2. Monoclonal Antibodies for HIV Prevention
Nyaradzo M. Mgodi (MBChB, MMed)
Principal Investigator
University of Zimbabwe College of Health Sciences Clinical Trials Unit

3. Conflict of Interest
No conflicts of interest to declare.

4. Presentation Outline Passive immunization
Antibodies for HIV prevention
VRC01 monoclonal antibody
AMP Study
Other monoclonal antibodies
Conclusion
Passive immunization
Antibody response to HIV infection
VRC01 monoclonal antibody
AMP Trial Design considerations
Eligibility criteria
Trial Monitoring
Study progress
Summary

5. Passive Immunization
Long history of use of antibodies against viral infections
Passive Antibody Prevention of HIV/SHIV in NHP for over 20 years
Polyclonal IgG protects Chimps from HIV infection
Polyclonal IgG protects against SHIV challenge
Use of mAbs (2F5, 2G12, F105) and protection against mucosal challenge
Protection with newer generation mAbs (PGT121, 3BNC117, , VRC01, VRC07)
Long history of use of antibodies against viral infections
Passive Antibody Prevention of HIV/SHIV in NHP for over 20 years
Polyclonal IgG protects Chimps from HIV infection
Polyclonal IgG protects against SHIV challenge
Use of mAbs (2F5, 2G12, F105) and protection against mucosal challenge
Protection with newer generation mAbs (PGT121, 3BNC117, , VRC01, VRC07)

6. Passive Immunization
Long history of use of antibodies against viral infections
Passive Antibody Prevention of HIV/SHIV in NHP for over 20 years
There are no human data regarding passive protection by HIV-1 monoclonal antibodies
NHP studies tell us that physiologically achievable levels of Ab could prevent HIV-1 infection
There are no human data regarding passive protection by HIV-1 monoclonal antibodies
Learn from Proof of Concept in Humans:
What type of Ab response can prevent HIV infection?
What level of Ab is needed to prevent infection?
Pertains to passive IgG infusion, or vectored delivery
Convert the mAb levels to serum level of neutralization needed to protect (e.g., neut titer 1:50, 1;500)
Provides a benchmark for vaccine development; i.e., what antibody level does a vaccine need to achieve

7. Antibodies for HIV Prevention
Many unanswered questions
Can antibodies prevent HIV-infection in humans?
What level of mAb is needed to protect?
Where and how does the mAb work?
Lumen, epithelial surface, mucosal, lymphoid tissue?
Are Fc-mediated effector functions (ADCC) needed for protection?
Can antibodies prevent HIV-infection in humans?
What level of mAb is needed to protect?
Where and how does the mAb work: lumen, epithelial surface, mucosal or lymphoid tissue?
Are Fc-mediated effector functions (ADCC) needed for protection?

8. Antibodies for HIV Prevention
Previous studies have shown that HIV-1 encounters a genetic bottleneck during transmission, often resulting in a genetically homogenous population of initial plasma viremia. Partially due to the host adaptive immunity, the early circulating virus evolves into a diverse population over time, with genetic diversity of up to 10% in the env gene within an infected individual.
B-cell responses to HIV-1 develop within approx. 1 week of detectable viraemia

9. Development of Broadly Neutralizing Antibodies (BnABs)
HIV-1
Antibody
The transmitted-
Founder virus
The initial neutralizing antibody response to HIV “autologous nAb”
Escape virus
Continuum with 10~20%- Broadly neutralizing antibodies
Previous studies have shown that HIV-1 encounters a genetic bottleneck during transmission, often resulting in a genetically homogenous population of initial plasma viremia. Partially due to the host adaptive immunity, the early circulating virus evolves into a diverse population over time, with genetic diversity of up to 10% in the env gene within an infected individual.
B-cell responses to HIV-1 develop within approx. 1 week of detectable viraemia
Initially: Ag-Ab complexes
Then circulating anti-gp41 antibodies within days
Circulating anti-gp120 antibodies weeks later
These binding Abs do not have a detectable effect on viraemia
nAbs against the infecting strain appear months later – these are not able to neutralise more divergent viruses
Autologous virus-neutralizing antibodies generally develop within the first months or year of infection, and there is a well-documented antibody-based selection process that results in ongoing viral escape from autologous neutralizing antibodies. Thus, circulating plasma viral Env variants are poorly neutralized by concurrent serum but are often potently neutralized by serum samples from later time points. Importantly, the early autologous neutralizing antibody response is usually highly strain specific; these antibodies do not appear to target conserved regions of Env and do not neutralize most heterologous viral isolates. Until recently, few broadly reactive HIV-1-neutralizing antibodies had been isolated; thus, the Env quasispecies in donors with such antibodies have not been characterized.
Development of Broadly Neutralizing Antibodies (BnABs)

