Executive Summary:  See Appendix A, Guideline [§ 870.6200a]
Dose and Endpoint for Risk Assessment: NOAEL = 10 mg/kg/day (MRID 45121527) based on eyelid ptosis and decreased approach response (both sexes) and red nasal staining (males) seen at LOAEL = 20 mg/kg/day (MRID 45121528).
Comments about Study/Endpoint/Uncertainty Factors:  This study was selected because dosing was oral and effects were observed following a single dose.  No other studies (including the developmental toxicity studies) showed effects that could be considered the result of a single dose.  The study is protective of effects in all populations.  A combined UF of 100x (inter- and intra-species uncertainty) was utilized.

A.3.2	Chronic Reference Dose (cRfD)

Study Selected:  Chronic Dietary - Rat and Chronic Dietary  -  Dog (co-critical studies)
MRID Nos.:   45121512 (rat); 45121529 (dog)
Executive Summary:  See Appendix A, Guideline [§ 870.4100a and b]
Dose and Endpoint for Risk Assessment: NOAEL = 2.3 mg/kg/day based on decreased body weight and weight gain in rats at LOAEL = 25.3 mg/kg/day and liver effects in dogs at LOAEL = 8.7 mg/kg/day.
Comments about Study/Endpoint/Uncertainty Factors:   These studies were selected because they both had the same NOAEL, were of the appropriate route (oral) and duration (chronic) and provided the most sensitive point of departure, including being protective for developmental, reproductive and neurotoxic effects.  The selected NOAEL is therefore protective of all populations.  A combined UF of 100x (inter- and intra-species uncertainty) was utilized.

A.3.3	Incidental Oral Exposure (Short- and Intermediate-Term)

Study Selected:  Subchronic oral toxicity  -  Dog
MRID No.:   45121524
Executive Summary:  See Appendix A, Guideline [§ 870.3150]
Dose and Endpoint for Risk Assessment: NOAEL = 6.28 mg/kg/day based on increased thyroid vacuolization and decreased food consumption and glucose in females; increased platelets, phosphate, bile acids, absolute and relative liver weights, and lymphoid hyperplasia of the gall bladder in males; and decreased albumin and increased triglycerides, N-demethylase and O-demethylase in both sexes seen at LOAEL = 24.99 mg/kg/day (25 mg/kg/day).
Comments about Study/Endpoint/Uncertainty Factors:  The route of exposure (oral) and study duration (90-day) are appropriate for this risk assessment.  This study was selected because it identified numerous effects and provided a sensitive point of departure that was consistent with the findings in other studies of similar duration that were under consideration in for this exposure scenario:  offspring NOAEL in the rat reproductive toxicity study (6.4 mg/kg/day, with a LOAEL of 33.9 mg/kg/day) and maternal NOAEL in the rabbit developmental toxicity study (5 mg/kg/day, with a LOAEL of 20 mg/kg/day), both based on decreased body weight/weight gain, and NOAEL of 7.8 mg/kg/day in the subchronic rat neurotoxicity study, based on decreased body weight and gain in females at 38.2 mg/kg/day.  The slightly higher NOAEL of the dog subchronic study compared to the reproductive and developmental studies was likely due to dose spacing.  All other NOAELs identified in the database for studies of the appropriate duration were higher.  A combined UF of 100x (inter- and intra-species uncertainty) was utilized.

A.3.4	Dermal Exposure (All Durations)

An endpoint for short- and intermediate-term dermal exposure was not selected.  No systemic or local dermal toxicity was observed at the high dose of 1000 mg/kg/day (limit dose) in the rat 21-day dermal toxicity study.   A comparison of the LOAELs from several other rat studies supported the conclusion that amicarbazone was poorly absorbed (see Section 4.2.1).

A.3.5	Inhalation Exposure (Short-, Intermediate- and Long-Term)

Study Selected:  Subchronic Oral Toxicity  -  Dog
MRID No.:   45121524
Executive Summary:  See Appendix A, Guideline [§ 870.3150]
Dose and Endpoint for Risk Assessment: NOAEL = 6.28 mg/kg/day based on increased thyroid vacuolization, decreased food consumption and glucose (females); increased platelets, phosphate, bile acids, absolute/relative liver weights and lymphoid hyperplasia of the gall bladder (males); and decreased albumin and increased triglycerides, N-demethylase and O-demethylase in both sexes seen at LOAEL = 24.99 mg/kg/day (25 mg/kg/day).
Comments about Study/Endpoint/Uncertainty Factors:  Subchronic inhalation data were not available for amicarbazone; therefore, an oral study of the appropriate duration was selected.  The endpoint selected for this exposure assessment is of the appropriate duration and is considered protective for potential effect to all populations, including infants and children and females of reproductive age (see Comments in A.3.5 for Incidental Oral Exposure).  In the absence of inhalation data, inhalation toxicity was assumed to be equivalent to oral toxicity.  A combined UF of 100x (10x each for inter- and intra-species uncertainty) was utilized.

A.4	Executive Summaries

A.4.1	Subchronic Toxicity

	870.3100	90-Day Oral Toxicity  -  Rat

      In a subchronic oral toxicity study (MRID 45121523), MKH 3586 (amicarbazone; 98.2% a.i., Lot/Batch #: 17004/93) was administered to 15 CDF[F-344]/BR rats/sex/group in the diet at dose levels of 0, 100, 250, 500, 1000, 2500, or 5000 ppm (equivalent to 0/0, 6.9/7.9, 18/21, 33/38, 67/78, 182/201, and 354/397 mg/kg/day [M/F], respectively) for 13 weeks.  An additional 15 rats/sex/group were similarly treated at 0 and 5000 ppm and further observed during a 4-week recovery period following dosing.

      No adverse treatment-related effects were noted in mortality, clinical signs, ophthalmoscopy, or gross pathology.

      Body weight was decreased (p<=0.05) during Weeks 2-13 in the >=1000 ppm females (decr 4-21%) and in the >=2500 ppm males (decr 6-20%).  Overall (Weeks 1-13) body weight gain (calculated by reviewers) was decreased at >=1000 ppm in both sexes (decr 17-62%).  Food consumption was decreased (p<=0.05) throughout the study at >=2500 ppm in both sexes (decr 6-24%).

