Novel Adenovirus Vector-Based Vaccines for HIV-1

1
Novel Adenovirus Vector-Based Vaccines for HIV-1
Dan H. Barouch Beth Israel Deaconess Medical
Center November 20, 2008
2
Rationale for the Development of Novel Adenovirus
Vector-Based Vaccines for HIV-1

• The Merck rAd5-Gag/Pol/Nef vaccine failed to show
  efficacy and may have resulted in increased HIV-1
  acquisition in individuals with pre-existing
  anti-Ad5 immunity
• Homologous rAd5 regimens may be limited by
• Pre-existing anti-Ad5 immunity
• Skewed/inadequate quality of T lymphocyte
  responses
• Limited magnitude and breadth of responses as a
  result of homologous vector re-administration
• Minimal protective efficacy against SIV challenge
  in rhesus monkeys
• Potential advantages of novel rAd vectors
  include
• Evasion of pre-existing anti-vector immunity
• Enhanced polyfunctionality/quality of T
  lymphocyte responses
• Augmented magnitude and breadth of responses
  utilizing heterologous rAd prime-boost regimens
• Improved protective efficacy against SIV
  challenge in rhesus monkeys

3
Protective Efficacy of Heterologous rAd
Prime-Boost Regimens in Rhesus Monkeys

• 22 Mamu-A01/B17-negative rhesus monkeys
  immunized with various rAd regimens expressing
  SIV Gag (week 0, 24)
• rAd26-Gag prime, rAd5-Gag boost (N6)
• rAd35-Gag prime, rAd5-Gag boost (N6)
• rAd5-Gag prime, rAd5-Gag boost (N4)
• Sham (N6)
• High-dose i.v. SIVmac251 challenge (week 52)
• Highly stringent challenge model
  (Mamu-A01/B17-negative rhesus monkeys, single
  SIV Gag antigen, i.v. SIVmac251)
• rAd5 alone and DNA/rAd5 regimens do not reduce
  peak or setpoint SIV RNA levels in this model
  (Casimiro et al. J. Virol. 79 15547-55 2005)

Liu et al. Nature, Nov 9, 2008 (advance online
publication)
4
Increased Magnitude and Breadth of Gag-Specific
Responses in rAd26/rAd5 Vaccinated Monkeys As
Compared with rAd5/rAd5 Vaccinated Monkeys
Gag ELISPOT Magnitude
Gag Epitope Breadth
Week
5
Improved Polyfunctionality of Gag-Specific
Responses in rAd26/rAd5 Vaccinated Monkeys As
Compared with rAd5/rAd5 Vaccinated Monkeys
6
Significant 1.4 Log Decrease in Peak SIV RNA in
rAd26/rAd5 Vaccinated Monkeys Post-Challenge
Peak SIV RNA Levels Day 14 Post-Challenge
Mean
Two-tailed Wilcoxon rank-sum tests
7
Long-Term Significant 2.4 Log Decrease in SIV RNA
in rAd26/rAd5 Vaccinated Monkeys Post-Challenge
Setpoint SIV RNA Levels Mean Day 112-500
Post-Challenge
Mean
death
Two-tailed Wilcoxon rank-sum tests
8
Clinical Survival Advantage in rAd26/rAd5
Vaccinated Monkeys for gt500 Days Post-Challenge
P0.03
P0.03
Fishers exact test
9
Anamnestic Gag-Specific Cellular Immune Responses
in rAd26/rAd5 Vaccinated Monkeys Post-Challenge
Day 0
Day 28
Day 56
Day 14
10
Anamnestic Gag-Specific Cellular Immune Responses
in rAd26/rAd5 Vaccinated Monkeys Post-Challenge
Gag Cytokine Functionality
Gag Epitope Breadth
11
Breadth and Magnitude of Gag-Specific Cellular
Immune Responses Correlate with Setpoint Viral
Loads
Gag ELISPOT Magnitude
Gag Epitope Breadth
Pre-Challenge
Post-Challenge
Spearman rank-correlation tests
12
Protection Correlated with Reduced Ki67
Proliferation of CCR5 Central and Effector
Memory CD4 T Lymphocytes
Central Memory CCR5 CD4
Effector Memory CCR5 CD4
Day
13
Protection Correlated with Preservation of
Central Memory CD4 T Lymphocytes
CD28CD95CD4/CD4 Cells Day 14 Post-Challenge
two-tailed Wilcoxon rank-sum test
14
Protection Correlated with Preservation of
CCR5CD4 T Lymphocytes
CCR5CD4/CD4 Cells Day 14 Post-Challenge
two-tailed Wilcoxon rank-sum test
15
Protection Correlated with Preservation of
Duodenal Memory CD4 T Lymphocytes
CD4/CD3 Cells Day 21 Post-Challenge
two-tailed Wilcoxon rank-sum test
16
Protective Efficacy of Heterologous rAd
Prime-Boost Regimens in Rhesus Monkeys