10. VRC01
Successful effort to isolate broadly neutralizing antibodies to HIV-1 from chronically infected donors
The first antibody to enter advanced human clinical trials is VRC01
Discovered in an elite viral controller.
human mAb targeting the CD4 binding site
Demonstrated protection in animal studies, and has acceptable human safety
Hence over the past several years, there has been a concerted and notably successful effort to isolate broadly neutralizing antibodies to HIV-1 from chronically infected donors
Over the past 5 years, a new generation of highly potent and broadly neutralizing HIV-1 antibodies has been identified. These antibodies can protect against lentiviral infection in nonhuman primates (NHP), suggesting that passive antibody transfer would prevent HIV-1 transmission in humans. The first antibody to enter advanced human clinical trials is VRC01, discovered in an elite viral controller. It is a human monoclonal antibody targeting the HIV-1 CD4 binding site. VRC01 demonstrated protection in animal studies, and has acceptable human safety. The availability of bNabs against HIV opens the exciting possibility of antibody-mediated prevention (AMP) of HIV infection.

11. AMP Study
A phase 2b study to evaluate the efficacy of VRC01 broadly neutralizing monoclonal antibody in reducing acquisition of HIV-1 infection

12. AMP Research Sites 47 sites in 11 countries
HVTN 704/HPTN 085, MSM + TG
HVTN 703/HPTN 081, Women
The study is being conducted by the HIV Vaccine Trials Network and the HIV Prevention Trials Network, in partnership with their combined clinical trial sites.

13. AMP Study: Two Harmonized Protocols
HVTN 703/HPTN 081
HVTN 704/HPTN 085
Sub-Sahara Africa
21 Sites, 7 Countries
1500 heterosexual women
years
Opened May 2016
Americas, Europe
26 Sites
2700 MSM and TG people
years
Opened April 2016
Placebo controlled trial of VRC01 mAb (IV), given on q2 month schedule
Powered to detect 60% efficacy; and to associate VRC01 plasma
level with protection

14. Rationale for Two Cohorts
As these are test-of-concept trials we selected the two populations in which novel biomedical interventions are needed
MSM + TG in the Americas
Heterosexual women in sub-Saharan Africa
We suspect that route of acquisition and genital tract immunology and anatomy may influence the distribution of VRC01 and potential efficacy
As these are Test-of-Concept trials we selected the two populations in which novel biomedical interventions are needed
MSM + TG in the Americas
Heterosexual women in sub-Saharan Africa
We suspect that route of acquisition and genital tract immunology and anatomy may influence the distribution of VRC01 and potential efficacy

15. Main Study Hypotheses
Administration of this broadly neutralizing antibody will reduce acquisition of HIV infection in these high risk populations;
The level of VRC01 antibody required for protection will vary by type of sexual exposure and not by clade;
The concentration of antibody in serum will be directly associated with the rate of protection;
higher levels of antibodies will give greater rates of protection than lower levels;
Breakthrough isolates will have greater resistance to neutralization and will exhibit molecular signatures associated with escape from neutralization.
Passive administration of VRC01 antibody will reduce acquisition of HIV infection in high risk populations
Doses selected will determine the activity of the antibody across a range of serum concentration in diverse populations across multiple geographic regions of the world
Level of VRC01 antibody required for protection will vary by type of sexual exposure
Concentration of antibody in serum will be directly associated with the rate of protection; that is, higher levels of antibody will give greater rates of protection than lower levels
Breakthrough isolates will have greater resistance to neutralization and will exhibit molecular signatures associated with escape from neutralization.
How long to follow participants for HIV infection?
How to ensure adequate variability in mAb characteristics over time and/or among mAb recipients to enable correlates assessment?
How to factor background prevention measures such as PrEP into the sample size calculations?
How to sample markers to allow accurate modeling of mAb characteristics over time?

