing first-line antiretroviral therapy. AIDS. 2009. 1;23(9):1127-34

Background

• The Malawi ART program scale-up:>150,000 patients started on d4T/3TC/NVP

• A substantial minority with have virologic failure and eventually clinical failure.

• In failing patients resistance will be present– Few data from Africa on resistance patterns

Characteristics of 101 Patients that Initiated Second-Line ART in Malawi

Hosseinipour et al. AIDS 23(9):1127-34 2009

d4T/3TC/NVP failures based on clinical/immunological criteria, confirmed by HIV-RNA >400

CONFIRMATION

• Similar findings have now been obtained in Capetown,South Africa by C. Orrell et al working with subtype C infected populations

• In India, it now appears as though K65R will also be an important mutation among first-line treatment failures who received d4T/3TC/NVP

RationaleDoes the nucleotide sequence trigger an increased

probability of the development of the K65R resistance mutation in subtype C ?

Biochemical analysis of the syntheses of (-)strand DNA from viral RNA and(+)strand DNA from viral (-)strand DNA by the RTs of subtypes B and C.

(+)strand DNA synthesis (1)

Only the subtype C sequence triggers a pausing site that increases the probability of a nucleotide misincorporation event which in turn leads to the K65R mutation.

(+)strand DNA synthesis (2)

The pausing patterns are driven by the nucleotide templates and are independent of the RT enzymes used (subtype B vs C).

Validation in cell culture

5‘-... AAG AAA AAA ...-3‘5‘-... AAA AAA AAA ...-3‘5‘-... AAG AAG AAA ...-3‘

NL4-3 (wt)

NL4-3 (K64K)

NL4-3 (K65K)

NL4-3 (K64K/K65K)

What is the propensity of different recombinant viruses to develop the K65R resistance mutation under N(t)RTI treatment ?

64 65 66

GK65R

Infections of MT-2 cells and CBMCs with these viruses followed by treatmentwith different N(t)RTIs (single drugs or in combination).

5‘-... AAA AAG AAA ...-3‘

Selections in CBMCs

The double mutant NL4-3 (64/65) acquires K65R more rapidly in CBMCs than wild-type NL4-3.

Drugs Virus

NL4-3 (wt) NL4-3 (64/65)

Mutation Week Mutation Week

TFV none >35 K65R 25 TFV + 3TC M184V 15 K65R 20

Mutations in MT-2 Cells after 10 Weeks

DRUGVIRUS

NL4-3 (wt) NL4-3 (64) NL4-3 (65) NL4-3 (64/65)3TC M184I Not done Not done M184I

FTC M184I M184I M184I M184I

ABC M184I M184I M184I K65R

ddI L74V M184I V75I K65R

d4T None None None K65R

TFV None None None K65R

ConclusionK65R will be a more important mutation in subtype C than subtype B viruses. This may affect both prevention research strategies as well as treatment options over time in areas in which subtype C viruses are predominant

Sexual Transmission of Drug Resistance Mutations

• Approximately 5-10% of all new HIV infections in developed countries now include at least one drug-resistance related mutation.

• Transmitted drug resistance is now increasingly being reported in developing countries.

• No information is yet available on whether K65R may be sexually transmitted.

CONCLUSION

• HIV genotyping should be performed on all patients prior to prescription of ARVs

• HIV genotyping should be performed on all patients prior to switching to a second-line regimen.

• The above considerations are not yet practical in terms of being implemented in many developing country settings.

REMERCIEMENTS

• Dimitrios Coutsinos

• Cedric Invernizzi

• Maureen Oliveira

• Daniela Moisi

• Bluma Brenner

MERCI BEAUCOUP