### p . 1 

# Ni



# -

:w 3
Test R,1~,thod Prr3tocul 16r the 1Vf1h A'ez trcrl Red ljptrrl,e Cvtotoxicith-,3sscrs > Phase III - L'ali<Jatiwl Stxclv : November 4, 2003



### TEST METHOD PROTOCO L

for the NHK Neutral Red Uptake Cytotoxicity Test

A Test for Basal Cytotoxicity for an In Vitro Validation Study Phase III November 4, 2003

Prepared b y The National Toxicology Program (NTP) Interagency Center for the Evaluation of

Alternative Toxicological Methods (NICEATM )



### Based on Standard Operating Procedure Recommendations from an International Workshop Organized by the Interagency Coordinating Commi ttee

on the Validation of Alternative Methods (ICCVAM)

National Institute of Environmental Health Sciences (NIEHS)

National Institutes of Health (NIH ) U.S . Public Health Service Department of Health and Human Services

ip . 2

Test Met hod PrrJtocol, fnr the ~VHK Neutral Rcrl Uptake ('i7ntosic•itv ,4csar Phase Ill - L'a1ie/crtiar Shrdv : November 4
. 200 ; 

## TEST METHOD PROTOCO L

The Normal Human Keratinocyte (NHK) Neutral Red Uptake Cytotoxicity Tes t A Test for Basal Cytotoxicity

Phase II I

1 . PURPOS E The purpose of this study is to evaluate the cytotoxicity of test chemicals using the Normal Human Keratinocyte (NHK) Neutral Red Uptake (NRU) cytotoxicity test . The data will be used to evaluate the intra- and inter-laboratory reproducibility of the assay and effectiveness of the cytotoxicity assay to predict the starting doses for rodent acute oral systemic toxicity assays . This test method protocol outlines the procedures for performing the cytotoxicity test and is in support of the in vitro validation study organized by NICEATM and the European Centre for the Validation of Alternative Methods (ECVAM) and sponsored by NIEHS, U .S . Environmental Protection Agency, and ECVAM . This test method protocol applies to all personnel involved with performing the cytotoxicity assay

. 

### A . NHK Neutral Red Uptake Cytotoxicity Tes t The NHK NRU test will be performed to analyze the in vitro toxicity of 60 blinded/coded test chemicals . This test will be used to determine IC20, IC50, and ICgo values for the predetermined set of test chemicals of varying toxicities
. 

### 11 . SPONSO R A . Name : National Institute of Environmental Health Sciences (NIEHS) ; The National Toxicology Program (NTP) Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM) 

### B . Address : P .O . Box 1223 3 Research Triangle Park, NC 27709 C . Representative : Named Representativ e III . IDENTIFICATION OF TEST AND CONTROL SUBSTANCES A . Test Chemicals : Blinded chemicals (60 ) B . Controls : Positive : Sodium Lauryl Sulfate Vehicle (Negative) : Assay mediu m Solvent (as directed) : Assay medium, DMSO, or ethanol as directed by the Study Management Team, for preparation of test chemical s IV . TESTING FACILITY AND KEY PERSONNELp . 3

Test :'Weihocl Protocol for the NHK Neutral Red Uptake CV7oto .rrcitv Assa v PhRare HI - Validation Studv : November 4, 200 3 A . Facility Information 1) Name : 2) Address : 3) Study Director : 

### 4) Laborato ry Technician(s) : 5) Scientific Advisor : 6) Quali ty Assurance Director : 7) Safety Manager : 8) Facili ty Management : B . Test Schedul e 1) Proposed Experimental Initiation Date : 2) Proposed Experimental Completion Date : 3) Proposed Repo rt Date : 

### V . TEST SYSTE M The NRU cytotoxicity assay procedure is a cell su rvival/viability chemosensitivity assay based on the abili ty of viable cells to incorporate and bind neutral red (NR), a supravital dye . NR is a weak cationic dye that readily penetrates cell membranes by non-ionic diffusion and accumulates intracellularly in lysosomes . Alterations of the cell surface or the sensitive lysosomal membrane lead to lysosomal fragili ty and other changes that gradually become irreversible . Such changes brought about by the action of xenobiotics result in a decreased uptake and binding of NR . It is thus possible to distinguish between viable, damaged, or dead cells, which is the basis of this assay . Healthy mammalian cells, when maintained in culture, continuously divide and multiply over time . A toxic chemical, regardless of site or mechanism of action, will interfere with this process and result in a reduction of the growth rate as reflected by cell number . Cytotoxicity is expressed as a concentration dependent reduction of the uptake of the NR after chemical exposure thus providing a sensitive, integrated signal of both cell integrity and growth inhibition . 

### VI . DEFINITION S A . . Hill function : a four parameter logistic mathematical model relating the concentration of test chemical to the response being measured in a sigmoidal shape . 

### Top - Bottom Y = Bo tt om + 

### 1 + 1 0 0

### og 1

### c50 

### - x)

### H i 

### usl

### ope where Y= response, X is the logarithm of dose ( or concentration), Bottom is the minimum response, Top is the maximum response, logIC50 is logarithm of X at the response midway between Top and Bottom, and HillSlope describes the steepness of the curve . B. Documentation : all methods and procedures will be noted in a Study Workbook ; logs will be maintained for general laborato ry procedures and equipment (e .g ., media preparation, test chemical preparation, incubator function) ; all optical densi ty data obtained from the spectrophotometer plate reader will be saved in electronic and paper formats ; all calculations of ICx values and other derived data will be in electronic and paper format ; all data will be archived .