• The heterologous rAd26/rAd5 regimen elicited
  improved quality, breadth, and magnitude of
  cellular immune responses as compared with the
  homologous rAd5/rAd5 regimen
• The heterologous rAd26/rAd5 regimen afforded a
  significant 1.4 log reduction of peak and 2.4 log
  reduction of setpoint SIV RNA as compared with
  controls for gt500 days post-challenge
• The homologous rAd5/rAd5 regimen failed to afford
  a significant reduction of peak or setpoint SIV
  RNA, consistent with prior studies

Liu et al. Nature, Nov 9, 2008 (advance online
publication)
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Protective Efficacy of Heterologous rAd
Prime-Boost Regimens in Rhesus Monkeys

• Thus, heterologous rAd prime-boost regimens can
  afford durable partial protection in the
  stringent SIV challenge model in which the
  homologous rAd5 regimen fails
• Protection correlated with Gag epitope-specific T
  lymphocyte responses and did not involve a
  homologous Env immunogen
• These data suggest that T cell based vaccines
  that are superior to the homologous rAd5 regimen
  may afford better protection against HIV-1
• We are not at the end of the road in terms of the
  development of T cell-based HIV-1 vaccines

Liu et al. Nature, Nov 9, 2008 (advance online
publication)
18
Safety of Novel rAd Vectors

• Are anamnestic Ad5-specific T lymphocyte
  responses following rAd5 vaccination a safety
  concern in individuals with baseline Ad5 NAb
  titers?
• Potential concern regarding cross-reactive T
  lymphocytes between Ad5 and rare serotype Ads?
• Collaborative study with D. Casimiro and M.
  Robertson, Merck
• 116 subjects from Merck phase 1 studies of
  rAd5-Gag
• Dose 1010 or 1011 vp
• Samples week 0 (pre-vaccine) and week 8
  (post-2nd vaccine) serum and PBMC
• Assays Ad NAb and ELISPOT assays with 104 MOI
  virus
• Peptide-specific assays and ICS assays in progress

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Ad5 ELISPOT Responses Are Nearly Universal and Do
Not Correlate with Ad5 NAb Responses at Baseline
Baseline Serum and PBMC Samples
P0.83
20
Higher Ad5 NAb Responses Following Vaccination in
Individuals with Baseline Ad5 NAbs gt18 vs lt18
P2.4x10-3
P5.4x10-4
P2.1x10-5
P2.0x10-6
P5.8x10-4
P2.0x10-6
lt 18
gt18
lt 18
gt18
Baseline Ad5 NAb
1010 vp Ad5-Gag
1011 vp Ad5-Gag
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No Detectable Ad26 NAb Responses Following
Vaccination
P0.88
P0.87
P0.81
P0.95
P0.79
P0.97
lt 18
gt18
lt 18
gt18
Baseline Ad5 NAb
1010 vp Ad5-Gag
1011 vp Ad5-Gag
22
No Detectable Ad35 NAb Responses Following
Vaccination
P0.48
P0.75
P0.35
P0.86
P0.51
P0.95
lt 18
gt18
lt 18
gt18
Baseline Ad5 NAb
1010 vp Ad5-Gag
1011 vp Ad5-Gag
23
No Detectable Ad48 NAb Responses Following
Vaccination
P0.86
P0.64
P0.84
P0.70
P0.79
P0.99
lt 18
gt18
lt 18
gt18
Baseline Ad5 NAb
1010 vp Ad5-Gag
1011 vp Ad5-Gag
24
Lower Ad5 ELISPOT Responses Following Vaccination
in Individuals with Baseline Ad5 NAbs gt18 vs lt18
P0.95
P0.91
P2.3x10-3
P8.3x10-3
P8.9x10-5
P0.043
P4.2x10-3
P0.53
lt 18
gt18
lt 18
gt18
Baseline Ad5 NAb
1010 vp Ad5-Gag
1011 vp Ad5-Gag
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No Detectable Ad26 ELISPOT Responses Following
Vaccination
P0.27
P0.85
P0.95
P0.39
P0.32
P0.83
P0.64
P0.80
lt 18
gt18
lt 18
gt18
Baseline Ad5 NAb
1010 vp Ad5-Gag
1011 vp Ad5-Gag
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No Detectable Ad35 ELISPOT Responses Following
Vaccination
P0.17
P0.49
P0.47
P0.55
P0.57
P0.75
P0.84
P0.56
lt 18
gt18
lt 18
gt18
Baseline Ad5 NAb
1010 vp Ad5-Gag
1011 vp Ad5-Gag
27
No Detectable Ad48 ELISPOT Responses Following
Vaccination
P0.85
P0.59
P0.55
P0.29
P0.40
P0.98
P0.75
P0.90
lt 18
gt18
lt 18
gt18
Baseline Ad5 NAb
1010 vp Ad5-Gag
1011 vp Ad5-Gag
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Safety of Novel rAd Vectors

