Reviewer: John Doherty

ReRegistration Branch III, HED (7509C)

Secondary Reviewer: Jess Rowland

Science Information Management Branch, HED (7509C)

**TXR \# 0050236**

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  **DER for a Special Non-Guideline Study with Human Volunteers**

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**Study Type:** Special Non-Guideline Cholinesterase Study with Human
Volunteers.

**DP Barcode No.:** D277372 **PC Code:** 058001

**Submission No.:** S602411

**Test Material:** Azinphos methyl (purity: 89.2 to 91.6%, batch number
703-0139).

**Citation:** P. McFarlane and S. Freestone, \"A Randomized Double Blind
Placebo Controlled Study with Azinphos-Methyl to Determine the No Effect
Level on Plasma and RBC Cholinesterase Activity After Repeated Doses.\"
Inveresk Research, Study No.: ICR 013580, April 15, 1999. MRID No.:
45476101

**Sponsor:** Bayer Corporation, 17745 South Metcalf, Stilwell, KS
66085-9104.

**In-Life Phase:** March 2, 1999 to April 15, 1999.

**Executive Summary:**

In this special 28-day dosing study (MRID No.: 45476101) with human
subjects (males only), a group of 4 volunteers were dosed as placebo
(lactose) and a group of 8 volunteers were dosed with 0.25 mg/kg/day of
azinphos methyl (89.1% to 91.6% purity) for 28 consecutive days. Dosing
was orally by capsule and the subjects were housed in a clinic
throughout the dosing period. The subjects were monitored for reactions
and samples of their blood were taken at predose (8 times) and daily
throughout the dosing period. On some days, a blood sample was taken
both prior to administering the dose and 4 hours after. The blood was
separated and assessed for both plasma cholinesterase (ChE) and red
blood cell acetylcholinesterase (RBC AChE). In addition, hematology,
clinical chemistry and urinalysis were evaluated as well as blood
pressure and ECG.

*Systemic Effects.* There were no reactions to treatment and blood
pressure and ECG parameters were not affected. Eight of the 12
volunteers were noted to have symptoms of a viral infection and some
were treated with paracetamol. This was not considered to affect the
interpretation of the study.

*Cholinesterase assessments.* The plasma ChE in IU/mL for the baseline
(mean  the standard deviation) was 69651327 (19%) for the placebo
group (4 subjects) and 53071048 (20%) for the azinphos methyl treated
group (8 subjects) meaning that the azinphos methyl group was already
24% less prior to test material administration. The RBC AChE in IU/mL
for the baseline was 10933255 (2.3%) for the placebo group and
11049478 (4.3%) for the azinphos methyl treated group prior to dosing.
The mean values and variance are as would be expected for assessment of
plasma ChE and RBC AChE from human subjects. The postdosing group mean
data were compared three ways in an effort to see if azinphos methyl
caused inhibition of either plasma ChE or RBC AChE. Neither comparison
of the group mean for the dosed group with i. the placebo group at each
time interval or ii. the dosed groups baseline mean (the most
appropriate method) indicated inhibition of either plasma ChE or RBC
AChE. In particular, the maximum decrease in plasma ChE was only 6% and
the maximum decrease for RBC AChE was 9% (which occurred only on one
day) when compared to the baseline mean. Also, samples taken 4 hours
after dosing on several occasions did not indicate inhibition. **In
conclusion, a dose of 0.25 mg/kg/day of azinphos methyl for 28 days did
not result in either clinical symptomology or inhibition of either
plasma ChE or RBC AChE in human males. The NOAEL is 0.25 mg/kg/day.**

**Classification:** Classification of this study is RESERVED pending
establishment of an Agency policy for classification of studies using
human subjects.

**Compliance:** A Combined Good Clinical Practice (CPMP/ICH/135/95) for
treatment of human subjects and a OECD Good Laboratory Practice
statement was provided (dated August 3, 1999). A Statement of Data
Confidentiality (no claim) was also provided (dated August 13, 1999).
Information on the volunteer consent form and other aspects of the
ethical treatment of the subjects such as the study being conducted in
accordance with the Declaration of Helsinki, as amended in 1975, 1983,
1989 and 1996 were provided.