Ip . 4

Test 1tlethoc/ Protocol for- the .M1WK Neutral Red Uptake C+-totoxicitr• Assa r Phase III - L'alri/ation Stuc%- : NuvernGer 4, 200 3
VII . PROCEDURES A . Material s 

### [Note : Suggested brand names/vendors are listed in parentheses . Equivalents may be used unless otherwise noted
. ] 1 . Cell Line s Normal Human Epidermal Keratinocytes (NHK ) 

### Non-transformed cells ; from cryopreserved primary or secondary cells (Clonetics #CC-2507 or equivalent) . Cells will be Clonetics NHK cells
. Cambrex [Cambrex Bio Science, 8830 Biggs Ford Road, Walkersville, MD 21793-0127 Cambrex Europe [Cambrex Bio Science Verviers, S .P .R .L . Parc Industriel de Petit Rechain, B-4800 Verviers, BELGIUM ] 2 . Technical Equipment 

### [Note : Suggested brand names/vendors are listed in parentheses . Equivalents may be used .] a) Incubator : 37°C f 1°C, 90 % ± 5 % humidity, 5 .0 % + 1% C02/ai r b) Laminar flow clean bench (standard : "biological hazard") c) Water bath : 37°C f 1° C d) Inverse phase contrast microscop e e) Sterile glass tubes with caps (e .g ., 5mL) f) Centrifuge (optionally : equipped with microtiter plate rotor) g) Laboratory balanc e h) 96-well plate spectrophotometer (i .e ., plate reader) equipped with 540 nm ± 10 nm filter i) Shaker for microtiter plate s j) Cell counter or hemocytometer k) Pipetting ai d 1) Pipettes, pipettors (multi-channel and single channel ; multichannel repeater pipette), dilution bloc k 

### m) Cryotube s n) Tissue culture flasks (75 - 80 em2, 25 cm2 ) o) 96-well flat bottom tissue culture microtiter plates (e .g ., Nunc # 167 008 ; Corning/COSTAR tissue culture-treated) p) pH paper (wide and narrow range) q) Multichannel reagent reservoi r r) Waterbath sonicator s) Magnetic stirre r t) Antistatic bar ionizer/antistatic gun (optional for neutralizing static on 96-well plates) u) Dry heat block (optional ) v) Adhesive film plate sealers (e .g ., Excel Scientific SealPlateTM ,Cat # STR-SEAL-PLT or equivalent ) w) Vortex mixer

4p . 5

Test .Vlethod Protoco( tor the ~VHK Neutral Red Uptake Cvtotaxieitv A sscr v Phase 111- VcatiJation Stucfv : ;Vovetn6er 4, 200 ,



### x) Filters/filtration device s [Note : Tissue culture flasks and microtiter plates should be prescreened to ensure that they adequately support the growth of NHK . Multi-channel repeater pipettes may be used for plating cells in the 96-well plates, dispensing plate rinse solutions, NR medium, and desorb solution . Do not use the repeater pipette for dispensing test chemicals to the cells . ]
3 . Chemicals, Media, and Ser a a) Keratinocyte Basal Medium without Ca++ (KBM®, Clonetics CC-3104) that is completed by adding the KBM® SingleQuots® (Clonetics CC-4131) to achieve the proper concentrations of epidermal growth factor, insulin, hydrocortisone, antimicrobial agents, bovine pituitary extract, and calcium (e .g ., Clonetics Calcium SingleQuots®, 300 mM CaCl2, Clonetics # CC-4202) . 

### b) HEPES Buffered Saline Solution (HEPES-BSS) (e .g ., Clonetics # CC-5022) c) 0 .025 % TrypsinlEDTA solution (e .g ., Clonetics # CC-5012 ) d) Trypsin Neutralizing Solution (TNS) (e .g ., Clonetics # CC-5002) e) Phosphate Buffered Saline (PBS ) f) Dulbecco's Phosphate Buffered Saline (D-PBS) [formulation containing calcium and magnesium cations ; glucose optional] (for rinsing ) g) Neutral Red (NR) Dye - tissue culture-grade ; liquid form (e .g ., SIGMA N 2889) ; powder form (e .g ., SIGMA N 4638 ) h) Dimethyl sulfoxide (DMSO), U .S .P analytical grade (Store under nitrogen @-20°C) i) Ethanol (ETOH), U .S .P . analytical grade (100 %, non-denatured for test chemical preparation ; 95 % can be used for the desorb solution ) j) Glacial acetic acid, analytical grad e k) Hanks' Balanced Salt Solution without CaZ+ or Mg 2+ (CMF-HBSS) (e .g ., Invitrogen # 14170) 1) Distilled H20 or any purified water suitable for cell culture and NR desorb solution (sterile) m) Sterile/non-sterile paper towels (for blotting 96-well plates)
B . Preparations of Media and Solution s [Note : All solutions (except NR stock solution, NR medium and NR desorb), glassware, pipettes, etc ., shall be sterile and all procedures should be carried out under aseptic conditions and in the sterile environment of a laminar flow cabinet (biological hazard standard) . All methods and procedures will be adequately documented . ] 1 . Media a) Routine Culture Medium/Treatment Mediu mKBM® (Clonetics CC-3104) supplemented with KBM® SingleQuots® (Clonetics CC413 1) and Clonetics Calcium SingleQuots® (CC-4202) to make 500 mL medium . Final concentration of supplements in medium are : 0 .0001 ng/mL Human recombinant epidermal growth factor 5 μg/mL Insuli n 0 .5 μg/mL Hydrocortisone

5p . 6

Test d9~thotl Protnrol for the AHK Ventral Red Uptake Cvtotoxicitv :3ssa v Phase III - Validation Sluov;; November 4 . 2003 -

