The Draize Rabbit Eye Test (DRET) is the regulatory ‘Gold Standard’ for assessing and categorizing ocular irritation/corrosivity. The DRET focuses attention on damage to a number of different ocular structures, which are scored and weighted based on toxicological importance. The structures are as follows: Cornea (CO) – 80 points, Conjunctiva (Conj) – 20 points, and Iris (IR) – 10 points.
The heaviest weighting is on corneal damage, which is 80 points out of the total 110-point scale devised by Draize. Corneal irritation scoring is based on assessment of opacities on the cornea, Conj irritation is assessed by increased vascularization, and iridial damage is assessed by function of the iris (ability to constrict or dilate pupil)and deepening of the rugae.
PorCORA – Corneal Irritation Focus
Since the CO scores have the heaviest weight, and most often are the drivers of eye irritation, we developed the Porcine Cornea Opacity Reversibility Assay (PorCORA), an ex vivo corneal model. The PorCORA can distinguish between a material’s potential to cause severe (reversible) versus corrosive (irreversible) damage. Excised cultured porcine corneas are topically dosed with a test material and kept in culture for 21 Days. Corneal damage is visually assessed and scored. If CO reverse and are not visible by Day 21, the test material is categorized as a non-corrosive material and deemed to not cause permanent ocular damage.
In internal validation studies, we tested 56 chemicals and dilutions of chemicals ranging from corrosive (GHS category 1) to non-irritating (GHS not categorized). Using Cooper Statistics, we arrived at an accuracy of 89% with a positive and negative predictivity of 85% (cat. 1) and 93% (not cat.1), respectively.
To determine if these Cooper Statistics could be improved, we used the drivers of classification concept based on Barroso et al., 2016*. Upon re-examination of our data based on this published database and methodology, we found that four chemicals (1,2,4-Triazole, N-Butanol, 2,5-Dimethyl-2,5-Hexanediol, and Potassium Cyanate) had invalid tests (animals euthanized prior to day 21) or produced irritation not driven by corneal opacities. These chemicals were removed from our dataset. Without these four chemicals the accuracy improved to 92%. Moreover, the major change was in our positive predictivity, which increased to 91%. The negative predictivity for this subset of chemicals remained the same.
Lastly, PorCORA’s predictivity was assessed based on CO persistence; i.e., materials that produced low CO scores (from Draize Rabbit Eye Tests). Of the 56 chemicals tested, 40 had low severity (i.e., CO mean scores < 3). The accuracy for persistence of low CO scores was 88% with positive and negative predictivity of 79%, and 92%, respectively.
* Barroso, J., Pfannenbecker, U., Adriaens, E., Alépée, N., Cluzel, M., De Smedt, A., Hibatallah, J., Klaric, M., Mewes, K., Millet, M., Templier, M., McNamee, P. 2016. Cosmetics Europe compilation of historical serious eye damage/irritation in vivo data analysed by drivers of classification to support selection of chemicals for development and evaluation of alternative methods/strategies: the Draize eye test Reference Database (DRD). Arch. Toxicol. 91:521-547.
Based on these data, the PorCORA was proven to be a valid test to assess a material’s potential to distinguish reversible versus irreversible eye damage.
Appropriate choices of validation chemicals, based on the drivers of classification, have proven valuable and should be applied to replacement ocular assays that previously failed to meet acceptance criteria.
PorCORA testing results are encouraging and future studies are planned that will pursue mixtures and chemical substances of unknown or variable composition, complex reaction products and biological materials. PorCORA
If you would like to find out more about PorCORA and other in vitro/alternative toxicology testing methods, please click here.
The FD&C Act prohibits the marketing of adulterated or misbranded cosmetics in interstate commerce and EU Regulation 1223/2009 aims to protect human health, reduce and regulate animal testing as well as make information more available to consumers, leading to the introduction of the product ingredient file concept.
In 2013, the European Union (EU) enacted the Directive 76/768/EC, the primary law that outlines cosmetics safety requirements. This Directive includes the 7th amendment which mandates prohibition of animal testing for cosmetic products and ingredients.
In accordance with European regulations, a Product Information File (PIF) must be authored for each cosmetic product and submitted to the competent authorities on demand.