A. **Study Constants and Materials**

1\. **Test Material:**

> Chemical: Azinphos methyl
>
> Chemical name:
> S-(3,4-dihydro-4-oxobenzo\[d\]-1,2,3)-triazin-3-ylmethyl)O,O-dimethyl

phosphordithioate

> Batch: 703-0139
>
> Purity: 89.2% to 91.6%
>
> Structure: No electronic structure available.
>
> CAS Number: 86-50-0.
>
> Description: Granulated powder.
>
> Supplier: Bayer Corporation

2\. **Vehicle of Placebo:**

> Chemical: Lactose
>
> Purity: No information provided. Standard stock preparation.
>
> Supplier: J M Loverage, Company
>
> Batch 28811

3\. **Test Subjects:**

> Species: Human volunteers-all males
>
> Race: All Caucasian
>
> Age: Criteria for inclusion in the study was to be between 18 and 50
> years of age. The mean age  the standard deviation of the placebo
> group was 35.39.5 years and was 29.39.6 years for the group dosed
> with azinphos methyl.
>
> Body Weight: 61.8 to 90.4 kg.
>
> Housing: From the day before the first dose until 24 hours after
> receiving the last dose the subjects resided in the clinic and
> remained under constant medical and nursing supervision and received a
> standardized diet.

Pages 19 to 22 of the study report describe many details for the
criteria that must be met to be included in this study. Each subject was
given a screening examination to assure that there were no medical
reasons for exclusion. In general, only individuals in good health and
not on drugs (prescription or otherwise), non-smokers and capable of
communicating with the medical staff were selected. Objections from the
subjects personal physician also was cause to preclude a persons
participation in the study. Agricultural workers and pesticide
applicators or persons exposed to an anti-cholinesterase within a month
of the dosing were not eligible. During the study, no alcohol or
caffeine or other medications were allowed. Note: During the study
several of the subjects received paracetamol to control headache and
viral symptoms, also, one subject received antibiotics. HED does not
consider that either treatment with paracetamol or the antibiotics would
compromise the study.

4\. **Study Protocol:** Table 1 illustrates the study protocol.

+--------+----------------+--------------------------------------------+
| Group  | Number of      | Assessments                                |
|        | Subjects       |                                            |
+--------+----------------+--------------------------------------------+
| P      | 4 males        | -General clinical exam (self reporting of  |
| lacebo |                | any possible symptoms).                    |
|        |                |                                            |
|        |                | -Systolic and diastolic blood pressure     |
|        |                | just prior to each dose.                   |
|        |                |                                            |
|        |                | -Electrocardiogram (12 lead), Hematology   |
|        |                | and Clinical Chemistry and Urinalysis:     |
|        |                | prior to dosing and on days 1, 7, 14, 21   |
|        |                | and 28.                                    |
|        |                |                                            |
|        |                | -Plasma ChE and RBC AChE assessments - on  |
|        |                | screening days -14, -12, -10, -8, -6, -4   |
|        |                | and -1; and then daily after dosing with   |
|        |                | special assessments on days on days 1, 2,  |
|        |                | 3, 4, 5, 7, 10, 14, 17, 21, 24 and 28 when |
|        |                | two blood samples were taken to include    |
|        |                | sampling *before* each dose *and* 4 hours  |
|        |                | after the dosing                           |
+--------+----------------+--------------------------------------------+
| 0.25   | 8 males        |                                            |
| mg     |                |                                            |
|        |                |                                            |
| az     |                |                                            |
| inphos |                |                                            |
|        |                |                                            |
| methyl |                |                                            |
+--------+----------------+--------------------------------------------+

5\. **Rationale for Dose Level Selection.** The dose level of 0.25
mg/kg/day was selected based on the results of animal studies and an
earlier study with human subjects that indicated that this would be a
NOAEL. for inhibition of plasma and RBC cholinesterase.

6\. **Dosing.** Each subject was dosed by capsule containing either the
placebo (lactose) or azinphos methyl approximately 5 minutes *after*
breakfast. Table 3 (page 38 of the study report, copy attached) shows
the amount in mg of placebo or azinphos methyl actually given to each
subject on each day.

7\. **Statistics:** The data were analyzed by the SAS (v6.07) program.
This system produced all summary tables and data listings. The study
report (page 31) discusses the use of Retrospective Power Calculation to
detect clinically relevant differences if the study was repeated.

The repeated measures ANOVA model was used for analysis of percentage
change from baseline plasma and RBC cholinesterases using the pooled
baseline values as covariate. This was done by comparing the goodness of
fit statistics (Akaike\'s Information Criterion and Schwart\'z Bayestan
Criterion) for both models including and excluding the pooled baseline
value. Table M1.1.1 (pages 491 to 501) presents the results of the
statistical tests.

**Specific Methods and Results**

1\. **Assessment for clinical reactions.**

All subjects remained on the study for the scheduled time. Comments on
the general health and adverse events or reactions that may *possibly*
be related to treatment for each subject are illustrated in Table 2.
Note: During the dosing period the investigators were blind to whether
or not the subject actually received azinphos methyl and they made their
determination regarding possibly treatment related effects based on the
symptoms only.

Table 2. Individual subject analysis for adverse effects. .