30 μg/mL Gentamicin 15 ng/mL Amphotericin B 0 .10 mm Calciu m 30 μg/mL Bovine pituitary extract Complete media should be kept at 2-8°C and stored for no longer than two weeks . NOTE : KBM® SingleQuots® contain the following stock concentrations and volumes : 0 .1 ng/mL hEGF 0 .5 mL 5 .0 mg/mL Insulin 0 .5 mL 0 .5 mg/mL Hydrocortisone 0 .5 mL 30 mg/mL Gentamicin, 15 ug/mL Amphotericin-B 0 .5 mL 7 .5 mg/mL Bovine Pituitary Extract (BPE) 2 .0 mL Clonetics Calcium SingleQuots® are 2 mL of 300mM calcium . 165 μl of solution per 500 mL calcium-free medium equals 0 .10 mM calcium in the medium
. 2 . Neutral Red (NR) Stock Solutio n The liquid tissue culture-grade stock NR Solution will be the first choice for performing the assay (e .g ., SIGMA #N2889, 3 .3 mg/mL) . Store liquid tissue culture-grade NR Stock Solution at the storage conditions and shelf-life period recommended by the manufacturer . If the liquid form is not available, the following formulation can be prepared . EXAMPLE : 0 .33 g NR Dye powder in 100 mL H2 0 The NR Stock Solution (powder in water) should be stored in the dark at room temperature for up to two months
. 3 . Neutral Red (NR) Medium EXAMPLE : 1 .0 mL (3 .3 mg NR dye/mL) NR Stock Solution 99 .0 mL Routine Culture Medium (pre-warmed to 37 C .)
The final concentration of the NR Medium is 33 u,g NR dye/mL and aliquots will be prepared on the day of application . [Note : The NR Medium shall be filtered (e .g ., Millipore filtering, 0 .2 - 0 .45 μm pore size) used to reduce NR crystals . Aliquots of the NR Medium should be maintained at 37 C (e .g ., in a waterbath) before adding to the cells and used within 30 min of preparation but also used within 15 min after removing from 37 C storage . ]

Ap . 7

Test Adc,thod Protorul for the A'HK Neutral Red t . f?tal-e Cvtutoxiriti- .4s.sa1- Phase 11I - Validation Stuclv : .'Y'ovemher 4 . 200 3 4 . Ethanol/Acetic Acid Solution (NR Desorb) 1% Glacial acetic acid solutio n 50 % Ethanol 49% H2O C . Method s 1 . Cell Maintenance and Culture Procedure s NHK cells are routinely grown as a monolayer in tissue culture grade flasks (e .g ., 25 cm2) at 37°C f 1°C, 90 % ± 5 % humidity, and 5 .0 % f 1% C02/air . The cells should be examined on a daily (i.e ., on workdays) basis under a phase contrast microscope, and any changes in morphology or their adhesive properties must be noted in a Study Workbook . 2 . Receipt of Cryopreserved Keratinocytes Upon receipt of cryopreserved keratinocytes, the vial(s) of cells shall be stored in a liquid nitrogen freezer until needed . 3 . Thawing Cells and Establishing Cell Culture s a) Thaw cells by putting ampules into a water bath at 37°C for as brief a time as possible . Do not thaw cells at room temperature or by hand . Seed the thawed cells into culture flasks as quickly as possible and with minimal handling . b) Slowly (taking approximately 1-2 min) add 9 mL of pre-warmed Routine Culture Medium to the cells suspended in the cryoprotective solution and transfer cells into flasks containing pre-warmed Routine Culture Medium (See Table 1) . c) Incubate the cultures at 37°C ± 1°C, 90 % ± 5 % humidity, 5 .0 % ± 1% C02/air until the cells attach to the flask (within 4 to 24 h), at which time the Routine Culture Medium should be removed and replaced with fresh Routine Culture Medium . d) Unless otherwise specified, the cells should be incubated at 37°C ± 1°C, 90 % f 5 % humidity, 5 .0 % + 1% C02/air and fed every 2-3 days until they exceed 50 % confluence (but less than 80 % confluent)
. 

### Table 1 . Guidelines for Establishing Cell Culture s Cells/25 cm flask 6 .25 x 10 1 .25 x 105 2 .25 x 105 (in approximately 5 niL) (2500/cm2) (5000/cm2) (9000/cm) 1 fl as k each cell concentratio n Approximate Time to Subculture 96+ hours 72 - 96 hours 48 - 72 hours Cells to 96-Well Plates 6 - 8 plates 6 - 8 plates 6 - 8 plates Cell growth guidelines - actual growth of individual cell lots may vary . 4 . Subculture of NHK Cells to 96-Well Plates

7p . 8

Test tt,fethod Protoco/ for the NHK atiaeatr, it Red Uptal-e Cs-tutoxiCitVAsscr v Phase III - Validation Staedv . November 4

. 200 3 [Note : It is impo rtant that cells have overcome the lag growth phase when they are used for the test . Keratinocytes will be passaged only into the 96-well plates and will not be subcultured into flasks for use in later assays ] a) When the keratinocyte culture in a 25 cm2 flask exceeds 50 % confluence ( but less than 80 % confluent), remove the medium and rinse the culture twice with 5 mL HEPES-BSS . The first rinse may be left on the cells for up to 5 minutes and the second ri nse should remain on the cells for approximately 5 minutes . Discard the washing solutions . b) Add 2 mL trypsin/EDTA solution to each flask an d remove after 15 to 30 seconds . Incubate the flask at room temperature for 3 to 7 min . When more than 50 % of the cells become dislodged, rap the fl as k sharply against the palm of the h an d . c) When most of the cells have become detached from the surface, rinse the fl as k with 5 mL of room temperature TNS . Ifmore than one flask is subcultured, the same 5 mL of TNS may be used to rinse a total of up to two flasks . d) Then ri nse the flask with 5 mL CMF-HBSS and transfer the cell suspension to a cent ri fuge tube . e) Pellet the cells by centri fugation for 5 min at approximately 220 x g . Remove the supern atant by aspiration . f) Resuspend the keratinocyte pellet by gentle trituration (to have single cells) in Routine Culture Medium . It is impo rtant to obtain a single cell suspension for exact counting . Count a sample of the cell suspension using a hemocytometer or cell counter . 4 g) Prepare a cell suspension
- 1 .6 - 2 .0 x10 cells/mL in Routine Culture Medium . Using a multi-channel pipette, dispense 125 μ1 Routine Culture Medium only into the peripheral wells (blanks) of a 96-well tissue culture microtiter plate . In the remaining wells, dispense 125 μl of the cell suspension (2x103