• Ad5 T cell responses nearly universal in subjects
  prior to vaccination likely driven by
  cross-reactive hexon-specific T cell responses
  among multiple common subgroup C Ads
• Ad26, Ad35, Ad48 T cell responses also common
• No correlation observed between Ad5 NAb titers
  and Ad5 T cell responses prior to vaccination
• Suggests that Ad5 NAb titers are not simply a
  surrogate marker for Ad5 T cell responses
• Similar baseline Ad5 T cell responses in subjects
  with baseline Ad5 NAbs gt18 as compared with lt18

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Safety of Novel rAd Vectors

• Following rAd5 vaccination
• Ad5 NAb responses higher in subjects with
  baseline Ad5 NAbs gt18 as compared with lt18
• Ad5 T cell responses lower in subjects with
  baseline Ad5 NAbs gt18 as compared with lt18
• No detectable increase in NAb or T cell responses
  to Ad26, Ad35, Ad48
• Consistent with STEP data to date (J. McElrath,
  N. Frahm)
• These data reduce the plausibility of the
  hypothesis that enhancement of HIV-1 acquisition
  in subjects with baseline Ad5 NAbs gt18 in the
  STEP study was due to anamnestic vaccine-elicited
  Ad5 T cell responses
• Cross-reactive T cell responses against rare
  serotype Ad vectors would pose even less of a
  concern
• Caveats functional ICS and mucosal responses TBD

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Rationale for the Development of Novel Adenovirus
Vector-Based Vaccines for HIV-1

• Novel rAd vectors are biologically different than
  rAd5 vectors
• Different cellular receptors
• Different tropism
• Different intracellular trafficking pathways
• Different innate immune responses
• Different phenotypes of adaptive immune responses
• Novel rAd vectors outperform rAd5 vectors in
  rhesus monkeys
• Evade pre-existing anti-vector immunity
• Enhance polyfunctionality/quality of T lymphocyte
  responses
• Augment magnitude and breadth of responses when
  combined into heterologous rAd prime-boost
  regimens
• Substantially improve protection against
  SIVmac251 in rhesus monkeys
• Novel rAd vectors likely safer than rAd5 vectors
  in humans
• Designed to circumvent anti-vector immunity
• No significant cross-reactive anti-vector humoral
  immunity with Ad5
• Extent of cross-reactive anti-vector cellular
  immunity under investigation
• NIH, FDA, and IRB approved initiation of our
  rAd26 phase 1 study

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Ad26.ENVA.01 Phase 1A StudyNIH IPCAVD Program

• Single-site, randomized, double-blinded,
  placebo-controlled phase 1A study to evaluate the
  safety and immunogenicity of the Ad26.ENVA.01
  vaccine vector (PI L. Baden)
• First-in-human study of a rAd26 vector
• 48 subjects at low risk for HIV infection and
  Ad26 seronegative
• Groups
• 109 vp dose months 0, 1, 6 10 vaccinees, 2
  placebos
• 1010 vp dose months 0, 1, 6 10 vaccinees, 2
  placebos
• 1011 vp dose months 0, 1, 6 10 vaccinees, 2
  placebos
• Max dose months 0, 6 10 vaccinees, 2 placebos
• Study in progress vaccine safe and well
  tolerated to date

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Ad5HVR48.ENVA.01 Phase 1A StudyNIH IPCAVD Program

• Single-site, randomized, double-blinded,
  placebo-controlled phase 1A study to evaluate the
  safety and immunogenicity of the Ad5HVR48.ENVA.01
  vaccine vector (PI L. Baden)
• First-in-human study of a hexon-chimeric rAd5
  vector
• FDA clinical hold re risk criteria lifted
  October 29, 2008
• Enrollment expected to begin in Jan 2009
• Likely more regulatory challenges for future
  development of rAd5HVR48 as compared with rare
  serotype rAd vectors

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Design of Optimal Heterologous rAd Prime-Boost
Regimen rAd5HVR48/rAd26 in Rhesus Monkeys
Prime
Boost
IFN-g ELISPOT responses prior to and following
boost immunization
34
Design of Optimal Heterologous rAd Prime-Boost
Regimen rAd35/rAd26 and rAd48/rAd26 in Mice
Boost
Prime
IFN-g ELISPOT responses following boost
immunization
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Desired Features of a Next-Generation T
Cell-Based HIV-1 Vaccine Candidate