  ---------------------------------------------------------------------------------
  \#            General Condition and Possible Reactions           HED Conclusion
  ------------- -------------------------------------------------- ----------------
  Placebos                                                         

  1             4 adverse events. **Viral illness** on day 27.     Subject did not
                Headache on day 27 (attributed to the              receive azinphos
                environment), myalgia on day 19 and mouth dryness  methyl.
                on day 27. .                                       

  5             13 adverse events. **Viral illness.** Chest pain   Subject did not
                on days 7 and 9, rhinitis day 17 ), rash on day 11 receive azinphos
                and pruritus on day 11, elevated ALT from day -14  methyl.
                to day 28, headache on day 14, 16, 18, 24, 26, The 
                headache and other symptoms were treated with      
                paracetamol and attributed to the ward environment 
                or virus.                                          

  8             0 adverse events.                                  

  12            0 adverse events.                                  

  Azinphos                                                         
  Methyl                                                           
  Treated                                                          

  2             14 adverse events. Both pre and post dose          Not related to
                headaches (on days -2, 3, 8, 21, 23, 27 and 28).   treatment.
                Treated with paracetamol and attributed to the     
                environment and a **viral illness.**               

  3             2 adverse events. Headache (treated with           Not related to
                paracetamol) on day 1 and rhinitis on day 14 and   treatment.
                thought to be related to a **viral illness.**      

  4             4 adverse events. Nausea thought to be related to  Not related to
                the diet. Headache (day 11) rhinitis and coughing  treatment.
                thought to be related to **viral illness.**        

  6             11 adverse events. Dietary related                 Not related to
                gastrointestinal symptoms and headache             treatment.
                (intermittent) treated with paracetamol.           

  7             5 adverse events. **Viral illness** related to     Not related to
                mouth dryness and coughing treated with            treatment.
                paracetamol. Raised ALT and GGT                    

  9             8 adverse events. Diet related indigestion, back   Not related to
                pain and raised AST.                               treatment.

  10            7 adverse events. **Viral illness** related to     Not related to
                rhinitis and coughing and headache (also           treatment.
                attributed to the ward conditions). Mouth ulcer    
                and facial pain treated with ibuprofen and         
                amoxycillin.                                       

  11            2 adverse events. **Viral illness** thought to be  Not related to
                related to lymphadenopathy and rhinitis treated    treatment.
                with paracetamol.                                  

  Overall                                                          
  Comment on                                                       
  treated                                                          
  subjects.                                                        
  Much the same                                                    
  symptoms that                                                    
  were reported                                                    
  in the                                                           
  placebo group                                                    
  without                                                          
  indications                                                      
  of increased                                                     
  intensity                                                        
  were also                                                        
  reported in                                                      
  the group                                                        
  dosed with                                                       
  azinphos                                                         
  methyl.                                                          
  ---------------------------------------------------------------------------------

Not all aliments that a subject reported are mentioned above since some
were very obviously not recognized as being response to treatment with
an organophosphate. For example, skin lesions are not mentioned.

It is concluded that none of the subjects dosed with azinphos methyl
developed symptoms indicative of organophosphate poisoning. Most of the
subjects (i.e. 8 of the 12 on the study) were reported to have developed
a viral illness with some subjects apparently having more viral related
symptoms than others. It should also be noted that there was no increase
in the severity of the symptoms in the subjects when compared with the
controls and the severity was graded as 1 or 2 (low degree).

Another apparent cause of adverse events was discomfort related to being
confined in the clinic. This is understandable.

**2. Specific tests**

***Blood pressure and heart rate.*** There were no changes in blood
pressure or heart rate in response to azinphos methyl administration.

***ECG***. There were no clinically significant effects on the ECG
patterns of the subjects on this study.

3\. **Clinical Chemistry**

***Hematology.*** Appendix K (pages K1 to K24 in Volume 2) indicates
that hemoglobin, red blood cells, hematocrit. mean cell hemoglobin
concentration, mean cell volume, white blood cells count (including
neutrophils, lymphocytes, monocytes. eosinophils. basophils, LUC (large
unclassified cells), and platelets were assessed.

There were no meaningful effects of azinphos methyl on these parameters.

***Clinical Chemistry.*** Appendix L (pages L1 to L23 in Volume 2)
indicates that urea, glucose. AST (aspartate aminotransferase), ALT
(alanine aminotransferase), LDH (lactate dehydrogenase), sodium,
potassium, chloride, TP (total protein), albumin, T.Bi (total
bilirubin), GGT (gamma glutamyl transferase) and creatinine were
assessed.

There were some increases in AST and ALT that resolved themselves and
were not considered to be related to treatment. For example they were
transient (self resolving) and considered to be within normal variation.