      In the liver, increases (p<=0.05, unless otherwise noted) were observed in absolute weight in the >=2500 ppm females (incr 13-15%, not statistically significant) and in the 5000 ppm males (incr 18%) and in relative (to body) weight in the >=1000 ppm females (incr 11-41%) and in the >=2500 ppm males (incr 21-43%).  Cholesterol was increased at >=1000 ppm in both sexes (incr 27-298%).  In the tissue samples collected at termination, O-demethylase activity was increased in the >=1000 ppm females (incr 33-89%) and in the >=2500 ppm males (incr 30 [not statistically significant]-60%), and N-demethylase activity was decreased in the >=1000 ppm males (decr 31-37%).  Minimal to marked hepatocytomegaly was observed in the >=1000 ppm males (9-10 treated vs 0 controls) and in the >=2500 ppm females (8-10 treated vs 0 controls)

      In the thyroid, increased incidence (# affected vs 0 controls) of minimal follicular cell hyperplasia was observed at >=2500 ppm in the males (2-7) and females (4-7).  Increased T4 activity was observed in the >=1000 ppm males, and increased T3 activity was observed in the >=1000 ppm males and in the >=2500 ppm females.

      In the spleen, increased incidence of hemosiderin pigmentation was observed in the >=1000 ppm males (4-5 treated vs 1 control) and in the >=2500 ppm females (3-10 treated vs 0 controls).  The following differences (p<=0.05, unless otherwise noted) in hematology parameters were observed: (i) red blood cells, hemoglobin, and hematocrit were decreased in the >=1000 ppm males (decr 3-11%); (ii) hemoglobin, hematocrit, mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCH) were decreased in the >=1000 ppm females (decr 3-15%); (iii) reticulocytes were increased at >=2500 ppm in the males (incr 33 [not statistically significant]-144%) and in the females (incr 47 [not statistically significant]-200%); (iv) platelets were increased in the >=2500 ppm males (incr 14-32%); and (v) MCH and MCV were decreased in the >=2500 ppm males (decr 2-4%).  Increased urinary pH was noted in the >=1000 ppm females, and increased urinary leukocytes were observed in the >=2500 ppm males and females.

      In the >=2500 ppm females, increased incidence (# affected vs 0 controls) of minimal to moderate corticomedullary atrophy of the bone (3-10), and minimal to moderate atrophy of the bone marrow (3-8) were observed.

      Additionally at 5000 ppm, red blood cells were decreased in the females, total protein was increased in the males and females, and globulins were increased in the males.   The following histopathological effects were observed:  minimal diffuse cytoplasmic vacuolization of the cortical epithelium cells of the adrenal glands in the males (10) and minimal cytoplasmic vacuolization of the pancreas in the males (10) and females (5).

      The only finding below 1000 ppm was increased (p<=0.05) cholesterol at 250 (incr 20-31% in males) and 500 ppm (incr 23-47% in both sexes).  In the 5000 ppm recovery group, all treatment-related effects showed signs of recovery; however, most parameters were still different (p<=0.05) from controls.

      The LOAEL is 1000 ppm (equivalent to 67/78 mg/kg/day [M/F]) based on decreased body weight (females) and overall (Weeks 1-13) body weight gains, decreased red cell indices, clinical chemistry (increased cholesterol, T4 [males], T3 [males], o-demethylase [females], and n-demethylase [males]), increased relative (to body) liver weight in females, and histopathological effects in the males (minimal hepatocytomegaly and minimal pigmentation in the spleen).  The NOAEL is 500 ppm (equivalent to 33/38 mg/kg/day [M/F]).

      This study is classified as acceptable/guideline and satisfies the guideline requirements (OPPTS 870.3100a; OECD 408) for a subchronic oral toxicity study in the rat.

	870.3100	90-Day Oral Toxicity - Mouse

      Not submitted.

	870.3150	90-Day Oral Toxicity  -  Dog

      In a subchronic oral study (MRID 45121524), MKH 3586 (Amicarbazone technical; 98.2-99.1% a.i., Lot/batch #: 05362/0005) was administered to 4 beagle dogs/sex/dose in the diet at doses of 0, 200, 800, or 2000 ppm (equivalent to 0/0, 6.74/6.28, 27.03/24.99, 57.40/62.11 mg/kg/day [M/F]) for up to 90 days.  There were no treatment-related effects on survival, neurological evaluations, urinalysis, or ophthalmoscopy.

      Food consumption was decreased by 22-43% (p<=0.05):  in the 800 ppm females on Days 6, 12, and 28; in the 2000 ppm males on Day 15; and in the 2000 ppm females on Days 2, 6, 12, and 28.  Additionally at 2000 ppm, one male was described as thin beginning on Day 21.  Body weights were decreased by 6-15% (not significant [NS]) in females throughout treatment, and overall (Days 0-91) body weight gains (calculated by reviewers) were decreased by 29-40% in both sexes at this dose.  Electrocardiography at the pre-terminal examination revealed the P-R interval was increased by 29% (p<=0.05) in the 2000 ppm males.  In the males, platelets were increased (p<=0.05) at >=800 ppm; and, additionally at 2000 ppm, activated partial thromboplastin time and hemoglobin were decreased (p<=0.05).

      Treatment-related effects were observed in the liver and gall bladder.  In the liver tissue samples, N-demethylase and O-demethylase activities were increased (p<=0.05) over controls in both males of >= 800 ppm and females of  >=200 ppm. N-demethylase and O-demethylase activities were increased (p<=0.05) by 62 and 42% over the controls, respectively,  in females of the 200 ppm group.  N-demethylase and O-demethylase activities were increased (p<=0.05) over controls by 212 and 79%, respectively, in males and by 195 and 142 %, respectively, in females, of the 800 ppm group.  At 2000 ppm, the increase (p<=0.05) in  N-demethylase and O-demethylase activities was 260 and 129%, respectively, in males, and 239 and 83%, respectively, in females.  Although terminal body weights were decreased by 13% (NS) in the 2000 ppm females, increases of 24-58% were noted in absolute (NS) and relative (p<=0.05) liver weights in the >=800 ppm males and 2000 ppm females.  Additionally at 2000 ppm, increased incidence (NS, unless otherwise noted) of the following microscopic findings were observed in the liver vs 0/4 controls: (i) bile pigmentation in males (1/4); (ii) individual cell necrosis in males (3/4) and females (4/4; p<=0.05); and hypertrophy in females (1/4).  Lymphoid hyperplasia of the gall bladder was increased (NS) in incidence and severity in the >=200 ppm males (2/4 to 3/4 treated vs 1/4 controls).  Additionally at 2000 ppm, abnormal texture of the gall bladder was noted (vs 0 controls) in males (1/4 treated) and females (4/4 treated).  Abnormal consistency of the gall bladder was observed in females (1/4 treated vs 0/4 controls).  The following microscopic findings were increased (NS) vs 0/4 controls: (i) hyperplasia of the gall bladder in males (2/4) and females (3/4); (ii) bile pigmentation in the gall bladder in males (2/4) and females (2/4); and (iii) chronic inflammation of the gall bladder in females (2/4).  The following clinical chemistry differences (p<=0.05) were noted:  (i) increased phosphate in the >=200 ppm males; (ii) increased bile acids in the >=800 ppm males and 2000 ppm females; (iii) increased triglycerides and decreased albumin in the >=800 ppm animals; (iv) decreased glucose in the 800 ppm females and 2000 ppm animals; (v) decreased total protein and aspartate aminotransferase in the 2000 ppm males; and (vi) increased alkaline phosphatase in the 2000 ppm females.

