There is a strong need for innovation in anti-tuberculosis drug development. The zebrafish larva is an attractive disease model in tuberculosis research. To translate pharmacological findings to higher vertebrates, including humans, the internal exposure of drugs needs to be quantified and linked to observed response.
In zebrafish studies, drugs are commonly dissolved in the external water, posing a challenge to quantify internal exposure. We developed experimental methods to quantify internal exposure, including nano-scale blood sampling, and to quantify the bacterial burden, using automated fluorescence imaging analysis, with isoniazid as paradigm compound. We used pharmacokinetic-pharmacodynamic modelling to quantify the exposure-response relationship responsible for the antibiotic response. To translate isoniazid response to humans, the quantitative exposure-response relationship in zebrafish was linked to simulated concentration-time profiles in humans, and two quantitative translational factors on sensitivity to isoniazid and stage of infection were included.
Blood concentration was only 20% of the external drug concentration. The bacterial burden increased exponentially and an isoniazid dose corresponding to 15 mg·L internal concentration (minimum inhibitory concentration) lead to bacteriostasis of the mycobacterial infection in the zebrafish. The concentration-effect relationship was quantified, and based on that relationship and the translational factors, the isoniazid response was translated to humans, which correlated well with observed data.
This proof-of-concept confirms the potential of the zebrafish larvae as tuberculosis disease model in translational pharmacology, and contributes to innovative anti-tuberculosis drug development which is strongly needed.

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