Prof. David KirklandKirkland Consulting

For many, the frequency of misleading positive results in vitro is unacceptable

Where follow-up testing in vivo is not permitted (e.g. cosmetics ingredients in EU) new products may be abandoned and businesses suffer

For other chemicals in vivo follow-up may be triggered by in vitro +ve when not otherwise required◦ Low tonnage industrial chemicals◦ Food flavours and additives

In such cases, unnecessary animal use occurs

ECVAM workshop (Kirkland et al, 2007) identified several “design” issues of mammalian cell tests thought to contribute to high level of misleading positives – including top conc.; extent & measures of cytotoxicity◦ Others will be discussed in Stefan Pfuhler’s group

Proposed revisions to ICH S2 guideline for pharmaceuticals suggested lowering top conc. for non-toxic drugs to 1 mM (Lutz Müller will present)

So are there data to suggest a reduction in the top conc. for non-pharmaceutical chemicals can also be considered?

ECVAM commissioned Jim and Liz Parry to review published literature◦ At what concs. do carcinogens that are –ve in

Ames test give detectable +ve responses in mammalian cells?

◦ Raffaella Corvi will discuss this review◦ I will discuss some of the “key” chemicals from

this review From the 19 chemicals identified (Kirkland et

al, 2008) as giving misleading +ve results in mammalian cells, 12 are only +ve above 1 mM, and 11 are only +ve above 2 mM◦ These would be avoided if lower top conc.

Chemical Lowest +ve concs.

Tert-butylhydroquinone Lowest +ve conc. in CA test not identified, but <100 µg/ml,

i.e. <1 mM

1,3-dihydroxybenzene +ve in CA test 20-80 µg/ml, i.e. from 0.18 mM upwards

Curcumin +ve for MN at 10 µM

Propyl gallate +ve in MLA at 1 µg/ml and in CA at 16 µg/ml,

i.e. at 0.005-0.075 mM

Ethyl acrylate +ve in MLA at 20 µg/ml (0.2 mM)

Eugenol +ve in MLA at 120 nl/ml (approx. 0.73 mM) although only +ve for CA at 300

µg/ml (1.83 mM)

2,4-dichlorophenol +ve in MLA at 40 µg/ml (0.25 mM) and in CA at 0.6 mM

+ve MLA = >GEF; +ve CA = >5% cells with abs

Chemical Lowest +ve concs.

D,L-menthol +ve in CA at 1.6-1.9 mM

Phthallic anyhydride +ve in CA at 10 mM

o-Anthranilic acid +ve in MLA at 886 µg/ml (6.47 mM)

2-ethyl-1,3-hexanediol +ve in CA at 4000 µg/ml (27.4 mM)

Ethionamide +ve in MLA at 500 µg/ml (3 mM) and in CA at 5-8 mM

Benzyl alcohol +ve in MLA and CA at 30-40 mM

Urea +ve in CA at >10 mM

Sodium saccharin +ve in CA at 8000 µg/ml (33.2 mM)

p-Nitrophenol =ve in CA at 1500 µg/ml (10.8 mM)

Sodium xylene sulfonate Equivocal in MLA at 4000 µg/ml (19.1 mM)

Isobutyraldehyde +ve in MLA at 250 µg/ml (3.47 mM) and in CA at 500 µg/ml (6.94 mM)

Sulfisoxazole Weak +ve in MLA at 1000 µg/ml (3.75 mM)