The Role of ADME/PK in the Extrapolation of In Vitro Toxicity Results to Equivalent In Vivo Exposures: Where it started with the acrylamide example and where we are now

Bas J. Blaauboer Em. Doerenkamp-Zbinden Chair on Alternatives

Division of Toxicology Institute for Risk Assessment Sciences

Utrecht University, Utrecht, the Netherlands

23 February 2015

Conflict of Interest

None This research was carried out at Utrecht University and partners.

Overview

The development of risk assessment schemes on the basis of non-animal methods

The ECITTS programme: parallel testing The case of acrylamide General description of integrating in vitro toxicity data

with PBBK modelling Other examples Possibilities, limitations, pitfalls

In vitro toxicology?

European Reseach Group for Alternatives in Toxicity Testing

Group of friends from different European countries.

Crucial: a workshop in 1991, Sweden A parallel testing strategy

ERGATT

ERGATT: development of the ECITTS scheme

Goal: design of a parallel testing strategy Find in vitro methodologies that predict systemic

toxicity for as many endpoints as possible and practical

Indispensable: inclusion of biokinetic factors Which methods were available in the areas of

neuro-, hepato-, rheno-, immuno- toxicity

THE ECITTS INTEGRATED TOXICITY TESTING SCHEME: THE APPLICATION OF IN VITRO TEST SYSTEMS TO THE HAZARD ASSESSMENT OF CHEMICALS* B. J. BLAAUBOER, M. BALLS, V. BIANCHI, G. BOLCSFOLDI, A. ÜUILLOUZO, G. A. MOORE, L. ÜDLAND, C. A. REINHARDT, H. SPIELMANN and E. WALUM ERGATT, Secretariat: c/o Research Institute of Toxicology, Utrecht University, PO Box 80.176, 3508 TD Utrecht, The Netherlands

Toxic. in Vitro Vol. 8, No. 4, pp. 845--846, 1994

Conclusion The information produced will contribute to the establishment of a scientifically based and efficient toxicological procedure for hazard assessment, based on knowledge of the mechanisms of toxic action and of biokinetic parameters, relevant to the in vivo toxicity of chemicals.

7

The ECITTS programme

Focus on neurotoxicity Selection of a group of chemicals Perform in vitro neurotoxicity testing, find sensitive

parameters Use low effect concentrations as a Point of

Departure for a reverse dosimetry Calculate an in vivo dose that would result in the

effect observed in the in vitro systems.

The acrylamide example

In vitro data on toxicity Kinetic model to predict dose causing toxic

effects

uptake (Ka)

distribution

[plasma] (Vd)

metabolism (Vmax, Km, Cli)

KINETICS

degeneration C*t/(C*t + Ct50)

100% effect

20% effect CNC

0% effect

Recovery (Krepair*t)

DYNAMICS KINETIC-DYNAMIC MODELLING

in vivo systemic toxicity

prediction of systemic toxicity

prediction of dynamics

prediction of target tissue

concentrations

in vitro data on dynamics

kinetics in vivo kinetic modelling (use known physiological

parameters)

in vitro data on kinetics

Toxicity testing: a more efficient approach

Health Council of the Netherlands. The Hague: Health Council of the Netherlands, 2001; publication no. 2001/24E.

ISBN: 90-5549-415-1 http://www.gr.nl/

(go to reports, 20 November 2001)

The example of glycol ethers in reprotox

Van Dartel and Piersma, Reprod Tox 2011, 32: 235-244

QIVIVE for glycol ether reproductive toxicity

Louisse et al, ToxSci 2010

Check on kinetic model

Louisse et al, ToxSci 2010

QIVIVE result: prediction of embryotox

Louisse et al, ToxSci 2010

In Vitro Biokinetics

Groothuis et al., Toxicology in press

Groothuis et al., Toxicology in press

What to measure in vitro: adaptation vs adversity

Incorporation in a MOS approach

In Vitro Based Risk Evaluation Approach

Blaauboer et al 2012 Altex

Why repeated dose toxicity

Exposures are more often over a prolonged period of time (as opposed to acute exposure)

Therefore, risk assessment should take repeated (or prolonged) exposure into account

Why does toxicity change over time

Acute toxicity: - direct and imminent effects - a more clear-cut relation between dose and concentrations at the target site

Repeated dose toxicity: - apart from acute effects, a more complicated relationship between dose effect.

Repeated dose: consequences

1. the target (cell) concentration of the test compound may change: - by accumulation - by changing the metabolic rate (induction/inhibition) over time (e.g. lindane)

Repeated dose: consequences

1. target cell concentration 2. By changing the cellular or molecular response:

- by adapting defense mechanisms - by exhaustion of defense mechanisms

QSAR >In Vitro Tox >PBBK>QIVIVE

Conclusions

1. Need to take in vitro biokinetics into consideration: will improve quality of in vitro toxicity data

2. Use of kinetic parameters to correlate in vitro effective concentrations to a dose in vitro is absolutely essential.

3. Use integrated transparent approach in improving the applicability of in vitro data in risk assessment.

Conclusions

5. Make optimal use of chemical biological and physiological knowledge: QSAR’s, cellular biology, systems biology, “omics”, etc.

6. This is necessary to deal with the huge demand for toxicological data

7. And: more science, less animals