Animal models: other Flashcards
What are the reasons for the use of animal models in TB drug and regimen development? (2)
- In vitro systems cannot address crucial component
- DS-TB: safe and highly effective treatment regimens are already available for active/latent infection
Which crucial components can in vitro systems not address in TB drug and regimen development? (5)
- Safety and tolerability of drugs
- PK properties of drug and drug-drug interactions
- Bacterial susceptibility to drugs in vivo
- Selection of in vivo drug resistance mechanisms
- Treatment duration
What are the common animal models for TB treatment? (5)
- Mice
- Guinea pigs
- Rabbits
- Zebrafish
- NHP
Why are guinea pigs, rabbits and zebrafish difficult model systems for TB?
They have drug metabolism, tolerance and toxicity issues –> cannot tolerate long durations of drug testing
TB: Which animal models have housing requirements that make it difficult to conduct statistically robust experiments? (3)
- Guinea pigs
- Rabbits
- NHP
Why is a mouse model the preferred model system for TB?
No other animal model has demonstrated equivalent or superior predictive value for translation to human clinical studies
What is the fundamental goal of an animal model for TB?
To have a model of TB treatment with translational value that provides critical information to inform the design of (human) clinical trials
What are NOT the goals for designing an animal model for TB? (2)
- Finding treatments for mouse TB
- Mimicking human disease
Which studies do you need to consider when selecting a TB mouse model? (2)
- PK studies conducted in uninfected mice (M/F)
- PD and PK/PD studies conducted in female TB infected mice
Why do you need to consider PK studies conducted in uninfected mice (M/F) when selecting a mouse model for TB? (4)
- Before testing in humans: to understand drug exposure in mice
- After testing in humans: to mimic exposure levels in humans
- Detect potential drug-drug interactions
- Identify PK differences between M/F mice
Why do you need to consider PD and PK/PD studies conducted in female TB infected mice when selecting a mouse model for TB? (4)
- Anti-TB activity and correlation with drug exposure
- PK differences between infected and uninfected mice
- Pharmacological parameters that drive activity
- Good companion drugs and characterize regimens
Tuberculosis: What factors do you need to consider in the research question? (5)
- M.Tuberculosis strain
- Mouse strain
- Primary outcomes
- Inoculation regimen
- Timelines
What factors do you need to consider when choosing an M.Tuberculosis strain? (3)
- Origin
- Virulence of the strain in mice
- Drug susceptibility
What are the most common M.tuberculosis strains used for TB treatment studies? (3)
- H37Rv (lab)
- Erdman (lab)
- Beijing lineage (clinical isolate)
What factors do you need to consider when choosing a mouse strain for TB experiments? (3)
- Susceptibility
- Course of infection and TB disease
- PK differences between mouse strains
What are the most common mouse strains used for TB treatment studies? (3)
- BALB/c
- C3HeB/FeJ
- Nude
What is special about the BALB/c mouse strain in TB research?
Immunocompetent –> possible to control infection
What is special about the C3HeB/FeJ mouse strain in TB research?
Caseous necrotic lung lesions & cavity formation –> human-like pathology
What is special about the nude mouse strain in TB research?
Lacking mature T cells –> immunocompromised
How do we quantify the primary outcome of TB treatment experiments? (2)
- Bactericidal activity
- Sterilizing activity
What is meant with bactericidal activity?
Change in lung bacterial load (CFUs) during treatment
What is meant with sterilizing activity?
Proportion of mice that are culture negative 3-6 months after stopping treatment
What does an altered bactericidal activity indicate in TB treatment experiments?
Speed and magnitude of killing
What does the sterilizing activity indicate?
Relative duration of treatment needed to eliminate the infection
Which two models exist for the inoculation regimen in TB treatment experiments?
- Acute/sub-acute model
- Chronic model
How does the acute/sub-acute inoculation model work?
Inoculation with high dose of TB -> makes mice unable to control infection
How does the chronic inoculation model work?