4\. **Cholinesterase Assessment.**

***General Preparation and Separation and Basic Assay.***

Blood samples (4.5 mL) were taken by venipuncture each day at screening,
on days -14, -12, -10, -8, -6, -4, -2, and -1 (before dosing) and on
days 1, 2, 3, 4, 5, 6, 7, 10, 14, 17, 21, 24 and 28 postdosing. Page 26
of the study report states that on postdosing days samples were taken
prior to dosing and 4 hours postdosing. However, the individual subject
data tables in Appendix M of the study report present data to indicate
that blood cholinesterase was measured every day of the study. The
samples were collected in tubes containing EDTA and centrifuged to
separate the plasma from the RBCs. These were shipped to IR laboratory
at Elphinstone Research Centre on wet ice and assayed the same day. The
actual time between sample collection and assay time was not stated and
may have been different for each day and there may have been different
interval times for each subject. . Plasma ChE and RBC AChE was assessed
following the SOP/CLC/043 using an Hitachi Analyzer. This analyzer
utilizes acetylthiocholine as the substrate and is a modification of
Ellman\'s original method.

***Plasma ChE and RBC AChE baseline values and variability of the
data.***

A general summary of the plasma ChE and RBC AChE for the baseline data
is presented in Table 3.

Table 3. Mean baseline plasma ChE and RBC AChE data.

+---------+------------------------------+----------------------------+
|         | Plasma ChE (IU/L)            | RBC AChE (IU/L)            |
|         |                              |                            |
|         | Placebo Group AZM Group      | Placebo Group AZM Group    |
+---------+------------------------------+----------------------------+
| B       | 69651327 (19%) 53071048   | 10933255 (2.3%)          |
| aseline | (20%)                       | 11049478 (4.3%)          |
| Values  |                              |                            |
|         | (range 5722 to 8757) (range  | (range 10663 to 11196)     |
|         | 3366 to 6840)                | (range 10394 to 11854)     |
+---------+------------------------------+----------------------------+
|         | Note: There is a 24%         | The placebo and treated    |
|         | difference between the       | group are very comparable  |
|         | placebo and treated group    | prior to dosing.           |
|         | before the start of AZM      |                            |
|         | dosing. This is likely due   | There is good precision    |
|         | to the subjects with the two | since the standard         |
|         | highest plasma ChE values    | deviations are small (2.3% |
|         | are in the placebo group and | and 4.3%)                  |
|         | the subject with the lowest  |                            |
|         | is in the AZM group.         |                            |
|         |                              |                            |
|         | The 19% and 20% standard     |                            |
|         | deviation shows poor         |                            |
|         | precision.                   |                            |
+---------+------------------------------+----------------------------+
| Com     | 57391071 (19%) 52561325   | 115951323(11%)           |
| parison | (25%)                       | 128101013(8%)            |
| of the  |                              |                            |
| b       | 62851199(19%)              | 12712961 (8%)            |
| aseline |                              |                            |
| values  | 64021129(18%)              | 115241296 (11%)          |
| with    |                              |                            |
| the     | 5715757 (13%)              | 113871280 (11%)          |
| acute   |                              |                            |
| study   |                              |                            |
| (a)     |                              |                            |
+---------+------------------------------+----------------------------+
|         | Similarly large standard     | The standard deviations    |
|         | deviations were obtained in  | for the subchronic study   |
|         | both studies.                | are smaller than for the   |
|         |                              | acute study meaning that   |
|         |                              | there was better precision |
|         |                              | in the acute study.        |
+---------+------------------------------+----------------------------+

(a). Refer to MRID No.: 44786901 for the acute study with humans and
azinphos methyl. The acute study had four dose levels for males and the
baseline is presented for each dose group. There were 12 subjects in the
placebo group for the acute study and 7 subjects in each group dosed
with AZM. This compares with only 4 subjects in the placebo groups and 8
subjects in the dosed group for the 28 day study.

Table 3 shows that the standard deviation is 19 to 20% of the mean for
the plasma ChE data (based on 4 subjects). This compares with a 13-25%
obtained in the previous acute study with azinphos methyl in human
subjects. The standard deviation for RBC AChE was only 2.3 to 4.3% for
the baseline values which indicates good precision. However, throughout
the course of the study the standard deviations for RBC AChE means were
as high as 15%. (i.e see day 1for the placebo group at 4 hours after
dosing in Appendix M, Table M2.2 also shown in Table 4 below).

There is much variation between the subject with the lowest (3366100
IU/L) baseline plasma ChE and the highest (8757442 IU/L) but these
recordings are within the normal range for human plasma ChE.