- 2 .5x103 cells/well) . Prepare one plate per chemical to be tested (see Figure 1, Section VILE .1) . h) Incubate cells (37°C f 1°C, 90 % ± 5 .0 % humidity, and 5 % f 1% C02/air) so that cells form a 20+ % monolayer (-48-72 h) . This incubation period assures cell recovery and adherence and progression to exponential growth phase . i) Examine each plate under a phase contrast microscope to assure that cell growth is relatively even across the microtiter plate . This check is performed to identify experimental and systemic cell seeding errors . Record observations in the Study Workbook
. 5 . Determination of Doubling Time a) A cell doubling time procedure was performed on the initial lot of cells that was used in the first cell culture assays of Phase la of the Validation Study . The doubling time only needs to be determined in Phase III if there is a change in the lot of cells used . Establish cells in culture and t rypsinize cells as per Section VILC .4 for subculture . Resuspend cells in appropriate culture medium . Use Table 1 to determine seeding densities .

RP
. 9

Test Method Protocol /iw the ArtfK :Veinal Red Uptake C's-totox?cih- A ssa v Phose 111- Validation Stw]V~ '

b) Seed five sets of cell culture vessels in triplicate for each cell type (e .g ., 15 tissue culture dishes [60mm x 15mm]) . Use appropriate volume of culture medium for the culture vessels . Note number of cells placed into each culture dish . Place dishes into the incubators (37°C ± 1°C, 90 %± 5 % humidity, 5 .0 % ± 1% C02/air)
. c) After 4-6 hours (use the same initial measurement time for each subsequent doubling time experiment), remove three culture dishes and t rypsinize cells . Count cells using a cell counter or hemocytometer . Cell viability may be determined by dye exclusion (e .g ., Try pan Blue ; Nigrosin) . Determine the total number of cells and document . Repeat sampling at 24 hr, 48 hr, 72 hr, and 96 hr post inoculation . Change culture medium at 72 hr or sooner in remaining dishes if indicated by pH drop . d) Plot cell concentration (per mL of medium) on a log scale against time on a linear scale . Determine lag time and population doubling time . The doubling time will be in the log (exponential) phase of the growth cu rve . Additional dishes and time are needed if the entire growth curve is to be determined (lag phase, log phase, plateau phase) .

D . Preparation of Test Chemical s The Study Management Team will provide direction on the solvent to be used for each test chemical . [Note : Preparation under red or yellow light is recommended to prese rv e chemicals that degrade upon exposure to light . ] 1 . Test Chemical in Solution a) Allow test chemicals to equilibrate to room temperature before dissolving and diluting . b) Prepare test chemical immediately prior to use . Test chemical solutions should not be prepared in bulk for use in subsequent tests . Ideally, the solutions must not be cloudy nor have noticeable precipitate . Each stock dilution should have at least 1-2 mL total volume to ensure adequate solution for the test wells in a single 96-well plate . The SMT may direct the Study Director to store an aliquot (e .g ., 1 mL) of the highest 2X stock solution (e .g ., low solubili ty chemicals) in a freezer (e .g ., -70°C) for use in future chemical analyses . c) For chemicals dissolved in DMSO or ethanol, the final DMSO or ethanol concentration for application to the cells must be 0 .5 %(v/v) in the vehicle controls and in all of the eight test concentrations . d) The stock solution for each test chemical should be prepared at the highest concentration found to be soluble in the solubili ty test (Test Method Protocol for Solubility Determination) . Thus, the highest test concentration applied to the cells in each range finding experiment is : 0 .5 times the highest concentration found to be soluble in the solubility test, if the chemical w as soluble in medium, o r 1/200 the highest concentration found to be soluble in the solubili ty test if the chemical was soluble in ethanol or DMSO .



### Qp .10

Test Alethocl Protocol Jnr the NHK Neutral Rec! L%ptr .rl-e Cvtutnxieih- As .sav Phase III - Validation Studt- : November -I

. 2003 e) The seven lower concentrations in the range finding experiment would then be prepared by successive dilutions that decrease by one log unit each . The following example illustrates the preparation of test chemical in solvent and the dilution of dissolved test chemical in medium before application to NHK cells . Example : Preparation of Test Chemical in Solvent Using a Log Dilution Schem e If DMSO was determined to be the preferred solvent at Tier 2 of the solubility test (i .e ., 200,000 μg/mL), dissolve the chemical in DMSO at 200,000 μg/mL for the chemical stock solution . 1) Label eight tubes 1- 8 . Add 0 .9 mL solvent (e .g., DMSO) to tubes 2 -- 8 . 2) Prepare stock solution of 200,000 Rg test chemical/mL solvent in tube # 1
. 3) Add 0 .1 mL of 200,000 ~t g/mL dilution from tube #1 to tube #2 to make a 1 :10 dilution in solvent ( i .e ., 20,000 μg/mL) . 4) Add 0 .1 mL of 20,000 μg/mL dilution from tube #2 to tube #3 to make another 1 :10 dilution (i .e ., 1 :100 dilution from stock solution) in solvent (i .e ., 2,000 μg/mL) 5) Continuing making serial 1 :10 dilutions in the prepared solvent tubes . 6) Since each concentration is 200 fold greater than the concentration to be tested, make a 1 :100 dilution by diluting 1 part dissolved chemical in each tube with 99 pa rts of culture medium ( e .g ., 0 .1 mL of test chemical in DMSO + 9 .9 mL culture medium) to derive the eight 2X concentrations for application to NHK cells . Each 2X test chemical concentration will then contain 1% v/v solvent . The NHK cells will have 0 .125 mL of culture medium in the wells prior to application of the test chemical . By adding 0 .125 mL of the appropriate 2X test chemical concentration to the appropriate wells, the test chemical will be diluted appropriately (e .g ., highest concentration in well will be 1,000 μg/mL) in a total of 0 .250 mL and the solvent concentration in the wells will be 0 .5% v/v
. 7) A test article prepared in DMSO or ethanol may precipitate upon transfer into the Routine Culture Medium . The 2X dosing solutions should be evaluated for precipitates and the results recorded in the workbook . It will be permissible to test all of the dosing solutions in the dose range finding assay and main experiments . However, doses containing test art icle precipitates should be avoided and generally will not be used in the ICx determinations for the definitive tests . Precipitates in 2X dosing solutions are permissible for range finder tests but not for definitive tests . Document all test chemical preparations in the Study Workbook. 2 . pH of Test Chemical Solution s P rior to or immediately after application of the test chemical to the 96-well plate, measure the pH of the highest 2X dosing concentration of the test chemical (i .e ., Cl in the test plate, see Figure 1) in culture medium . Use pH paper (e .g ., pH 0