A key part of the PIF is a safety assessment or Cosmetic Product Safety Report, which is a safety assessment that provides:
Toxicological profile of each substance in the finished product (including Hazard Identification)
Chemical and physical specifications of the substances
Exposure level for each substance
A risk characterization for each substance
Expert Cosmetic Safety Testing Partner
MB Research Labs has been the premier choice in conducting product safety assessments for the cosmetics, personal care, chemical and pharmaceutical industries for over 45 years. Our expertise is sought out to ensure the safety our partners’ cosmetic ingredients. MB Research is a leader in the use and development of In Vitro and Alternative Toxicology Tests and continue to introduce new testing methods regularly.
The California Cruelty-Free Cosmetics Act makes it unlawful for cosmetic manufacturers to sell any cosmetic in California if the final product or any component of the product was tested on animals and goes into effect Jan. 1, 2020.
Products that have undergone testing on animals before that date can still be sold in California. Earlier in the month, the bill passed the state legislature after it was narrowed in scope.
Are You Ready With In Vitro Testing?
MB Research Labs is positioned to help manufacturers with a suite of in vitro and alternative (non-animal) tests for cosmetic safety testing. MB has over 45 years of toxicology testing experience and over 25 years of testing using non-animal test methods.
The Organization for Economic Co-Operation and Development (OECD) has prescribed the use of a weight-of-evidence (WoE) analysis, integrated with a sequential testing strategy, for the classification of acute eye hazards. The October 2017 revision to the Health Effects Test Guideline No. 405 outlines a stepwise strategy that includes Step 6, “Perform validated and accepted in vitro or ex vivo ocular test(s),” specifying only four possible tests: three designed to identify severe eye irritation/ corrosion (GHS Category 1) and one to identify non-irritants (GHS No Category), the top-down and bottom-up approaches, respectively. The GHS Category 2 (eye irritant) classification is impossible by any one bottom-up or top-down test.
The EpiOcular™ Eye Irritation Test; EIT (OECD 492), as a bottom-up test, either determines a material to be No Category, or that it causes eye effects, but cannot discriminate between eye irritation, serious eye damage, and corrosion.
Conversely, the top-down Bovine Corneal Opacity and Permeability; BCOP Test (OECD 437), is used for ruling in or ruling out Category 1 effects (serious eye damage/corrosion). By using a dual-assay/approach system – the combination of the EIT and BCOP test – we have determined, with a high degree of accuracy, GHS Acute Eye Hazard Category 2 chemicals that cause reversible irritation to the eye.
A Double Elimination occurs when a BCOP test rules out GHS Category 1 (severe irritation/corrosion) and the EIT rules out GHS No Category (non-irritant), analysis of the combined results concludes the only other possible designation – Category 2 (irritant). The classification defaults to Category 2A for labeling and handling purposes because at present differentiation between category 2A and 2B cannot be made. Using this approach, we correctly identified 87% of the Category 2A/B chemicals as Category 2 after testing 42 chemicals (nine, 15, and 18 in Category 1, 2A/B, and No Category, respectively).
As a result of this analysis, we are encouraged by the potential of the BCOP-EIT dual-assay system, coupled with WoE evaluation, to correctly assign unknowns into GHS Category 1, Category 2A, and No Category Acute Eye Hazards without the use of less predictive and more expensive in vitro tests. Moreover, in keeping with the OECD’s recommendations, we predict that such a system would greatly reduce reliance on the Draize Rabbit Eye Tests.
MB Research Labs is honored to be attending the 10th World Congress on Alternatives and Animal Use in the Life Sciences. We will be presenting several posters focusing on the use and development of in vitro and alternative toxicology methods that are used in our laboratories.
Scientific Posters presented by MB Research Labs on the Use and Development of In Vitro and Alternative Toxicology Test Methods
Currently, it is generally accepted that no single in vitro eye irritation test will be able to replace the in vivo Draize eye test
to predict across the entire range of irritation for different chemical classes. Several labs (including MB Research) have been working on strategic combinations of several in vitro and alternative test methods within a (tiered) testing strategy that could replace the Draize Rabbit Eye Test.
Available In Vitro & Alternative Eye Irritation Test Methods
MB Research Labs is now offering the new OptiSafe™ – an in vitro test method in which a test substance is applied to a semi-permeable membrane. Damage to macromolecules in the membrane is measured to assess the test substance’s potential to cause eye irritation.
OptiSafe™ Background Information
OptiSafe™ is an acute in vitro irritation test method used to determine the ocular irritation potential based of a test substances utilizing a set of biochemical tests (mostly performed in parallel; “multiplexed”) which evaluate the potential of the test substance ability to disrupt, denature and degrade biological molecules. These measured values are relevant to GHS and EPA standard ocular safety classification systems.
