1. Experimental Medicine Trials of Promising HIV Candidates
Robin Shattock

2. Experimental Medicine Trials - Why
Scientific:
Animal models are not fully predictive of human responses
There are germ line differences between humans and experimental animals
Recognized need for human immunogen discovery
NGS and ’omics can provide valuable information from a few subjects
Financial:
Unsustainable to continue to put “wishful” candidates into expensive phase 3 trials
Better allocation of resources to increase likelihood of success
Logistical:
Public Health need to accelerate HIV vaccine development
Increasing difficulty of conducting large scale efficacy trials
Ethical:
Enrolling volunteers in vaccine trials with higher probability of success
Reducing the number of volunteers exposed to unsuccessful vaccine candidates

3. Experimental Medicine Trials - What
Designed to accelerate development and decrease risk of late-stage failure.
Address questions not capable of definitive solution in animal models
Facilitate early cross-talk between preclinical and clinical research (para-clinical)
Enable validation and sequential iterations for structural design based
Hypothesis testing of novel concepts prior to formal product development
Provide in depth analysis of human immune repertoire responses
Involve intense sampling – blood mucosal, lymph node biopsies, bone marrow, etc.

4. and how can it guide vaccine development ?
What do we know about the development of bnAbs in HIV-1 infected subjects
and how can it guide vaccine development ?
Time
months
Time
years
Identified key signatures of the development of bNAbs infected individual – determine the extent to which these are valuable to vaccine design 1%
20%
Gruell & Klein Nature Medicine 2014:20: 478-9

5. The road ahead: Three main strategies heading to the clinic
gp120, gp140 subunits
Trimer mimics (native trimer) – eg SOSIP, UFO, Linker designs
Epitope mimics: Binding sites of broadly neutralizing antibodies (Scaffolds) – germline engagement (eg eOD-GT8)
Our overall strategy for generation of immunogens.
Nucleic acid and viral vectors platforms (surface expression of native trimers)
Likely a combination of elements – heterologous prime-boost

6. (Native-like trimers)
B cell immunogen design: SOSIP trimers
SOSIP.664 trimers
Induction of autologous Tier 2 NAbs
SOSIP.v5 trimers
Improved trimerization
Increased stability
Reduced V3 non-NAb epitope exposure
Reduced CD4i non-NAb epitope exposure
Improved bNAb exposure
Reduced V3 immunogenicity and Tier 1A NAb induction
Autologous neutralization titers
Uncleaved gp140
(Non-native trimers)
SOSIP.664 gp140
(Native-like trimers)
P <
50% protection
80% protection
Improves existing trimers
Allows making new trimers
AMC008 SOSIP.v4.2
bNAb PGV04
bNAb 35O22
Sanders et al PLoS Path. 9:e
Sanders et al Science 349:aac4223
De Taeye et al Cell
Sanders: AMC

7. B cell immunogen design: Trimer cross-linking
Positively-selected trimers have native
morphology and improved antigenicity
V3 negatively-selected trimers have native
morphology and improved antigenicity
Stability under SDS PAGE
Cryo-EM model of GLA cross-linked, PGT151-bound BG505 trimer
Summary
BG505 and B41 trimers have been cross-linked using two different chemistries (GLA and EDC)
Cross-linked trimers become more stable and have reduced non-NAbs binding
Positive and negative selection of cross-linked trimers optimises antigenicity and morphology
Unmodified and cross-linked trimers have similar rabbit immunogenicity and induce neutralizing antibodies
Schiffner et al J. Virol. 87:
Schiffner et al J. Virol. 90:
Sattentau:UOXF

8. Pressing clinical questions
Interval – (markers of contraction (0-1, 0-3, 0-6 etc)
Dose – prime vs boost – (increasing/decreasing/fractional dose).
Adjuvants (multiple)
Route - ID, IM, SC, mucosal
B cell memory durability, SHM, plasmacell number/durability.
Quality of TfH response
Longevity - protein only or vector prime- protein boost
Antigen(s) germline, lineage, sequential, cocktails.
Antigen presentation: soluble, membrane bound, particle, VLP, scaffold.

9. Major bottleneck is the cost and speed of GMP manufacturing
Clinical
Preclinical

10. Genetic approaches can cut costs and time
Advantages
– membrane context
Disadvantage
- structural diversity

11. Manufacture of native-like trimers
Appropriate scale, cost and timelines of manufacture
- without compromising safety or quality
Harnessing generic process platforms
Candidates selection on basis of thorough characterisation:
Biochemical (SDS-PAGE, BN-PAGE),
Biophysical (DLS and differential scanning calorimetry DSC),
Structural (cryo-EM and X-ray crystallography)
Antigenicity (ELISA, SPR, isothermal titration calorimetry (ITC)).
Glycosylation profile
Immunogenicity rabbits/NHPs
ConM-SOSIP and ConS-linker versions
-with and without cross-linking
in GMP production (Polymun)
Additional candidates based on germline and
lineage designs in preclinical assessment

12. Serum Effect of spacing between HIV-antigen priming and boosting ?
Group A
Group B
Kratochvil S, et al
Front Immunol. 2017 
2nd
3rd
4th
2nd
3rd
4th
Ag-specific
IgG/A/M
[ng/ml]
grey bars timing of immunisations
IgG-Subclasses
Ag-specific
[ng/ml]
2nd
3rd
4th
Study days

13. HIV Vaccine Pipeline – EAVI2020
Basic
research
Applied
research
Preclinical development
Experimental Medicine studies
manufacture
Clinical candidates to elicit bnAbs
Native like trimers and combinations Q1 2018
Germline targeting trimers Q2 2018
Lineage based trimers Q4 2018
NIH BG505-SOSIP Q1 2018
Pre-clinical candidates to elicit bnAbs
HIV ENV trimers
Glycan priming
gp41
Improve the breadth of CMI vaccines
Conserved-Mosaic Antigens: chAd, MVA: HIV neg 2018
HTI: DNA, chAd, MVA: HIV neg 2018
Conserved-Mosaic Antigens: chAd, MVA: HIV pos 2019
HTI: DNA, chAd, MVA: HIV pos 2019
Vectors - to improve breadth and durability
DNA
RNA
BCG
IDLV

14. Clinically-Informed Reverse Vaccinology
Iterative immunogen testing and refinement Ag
It is abundantly clear that classical RV approaches (in silico) have been unable to design effective vaccines for HIV - where the antigenic determinants of bnAbs are already well defined but are too variable or unstable to induce a protective immune-response. What we are proposing is a program of clinically directed RV, this represents a significant change in approach that synergistically combines human immunology, structural biology and bioinformatics to identify and design better immunogens
it will give unprecedented insight into human adaptive immune responses to HIV-1 vaccine immunization.
Directing responses to towards broadly neutralizing (protective) antibodies
B cell cloning, functional analysis and NGS
assess Ab repertoire response
germline engagement,
SHM,
CDR length
epitope specificity
neutralisation
Iterative immunogen design
modulate bnAb epitope exposure
stabilize conformation
reduce off-target responses
increase breadth
increase effective T cell help *
ADCC, ADCP, ADCVI
Complement *
Molecular characterization
Structural modeling
Antibody-immunogen interaction

15. Thank you for your attention