- 14 to estimate and pH 5

- 10 to determine more precise value ; or Study Director's discretion) . The pH paper should be i n


## i np .11

Test Method 1'rotoiol jbr the ,VF(K Neutral Red t'ptul,e ('>>totoxicitv,4s .sa v Phase III - Y'ali~fution Jtudv : !Vo vemher 4, 200

3 contact with the solution for approximately one minute . Document the pH and note the color of the 2X concentration medium (i .e ., in the EXCEL® template) . Medium color for all dosing dilutions should be noted in the workbooks . Do not adjust the pH . 3 . Concentrations of Test Chemical a) Range Finder Experiment Test eight concentrations of the test chemical by diluting the stock solution with a constant factor covering a large range. The initial dilution series shall be log dilutions ( e .g ., 1 :10, 1 :100, 1 :1000, etc .) . If a range finder experiment does not generate enough cytotoxicity, then higher doses should be attempted . If cytotoxicity is limited by solubility, then more stringent solubility procedures to increase the stock concentration (to the maximum concen tration speci fi ed in Section VII .D .3 .b .) should be employed . Place the highest test chemical concentration into an incubator (37°C ± 1°C, 90 % ± 5 % humidity, 5 .0 % ± 1% C02/air) and stir or rock for up to 3 hours, if necessa ry, to facilitate dissolution . For stocks prepared in medium, vessel caps should be loose to allow for CO2 exchange . Proceed with dosing solution preparation and dosing . If a range finding test produces a biphasic curve, then the doses selected for the subsequent main experiments should cover the most toxic dose-response range (see Example 1
- the most toxic range is 0 .001

- 0 .1 μg/mL) . Example 1 - Biphasic Curve Neutral Red Uptake 125 %
100% 75% Z _m > 50% 25 % 0% 0 .001 0 .010 0 .100 1 .000 10 .000 100 .000 1000 .000 10000 .000 Concentration (pg/mL)

b) Main Experimen t [Note : After the range finding assay is completed, the definitive concentration-response experiment shall be performed three times on three different days for each chemical (i .e ., one plate per day per chemical) . ] Depending on the slope of the concentration-response curve estimated from the range finder, the dilution/progression factor in the concentration series of the main experiment

11p .12

Test Adz,thod Protocol jor the VHK Nerrtrnl Red C.~ptuke C vtotox h- iti- Assav Phase III - Validation Studr- : November 4

. 1(03 should be smaller (e.g ., dilution factor of 6410 = 1 .47) . Cover the relevant concentration range around the IC50 (> 0 % and < 100 % effect) preferably with several points of a graded effect, but with a minimum of two points, one on each side of the estimated IC50 value, avoiding too many non-cytotoxic and/or 100 %-cytotoxic concentrations . Experiments revealing less than one cytotoxic concentration on each side of the IC5 0 value shall be repeated, where possible, with a smaller dilution factor ( see Section VII .E .5 .a .4) . Each experiment should have at least one cytotoxicity value > 0 % and < 50 .0 % viability and at least one cytotoxici ty value > 50 .0 % and < 100 % viability . A progression factor of 1 .21 [1 2 ~10] is regarded the smallest factor achievable and will be the lowest dosing interv al required. ) Determine which test chemical concentration is closest to the IC50 value (e .g ., 50 % cytotoxici ty ) . Use that value as a central concentration and adjust dilutions higher and lower in equal steps for the de finitive assay. Maximum Doses to be Tested in the Main Experiments If minimal or no cytotoxici ty was measured in the dose range finding assay, a maximum dose for the main experiments will be established as follows : For test chemicals prepared in Routine Culture Medium, the highest test a rticle concentration that may be applied to the cells in the main expe riments will be either 100 mg/mL, or the maximum soluble dose . Test chemical will be weighed into a glass tube and the weight will be documented . A volume of Routine Culture Medium will be added to the vessel so that the concentration is 200,000 μg/mL ( 200 mg/mL) . The solution is mixed using the mechanical procedures specified in Test Method Protocol for Solubility Determination . If complete solubili ty is achieved in medium, then 7 additional serial stock dosing solutions may be prepared from the 200 mg/mL 2X stock . If the test chemical is insoluble in medium at 200 mg/ml, proceed by adding medium, in small incremental amounts, to attempt to dissolve the chemical by using the sequence of mixing procedures specified in Test Method Protocol for Solubility Determination . More stringent solubili ty procedures may be employed if needed based on results from the range fi nder experiment (Section VII .D .3 .a .) . The highest soluble stock solution will be used to prepare the 7 additional serial stock dosing solutions . For test chemicals prepared in either DMSO or ethanol, the highest test a rticle concentration that may be applied to the cells in the main experiments will be either 2 .5 mg/mL, or less, depending upon the maximum solubility in solvent . Test chemical will be weighed into a glass tube and the weight will be documented . A volume of the appropriate solvent (determined from the original solubili ty test) will be added to the vessel so that the concentration is 500,000 μg/mL ( 500 mg/mL) . The solution is mixed as specified in Test Method Protocol for Solubility Determination . If complete solubility is achieved in the solvent, then 7 additional serial stock dosing solutions may be prepared from the 500 mg/mL 200X stock . If the test chemical is insoluble in solvent at 500 mg/ml, proceed by adding solvent, in small incremental amounts, to attempt to dissolve the chemical by using the sequence of mixing procedures . The highest soluble stock solution will be used to prepare the 7 additional serial stock dosing solutions . If precipitates are obse rv ed in the 2X dilutions, continue with the experiment, make the appropriate observations and documentation, and repo rt data to the SMT
.

