Life-Edesia meeting 10-11 December 2014

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Last news from ECHA on alternative methods

in compliance with the REACH: the Read-

Across

Maria Teresa Russo

Centro Nazionale Sostanze Chimiche

Istituto Superiore di Sanità

Roma

REACH regulation2

REACH is the Regulation on Registration, Evaluation, Authorisation

and Restriction of Chemicals. It entered into force on 1st June 2007. It

streamlines and improves the former legislative framework on chemicals

of the European Union (EU).

Two of the major aims are:

1. To ensure high protection of human health

2. To promote alternative methods

Besides the possible adaptations of the standard information

requirements (based on the specific conditions listed in column 2 of

Annexes VII to X or on the more general conditions given in Annex XI

of the regulation), REACH provides the registrant also with the

possibility to submit information from non-animal tests.

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2) Promoting alternatives methods:

• comparing substances with similar ones;

• grouping them together into logical

categories;

• specialized computer modelling (QSAR

toolbox);

• bringing together a weight of evidence;

• and non-animal tests (for example, in vitro

studies using cells rather than animals)

REACH keeps the number of animal tests to

an essential minimum

1) The principle of data sharing introduced

by REACH----Reliable and adequate studies

must not be repeated.

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• comparing substances with similar ones

• grouping them together into logical

categories

By using this adaptation, registrants do not

need to test their substance(s)

one-by-one to fulfil their information

requirements

This strategy allows to avoid unnecessary

animal testing

READ ACROSS

The second report under Article 117(3) of the REACH Regulation shows

that registrants make use of alternative testing methods and strategies.

Building categories and predicting substance properties by read-across is

the most widely used method. In fact up to 75% of the analyzed dossiers

contains read-across at least for one endpoint (*).

Moreover, where possible the in vitro tests are used by the registrants: (*)

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The feedback of the registrants

(*) second report under Article 117(3) published on the 2 June 2014

ECHA’s database

by 1° October 2013

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Relative proportions of the principal options to fulfil information

requirements for human health endpoints for the substances

(phase-in, at or above 100 tonnes per year and at or above 1 000tonnes per year, 3 662 substances).

Read across is applied to all Human health endpoints

Data from: second report under Article 117(3) published on the 2 June 2014

Legend

ES – Experimental studies

WE – Weight of evidence

RA – Read-across

QS – (Q)SAR

TP – Testing proposal

FO – Flags to omit study

NR – Not reported

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Read across is applied to Environmental endpoints

Relative proportions of the principal options to fulfil information

requirements for environmental endpoints for the substances (phase-in,

at or above 100 tonnes per year and at or above 1 000 tonnes per year,

3662 substances)

Data from: second report under Article 117(3) published on the 2 June 2014

Read-across developments

REACH provides the possibility to adapt a standard

requirement for a test by read-across (Ax XI, 1.5)

Registrant is responsible for building the case

ECHA and the MSs are responsible for the evaluation

Need for a structured approach – Read-across

Assessment Framework (RAAF)

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9 History:

• RAAF discussed at ECHA in 1st WS in 2011

• ECHA further developed RAAF

• First Inclusion of refinements. E.g. More types of

read-across covered (Scenarios)

• Further refinements of RAAF in the last WS,

October 2014

Read-across Assessment Framework (RAAF)

RAAF is a tool for the assessment of read-across by ECHA

toxicologists

It is not guidance for registrants!

However, knowledge about how ECHA assesses read-across

helps registrants to prepare better-focused read-across

proposals.

10WHY THE RAAF?

• It allow the assessors to addresses the scientific

aspects of read-across in a structured and

consistent way;

• To guide the expert to focus on the scientific

aspects that are deemed crucial by ECHA;

• To create a systematic grading of cases based

on scientific credibility, thus indicating

limitations in reasoning and in supporting

evidence.

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Tier I = Administrative screening

Tier II = structure and rules to facilitate a

consistent scientific assessment

Cases cannot be accepted using

only a Tier-I assessment!

TWO TIERS for RAAF

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Tier II

structure and rules of RAAF

13Read-across always requires a convincing scientific

explanation.

It should be shown why structural differences between

source and target:

• Either do not influence an effect originating from

their common structural features,

• Or do so in a regular manner resulting in a regular

pattern (i.e. trend).

Basic principles

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Scientific explanation can be:• An explanation why read-across is possible in

explicit mechanistic terms.

• A causal relationship demonstrated by a trend

between an independent variable and a

dependent variable (property to read-across).

• Both, an explanation in mechanistic terms

and a trend are used to show that read-across is

possible.

Structural similarity as such is never

sufficient! (See also Maggiora et al., 2014*);

Small structural differences can have a strong

and often unexpected impact on toxicity.

A Challenge: Prediction by read-across

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•The enantiomers of the valproic acid analogue 2-n-propyl-4-pentynoic acid (4-yn-VPA): asymmetric synthesis and

highly stereoselective teratogenicity in mice

Regulatory Toxicology and Pharmacology 56 (2010) 67–81 .

•Hauck RS, Nau H. Pharm Res. 1992 Jul;9(7):850-5.