      Incidences of thyroid vacuolization were increased (NS; vs 0 controls) in the >=800 ppm females (1-3/4) and the 2000 ppm males (1/4).  Additionally at 2000 ppm, absolute and relative thyroid weights were increased (NS) by 11-39% in both sexes, and incidences of cystic follicles and C-cell hyperplasia were increased (NS) in the thyroid in males (1/4 treated vs 0/4 controls).  However, there were no effects of treatment on levels of T4, T3, or thyroid stimulating hormone.  Kidney pigmentation was increased in the 2000 ppm males (2/4 treated vs 0/4 controls).

      The only findings at 200 ppm were considered adaptive and not adverse.  The increases in N-demethylase and O-demethylase in females (incr. 42-62%) and phosphate and bile acids in males (incr. 8-20%) were considered adaptive because, at this dose, they were not corroborated by gross or microscopic evidence of an adverse effect (such as the liver necrosis noted at 2000 ppm).  Food consumption was decreased only on Day 12 and did not affect body weights or body weight gains at this dose.  Finally, lymphoid hyperplasia was noted in the gall bladder in males, but was only marginally increased (2/4 treated vs 1/4 controls).

      The LOAEL for this study was 800 ppm (equivalent to 27.03/24.99 mg/kg/day in M/F) based on: increased thyroid vacuolization and decreased food consumption and glucose in females; increased platelets, phosphate, bile acids, absolute and relative liver weights, and lymphoid hyperplasia of the gall bladder in males; and decreased albumin and increased triglycerides, N-demethylase, and O-demethylase in both sexes.  The NOAEL is 200 ppm (equivalent to 6.74/6.28 mg/kg/day in M/F).

      This study is classified acceptable/guideline and satisfies the guideline requirement (OPPTS 870.3150; OECD 409) for a 90-day oral toxicity study in the dog.

	870.3200	21/28-Day Dermal Toxicity  -  Rat

      In a 21-day dermal toxicity study (MRID 45121525), MKH 3586 (amicarbazone; 98.5% a.i., Lot/Batch # 05362/0005) was applied undiluted to the shaved intact skin of 10 Sprague-Dawley rats/sex/dose at 0, 200, 500, or 1000 mg/kg bw/day (limit dose) for 6 hours/day. The females received 17 applications and the males received 18 applications over a period of 21 and 22 days, respectively.  Both sexes were dosed for 5 consecutive days during the first two weeks.  During the third week, the females and males were dosed for 7 and 8 consecutive days, respectively, prior to terminal sacrifice.

      No compound-related effects on mortality, clinical signs, body weight, body weight gain, food consumption, ophthalmoscopic examinations, hematology, clinical chemistry, organ weights, or gross or histopathological parameters were observed in either sex.  No treatment-related signs of dermal irritation were observed.

	The LOAEL was not observed.  The NOAEL is 1000 mg/kg/day.

      This study is classified acceptable/guideline and satisfies the guideline requirement (OPPTS 870.3200) for a 21 day dermal toxicity study in the rat.

	870.3465	90-Day Inhalation  -  Rat

      Not Submitted.

A.4.2	Prenatal Developmental Toxicity

	870.3700a Prenatal Developmental Toxicity Study  -  Rat

      In a developmental toxicity study (MRID 45121530), MKH 3586 Technical (Amicarbazone; 98.1-98.5% a.i.; Lot/Batch # 05362/0005) in 0.5% aqueous carboxymethylcellulose and 0.4% Tween 80 solution was administered daily by oral gavage at a dose volume of 10 mL/kg bw to 30 female Sprague Dawley rats/group at dose levels of 0, 15, 100 or 300  mg/kg/day on gestation days (GD) 6 through 19.  All dams were sacrificed on GD 20; their fetuses were removed by cesarean and examined.  In a supplemental developmental toxicity study (MRID 45121531), conducted to determine whether the skeletal findings observed in the definitive developmental toxicity study at 15  mg/kg/day were incidental and not compound-related,  MKH 3586 Technical (Amicarbazone; 97.8-97.9% a.i.; Lot/batch #05362/0005) in 0.5% (w/v) aqueous carboxymethylcellulose and 0.4% (w/v) Tween 80 solution was administered daily by oral gavage at a dose volume of 10 mL/kg to 30 female Sprague-Dawley rats/group at nominal dose levels of 0, 5 or 15  mg/kg/day on gestation days (GD) 6-19.  All dams were sacrificed on GD 20; their fetuses were removed by cesarean and examined.

      In the main study, hard stools were observed in 9/20 dams at 100 mg/kg/day and 22/27 dams at 300 mg/kg/day beginning several days after dosing began.  At 300 mg/kg/day, clonic convulsions were observed in 3/27 dams.  The death of one pregnant female at 300 mg/kg/day was not clearly treatment-related.  Body weights were dose-dependently decreased (p<=0.05) at 100 (↓7-8%) and 300 (↓4-13%) mg/kg/day on GD 7-20, resulting in decreased (statistics not performed) body weight gains for GD 6-20 both when corrected for (↓45-67%) and uncorrected for (↓19-44%) gravid uterine weights.  Gravid uterine weights were slightly lower than controls (↓14%, not significant), due in part to lower fetal weights.  Food consumption was decreased (p<=0.05) at 100 mg/kg/day on GD 6-9 (↓24-42%) and at 300 mg/kg/day on GD 6-12 and 14-15 (↓15-67%).  Terminal body weights were decreased (p<=0.05) at 100 (↓8%) and 300 (↓13%) mg/kg/day.  The 300 mg/kg/day dams demonstrated increased (p<=0.05) absolute (↑12%) and relative liver weights (incr. 28%).  The maternal LOAEL is 100 mg/kg/day, based on decreased body weights/body weight gains and food consumption, and increased occurrence of hard stools.  The maternal NOAEL is 15 mg/kg/day.