1?p .13

Test .Liethod Protocol for the tVHK Arerrtral Red Uptake CVt0tOYiL'itVASSU V Phase 111- Validation Studv : November 4, 200-

1 c) Test Chemical Dilution s The dosing factor of 3 .16 (= 2~10) divides a log into two equidistant steps, a factor of 2 .15 (= 3410) divides a decade into three steps . The factor of 1 .47 (= 6~10) divides a log into six equidistant steps, the factor of 1 .78 (4~10) divides a log into four equidistant steps, and the factor of 1 .21 (= 12410) divides the log into 12 steps
. EXAMPLE : 10 31 .6 100 10 21 .5 46 .4 100 10 14 .7 21 .5 31 .6 46 .4 68 .1 100 10 12 .1 14 .7 17 .8 21 .5 26 .1 31 .6 38 .3 46 .4 56 .2 68 .1 82 .5 100 The technical production of decimal geometric concentration series is simple . An example is given for factor 1 .47 : Dilute 1 volume of the highest concentration by adding 0 .47 volumes of diluent. After equilibration, dilute 1 volume of this solution by adding 0 .47 volumes of diluent
. . . (etc .)
. E . Test Procedur e 1 . 96-Well Plate Configuratio n The NHK NRU assay for test chemicals will use the 96-well plate configuration shown in Figure 1 .



### VIp . 14

Test ,L[ethocl Protocol for the VHK Neutral Red Uptake ('iootoxicitv,3ssa v Phase 111- Validation stmjv : November 4, 200 3

Figure 1 . 96-Well Plate Configuration for Positive Control ( PC) and Test Chemical Assays
1 2 3 4 5 6 7 8 9 10 11 1 2
A VCb VCb Czb . C2b, :Cab C,41~, C5b C 6b C7b CSb- VCb VCb B VCb VC1 Ct C2 C3 C4 C5 C6 C7 C8 VC2 VCb C V~b VC1 C1 C2 C3 C4 C5 C6 C7 C8 VC2 VGb D VCb VCI Ci C2 C3 C4 C5 C6 C7 C8 VC2 VCb E VCb VCl CI C2 C3 C4 C5 C6 C7 C8 VC2 VCb F VCb VC1 IC, C2 C3 C4 C5 C6 C7 C8 VC2 VCb G VCb,~ VC1 C, C2 C3 C4 C5 C6 C7 C8 VC2 VCb H VCb . VCb Qb C lb C3 b C4b C 4 b c bb C7ts- , Cab, VCb, VCb ;

VC1 and VC2 = VEHICLE CONTRO L Ct -C8 = Test Chemicals or PC ( SLS) at eight concentrations (C1 = highest, C8 = lowest) b = BLANKS ( Test chemical or PC, but contain no cells) VCb = VEHICLE CONTROL BLANK ( contain no cells )
2 . Application of Test Chemica l a) Two optional methods for rapidly applying the 2X dosing solutions onto the 96-well plates may be utilized . 1) The first method is to add each of the 2X dosing solutions into labeled, sterile rese rv oirs ( e .g ., Corning/Costar model 4870 sterile polys ty rene 50 mL reagent reservoirs or Co rning/Transtar model 4878 disposable reservoir liners, 8-channel ; or other multichannel reservoirs) . 2) The second method utilizes a "dummy" plate ( i .e., an emp ty sterile 96-well plate) prepared to hold the dosing solutions immediately prior to treatment of the test plate (with cells) . The test chemical and control dosing solutions should be dispensed into the dummy plate in the same pattern/order as will be applied to the plate containing cells . More volume than needed for the test plate (i .e . greater than 125 μl/well) should be in the wells of the dummy plate . At the time of treatment initiation, a multi-channel micropipettor is used to transfer the 2X dosing solutions, from the reserv oirs or dummy plate, to the appropriate wells on the treatment plate (as described in step c . below) . These methods will ensure that the dosing solutions can be transferred rapidly to the appropriate wells of the test plate to initiate treatment times and to minimize the range of treatment initiation times across a large number

14p .15

Test Alethod Protocul tin the NHK laeartrcal fled Uptake Cvtvtoxtcitl; Assa y Phase III - VulWaiiarr Stat(Jv : N'overraher 4, 200

