projeto praça onze universidade federal do rio de janeiro clinical trials at aids vaccine ‘09...
TRANSCRIPT
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Projeto Praça OnzeUniversidade Federal do Rio de Janeiro
Clinical Trials at AIDS Vaccine ‘09
Scientific Journalists Training ProgramGlobal HIV Vaccine Enterprise
Paris, October 19, 2009
Mauro SchechterPrincipal Investigator, Projeto Praça Onze
Professor of Infectious DiseasesUniversidade Federal do Rio de Janeiro
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Development of HIV vaccines
Laboratory and animal protection experiments
20–50 HIV-negative volunteers (lower risk); safety and immunogenicity I I
II II
III III
IV IV
100s of HIV-negative volunteers (lower and higher risk); safety, immunogenicity; doses, routes of administration, different populations
1000s of HIV-negative volunteers (higher risk); efficacy
Effectiveness; operational research
Pre-clinical phase
Clinical Phases
*
*
* Randomized clinical trials
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Randomised Controlled Trials (RCTs)
• Experimental, (usually) longitudinal, prospective
• Randomised – ensures that treatment groups are similar at start of trial; any differences are due to chance only
• Controlled – control group allows to conclude that outcome is due to the test vaccine rather than some other factor
• Comparison is usually between a new regimen or intervention and an existing standard of care or placebo
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Generalisability• Participants can be different from those that will use the vaccine
• Eligibility criteria often leads to groups of patients being excluded (e.g. STI co-infection)
Length of trial and primary endpoints• Typically 1-3 years long, thus efficacy of over the longer-term is not
assessed
• Surrogate markers versus clinical events
Limitations of randomized clinical trials
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Follow-up of patients• Participants are generally seen more regularly and followed more
intensely than in routine practice - this may influence behaviour, etc.
• Feasibility• Potential participants may not want to leave an important decision
up to chance
• Rare events are difficult to assess in RCTs as long follow-up periods and large numbers of patients are required
• Ethics• It may be unethical to withhold an intervention to form a control
group
Limitations of randomized clinical trials
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Practical aspects of clinical trials
• Question being studied
• Trial population/Control group
• Trial design
• Analysis (pre-specified vs. post-hoc)
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Practical aspects of clinical trials
• Question being studied
• Trial population/Control group
• Trial design
• Analysis (pre-specified vs. post-hoc)
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Practical aspects of clinical trials
• Question being studied
• Trial population/Control group
• Trial design
• Analysis (pre-specified vs. post-hoc)
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Trial populations
• Explicit and objective inclusion and exclusion criteria are required for any RCT
• Narrow and restrictive inclusion criteria can allow to focus on a specific group of people and reduce variability in the outcome
• However, included participants may not be representative of those who may receive the vaccine in the future
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The need for a control group
• ‘Hawthorn effect’: observation that patients in clinical trials generally do better than similar patients on same treatment (closer monitoring, clear treatment plan, enthusiastic team, etc.)