Evaluated Mechanisms of Ocular Injury and Prediction Models
Different ocular irritants including, acids/bases, alcohols/aldehydes/ketones, strong oxidants and reactive chemicals/mixtures, damage the cornea and other tissues through additive and/or synergistic chemical reactions and biophysical effects.
Evaluated mechanisms of injury include:
Denaturation of specific water insoluble polymers that model the phospholipid bilayer of cells (which can occur at the corneal epithelium and conjunctiva).
Direct denaturation of macromolecules that model ordered collagen (which can occur at the corneal stroma).
Indirect denaturation of molecules across a membrane via osmotic effects (osmotic effects across the corneal epithelium and stroma can damage the cornea).
Potential to damage tissue via excessive oxidation and reactivity (which can occur at the epithelium, stroma, conjunctiva and iris).
Potential to damage tissues via extreme buffering (which can occur at the epithelium, stroma, conjunctiva and iris).
NICEATM reviewed a validation study conducted by the OptiSafe™ test method developer, Lebrun Labs, and concluded that the study data indicated that the OptiSafe™ method compared favorably to other in vitroocular toxicity testing methods. NICEATM is currently coordinating a validation study of the OptiSafe™ test method to demonstrate the reproducibility of the method among Lebrun Labs and two naïve laboratories. The study received support from an NIEHS Small Business Innovation Research grant. The study is ongoing and is expected to be completed in mid-2018.
MB Research Labs is a primary testing source using OptiSafe™ and has been deeply involved in the validation of OptiSafe™.
Utility of OptiSafe™
OptiSafe™ can be used to determine the irritation potential of cosmetics, creams, and a wide variety of consumer products. Results are presented as GHS, EPA classifications, an ocular irritation score and class.
OptiSafe™ can be used for:
Screening Finished Products for Ocular Irritation.
Ocular safety testing during product development for knowledge based formulation. (Products that irritate do not last long in the marketplace).
The Advantages of OptiSafe™ include:
Accurate Ocular Irritancy Test
High Sensitivity for Mild and Moderate Irritants
1 year shelf life
Neither uses nor harms animals
MB Research Labs performs many other in vitro eye and dermal irritation tests for screening of cosmetics, consumer products, pharmaceuticals and chemicals.
OptiSafe™ is a trademark of Lebrun Labs, LLC and used here with permission.
The LLNA-BrdU ELISA is conducted at MB Research Labs and is based upon the OECD 442B Testing Guideline. The LLNA is an alternative toxicology assay for dermal sensitization using CBA/J mice. The LLNA is an alternative to guinea pig studies that require more animals and long test durations.
To determine the sensitizing potential of topically applied test material utilizing the LLNA, and measurement of lymphocyte proliferation by BrdU incorporation detected by ELISA.
Irritation Screen Test:
An initial Irritation Screen is performed using 3-5 highest achievable concentrations. The screen consists of 2 animals per concentration that will be dosed in an identical manner to that of the main test. Ear measurements will be taken prior to dosing on Study Days 1 and 3, and prior to euthanasia on Study Day 6. Measurements taken on Study Days 3 and 6 will be compared to pre- dosing measurements. If there is no effect, or an increase of <25% in ear thickness, the same concentrations will be assayed in definitive test.
However, if significant ear swelling (ES) is present (>25% over control), then an extended screen (Quantitative Irritation Test; QIT) is recommended. The QIT is similar to the Irritation Screen except 4-6 concentrations will be assayed to determine the highest non-irritating concentration.
Definitive Sensitization Test:
The main test will be conducted by topically applying test material to the dorsum of the ears at the 3-5 highest achievable concentrations (100 [liquid only], 50, 25, 10, 5, 2.5, 1, 0.5, etc.), which do not cause severe irritation or overt systemic effects. Ear measurements will be taken on Study Days 1 (prior to first dosing), 3 (approximately 48 hours after initial dosing) and 6 (prior to euthanasia). Animals will be injected with BrdU on Study Day 5, approximately 24 hours prior to euthanasia. Auricular lymph nodes will be collected on Study Day 6, a single-cell suspension will be created and lymph node cells (LNC) will be assayed for BrdU incorporation via ELISA.
A Positive Response is when a Stimulation Index (SI) is greater than or equal to 1.6 (relative to that of control lymph nodes).
A “Borderline Positive Response” is defined as an SI from 1.6 to 1.9; additional information and testing may be needed.