      There were no abortions, premature deliveries, late resorptions or complete litter resorptions.  No effects of treatment were noted on numbers of litters, live fetuses, dead fetuses, early resorptions, placental weight, sex ratio or post-implantation losses.  Decreased (p<=0.01) body weights were observed in the 300 mg/kg/day male and female fetuses (↓13-16%).  There were no treatment-related external, visceral or skeletal variations or malformations.  Multiple dose-related increases (p<=0.05) in retardations of fetal skeletal development were noted.  At >=100 mg/kg/day, incomplete ossification/unossification was observed in:  (i) parietal bones, (ii) interparietal bones; (iii) supraoccipital bones; (iv) squamosal bones; (v) zygoma; (vi) pubis; (vii) xiphoid; and (viii) metacarpals.  Enlargement was observed in the sagittal and squamosal sutures and posterior fontanelle.  Additionally at 300 mg/kg/day, incomplete ossification/unossification was observed in:  (i) nasal bones; (ii) lumbar arches; (iii) sacral arches; (iv) sacral centra; (v) caudal centra; (vi) metatarsals; (vii) manubrium; (viii) sternebrae, segments 2, 3, 4 and 5; (ix) ribs; (x) hyoid body; and (xi) caudal arches.  Enlargement was noted in the frontal, coronal and lamboidal sutures.  No dose-related skeletal findings were noted in the supplemental developmental toxicity study, confirming that skeletal findings observed in the definitive developmental toxicity study at 15 mg/kg/day were probably not compound-related. The developmental LOAEL is 100 mg/kg/day, based on multiple skeletal developmental retardations.  The developmental NOAEL is 15 mg/kg/day.

      This study is classified acceptable/guideline (OPPTS 870.3700a) and satisfies the requirements for a developmental study in the rat.  The Registrant is asked to provide (1) appropriately stained (Alizarin red S and Alcian blue) historical controls for skeletal variations and (2) breeding records for control animals as confirmatory data.

	870.3700b Prenatal Developmental Toxicity Study - Rabbit

      In an oral developmental toxicity study (MRID 45121627), MKH 3586 (Amicarbazone; Lot/batch # 05362/0005; 98.2% a.i.) was administered in 0.5% carboxymethylcellulose in demineralized water via gavage, in a dosing volume of 5 mL/kg, to 22-23 female Himalayan CHBB:HM rabbits/group at dose levels of 0, 5, 20 or 70 mg/kg/day on gestation days (GD) 6 through 28.  All surviving does were sacrificed on GD 29 and their fetuses were removed by cesarean and examined.  Because the control group exhibited an unusually low incidence of malformations, causing the MKH 3586-treated groups to appear to have increased malformation rates by comparison, a supplementary study (MRID 45121626) was conducted with 22 rabbits/group at dose levels of 0 and 70  mg/kg/day to determine whether MKH 3586 caused treatment-related malformations at that dose.

      Maternal toxicity:  At >=20 mg/kg/day in the main study, body weight gains were decreased during treatment (p<=0.05; decr. 29-30%) compared to concurrent controls (GD 6-29).  The decreases during the treatment interval resulted in decreased overall (decr. 10-120%; GD 0-29) body weight gains either uncorrected or corrected for gravid uterine weight, but it is noted that due to a relatively large mean gain during pretreatment (GD 0-6) compared to the other groups, cumulative GD 0-29 gain at 70 mg/kg/day was less than at 20 mg/kg/day (mean body weight at 70 mg/kg/day was about 4% less than controls during treatment, but not significant).  Mean body weights were slightly lower than controls (↓3-4%, not significant) throughout most of treatment.  At 70 mg/kg/day, in the main study, one doe aborted on Day 21.  This animal displayed multiple signs of maternal toxicity (ears cold to touch, reduced feces and urine output, discolored urine and decreased food and water consumption).  Decreased urination in the supplementary study, decreased water consumption in the main and supplementary studies and ears cold to the touch in the supplementary study were observed (in a few animals on GD 6-7 but generally later).  In the supplementary study, body weight gains were decreased (decr. 29%; not significant) during the treatment interval (GD 6-29), resulting in decreased (decr. 23-24%; not significant) overall (GD 0-29) uncorrected or corrected body weight gains.  Body weights also were decreased (p<=0.05) from GD 11-29 (decr. 3-4%).  Maternal food consumption was decreased during GD 6-21 in the main study (p<=0.05; decr. 14-43%) and during GD 6-21 and 24-27 in the supplementary study (decr. 11-48%).  There was an increase in partially necrotic placentas (above historical control range) in the main and supplementary studies (2.2-2.4% fetuses; 11.1-15.0% litters) compared to controls (0.0-0.7% fetuses; 0.0-4.5% litters) and in coarse grained placentas in the main study (8.7% fetuses; 15.0% litters) compared to controls (0%).  No effects on maternal gross pathology were reported.  The maternal toxicity LOAEL is 20 mg/kg/day based on decreased body weight gains during treatment.  The maternal toxicity NOAEL is 5 mg/kg/day.

      Developmental toxicity:  At 70 mg/kg/day, in the main study, a slight, non-significant decrease in fetal weights (↓5-6%) was seen.  There was an increased (p<=0.05) incidence of incomplete ossification of the 5[th] medial phalanx digit, on both the right (39.4% fetuses; 70.0% litters) and left (40.9% fetuses; 70.0% litters) sides.  In the supplementary study, fetal weights were decreased (p<=0.01; decr. 11-13%);  Slightly thickened right 6[th] (2.9% fetuses; 16.7% litters) and left 7[th] (9.4% fetuses; 38.9% litters) ribs and incomplete ossification of the 13[th] caudal vertebra (6.5% fetuses; 38.9% litters) were observed.  There were no effects of treatment the number of resorptions (early, late or complete litter), number of fetuses (live or dead), number of litters, post-implantation loss, fetal weights or sex ratio in either the main or the supplementary studies.   The main study findings were supported by the supplementary study.  The developmental toxicity LOAEL is 70 mg/kg/day based on decreased fetal weights and increased incidences of incomplete ossification of the 5[th] medial phalanx digit (bilateral) and the 13[th] caudal vertebra and slightly thickened ribs.  The developmental toxicity NOAEL is 20 mg/kg/day.

      This study is classified acceptable/guideline (OPPTS 870.3700b; OECD 414) and satisfies the requirements for a developmental study in the rabbit.

A.4.3	Reproductive Toxicity

	870.3800 Reproduction and Fertility Effects  -  Rat

      In a two-generation reproduction toxicity study (MRID 45121625), MKH 3586 Technical (Amicarbazone; 98.2-99.1% a.i.; Lot/batch #05362/0005) was administered in the diet to 30 Sprague-Dawley rats/sex/dose at nominal dose levels of 0, 100, 500 or 1000 ppm (equivalent to 0/0, 6.4/7.3, 33.9/38.7 or 73.2/84.0 mg/kg bw/day in males/females).  The P and F1 parents were given test diets for 10 weeks before they were mated to produce the F1 and F2 litters.  The F1 pups were weaned at 21 days of age, and approximately 30 pups/sex/group (1 pup/sex/litter as nearly as possible) were randomly selected as parents of the F2 generation.  Sperm parameters were not evaluated in the parental males, and sexual maturation and developmental landmarks were not evaluated in the offspring.