• Therefore, a control group provides the opportunity to see ‘what would have happened without the new intervention’
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The need for randomisation
• Patient allocation to new intervention or control groups is determined purely by chance
• Thus, any differences between the different arms of the trial are due to chance alone
• This includes both known and unknown factors
• Thus, provided individuals are treated similarly during the study period, any differences in outcome between the two groups can be attributed to the intervention
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Practical aspects of clinical trials
• Question being studied
• Trial population/Control group
• Trial design
• Analysis (pre-specified vs. post-hoc)
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Blinding
• Bias can occur if a patient or treatment team are aware of treatment allocation
• Patient: psychological effect on behaviour
• Clinical team: intensity of counselling
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Types of RCTs
• Parallel group: each patient is randomised to receive only one of the two different strategies
• Crossover trial: each patient receives first one treatment strategy then the other, but the treatment order is randomised
• Cluster randomised: each ‘cluster’ of patients (hospitals, outpatient clinics) randomised to receive one of the two different treatment strategies
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Parallel design trials
Randomisation
New intervention
Control group
Present time
Compare treatment
groups
Follow individuals
Starting point
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Cross-over trials
Randomisation
New Intervention
Control group
Present time Future timeFollow individuals
Starting point
New Intervention
Control group
Wash out
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Crossover trial
• Crossover trials are particularly useful for short term outcomes in chronic conditions
• The treatment must be one that does not permanently alter the disease or condition under study
• The main limitation of a crossover trial is that the effect of the first treatment administered may carry over and alter subsequent responses
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Cluster randomised trials
Randomisation of Hospital/Clinic
New Intervention
All patients at hospital/clinic receive new intervention
All patients at
hospital/clinic
receive new
intervention
Control group
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Clinical Trials at AIDS Vaccine ‘09
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SS01-02Clinical outcomes from the STEP study
Background
• 3,000 men and women
• 3 doses of MRKAd5 gag/pol/nef vaccine or placebo
• Vaccinations stopped after a pre-specified interim analysis in Ad5 seronegative participants demonstrated no protective effect on HIV acquisition or early plasma viral load
• Further analysis demonstrated an increased hazard ratio (HR) for HIV acquisition among Ad5 seropositive and uncircumcised vaccinees vs. placebo recipients
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SS01-02Clinical outcomes from the STEP study
Objective
• To compare rates of HIV acquisition among vaccine vs. placebo recipients
Methods
• Pre-unblinding data were frozen as of Oct 17, 2007;
• Post-unblinding data are from Oct 18, 2007 through January 23, 2009
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SS01-04Interim efficacy analysis
of Phambili study
Background
• Step sister study conducted in South Africa
• In September 2007, because of results of the Step study, vaccinations were suspended but follow up
Objective
• To compare rates of HIV acquisition among vaccine vs. placebo recipients
Methods
• Pre-unblinding and post-unblinding data
• 801 participants enrolled, 7% received all 3 study injections; 66% received two; and 27% received one
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OA04-01Safety and immunogenicity of
LIPO-5, a HIV-1 lipopeptide vaccine
Background
• The vaccine includes 5 long peptides, containing multiple CD8+ and CD4+ T-cell epitopes
• Phase 1 studies have shown that vaccine dosage at 500µg/lipopeptide elicits cellular immune responses
Objective
• Investigate if HIV-LIPO5 immunogenicity varies with the dosage
Methods
• ELISpot and PBMC lymphoproliferation were assessed at baseline, two weeks after each injection, and at week 48
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OA04-02
• Strong HIV-specific CD4 and CD8 T-lymphocyte proliferation in HIV-1 DNA prime/ modified vaccinia virus Ankara (MVA) heterologous boost vaccinees
OA04-03
• Characterization of cell-mediated immune responses generated by recombinant modified vaccinia Ankara (rMVA)-HIV-1 in a phase I vaccine trial
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OA04-05Safety and viral load changes in HIV-1 infected
subjects treated with autologous dendritic immunetherapy following ART discontinuation
Background
• In a phase 1 trial, immunotherapy consisting of a monocyte-derived dendritic cells and RNA encoding autologous HIV antigens derived from the patient’s own pre-ART plasma induced immunogenicity in most patients
Objective
• Assess the safety and proportion of patients demonstrating viral load < 1000, <5000 and <10,000 copies/mL during the 12 week ART structured treatment interruption (STI)
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TAKE HOME MESSAGES
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Take home message # 1
How to interpretwhat scientists predict a trial will show
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“All predictions are difficult, particularly when they involve the future”
Dan Quayle
Former US Vice-President
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Take home message # 2
How to interpretwhat reputable scientists mean when
they criticize trials that will be conducted by other reputable scientists
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“If we knew what we are doing, we wouldn't call it
research.”
– Albert Einstein
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Take home message # 3
How to interpretwhat scientists say
they have learned from a trial
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“Half of what we have taught you is wrong.
Unfortunately, we do not know which half.”
– C. Sidney Burwell, M.D.
Address to the graduation class
Harvard Medical School
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Merci !Thank You !Obrigado !