• Key features desired in a next-generation T
  cell-based HIV-1 vaccine
• Vectors that avoid pre-existing vector-specific
  NAbs and that can be combined into a heterologous
  prime-boost regimen
• Antigens that improve cellular immune breadth and
  that optimize coverage of global virus diversity

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Desired Features of a Next-Generation T
Cell-Based HIV-1 Vaccine Candidate

• Importance of cellular immune breadth
  increasingly clear
• Gag breadth critical for vaccine control of SIV
  challenge in NHPs
• Gag breadth critical for immune control of HIV in
  humans (B. Walker)
• In the STEP study, only limited breadth achieved
  by Merck rAd5-Gag/Pol/Nef vaccine (J. McElrath,
  N. Frahm, F. Li)
• Mean of only 2-3 epitopes per vaccinee (and only
  1 Gag epitope)
• Gag epitopes not directed against conserved
  regions of Gag
• 0 (zero) Gag epitopes in vaccinees with
  pre-existing Ad5 NAbs
• Trend observed between Gag breadth and setpoint
  viral loads
• Critical to improve breadth of Gag-specific
  cellular immune responses in a next-generation T
  cell-based HIV-1 vaccine

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Desired Features of a Next-Generation T
Cell-Based HIV-1 Vaccine Candidate

• We are currently exploring several antigen
  strategies together with B. Korber to improve
  cellular immune breadth
• M mosaic Gag/Pol/Env antigens (2-valent)
• M consensus Gag/Pol/Env antigens
• Optimal natural clade C Gag/Pol/Env antigens

38
Desired Features of a Next-Generation T
Cell-Based HIV-1 Vaccine Candidate

• Next generation T cell-based HIV-1 vaccines will
  face a higher bar to advance into efficacy
  studies
• Novel vector regimen
• Heterologous rAd prime-boost regimen using
  serologically distinct rare serotype rAd vectors
• Preclinical evidence of superior protective
  efficacy compared with the homologous rAd5
  regimen against SIV challenge in rhesus monkeys
• Novel antigen concept
• Antigen set optimized for augmented cellular
  immune breadth and improved coverage of global
  viral diversity
• Preclinical evidence of superior breadth compared
  with best natural clade C sequences using global
  PTE peptides in rhesus monkeys

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Conclusions

• The failure of the Merck rAd5-Gag/Pol/Nef vaccine
  clearly represents a product failure but may
  not represent a concept failure of T cell based
  vaccines in general
• SIV challenge studies in rhesus monkeys show that
  heterologous rAd prime-boost regimens with rAd26
  vectors outperform homologous rAd5 regimens
• Prototype rAd26 vector under evaluation in a
  phase 1 study
• Novel antigen sets aimed at improving cellular
  immune breadth under evaluation in NHP studies
• Evaluation of a heterologous rAd prime-boost
  regimen using two rare serotype rAd vectors
  expressing HIV-1 Gag/Pol/Env optimized for global
  coverage may therefore be warranted

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Acknowledgements

• Beth Israel Deaconess, Harvard Medical School
• Peter Abbink
• Ritu Bradley
• Sarah Clark
• Rebecca Dilan
• David Kaufman
• Sharon King
• Annalena LaPorte
• Hualin Li
• Jinyan Liu
• Diana Lynch
• Lori Maxfield
• Joseph Nkolola
• Kara OBrien
• Elizabeth Rhee
• Ambryice Riggs
• Larissa Sasgen
• Nate Simmons
• Faye Stephens

• Crucell Holland BV
• Marcel Brink
• Nico Bunnik
• Jerome Custers
• Frans Delemarre
• Jaap Goudsmit
• Anneke Griffioen
• Guus Hateboer
• Menzo Havenga
• Evert Heemskerk
• Lennart Holterman
• Karin Hoogendoorn
• Peter Karels
• Erica Kerkvliet
• Matthijs Koorevaar
• Fija Lagerwerf
• Angelique Lemckert
• Giuseppe Marzio
• Maria Grazia Pau

• CHAVI
• Bart Haynes
• Bette Korber
• Norman Letvin
• Merck Research Labs
• Danny Casimiro
• Sheri Dubey
• John Shiver
• VRC, NIAID, NIH
• Charla Andrews
• Phil Gomez
• Gary Nabel
• Rebecca Sheets
• DAIDS, NIAID, NIH
• Chris Butler
• Massimo Cardinali

• Crucell Holland BV cont.
• Ronald Vogels
• Miranda Weggeman
• Mo Weijtens
• Sander Worst
• Childrens Hospital, Harvard Medical School
• Bing Chen
• Stephen Harrison
• New England Primate Research Center
• Angela Carville
• Keith Mansfield
• IAVI
• Nick Jackson
• Wayne Koff
• SRI