***Assessment for Inhibition of Plasma ChE and RBC AChE Based on Group
Mean Data.***

Table 4 illustrates group mean data for plasma ChE and RBC AChE
assessments at selected time intervals. The potential for azinphos
methyl to inhibit both plasma ChE or RBC AChE was assessed three ways.

i\. by comparison of the day to day value for the azinphos methyl
treated group with the same day value for the placebo group.

Since plasma ChE for the group that was to receive the azinphos methyl
was already 24% less than the placebo before the start of dosing, all
values were remained about 17 to 24% less than the placebo throughout
dosing. Thus, there was no inhibition. The lowest decease for RBC AChE
was only 3% but many values were higher for the dosed group relative to
the placebo group.

ii\. by comparison of the same day predosing cholinesterase data with
the cholinesterase data obtained 4 hours after dosing.

The maximum difference was 9% decrease for the 10 hour sample but his
was not sustained and the 4 hour sample was low for the placebo (5%,
i.e. 10346/10933 = 0.946 or 5%) group also indicating an experimental
variation and not true inhibition.

iii\. by comparison of the azinphos methyl group data obtained each day
with the predosing baseline value.

Table 4 shows that at day 10 the 4 hour postdosing sample was 7% lower
than the

predosing assessment. However, the placebo group was also 8% lower after
4 hours. Thus,

the 7% decrease is not considered inhibition.

Neither of these three methods resulted in an indication that azinphos
methyl inhibited either plasma ChE or RBC AChE at any time interval.

***Assessment of plasma ChE and RBC AChE inhibition based on analysis of
individual subjects.***

Table 5 illustrates the plasma ChE and RBC AChE data for each subject on
the study.

***Plasma ChE.*** Table 5 shows that in the placebo group plasma ChE can
be reduced to 86% and elevated to 110% above the baseline obtained by
repeated samplings both before and during the dosing period. Table 5
also shows that for the subjects dosed with azinphos methyl their
predosing baseline can be as low as 84% (subject #11) of his baseline
mean. During the dosing period, one subject (#9) in the azinphos methyl
group was reduced to as much as 83% of his baseline mean. Thus, there is
no indication of inhibition of plasma ChE when the individual subject
data are evaluated.

Table 4. Comparison of Plasma ChE and RBC AChE in the Placebo and
Azinphos Methyl Dosed Groups Based on Group Mean Data.

+------+------------------------------+--------------------------------+
| Day  | Plasma ChE (IU/L)            | RBC AChE (IU/L)                |
|      |                              |                                |
| \    | Placebo 0.25 AZM %Diff. (b)  | Placebo 0.25 AZM %Diff. (b)    |
| (a\) | %Diff.(c)                    | %Diff (c)                      |
+------+------------------------------+--------------------------------+
| Bas  | 69651327 53071048 -24% \-- | 10933225 11409478 +4%        |
| elin |                              |                                |
| e(e) |                              |                                |
+------+------------------------------+--------------------------------+
| 1    | 65321153 4980965 -24% -6%  | 10738699 11220811 +5% \~     |
|      |                              |                                |
|      | 64651170 4985988 -24% -6%  | 116811723 11683803 \~ +2%    |
|      |                              |                                |
|      | (\~) (d) (\~)                | (+9%) (+4%)                    |
+------+------------------------------+--------------------------------+
| 4    | 66691258 5219959 -22% \~   | 9543956 11256791 +18% \~     |
|      |                              |                                |
|      | 64201502 5139957 -20% -3%  | 10742812 11170928 +4% -2%    |
|      |                              |                                |
|      | (-4%) (\~)                   | (+13%) (\~)                    |
+------+------------------------------+--------------------------------+
| 8    | 64401363 5098989 -21% -4%  | 10706539 11151610 +4% -2%    |
+------+------------------------------+--------------------------------+
| 10   | 67681546 5323960 -17% \~   | 11263643 112331139 \~ \~     |
|      |                              |                                |
|      | 67331286 5250970 -22% \~   | 103461323 10399733 \~ -9%    |
|      |                              |                                |
|      | (\~) (\~)                    | (-8%) (-7%)                    |
+------+------------------------------+--------------------------------+
| 12   | 64521288 50951080 -21% -4% | 117701499 113931163 -3% \~   |
+------+------------------------------+--------------------------------+
| 16   | 65451195 52081010 -20% -2% | 10953539 10992515 \~ -4%     |
+------+------------------------------+--------------------------------+
| 21   | 70131425 54371010 -22% +2% | 10587224 10909728 +3% -4%    |
|      |                              |                                |
|      | 67911179 5432998 -20% +2%  | 10383339 115521363 +11% \~   |
|      |                              |                                |
|      | (3%) (\~)                    | (-2%) (+6%)                    |
+------+------------------------------+--------------------------------+
| 24   | 71721617 5477931 -24% +3%  | 115551297 11425898 \~ \~     |
|      |                              |                                |
|      | 69891224 56371079 -19% +6% | 116201715 11391675 -2% \~    |
|      |                              |                                |
|      | (3%) (+3%)                   | (\~) (\~)                      |
+------+------------------------------+--------------------------------+
| 28   | 68191537 5512964 -19% +4%  | 113811043 11488694 \~ \~     |
|      |                              |                                |
|      | 67521418 5560888 -18% +5%  | 11428525 11326895 \~ \~      |
|      |                              |                                |
|      | (\~) (\~)                    | (\~) (\~)                      |
+------+------------------------------+--------------------------------+