      Parental toxicity:  At 500 ppm, P males and females had reduced cumulative body weight gain during the premating period (males ↓9%, days 0-105 and females ↓20%, days 0-70), although no significant decreases in mean body weight were observed due to higher mean body weights compared to controls.  Food consumption was slightly but statistically significantly reduced only during the first week of treatment.  F1 males and females showed sporadic statistically significant decreases in mean body weight during premating (↓5-20%, males and ↓6%, females).  Cumulative gain decreased 5% in males (days 0-98) and 8% in F1 females (days 0-70), with no decreases in food consumption.  Mean body weights during gestation were reduced in F1 females only (↓6-11%).  Statistically significant reductions in mean body weight of F1 females during lactation (↓6-8%) were not accompanied by reduced gain.  At 1000 ppm, P generation males showed reduced cumulative gain during premating (↓12%, days 0-105); statistically significant reductions in mean body weights were not observed due to higher initial mean body weight compared to controls.  Significantly reduced mean body weights were observed in females during days 0-70 (↓4-6%) and cumulative gain was reduced by 29%.  Significantly decreased body weight in F1 males (↓6-12%, days 0-98) and females (↓10-14%, days 0-70) were observed for the entire premating period; this was due largely to lower initial weights in both sexes, with cumulative gain reduced by 4% in males and 13% in females.  Statistically significant reductions in mean body weights were observed during gestation in both P (↓6-7%) and F1 (↓11-12%) females, along with reduced gain (↓11-12%).  Mean body weights were significantly decreased throughout lactation for P females (↓7-18%) and F1 females (↓10-13%) despite increased food consumption, although cumulative gain was not affected.  Terminal body weights were decreased (p<=0.05) in F1 males and females.  Relative liver weights were slightly increased (p<=0.05) in both P and F1 male and females (↑11-15%), due in part to reduced terminal body weights.  Minimal to slight hepatocytomegaly was noted in F1 males (10/30) compared to controls (0/30), but no microscopic pathology consistent with liver toxicity was observed.  No treatment-related findings were noted at 100 ppm.  The parental toxicity LOAEL is 500 ppm (equivalent to 33.9/38.7 mg/kg bw/day [M/F]), based on decreased body weight/weight gain in both sexes.  The NOAEL is 100 ppm (6.4/7.3 mg/kg bw/day [M/F]).

      Offspring toxicity:  At 500 ppm, decreased body weights were observed on PND 14 and 21 in F1 and F2 pups; cumulative gains for these groups were decreased 10-13% (p<=0.05).  At 1000 ppm, decreased (p<=0.05) body weights were noted on PND 4, 7, 14 and 21 in F1 pups, and on PND 7, 14 and 21 in F2 pups(↓10-23%).  Cumulative gains for this period were decreased 20-25% (p<=0.01).  There were no effects of treatment on the birth, live birth, viability or lactation indices, sex ratio or gross pathology in the F1 or F2 pups.  No treatment-related findings were noted at 100 ppm.  The LOAEL for offspring toxicity is 500 ppm (equivalent to 33.9/38.7 mg/kg bw/day [M/F]), based on decreased pup body weights and overall body weight gains.  The NOAEL is 100 ppm (equivalent to 6.4/7.3 mg/kg bw/day [M/F]).

      Reproductive effects:  The reproductive toxicity LOAEL was not observed.  The reproductive toxicity NOAEL is 1000 ppm (equivalent to 73.2/84.0 mg/kg bw/day [M/F]).

      This study is classified as acceptable/guideline and satisfies the guideline requirements (OPPTS 870.3800; OECD 416) for a three-generation reproduction study in the rat.

A.4.4	Chronic Toxicity

	870.4100a (870.4300) Chronic Toxicity  -  Rat

      In a combined chronic toxicity/carcinogenicity study (MRID 45121512), 50 Fischer 344 rats/sex/dose were exposed to MKH 3586 (Amicarbazone; 98.1-98.6% a.i.; Lot/Batch #: 05362/0005) in the diet at concentrations of 0, 50, 500, or 1250/1000 (M/F) ppm (equivalent to 0/0, 2.3/2.7, 25/30, and 67/65 mg/kg/day in males/females) for up to 24 months.  An additional group of 20 (control and high dose) or 10 (low and intermediate dose) rats/sex/dose were similarly treated and sacrificed at 12 months.

      Mortality, clinical signs, ophthalmoscopic findings, food consumption, hematology, clinical chemistry, urinalysis, and gross and microscopic pathology for both sexes at all doses were unaffected by treatment.  No treatment-related findings were noted at 50 ppm.

      In the interim study at 1250/1000 ppm, decreases (p<=0.05) in body weight were noted throughout most of the 12 months (decr. 5-15%); decreases in body weight gain (calculated by the reviewers) were observed at Weeks 1-13 (decr. 13-25%), 13-50 (decr. 19-27%), and overall (Weeks 1-50, decr. 15-26%); and body weights were decreased (p<=0.05) at the interim sacrifice (decr. 10-16%).  In the main study, decreases (p<=0.05) in body weight were generally observed throughout the 24 months in the 500 ppm females (decr. 3-11%) and in the 1250/1000 ppm groups (decr. 3-18%).  Decreases in body weight gain were observed at >=500 ppm at Weeks 1-13 (decr. 5-24%; both sexes), 13-50 (decr. 26-32%; females only), 50-102 (decr. 43-60%; males only), and overall (Weeks 1-102, decr. 9-23%; both sexes).  Body weights were also decreased (not significant) at the terminal sacrifice in the 1250/1000 ppm groups (decr. 8-9%).

      The LOAEL is 500 ppm (equivalent to 25.3/29.5 mg/kg/day [M/F]) based on decreased body weights in females and body weight gains in both sexes.  The NOAEL is 50 ppm (equivalent to 2.3/2.7 mg/kg/day [M/F]).

      At the doses tested, there was not a treatment related increase in tumor incidence 	when compared to controls.  Dosing was considered adequate, based on decreased body weights in females and body weight gains in both sexes.

      This study is classified as acceptable/guideline and satisfies the guideline requirements (OPPTS 870.4300; OECD 453) for a combined chronic toxicity/carcinogenicity study in rats.