3 of treatment plates, and to prevent "out of order" dosing . Do not use a multichannel repeater pipette for dispensing test chemical to the plates
. b) After 48 - 72 h (i .e ., after cells attain 20+ % confluency [see Section Vll .C .4(h)]) incubation of the cells, add 125 μl of the appropriate concentration of test chemical, the PC, or the VC (see Figure 1 for the plate configuration) directly to the test wells . Do not remove Routine Culture Medium for re-feeding the cells . The dosing solutions will be rapidly transferredfrom the 8-channel reservoir (or dummy plate) to the test plate using a single delivery multichannel pipettor . For example, the VC may be transferred first (into columns 1, 2, 11, and 12), followed by the test article dosing solutions from lowest to highest dose, so that the same pipette tips on the multi-channel pipettor can be used for the whole plate . [The Vehicle Control blank (VCb) wells (column 1, column 12, wells A2, A11, H2, H11) will receive the Vehicle Control dosing solutions (which should include any solvents used) . Blanks for wells A3 - A10 and H3 - H10 shall receive the appropriate test chemical solution for each concentration (e .g ., wells A3 and H3 receive C, solution) .] Incubate cells for 48 h ± 0 .5 h (37°C 7L 1°C, 90 % ± 5 % humidity, and 5 .0 % + 1% C02/air)
. c) Positive Control : For each set of test chemical plates used in an assay, a separate plate of positive control concentrations will be set up following the concentration range established in the development of the positive control database in Phase I of the Validation Study . If multiple sets of test chemical plates are set up, then clearly designate the positive control plates for each set ; each set will be an individual entity . The Study Director will decide how many test chemical plates will be run with a positive control plate . The mean IC50 ± two and a half standard deviations (SD) for the SLS acceptable tests from Phases la, Ib, and II (after the removal of outliers) are the values that will be used as an acceptance criterion for test sensitivity for the NHK NRU assay . This plate will follow the same schedule and procedures as used for the test chemical plates (including appropriate chemical concentrations in the appropriate wells and meeting test acceptance criteria see Sections VII .E .1, E .2, and E .5) . 3 . Microscopic Evaluatio n After at least 46 h treatment, examine each plate under a phase contrast microscope to identify systematic cell seeding errors and growth characteristics of control and treated cells
. Record any changes in morphology of the cells due to the cytotoxic effects of the test chemical, but do not use these records for any quantitative measure of c otoxicity
. Undesirable growth characteristics of control cells may indicate experimental error and may be cause for rejection of the assay . Use the following Visual Observations Codes in the description of cell culture conditions . Numerical scoring of the cells (see Section VILE .3) should be determined and documented in the Study Workbook and in the appropriate section of Addendum 11 of the EXCEL® study template
.

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Test iVethod Protocol for the ,VIfK ;Ve rrtral Red Uptcrl c : C'rtutoxicit4- Assa n Phase III - Vali,lation Sti«,fr : November 4, 200 ;

Visual Observations Code s Note Code Note Text 1 Normal Cell Morphology 2 Low Level of Cell Toxicity 3 Moderate Level of Cell Toxicity 4 High level of Cell Toxicity 1P Normal Cell Morphology with Precipitate 2P Low Level of Cell Toxicity with Precipitate 3P Moderate Level of Cell Toxicity with Precipitate 4P High level of Cell Toxicity with Precipitate 5P Unable to View Cells Due to Precipitate 4. Measurement of NR U a) Carefully remove (i .e ., "dump") the Routine Culture Medium (with test chemical) and rinse the cells very carefully with 250 μL pre-warmed D-PBS . Remove the rinsing solution by dumping and remove excess by gently blotting on paper towels . Add 250 μL NR medium (to all wells including the blanks) and incubate (37°C ± 1°C, 90 % ± 5 % humidity, and 5 .0 % f 1% C02/air) for 3±0 .1 h . Observe the cells briefly during the NR incubation (e .g ., between 2 and 3 h- Study Director's discretion) for NR crystal formation . Record observations in the Study Workbook . Study Director can decide to reject the experiment if excessive NR crystallization has occurred
.b) After incubation, remove the NR medium, and carefully rinse cells with 250 μL prewarmed D-PBS
. c) Decant and blot D-PBS from the plate . (Optionally : centrifuge the reversed plate .) d) Add exactly 100 μL NR Desorb (ETOH/acetic acid) solution to all wells, including blanks
. e) Shake microtiter plate rapidly on a microtiter plate shaker for 20 - 45 min to extract NR from the cells and form a homogeneous solution . Plates should be protected from light by using a cover during shaking . f) Plates should be still for at least five minutes after removal from the plate shaker (or orbital mixer) . If any bubbles are observed, assure that they have been ruptured prior to reading the plate . Measure the absorption (within 60 minutes of adding NR Desorb solution) of the resulting colored solution at 540 nm ± 10 nm in a microtiter plate reader (spectrophotometer), using the blanks as a reference . [Phases la and lb data show the mean OD value for the plate blanks to be 0 .055 ± 0 .035 for NHK cells (± 2 .5 standard deviations ; data from 3 labs ; N = 156) . Use this range as a guide for assessment of the blank values .] Save raw data in the Excel format as provided by the SMT
. 5 . Quality Check of Assa y a) Test Acceptance Criteria