16. Why Study VRC01? Broadly neutralizing & potent in lab studies
Promising antibody for HIV prevention
Broadly neutralizing & potent in lab studies
Good results in early Phase I studies
May supplement other prevention approaches
Move the HIV vaccine search forward
Teach us the amount of antibody a vaccine may need to elicit to prevent HIV
Help us find a safe, effective HIV vaccine more efficiently
PREVENTION
HIV VACCINE

17. AMP Study Objectives PRIMARY SECONDARY
Safety & Tolerability of VRC01 infusion
Reactogenicity, AEs, SAEs, discontinuation rates
Efficacy to prevent HIV infection
HIV infection by week 80 in those HIV-negative at enrollment
Develop a marker(s) of VRC01 that correlates with the level and antigenic specificity of efficacy
Serum VRC01 concentration
Serum mAb effector functions
Breakthrough HIV infection sequences
VRC01 neutralization sensitivity of, & effector functions against, HIV strains from infected trial participants
PRIMARY
SECONDARY

18. Primary Efficacy Analysis
Target parameter for prevention of HIV-1 infection:
Cumulative Incidence by Week 80 mAb group
Cumulative Incidence by Week 80 control group
Primary hypothesis test*:
H0: PE ≤ 0% vs. H1: PE > 0%
A Phase 2b test-of-concept trial
Rida, Fleming et al. (1996); Fleming and Richardson (2004), Gilbert (2010)
PE = 1 −
× 100%
*1-sided level Wald test

19. Compare Randomized Groups
Secondary Objective: Identify VRC01 Markers as Correlates of Protection (CoPs) to Prevent HIV-1
Compare Randomized Groups
Compare PE of the low and high mAb dose groups
Case-Control Analysis
Assess how PE varies over subgroups defined by VRC01 markers over time
Sieve Analysis
Assess how PE depends on HIV-1 genetics in the VRC01 footprint

20. Which mAb Markers to Assess as Correlates?
Serum concentration of mAb (BAMA or ELISA)
Advantage: Marker defined without reference to a particular HIV-1(s)
Serum mAb effector functions to HIV-1 Envs representing variability of mAb footprints
Advantage: May link to immunogenicity endpoints that would be used in future vaccine trials
Effector functions: Neutralizing antibodies, ADCC, ADCP, virion capture, etc.

21. North + South American MSM (2700) sub-Saharan African women (1500)
AMP Study Schema
Cohort
IV Treatment n=
Schedule
North + South American MSM (2700)
HVTN 704 / HPTN 085
VRC01 10 mg/kg
900
Every 8 wks x 10 doses over
22 months
VRC01 30 mg/kg
Placebo Control
sub-Saharan African women (1500)
HVTN 703 / HPTN 081
500
Two different infusion doses: important to know if lower dose of 10 mg/kg can protect
All subjects provided an HIV “prevention package”

22. HVTN 703/HPTN 081 (July 2017) Enrollment: 884 (118% of expected)
Retention: 96% of 3,266 visits
Adherence: 99% of 1,948 infusions

23. HVTN 704/HPTN 085 (July, 2017) Enrollment: 1,429 (116% of expected)
Retention: 96% of 7,905 visits
Adherence: 99.9% of 4,328 infusions

24. What happens with success?
Best case…
We find that low doses (e.g. levels at 5-10 ug) can protect against acquisition Translate that into:
Single dose administration of mAbs to achieve this level
immunogen that achieves this level of neutralization
Incentive to develop next generation mAb (more potent, longer half life)
Options for genetic immunization to provide medium to long-term protective antibody levels
Knowledge that neutralizing mAb can protect will guide vaccine field
It is also important to note that bnAbs may play a role in immunotherapy for HIV infection as part of an eradication or cure strategy.