Data are from Appendix M Tables M2.1(plasma ChE) and M2.2 (RBC AChE)
pages M45 to M56.

\(a\) Days \"baseline\", 1, 4, 8, 10, 12, 16, 21, 24 and 28 were
selected for inclusion in this table to show representative values. Days
1, 4, 10, 21, 24 and 28 also were days on which blood samples were taken
before the azinphos methyl was administered and 4 hours after
administration.

\(b\) The percent difference between the mean for the azinphos methyl
dosed group and the mean for the placebo is calculated for each day.

\(c\) The percent difference between the mean for the azinphos methyl
dosed group at each day is calculated based on the mean baseline value
for the azinphos methyl group.

\(d\) The value for plasma ChE or RBC AChE obtained prior to dosing is
compared with the value obtained 4 hours after dosing.

(e). The baseline is the mean  the standard deviation for the value of
the cholinesterase made on days -14, -12.-10, -8, -6, -4, -2 and -1.
Each days predosing value is presented in Tables M2.1 and M2.2.

\~indicates that the value was essentially the same as the baseline.

Table 5. Individual subject analysis. The baseline mean  the standard
deviation is presented together with the lowest and the highest reading
over the course of the 28 day *dosing* period.

+------+-------------------------------+-------------------------------+
| Sub  | Plasma ChE (IU/L)             | RBC AChE (IU/L)               |
| ject |                               |                               |
|      | Baseline Data Dosing Data     | Baseline Data Dosing Data     |
| Nu   |                               |                               |
| mber |                               |                               |
+======+===============================+===============================+
| Plac |                               |                               |
| ebos |                               |                               |
+------+-------------------------------+-------------------------------+
| 1    | Mean: 6258264                | Mean: 108671141              |
|      |                               |                               |
|      | Low: 5827 (93%) Low: 5590     | Low: 9455 (87%) Low: 9104     |
|      | (89%)                         | (84%)                         |
|      |                               |                               |
|      | High: 6692 (107%) High: 6813  | High: 12789 (118%) High:      |
|      | (109%)                        | 12606 (116%)                  |
+------+-------------------------------+-------------------------------+
| 5    | Mean: 8757442                | Mean: 110041502              |
|      |                               |                               |
|      | Low: 8215 (94%) Low: 7670     | Low: 9144 (83%) Low: 8696     |
|      | (88%)                         | (79%)                         |
|      |                               |                               |
|      | High: 9390 (107%) High: 9666  | High: 13699 (125%) High:      |
|      | (110%)                        | 12914 (117%)                  |
+------+-------------------------------+-------------------------------+
| 8    | Mean: 5722                    | Mean 10663                    |
|      |                               |                               |
|      | Low: 5384 (94%) Low: 4927     | Low: 9663 (91%) Low: 9074     |
|      | **(86%)**                     | (85%)                         |
|      |                               |                               |
|      | High: 6092 (106%) High: 6099  | High: 12794 (120%) High:      |
|      | (107%)                        | 13719 (129%)                  |
+------+-------------------------------+-------------------------------+
| 12   | Mean: 7121                    | Mean: 11196                   |
|      |                               |                               |
|      | Low: 6930 (97%) Low: 6195     | Low: 10096 (90%) Low: 8672    |
|      | (87%)                         | **(77%)**                     |
|      |                               |                               |
|      | High : 7501 (105%) High: 7612 | High: 11855 (106%) High:      |
|      | (107%)                        | 13570 (121%)                  |
+------+-------------------------------+-------------------------------+
| Ove  |                               |                               |
| rall |                               |                               |
| com  |                               |                               |
| ment |                               |                               |
| on   |                               |                               |
| p    |                               |                               |
| lace |                               |                               |
| bos. |                               |                               |
| Pl   |                               |                               |
| asma |                               |                               |
| may  |                               |                               |
| be   |                               |                               |
| as   |                               |                               |
| low  |                               |                               |
| as   |                               |                               |
| 86%  |                               |                               |
| and  |                               |                               |
| as   |                               |                               |
| high |                               |                               |
| as   |                               |                               |
| 110% |                               |                               |
| of   |                               |                               |
| b    |                               |                               |
| asel |                               |                               |
| ine, |                               |                               |
| RBC  |                               |                               |
| may  |                               |                               |
| be   |                               |                               |
| as   |                               |                               |
| low  |                               |                               |
| 77%  |                               |                               |
| and  |                               |                               |
| as   |                               |                               |
| high |                               |                               |
| as   |                               |                               |
| 129% |                               |                               |
| of   |                               |                               |
| b    |                               |                               |
| asel |                               |                               |
| ine. |                               |                               |
+------+-------------------------------+-------------------------------+
| Azin |                               |                               |
| phos |                               |                               |
| Me   |                               |                               |
| thyl |                               |                               |
| Tre  |                               |                               |
| ated |                               |                               |
+------+-------------------------------+-------------------------------+
| 2    | Mean: 5684 Day 11: 5589 (98%) | Mean: 10394 Day 11: 10111     |
|      |                               | (97%)                         |
|      | Low: 5348 (94%) Low: 5140     |                               |
|      | (90%)                         | Low: 9189 (88%) Low: 9228     |
|      |                               | (89%)                         |
|      | High: 6093 (107%) High: 6625  |                               |
|      | (117%)                        | High: 11162 (107%) High:      |
|      |                               | 11815 (114%)                  |
+------+-------------------------------+-------------------------------+
| 3    | Mean: 4807 Day 11: 4979       | Mean: 11079 Day 11: 10247     |
|      | (+104%)                       | (92%)                         |
|      |                               |                               |
|      | Low: 4625 (96%) Low: 4101     | Low: 10009 (90%) Low: 9017    |
|      | (85%)                         | (81%)                         |