Inoculation with lower dose -> mice are able to control the infection (chronic, stable)
What does/doesn’t the chronic model show?
Shows killing, but doesn’t show inhibition or slowing of growth (due to stable population)
What is the timeline range of TB treatment experiments?
9 weeks - 1.5 years
Why are female mice preferred for TB treatment experiments?
Can be housed together for long durations -> male mice harm/kill on another
What is the current dose-finding regimen for antibiotics?
potency of a drug in vivo (MIC) - exposure to the bug in vivo (PK) –> antimicrobial efficacy of the drug –> effect on host
What does MIC stand for? Why is this used?
Minimal inhibitory concentration –> in vitro characteristics of an antibiotic
What is the optimal approach in case a high concentration of antibiotics is rapidly cleared?
Frequent dosing with lower doses
What are ways to study the optimum dosing regimen of antibiotic X in patients? (3)
- In vitro
- In vivo in animals
- In vivo in clinical trials
What are the advantages of in vitro testing for the optimum dosing regimen of antibiotic X in patients? (4)
- Cheap
- Simple
- Fast results
- Translational value is increasing
What are the DISadvantages of in vitro testing the optimum dosing regimen of antibiotic X in patients? (3)
- Often only studies a single dose
- Artificial growth medium
- Translational value unclear
What are the advantages of in vivo (animal) testing for the optimum dosing regimen of antibiotic X in patients? (3)
- Relatively cheap
- Fast results
- Antimicrobial efficacy at specific body sites
What are the DISadvantages of in vivo (animal) testing the optimum dosing regimen of antibiotic X in patients? (4)
- Ethical concerns
- Mouse is not man
- Most human pathogens are non-pathogenic in rodents
- Requires advanced personnel training
What is the advantage of in vivo (clinical trial) testing the optimum dosing regimen of antibiotic X in patients?
In humans –> short time to implementation –> easy translation
What are the DISadvantages of in vivo (clinical trial) testing the optimum dosing regimen of antibiotic X in patients? (3)
- May be disadvantageous for volunteer/patients
- Time consuming
- Expensive
Antibiotics: Which mouse model can be used to prevent interference from the immune system?
Neutropenic mice, thigh and lung infection
Where can you measure local antibiotic concentrations?
Epithelial lung fluid (BAL)
What is the common compound to induce neutropenia?
Cyclophosphamide
Antibiotics: How can the amount of mice be reduced?
By injecting 2 strains per mouse (1/thigh)
Antibiotics: mice are sampled at different timepoints (q), depending on?
Expected half-life (t1/2)
Which readout is used in antibiotic experiments?
Colony-forming unit (CFU)
CFU can be used to determine the bacteriostatic dose. This can be used for the treatment of which type of infections?
Treatment of milder infections
CFU can be used to determine the 1 or 2 log kill doses. This can be used for which type of infections?
Severe infections
What does AUC stand for?
Area under the curve = total systemic exposure of drug
What does Cmax stand for?
Highest concentration of the drug in blood
How can the PK be defined in an equation? (3)
- PK = AUC/MIC
- PK = Cmax/MIC
- T > MIC
What is the pharmacodynamic index?
Quantitative model to establish the relationship between pharmacokinetic and pharmacodynamic parameters
The pharmacodynamic index can be divided into three categories:
- Time-dependent
- Cmax-dependent
- AUC-dependent
How can efficacy be described in the time-dependent pharmacodynamic index? What kind of dosing regimen is best?
q6 > q12 > q24 –> frequent dosing more effective
How can efficacy be described in the Cmax-dependent pharmacodynamic index? What kind of dosing regimen is best?
q6 < q12 < q24 –> single high dose is more effective
How can efficacy be described in the AUC-dependent pharmacodynamic index? What kind of dosing regimen is best?
q6 = q12 = q24 –> dosing fréquence is not of influence
T1/2 is/is not the same between mice and man
Not the same