Washington D.C., USA, 22-27 July 2012www.aids2012.org

Changing Patterns of NRTI and PI Resistance Mutations Between

2006 and 2011 in ART experienced SA patients

Gert van Zyl1, Mathilda Claassen1, Susan Engelbrecht,2 Tulio De Oliveira2,

Wolfgang Preiser3, Natasha Wood4, Simon Travers4, Robert Shafer5

1National Health Laboratory Service, Tygerberg, Coastal Branch, South Africa; 2Division of Medical Virology, Stellenbosch University, Faculty of Health Sciences, Parow, South Africa;

3Africa Centre for Health and Population Studies, University of KwaZulu-Natal, South Africa; 4South African National Bioinformatics Institute(SANBI), University of Western Cape, South

Africa; 5Division of Infectious Diseases, Center for AIDS Research, Stanford University Medical Center, Stanford, CA, United States of America

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Background (1)

• Toxicity of stavudine (D4T), resulted in it being replaced by TDF in adults and ABC in children, for South African patients, newly initiated on therapy since April 2010

• In addition, in patients with symptoms or signs of toxicity, TDF or ABC could substitute D4T or AZT

• This resulted in a rapid increase in the use of TDF in adults and ABC in children

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Background (2)

• In vitro data suggests that sub-type C strains may be more prone to developing the K65R mutation

• However the particular TDF drug combination used may be a stronger predictor (Tang et al. 2012) of K65R

• Limited data on the prevalence of TDF associated mutations (K65R, Y115F, K70E) and ABC associated mutations (L74V/I, Y115F) in patients in SA receiving these ‘new’ regimens.

• Study conducted to assess the prevalence of resistance associated mutations (RAMs) when virologic failure occurs and associations with particular regimens.

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METHODS

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Methods(1)

Study population• Specimens received from over South Africa,

from many public health hospitals and clinics, majority from Gauteng and Western Cape Provinces.

• Doctors complete a request form that is used for antiretroviral roll-out (designed for CD4 and VL monitoring) and contains a limited field for current therapy only.

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Section of the request form: current therapy

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Methods(2)

Test method:• Validated in-house antiretroviral genotypic resistance

assay was used: spans PR and amino acids 1-262 of RT

Sequence processing:• Nucleotide FASTA files, from all patients were imported

and resistance interpretations performed using Sierra, The Stanford HIV Web Service (Version 1.0).

Inclusion:• Patients with sequence AND recorded current therapy

were included• 1525 specimens (from 1293 patients) from May 2006 to

September 2011

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RESULTS: THERAPY USAGE

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Increase in number of patients tested over study period

2006 2007 2008 2009 2010 20110

50

100

150

200

250

300

<15 years (n=557)≥ 15 years (n=725)

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D4T AZT TDF DDI ABC 3TC0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

200620072008200920102011

Adult TDF use increases as D4T, AZT and DDI use decreases

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D4T AZT TDF DDI ABC 3TC0%

20%

40%

60%

80%

100%

120%

200620072008200920102011

Paediatric ABC use increases as D4T use decreases

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RESULTS: RESISTANCE OUTCOMES AND ASSOCIATIONS

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D4T/TDF/ABC + 3TC associated with different NRTI mutation patterns

M184V/I ≥3 TAMs K65R K70E L74V L74I Y115F0%

10%

20%

30%

40%

50%

60%

70%

80%

D4T (n=729)ABC (n=96)TDF (n=139)

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M184V/I

3-or-more TAMs

A62VK65R

A62V+K65RK70E

Y115F0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

TDF, 3TC, EFV (n=105)TDF, 3TC, NVP (n=8)TDF, 3TC, LPV/r (n=28)

TDF associated RAMs frequency also dependent on other regimen components

A62V – restores fitness ~ K65R

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Patients on NVP may be more likely to have TDF-associated mutations

p=0.009

6562%

4038%

TDF,3TC,EFV (n=105)

1; 13%

7; 88%

TDF,3TC, NVP (n=8)

No TDF RAMs

K65R/K70E/Y115F

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Mutations when ABC+ 3TC is used with PI or NNRTI

M184V/I

3-or-more TAMs

K65RK70E

L74V

L74I

Y115F0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

ABC, 3TC, EFV (n=50)ABC, 3TC, NVP (n=4)ABC, 3TC, LPV/r (n=71)

Fewer patients on LPV/r had ABC associated RAMs; p< 0.001

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LPV-associated major PI resistance mutations

Patients with major PI resistance: n=42

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DRV RAMs in about 4% of patients on LPV

V32I I50V L76V Total Paediatric0

2

4

6

8

10

12

14

16

18

20

Frequency

14 of 18 had history of LPV/r use

RTV as single PI historically used?

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EFV and NVP select different mutations

K101E/P

K103N V106M Y181C G190A0%

10%

20%

30%

40%

50%

60%

EFV (n=816)NVP (n=84)

EFV vs. NVP for: V106M and Y181C p< 0.001

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Conclusion (1)

• When antiretroviral failure occurs on a TDF regimen a high prevalence of TDF RAMs (K65R, Y115F, K70E or A62V) are observed – this concurs with other SA data (Sunpath et al. CROI 2012)

• The prevalence of TDF RAMs may be more common after NVP failure (7/8) than EFV (40/105) failure.

• Failure on an ABC regimen is associated with a high prevalence of L74V/I or Y115F.

• LPV/r regimen protects against TDF- or ABC- RAMs.

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Conclusion (2)

• Prevalence of major PI resistance mutations ~ 10% in LPV/r treated patients who fail (similar UK cohort, Barber et al. 2012)

• 14 of 42 with LPV associated RAMs have DRV cross resistance

• Historic use of RTV as single PI in children could have contributed to relative high prevalence of PI resistance

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Conclusion (3)

• Although the prevalence of TDF-associated mutations on TDF failure is high – current data shows that the TDF, FTC/3TC, EFV failure rate is low.

• D4T therapy failure results in a therapeutic dilemma – unknown whether patient has K65R or TAMs – and whether AZT or TDF should be preferred

• In contrast, on TDF or ABC regimen failure, RAMs are predictable and second-line options are likely to be effective.

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Acknowledgements• Specimens and results: We would like to

thank Ronell Taylor, who compiled the database, the clinicians across South Africa, who provided specimens and clinical information, and National Health Laboratory Service technologists, who received the specimens and processed them.

• Database support: We would like to thank Tommy Liu, Stanford Resistance Database, for support with Sierra, The Stanford HIV Web Service.