|      |                               |                               |
|      | High: 5779 (120%)             | High: 11242 (101%)            |
+------+-------------------------------+-------------------------------+
| 4    | Mean: 3366100 Day 11: 3744   | Mean: 113612291 Day 11:      |
|      | (+112%)                       | 11494 (\~)                    |
|      |                               |                               |
|      | Low: 3185 (95%) Low: 3141     | Low: 9051 **(80%)** Low: 9290 |
|      | (93%)                         | (82%)                         |
|      |                               |                               |
|      | High: 6014 (177%)             | High: 11996 (106%)            |
+------+-------------------------------+-------------------------------+
| 6    | Mean: 5639 Day 11: 6003       | Mean: 11215 Day 11: 10781     |
|      | (107%)                        | (96%)                         |
|      |                               |                               |
|      | Low: 5434 (96%) Low: 5411     | Low: 9573 (85%) Low: 9054     |
|      | (96%)                         | (81%)                         |
|      |                               |                               |
|      | High: 6840 (121%)             | High: 13071 (117%)            |
+------+-------------------------------+-------------------------------+
| 7    | Mean: 6209 Day 11: 6662       | Mean: 10811 Day 11: 10444     |
|      | (107%)                        | (97%)                         |
|      |                               |                               |
|      | Low: 5972 (96%) Low: 5726     | Low: 9276 (86%) Low: 9436     |
|      | (92%)                         | (87%)                         |
|      |                               |                               |
|      | High: 6759 (109%)             | High: 11998 (111%)            |
+------+-------------------------------+-------------------------------+
| 9    | Mean: 4914 Day 11: 4691 (95%) | Mean: 11194 Day 11: 10425     |
|      |                               | (93%)                         |
|      | Low: 4682 (95%) Low: 4078     |                               |
|      | **(83%)**                     | Low: 9265 (83%) Low: 8533     |
|      |                               | **(76%)**                     |
|      | High: 5092 (104%)             |                               |
|      |                               | High: 13385 (120%)            |
+------+-------------------------------+-------------------------------+
| 10   | Mean: 6840 Day 11: 6610 (97%) | Mean: 10483 Day 11: 10852     |
|      |                               | (104%)                        |
|      | Low: 6358 (93%) Low: 5891     |                               |
|      | (86%)                         | Low: 9269 (88%) Low: 9668     |
|      |                               | (92%)                         |
|      | High: 6947 (102%)             |                               |
|      |                               | High: 13895 (133%)            |
+------+-------------------------------+-------------------------------+
| 11   | Mean: 4998365 Day 11: 4794   | Mean: 118541269 Day 11:      |
|      | (96%)                         | 11789 (\~)                    |
|      |                               |                               |
|      | Low: 4214 **(84%)** Low: 4362 | Low: 10341 (87%) Low: 9436    |
|      | (87%)                         | (80%)                         |
|      |                               |                               |
|      | High: 5602 (112%)             | High: 13881 (117%)            |
+------+-------------------------------+-------------------------------+
| Ove  |                               |                               |
| rall |                               |                               |
| Com  |                               |                               |
| ment |                               |                               |
| on   |                               |                               |
| tre  |                               |                               |
| ated |                               |                               |
| s    |                               |                               |
| ubje |                               |                               |
| cts. |                               |                               |
| T    |                               |                               |
| here |                               |                               |
| was  |                               |                               |
| no   |                               |                               |
| in   |                               |                               |
| dica |                               |                               |
| tion |                               |                               |
| of   |                               |                               |
| in   |                               |                               |
| hibi |                               |                               |
| tion |                               |                               |
| of   |                               |                               |
| ei   |                               |                               |
| ther |                               |                               |
| pl   |                               |                               |
| asma |                               |                               |
| ChE  |                               |                               |
| or   |                               |                               |
| RBC  |                               |                               |
| A    |                               |                               |
| ChE. |                               |                               |
| The  |                               |                               |
| abso |                               |                               |
| lute |                               |                               |
| v    |                               |                               |
| alue |                               |                               |
| of   |                               |                               |
| the  |                               |                               |
| lo   |                               |                               |
| west |                               |                               |
| v    |                               |                               |
| alue |                               |                               |
| is   |                               |                               |
| b    |                               |                               |
| elow |                               |                               |
| the  |                               |                               |
| mean |                               |                               |
| is   |                               |                               |
| a    |                               |                               |
| bout |                               |                               |
| the  |                               |                               |
| same |                               |                               |
| as   |                               |                               |
| the  |                               |                               |
| abso |                               |                               |
| lute |                               |                               |
| v    |                               |                               |
| alue |                               |                               |
| as   |                               |                               |
| the  |                               |                               |
| hi   |                               |                               |
| gher |                               |                               |
| v    |                               |                               |
| alue |                               |                               |
| is   |                               |                               |
| a    |                               |                               |
| bove |                               |                               |
| the  |                               |                               |
| m    |                               |                               |
| ean. |                               |                               |
+------+-------------------------------+-------------------------------+