•IARC (http://www.inchem.org/documents/iarc/suppl7/naphthylamine1.html),

(http://www.inchem.org/documents/iarc/suppl7/naphthylamine2.html)

•The comparative toxicity of chlorinated dibenzo-p-dioxins in mice and guinea pigs. McConnell E.E. et al. (1978)

Toxicology and Applied Pharmacology 44: 335-356

Minor differences in chemical structure may lead to

significant differences in the properties of the substance

161. External exposure to different substances (source and

target) results in internal exposure to the same toxic

substances, due to chemical or biological conversion,

and thereby the same toxicity;

(External different exposure- the same toxic internal

exposure)

2. External exposure to different substances (source and

target) results in internal exposure to different

substances, which, nevertheless do not differ in toxicity.

(External different substances- the internal exposure is to

different substances with the same toxicy)Or a special case of the second basic type:

2a The potentially sensitive organ/tissue cannot be reached by

source and target due to their common structural

characteristics.

No absorption, complete binding, etc.

Scientific explanations of the RAAF

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Types of read-across in the RAAF

Type depends on the scientific explanation and

whether the:

• analogue approach (scenario 1 and 2)

or

• category approach (scenario 3, 4 and 5)

applies.

The RAAF distinguishes five basic types of

read-across.

These are called: SCENARIOS.

one source to one target

from several sources to one target

Each read-across proposal is expected to be covered

by only one of these five scenarios.

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Structure of RAAF

During the assessment crucial scientific aspects have to be

addressed for each scenario, because they determine the

validity of the read-across.

SCENARIO-ASSESSMENT ELEMENTS (AEs)

For each AE the assessor has to select one of a number of

predefined options that represents a possible opinion on the AE.

The options depend on the AE. Different AEs often have

different options.

AEs -Assessment Options (AOs)

Each AO is linked to a predefined numerical score.

The AO and the associated score indicates the

strength/weakness of the case as regards the considered AE

Assessment Options----Scores

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Accepted cases

Highest score: 5 = No

appreciable extra

uncertainty; case

succeeds with flying

colours.

Middle score: 4 =

Average extra

uncertainty.

Lowest score: 3 =

Highest allowable extra

uncertainty.

Rejected cases

Highest score: 2 = Based

on the information

provided, the case has to

be rejected, but

additional information

might lead to acceptance.

Lowest score: 1 = It is

not expected that

additional information

can lead to acceptance.

Scores and decisions

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RAAF provides:

• A structured approach ensuring consistency;

• a tool to reject or accept the read-across

case;

• an improved systematic documentation of the

assessment;

• A better indication of scientific robustness and

uncertainty of the read-across.

Outcomes of the RAAF

21 • Property to property read-across (e.g. across endpoints)

• Negative versus positive read-across (In cases where

absence of toxicity is being predicted, the read-across

justification should contain as many lines of evidence as

possible, including QSAR predictions, toxicokinetic

information, etc.)

• Bias – e.g. omitted category members

• Test on real cases, use in Substance Evaluation

The goal of illustrative case studies could serve to develop

a series of ‘guiding principles’ that would be helpful to

both the regulated and regulators

Elements to be discussed and future activity for RAAF

ECHA announced the publication in the

appropriate format of the RAAF in 2015

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Considerations on the use of predictive models

The information from the individual tools was combined with a weight of

evidence approach and the expert knowledge, the result is a better prediction of

the potential toxicity.

The combination use of the existing data and modelling approach improve

the predictivity.

The CAESAR developmental toxicity

model is a QSAR based model

Is a system which reports

structural alerts relating to

developmental, teratogenic

and testicular toxicity.

It is a profiler that determine the potential for

oestrogen receptor binding. They are associated with

endocrine distruption and may act as iniziating event,

eliciting reproductive or developmental toxicity

effects.

Is the approach used to generate

categories of compunds based on

structural similarity approach from

which a read-across estimate of

toxicity could be made

The in silico- in vitro integrated approach of LIFE-Edesia is a winning strategy

*M. Hewitt, C.M. Ellison, S.J. Enoch, J.C. Madden, M.T.D.

Cronin, Reproductive Toxicology 30 (2010) 147–160

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Thanks for your attention!

24 Scenarios

1: taget and sorce are converted in the same

toxicant

2: taget and sorce are converted in different

toxicant with the same effect

3:read across is based only on the analysis of trend,

no scientific explanation is present

4: read is across based on the analysis of trend, a

scientific explanation confirms the trend

5: is a group without a trend for the effect to be

read across. This means that a scientific

explanation makes clear that the target will do the

same.

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• Leads the assessor to aspects of the read-across deemed

crucial (assessment elements);

• Provides options for each of these aspects (assessment

options);

• Asks the expert to form an opinion on the R-A as

regards to the aspects of the R-A under consideration;

• Asks the expert to select one of the options based on

this opinion;

• Links the options with a quality/uncertainty

indicator(score) for the considered aspect;

• The aspects with the lowest quality indicator

determines the overall outcome of the assessment of

the R-A case (weakest-link principle).

What “does” the RAAF?