	870.4100b Chronic Toxicity - Dog

      In a chronic oral study (MRID 45121529), MKH 3586 (Amicarbazone technical; 98.1-98.6% a.i., Lot/batch #: 05362/0005) was administered to 4 beagle dogs/sex/dose in the diet at doses of 0, 75, 100, 300 or 1200 ppm (equivalent to 0/0, 1.6/1.8, 2.5/2.3, 8.9/8.7 or 31.5/34.6 mg/kg/day [M/F]) for one year.  In addition to the typical parameters, the investigators evaluated heart rate, blood pressure, electrocardiography (ECG), cortisol, body temperature, circulating thyroid hormones, hepatic enzymes (o-demethylase, n-demethylase and P-450), neurological parameters (mental status/behavior, gait, postural status, postural reactions and spinal/cranial reflex tests) and immunological parameters (cell phenotyping via flow cytometry and immunoglobulin determination).
      At >=300 ppm, absolute and relative liver weights were dose-dependently increased by 26-41% in males.  O-demethylase activity was dose-dependently increased by 83-158% in males, and cytochrome P-450 activity was increased by 67-73% in females.  Increases in triglycerides (incr. 8-137%) and cholesterol (incr. 16-93%) were observed throughout treatment in both sexes.  Globulin was increased by 18% in females at Day 363.

      Additionally at 1200 ppm, absolute and relative liver weights were increased by 13-16% in the females.  Slight liver hypertrophy and dilatation of the sinusoids were observed in males (1/4 each treated vs 0/4 each controls).  In the liver tissue samples collected at study termination, N-demethylase activity was increased by 30% over controls in males, and O-demethylase activity was increased by 65% in the females.  Cytochrome P-450 activity was increased by 88% in the males.  Albumin was decreased by 9-15% and bile acids increased by 50-100% throughout treatment in both sexes.  Lactate dehydrogenase was increased in males by 179-259%.  Gamma glutamyl transferase was increased by 43% in females at Day 363.  Increased platelets were observed in both sexes (all time points, 18-38% in males and 9-27% in females).  Reductions in % eosinophils in females throughout the study were seen but a clear dose-response was not observed.  Mild abnormal neurological signs were observed in three females at 6 months (abnormal postural reactions) and one female at 12 months (abnormal postural reactions, Hami-standing deficit and lateral hopping deficit).  The study authors concluded that these deficits were not due to direct neurotoxicity but were instead neuromuscular effects possibly secondary to thymic atrophy (see Discussion of this DER for details).  Absolute and relative thymus weights were decreased by 35-40% in the 75 ppm and 1200 ppm males.  These decreases corresponded to the minimal to slight thymic atrophy observed microscopically; however, they were not dose-related or significantly different from the controls.  Thymic atrophy was observed in the 1200 ppm males (from control to high dose, 0/4, 2/4, 1/4, 0/4 and 4/4, p<=0.05 at 1200 ppm) and females (1/4 treated vs 0/4 controls, NS).  The female with persistent neuromuscular effects had thymic atrophy and reduced B cells; findings appeared to be treatment-related.   However, in males thymic atrophy was not dose-related in severity and did not show a strong dose-response for incidence.  Based on findings in females thymic atrophy in males may be treatment related, but a clear dose-response was not observed.  The only findings at 100 ppm were increased O-demethylase activity (incr. 42%) and triglycerides (incr. 43-74%) in males and increased cholesterol in females (incr. 21-29%) but were insufficient to be considered adverse.  Slightly reduced hematocrit and hemoglobin in males at 181 days (decr. 5-8%, p<=0.05) T 100, 300 and 1200 ppm may have been related to treatment but were not considered adverse due to small change and lack of persistence.  There were no effects of treatment on survival, quantitative electroencephalography, body weights/weight gains, food consumption, ophthalmoscope, immunoglobulin quantification, urinalysis or gross pathology.

      The LOAEL is 300 ppm (equivalent to 8.9/8.7 mg/kg/day, M/F), based on effects on the liver, including: increased absolute and relative liver weights, and O-demethylase in males; increased globulin and cytochrome P450 in females; and increased triglycerides and cholesterol in both sexes.  The NOAEL is 100 ppm (equivalent to 2.5/2.3 mg/kg/day, M/F).

      This study is classified as acceptable/guideline and satisfies the guideline requirement (OPPTS 870.4100b, OECD 452) for a chronic oral toxicity study in dogs.

A.4.5	Carcinogenicity

	870.4200a Carcinogenicity Study  -  rat

      See 870.4100 (4300), above.

	870.4200b Carcinogenicity (feeding)  -  Mouse

      In a carcinogenicity study (MRID 45121604), 50 CD-1 (ICR)BR mice/sex/dose were exposed to MKH 3586 (amicarbazone; 98.1-98.6% a.i.; Lot/Batch #: 05362/0005) in the diet at concentrations of 0, 100, 1500, or 4000 ppm nominally (equivalent to 0/0, 15.7/17.9, 244.7/275.0, and 709.0/806.3 mg/kg/day in males/females) for up to 78 weeks.

      No adverse treatment-related effects were observed on mortality, food consumption, or gross pathology.  No treatment-related findings were noted at 100 ppm.

      At 4000 ppm, body weights were generally decreased (p<=0.05) at Weeks 3-57 in the males (decr. 3-5%), and at Weeks 53-74 in the females (decr. 5-7%).  This was reflected in decreased body weight gains in males at Weeks 1-13 (decr. 16), and in both sexes at Weeks 1-52 (decr. 14-22) and Weeks 1-78 (decr. 9-13).

      A subclinical treatment-related anemia was observed in the 4000 ppm males.  Decreases (not statistically significant [NS]) in erythrocytes (decr. 11%), hemoglobin (decr. 8%), and hematocrit (45% treated vs 49% controls) were noted at 12 months, and decreases (NS) in erythrocytes (decr. 13%) and hemoglobin (decr. 11%) were noted at 18 months.  At 18 months, decreased (p<=0.05) hematocrit (41% treated vs 47% controls), and increased (p<=0.05) red cell distribution width (15.1% treated vs 13.4% controls) and reticulocytes (4.9% vs 2.6% controls) were observed.  Increased (p<=0.05) hemoglobin distribution width was noted at 12 and 18 months (incr. 12-16%).  Also, hemosiderin pigmentation of the spleen, thought to be hemoglobin-derived, was noted (p<=0.05) in the 1500 ppm males (34%; mild) and the 4000 ppm group (62-66%; moderate).

      The LOAEL is 4000 ppm (equivalent to 709.0/806.3 mg/kg/day [M/F]), based on decreased body weight and body weight gains in males and females, and subclinical anemia and hemosiderin pigmentation of the spleen in males.  The NOAEL is 1500 ppm (equivalent to 244.7/275.0  mg/kg/day [M/F]).

      At the doses tested, there was not a treatment-related increase in tumor incidence when compared to controls.  Dosing was considered adequate based on decreased body weight and body weight gains in males and females, and subclinical anemia and hemosiderin pigmentation of the spleen in males.