Data are from Tables M3 in Appendix M. The first entry: is the mean of
the 8 baseline assessments  the standard deviation. The standard
deviation was calculated by the reviewer. Not all baseline entries are
accompanied by the standard deviation. The high and low values are those
that occurred following dosing. The percentage in () is the change
relative to the baseline for that individual.

***RBC AChE.*** Table 5 shows that in the placebo group, RBC ACHE can be
reduced to 77% (subject #12) of the baseline mean whereas the maximum
decrease in the treated group was 76% (subject #9\'s baseline mean.
There were many values that were higher than the mean during the course
of the study. For example, subject #9 which had the largest decrease of
23% on day 14 also had a value that was 20% higher than the baseline
mean. The graphs of this individuals cholinesterase data are appended.
Thus, there is no indication that there was inhibition of RBC AChE based
on individual subject data.

***Analysis at day 11.*** Based on the review of a similar study with
one other organophosphate (diazinon, MRID No.: 45184301), the inhibition
of plasma ChE plateaued at approximately day 11. Thus, data from day 11
are presented in Table 5 since if there was inhibition it would be
expected to have been evident on this day. The eight subjects had plasma
ChE of 98%, 104%, 112%, 107%, 107%, 95%, 97% and 96% mean and RBC AChE
of 97%, 92%, \~100%, 96%, 97%, 93%, 104% and \~100% of the predose mean.
There was also no pattern of inhibition at later days that would
indicate that the time to plateau for azinphos methyl was longer than
for diazinon. Thus, there is no indication of biologically meaningful
inhibition in any of the subjects.

**Discussion and Conclusions.**

1\. **Study Author\'s Conclusion.**

The study author (page 56 of the study report) concluded that there were
no adverse effects of azinphos methyl and that there was no clinically
relevant reductions in plasma or RBC cholinesterase at a dose level of
0.25 mg/kg/day for 28 days.

2\. **Discussion and Conclusion.**

The reviewer concurs with the study author that there was no
biologically meaningful inhibition of either plasma ChE or RBC AChE in
the human subjects dosed daily for 28 days with 0.25 mg/kg of azinphos
methyl by oral capsule. There were also no indications that the subjects
experienced adverse reactions to daily administration of azinphos methyl
for 28 days.

3\. **Classification and Study Deficiencies.**

The classification of this study is being reserved until the Agency
formulates a policy for classifying studies with human subjects.

There were no study deficiencies that would compromise the
interpretation of the study. There were some reporting problems in that
some critical information on methods and procedures were scattered in
Appendixes of the study and not in the study methods and materials
section. Also, Table 3 of the study report was found to be misleading in
that it does not specifically state that the placebo group was dosed
with lactose since only a weight of material administered was given.