25. What happens with success?
Success only at high doses…
Immunogen design will be difficult
Non-neutralizing approaches emerge or combination with neutralizing antibodies
Develop product that allows high doses to be present for prolonged time periods
Target for genetic immunization
Includes suicide gene to turn off when desired.
Best case…
• We find that low doses (e.g. levels at 5-10 ug) can
protect against acquisition.
Translate that into:
a) immunogen that achieves this level of neutralization
b) develop product that allows long term administration
by subcutaneous or IM administration
c) move to genetic immunization to provide long term low
dose concentrations

26. What about other monoclonal Antibodies?
To advance the field of antibody-mediated prevention, there is a need to develop and evaluate improved bnAbs for use in long-acting formulations and possibly in combination with other bnAbs (as a “cocktail”) to enhance efficacy.
The public health impact could be great for an easy-to-administer (SC or IM) bnAb approach that has a very long (>6 months) duration of HIV prevention efficacy. This approach, including one or more bnAbs, has the promise of yielding another long-acting HIV prevention method that does not require daily adherence to product use, and does not risk the development of ARV resistance.

27. VRC07 – 523 LS
New generation of highly potent and broadly neutralizing HIV-1 antibodies has been identified
Enhance the neutralization potency and breadth of VRC01 via
Next-generation sequencing, computational bioinformatics, and structure-guided design
One variant is VRC07-523,
5- to 8-fold more potent than VRC01,
Neutralized 96% of viruses tested,
Displayed minimal autoreactivity.
Over the past 5 years, a new generation of highly potent and broadly neutralizing HIV-1 antibodies has been identified. These
antibodies can protect against lentiviral infection in nonhuman primates (NHPs), suggesting that passive antibody transfer
would prevent HIV-1 transmission in humans. To increase the protective efficacy of such monoclonal antibodies, we employed
next-generation sequencing, computational bioinformatics, and structure-guided design to enhance the neutralization potency
and breadth of VRC01, an antibody that targets the CD4 binding site of the HIV-1 envelope.
Here, we used next-generation sequencing of antibody gene transcripts to identify heavy-chain somatic variants of VRC01 with enhanced neutralization potency. The somatic
variant with highest potency, VRC07, was subjected to an iterative process of computational and structure-guided optimization which identified mutations that optimized neutralization potency and minimized autoreactivity in vitro.
The public health impact could be great for an easy-to-administer (SC or IM) bnAb approach that has a very long (>6 months) duration of HIV prevention efficacy. This approach, including one or more bnAbs, has the promise of yielding another long-acting HIV prevention method that does not require daily adherence to product use, and does not risk the development of ARV resistance.
Rudicell et al. J. Virol (2014)

28. VRC01 LS Variant
A bnAb directed to the CD4-binding site of the HIV-1 envelope (Env) protein (denoted VRC01)3 was modified by site-directed mutagenesis to increase its binding affinity for FcRn. This enhanced FcRn-binding mutant bnAb, denoted VRC01-LS, displayed increased transcytosis across human FcRn-expressing cellular monolayers in vitro while retaining FcγRIIIa binding and function, including antibody-dependent cell-mediated cytotoxicity (ADCC) activity, at levels similar to VRC01 (the wild type). VRC01-LS had a threefold longer serum half-life than VRC01 in non-human primates and persisted in the rectal mucosa even when it was no longer detectable in the serum. Notably, VRC01-LS mediated protection superior to that afforded by VRC01 against intrarectal infection with simian–human immunodeficiency virus (SHIV). These findings suggest that modification of FcRn binding provides a mechanism not only to increase serum half-life but also to enhance mucosal localization that confers immune protection. Mutations that enhance FcRn function could therefore increase the potency and durability of passive immunization strategies to prevent HIV-1 infection.
Fc region binds with high affinity to FcRn at acidic pH (<6.5) in endosome
Protects antibody from endosomal degradation
IgG released back into circulation at physiological pH (7.4)
Results in prolonged circulating half life

29. Combined Antibodies: Improved Potency and Breadth
Kong, Montefiori Korber et al. J. Virol (2015)

30. Conclusion: Why Antibodies for HIV Prevention?
Reasonable likelihood that antibodies will work
Likely to be safe and well tolerated
We want to PREVENT, and END HIV…
Whether through an mAb, or
Through an HIV vaccine, or
Through an intra-vaginal ring, or
Through oral PrEP, or
Through a long acting injectable agent
“The secret is to gang up on the problem (HIV), rather than compete against each other” - adapted, Thomas Stallkamp
It is also important to note that bnAbs may play a role in immunotherapy for HIV infection as part of an eradication or cure strategy.

31. Saving Lives Through Innovative Research Strategies
Thank you
Saving Lives Through Innovative Research Strategies