      This study is classified as acceptable/guideline and satisfies the guideline requirements (OPPTS 870.4200b; OECD 451) for a carcinogenicity study in mice.

A.4.6	Mutagenicity

	Gene Mutation
Guideline 870.5100, bacterial reverse gene mutation assay, Salmonella typhimurium strains TA98, TA100, TA102, TA1535, and TA1537
MRID 45121617
Acceptable/guideline
0, 16, 50, 158, 500, 1581 or 5000 ug/mL triazolinon (an intermediate of amicarbazone) in the presence or absence of S9 activation
There was no evidence of induced mutant colonies above background in the presence or absence of S9 activation.
Guideline 870.5100, bacterial reverse gene mutation assay, Salmonella typhimurium strains TA98, TA100, TA102, TA1535, and TA1537
MRID 45121616
Acceptable/guideline
0, 16, 50, 158, 500, 1581 or 5000 ug/mL oxadiazolinon (an intermediate of amicarbazone) in the presence or absence of S9 activation
There was no evidence of induced mutant colonies above background in the presence or absence of S9 activation.
Guideline 870.5100, bacterial reverse gene mutation assay, Salmonella typhimurium strains TA98, TA100, TA102, TA1535, and TA1537
MRID 45121519
Acceptable/guideline
0, 16, 50, 158, 500, 1581 or 5000 ug/mL technical amicarbazone in the presence or absence of S9 activation
There was no evidence of induced mutant colonies above background in the presence or absence of S9 activation.
Guideline 870.5300, mammalian forward gene mutation assay, V79 Chinese lung fibroblast cells
MRID 45121514
Acceptable/guideline
0, 250, 500, 1000, 2000 or 4000 ug/mL for 5 hours in the presence or absence of S9 activation
There was no evidence of induced mutant colonies above background in the presence or absence of S9 activation.

	Cytogenetics
Guideline 870.5375, in vitro mammalian chromosomal aberration assay (V79 Chinese hamster lung fibroblast cells)
MRID 45121513
Acceptable/guideline
0, 1000, 2000, 3000, 4000 or 5000 ug/mL for 4 hours; harvested at 18 hours post-exposure.  Trial 1 0, 3000, 4000 or 5000 ug/mL; harvested at 18 or 30 hours post-exposure.
There was no evidence of an increased frequency of chromosomal aberration induced above background in the presence or absence of S9 activation.

	Other Genotoxicity
Guideline 870.5395, in vivo mammalian erythrocyte micronucleus test (NMRI mouse)
MRID 45121515
Acceptable/guideline
0 or 100 mg/kg administered via intraperitoneal injection; evaluated at 16, 24 and 48 hours post-dosing.
There was no significant increase in the frequency of micronucleated polychromatic erythrocytes above background in bone marrow at any treatment time.

A.4.7	Neurotoxicity

	870.6100 Delayed Neurotoxicity Study  -  Hen

      Not required.

	870.6200 Acute Neurotoxicity Screening Battery

      In an acute oral neurotoxicity study (MRIDs 45121528), MKH 3586 (amicarbazone; 98.2% a.i., Lot/Batch # 17004/93) in 0.5% methylcellulose-0.4% Tween 80 in deionized water was administered in a single dose by gavage (10 mL/kg) to fasted Fischer 344 rats (12/sex/dose) at doses of 0, 20, 150 or 600 mg/kg in males and 0, 20, 100 or 400 mg/kg in females.  All animals were observed for up to 14 days post-dosing.  Functional observational battery (FOB) and motor activity were evaluated pretreatment and on Days 0 (at the time of peak effect, approximately 3 hours post-dosing), 7 and 14.  At termination, 6 rats/sex/group were perfused in situ for neurohistological examination and tissues from the control and 600/400 mg/kg groups were examined microscopically (brain tissue sections at level 5 from the 150/100 mg/kg groups were also evaluated).  Additionally, two nonguideline acute oral studies were submitted.  The purpose of the first study (MRID 45121526) was to investigate neuropathology (in particular, the time of peak effect and the possible effects on other brain regions at other time points) and to establish if a dose of 400 mg/kg produces changes in quantitative electroencephalography (qEEG) at 8 hrs or 1, 3, 7, 15 or 28 days following acute exposure to seven sets of 6 female rats/dose group at 0 or 400 mg/kg.  Groups were sacrificed at 8 hrs and 1, 3, 7, 15 or 28 days post-dosing for neuropathological evaluation.  The purpose of the second study (MRID 45121527) was to establish a NOAEL for clinical signs and FOB (the most sensitive parameters) in 6 rats/sex/dose group at 0, 2.5 or 10.0 mg/kg, single gavage dose.  Acceptable positive control data (MRIDs 42770301 and 43656301) were previously reviewed.

      At 20 mg/kg, during the FOB, increased incidences (# affected/12 vs. 0 controls) of eyelid ptosis (1-3 of both sexes during home-cage and 7 males in the open-field) and decreased approach response (no reaction in 2-6, both sexes) were observed on Day 0 (approximately 3 hours post-dosing).  Additionally, eyelid ptosis and red nasal stain were noted during daily clinical observations in the males on Day 0.

      At >=150/100 mg/kg, increased incidences of oral stain, red nasal stain and urine stain (females only) were noted as clinical signs beginning on Day 0 and persisting up to one week, except for urine stain (Day 14).  The following treatment-related FOB effects (# affected/12 vs. 0/12 controls, unless otherwise indicated) were observed on Day 0 (approximately 3 hours post-dosing):  home cage, eyelid ptosis in both sexes (9-12); handling, (i) palpebral closure (half-closed to completely closed) in the females (1-12), (ii) ease of removal (minimal resistance with vocalizations to avoiding the hand) in males (1-6), (iii) mild nasal stain (red or clear) in both sexes (2-11), and (iv) mild oral stain (clear or red) in both sexes (2-7); open field, eyelid ptosis in the males (9-12) and in the females (6-11 treated vs 1 control); and reflex/physiologic, decreased approach response (no reaction) in the males (7-11 treated vs 4 controls) and impaired righting reflex (slight incoordination to landing on side) in the females (2-4).  Additionally, decreases (p<=0.05) in mean body temperature were observed in both sexes (34.5-36.4̊C treated vs. 37.0-37.1̊C controls).  Total locomotor activity was dose-dependently decreased on Day 0 in the >=100 mg/kg females (↓30-43%, not statistically significant) and both total motor/locomotor activities reduced in males at 150 mg/kg (↓56-66%, not significant).