tFp .17

Test Method Protoccrl the the NHK rlreutrirl Red Uptak e Phase 111- Validation Stwlv :
All acceptance criteria (i .e ., criteria 1, 2, and 3) must be met for a test to be acceptable
. 1) The PC (SLS) ICso must be within two and a half (2 .5) standard deviations of the historical mean established by the Test Facility (as per VILE .2 .c), and must meet criteria 2 and 3, and must have an r2 (coefficient of determination) value calculated for the Hill model fit (i .e ., from PRISM® software) > 0 .85
. 2) The left and the right mean of the VCs do not differ by more than 15 % from the mean of all VCs
. 3) At least one calculated cytotoxicity value > 0 % and < 50 .0 % viability and at least one calculated cytotoxicity value > 50 .0 % and < 100 % viability must be present
. Exception : If a test has only one point between 0 and 100 % and the smallest dilution factor (i .e ., 1 .21) was used and all other test acceptance criteria were met, then the test will be considered acceptable
. Stoaaing Rule for Insoluble Chemicals : If the most rigorous solubility procedures have been performed and the assay cannot achieve adequate toxicity to meet the test acceptance criteria after three definitive trials, then the Study Director may end all testing for that particular chemical . [Note : A corrected mean OD540 f tonm of 0 .205 - 1 .645 for the VCs is a target range but will not be a test acceptance criterion . Range determined from Phase lb VC OD values from 3 laboratories (mean + 2 .5 standard deviations, N = 69)
. ] b) Checks for Systematic Cell Seeding Error s To check for systematic cell seeding errors, untreated VCs are placed both at the left side (row 2) and the right side (row 11 for the test plates) of the 96-well plate . Aberrations in the cell monolayer for the VCs may reflect a volatile and toxic test article present in the assay . If volatility is suspected, then proceed to Section VILE .6
. Checks for cell seeding errors may also be performed by examining each plate under a phase contrast microscope to assure that cell quantity is consistent
. 6 . Volatility of Test Chemical s Highly volatile test chemicals may generate vapors from the treatment media during the test chemical treatment incubation period . These vapors may become resorbed into the treatment medium in adjacent wells, such that culture wells nearest the highest doses may become contaminated by exposure to resorbed test article vapors . If the test chemical is particularly toxic at the doses tested, the cross contamination may be evident as a significant reduction in viability in the vehicle control cultures (i .e ., VC I) adjacent to the highest test chemical doses
. If potential test article volatility is suspected (e .g ., for low density liquids) or if the initial range finder test (non-sealed plate) results show evidence of toxic effects in the control cultures (i .e ., > 15 % difference in viability between VC1 [column 21 and VC2 [column 11]), then seal the subsequent test plates by the following procedure
.

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Test VIethod Pr•oto(ol jbr the Al-1K Neutral Red Uptak ePha,se 111- L'alidatrorr S/rrdv

_ November 4, 1003

a) Plate Sealer Metho d 1) Plates and chemicals will be prepared as usual according to Sections VILD and VII .E
. 2) Immediately after the 96-well culture plate has been treated with the suspected volatile chemical ( Section VIl .E .2 .b), apply the adhesive plate sealer (e .g ., using a hand, microplate roller, etc .) directly over the culture wells . Assure that the sealer adheres to each culture well (well tops should be dry) . Place the 96-well plate cover over the sealed plate and incubate the plate under specified conditions (Section VIl .E .2 .b) . [Note : Do not jam the plate lid over the film to avoid deforming the sealer and causing the sealer to detach from culture wells . Loose fit of the plate lid is acceptable
. ] 3) At the end of the treatment period, the plate sealer should be carefully removed to avoid spillage . Continue with the NRU assay as per Section VILE .4
. F . Data Analysi s The Study Director will use good biological/scientific judgment for determining "unusable" wells that will be excluded from the data analysis and provide explanations for the removal of any data from the analysis
. A calculation of cell viability expressed as NRU is made for each concentration of the test chemical by using the mean NRU of the six replicate values (minimum of four acceptable replicates wells) per test concentration . This value is compared with the mean NRU of all VC values . Relative cell viability is then expressed as percent of untreated VC . If achievable, the eight concentrations of each chemical tested will span the range of no effect up to total inhibition of cell viability . Data from the microtiter plate reader shall be transferred to the Excel® spreadsheet template provided by the SMT . The template will automatically determine cell viability, IC50 values by linear interpolation, and perform statistical analyses (including statistical identification of outliers) . The template will also calculate the concentrations associated with 20 %, 50 %, and 80 % viability using the Hill slope and EC50 (i .e ., IC50) from the Hill function analysis
. The Hill function analysis shall be performed using statistical software (e .g ., GraphPad PRISM® 3 .0) and a template specified by the SMT to calculate IC20, IC5o, and IC80 values (and the associated confidence limits) for each test chemical . The Testing Facility shall report data using at least three (3) significant figures and shall forward the results from each assay to the SMT through the designated contacts in electronic format and hard copy upon completion of testing . The SMT will be directly responsible for the statistical analyses of the Validation Study data . VIlI . REFERENCE S Clonetics Normal Human Keratinocyte Systems Instructions for Use, AA-1000-4-Rev .03/00
. (http ://www .clonetics .com)
.

1Rp .19
Test Rlclhod Protocul for the :VHK Neutral Red t~rake Cvtotoxicih~ Assa v Phase I11- d"Crih lation Studv : November 4

. 2(11) ; Hackenberg, U . and H . Bartling . 1959 . Messen und Rechnen im pharmakologischen Laboratorium mit einem speziellen Zahlensystem (WL24-System) . Arch . Exp . Pathol
. Pharmakol . 235 : 437-463
. Triglia, D ., P .T . Wegener, J . Harbell, K . Wallace, D . Matheson, and C . Shopsis . 1989
. Interlaboratory validation study of the keratinocyte neutral red bioassay from Clonetics Corporation . In Alternative Methods in Toxicology, Volume 7 . A .M . Goldberg, ed ., pp . 357-365

. Mary Ann Liebert, Inc ., New York
. Test Method Protocol for Solubility Determination . In Vitro Cytotoxicity Validation Study . Phase III . August 29, 2003 . Prepared by The National Toxicology Program (NTP) Interagency Center for the Evaluation of Alternative Toxicological Methods (NICEATM)

.

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Test Rkthoc/Protocol /br the iVHK 'Verttrcrl Red Uptcrl-e Cvtotoricitv .4ssa v Phase 111- Y"alidatiorr Jhrdv : November 4, ZOl) ; 

### IX . APPROVAL

SPONSOR REPRESENTATIVE DATE
(Print or type name )

Testing Facility STUDY DIRECTOR DATE (Print or type name)



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