      At 600/400 mg/kg, treatment-related mortality was observed in the males (5/12) and females (1/12) on Days 0 or 1 post-dosing.  Increased incidences of the following were noted at the daily clinical evaluation on Day 0 in both sexes: eyelid ptosis (5-6), clear nasal discharge (4-5) and salivation (3-4).  The following treatment-related effects were observed in the FOB evaluation on Day 0 in both sexes (unless otherwise indicated):  home cage, (i) repetitive forepaw movements (1-3), (ii) decreased activity (1-3), (iii) mild tremors (3 males) and (iv) chewing movements (2 males); handling, palpebral closure (half-closed to completely closed) in the males (12) and rigid muscle tone (1-4); open field, (i) mild tremors (3 males), (ii) decreased arousal, some to minimal movement (6 treated females vs 1 control) and (iii) tail mutilation (2 females); and reflex/physiologic, decreased approach response (no reaction) in the females (11 treated vs 4 controls) and impaired righting reflex, slight incoordination to landing on side in males (3 treated vs 1 control).  The only FOB effects that persisted were red nasal stain in one 600 mg/kg male and red oral stain in one 400 mg/kg female on Day 7 and tail lesions (due to self-mutilation) in two 400 mg/kg females on Days 7 and 14.  Lack of motor/locomotor effects in males at 600 mg/kg may have been related to the excessive toxicity/mortality at that dose, based on extreme variability of activities in individual animals of that group.  Slight neuronal necrosis in the midline of the thalamus (reuniens nucleus) was observed in 1/6 male and 1/6 female (both animals survived to Day 14).  No compound-related effects on body weight, brain weight or gross pathology were observed at any dose.

      The two nonguideline neurotoxicity studies satisfied the purposes for which they were intended.  The first study (MRID 45121526) verified the neuropathological effects observed in the main study high-dose males and females and the time of peak effect at 400 mg/kg.  One female sacrificed 24 hr post-dosing had slight neuronal necrosis of the thalamus in the area of the reuniens nucleus.  Quantitative EEG demonstrated treatment-related electrophysiological changes, primarily increases in total power, absolute delta, theta and alpha, and total power within the theta-beta range at 3, 8 and 24 hr post-dosing (under normotonic, auditory, visual and somatosensory stimulus conditions).  A NOAEL for neurotoxicity was not established in the guideline study; the supplemental study MRID 45121527 established a NOAEL for clinical signs and FOB parameters at 10 mg/kg.

      The neurotoxicity LOAEL is 20 mg/kg based on eyelid ptosis and decreased approach response (both sexes) and red nasal stain (males).  The NOAEL is 10 mg/kg.

      The study is classified as acceptable/guideline in conjunction with MRID 45121527 and satisfies the guideline requirement (OPPTS 870.6200a; OECD 424) for an acute neurotoxicity screening battery in rats.

	870.6200 Subchronic Neurotoxicity Screening Battery

      In a subchronic neurotoxicity study (MRID 45121532), MKH 3586 (amicarbazone; >=98.2% a.i., Lot/Batch # 17004/93) was administered in the diet for 13 weeks to 12 Fischer 344 rats/sex/dose at doses of 0, 100, 500 or 1000 ppm (equivalent to 0/0, 6.7/7.8, 33.4/38.2 or 66.5/75.8 mg/kg/day [M/F]).  Functional observational battery (FOB) and motor activity were evaluated during Weeks -1 (prior to dosing), 4, 8 and 13.  At termination, 6 rats/sex/group were perfused in situ, and tissues from the control and 1000 ppm groups were examined microscopically.  Acceptable positive control data (MRIDs 42770301 and 43656301) were previously reviewed by the Agency.

      No compound-related effects on mortality, clinical signs, FOB, motor or locomotor activity, ophthalmology, brain weight or gross and neuropathology parameters were observed at any dose.  Motor activity data indicated that habituation was unaffected by treatment.

      In the >=500 ppm females, decreases (p<=0.05) were observed in body weights (↓ 6-7%, Weeks 10-13), overall (Day 0-91) body weight gains (calculated by reviewers, decr 17-22%).  Food consumption was reduced (↓ 6-12%) when expressed as g/animal/day but total mean food consumption for the entire study was comparable for all groups on a g/kg bw/day basis (91.0, 90.3, 88.5 and 87.8 g/kg bw/day, controls to high dose).  Body weights, overall body weight gains and food consumption were similar to controls throughout the study in the males.  The LOAEL is 500 ppm (equivalent to 38.2 mg/kg/day [females]) based on decreased body weight and overall body weight gain.  The NOAEL is 100 ppm (equivalent to 7.8 mg/kg/day [females]).  A NOAEL was not established for males.

	No evidence of neurotoxicity was observed at any dose.

      The submitted study is classified as acceptable/guideline and satisfies the guideline requirements (OPPTS 870.6200b) for a subchronic neurotoxicity screening battery in rats.

	870.6300 Developmental Neurotoxicity Study

      In a developmental neurotoxicity study (2001, MRID 45441301), MKH 3586 (97.8-98.4% a.i., batch # 05362/0005) was administered to parent female Wistar rats in the diet at concentrations of 0, 100, 500 or 1000 ppm from gestation day 0 through postnatal day (PND) 21.  The average daily intake of MKH 3586 was approximately 0, 8, 39 and 91 mg/kg/day during gestation and 0, 17, 84, and 177 mg/kg/day during lactation, for the 0, 100, 500, and 1000 ppm groups, respectively.  A Functional Operational Battery (FOB) was performed on 10 dams/dose on gestation days 6, 13, and 20 and on and lactation days 4, 11, and 21.  On postnatal day 4, litters were culled to yield four males and four females.  Offspring, representing at least 20 litters/dose, were allocated for periodic detailed clinical observations including (abbreviated FOB), assessment of motor activity, assessment of auditory startle response habituation, assessment of learning and memory, and neuropathology at study termination (day 75 of age).  Thyroid and neural tissues (10/sex/dose) were assessed histologically on PND 11 and at study termination.  Pup physical development was assessed by bodyweight, and sexual maturation of females (age at vaginal opening) and of males (age at completion of balano-preputial separation) was determined.

      Maternal Toxicity. Treatment-related effects were limited to body weight and gain, increased food consumption and decreased food efficiency.  During gestation, body weight at 1000 ppm was decreased (p<0.05) of 5% on GD 6, with differences persisting to GD 20 (4%, p < 0.05) associated with a 12% decrease (p<0.05) in body weight gain from GD 0 to GD 20.  The high dose group was also associated with increased food consumption (13%) and associated decrease in feed efficiency (22%).   During lactation, maternal body weight was decreased for high-dose rats; decreases averaged 4% on LD 0 to 9% on LD 14 and LD 21 (p<0.05 or 0.01).   Non significantly lower body weights were noted for the 500 ppm dose group of 2-3% but body weight gain during lactation was reduced 28% at 500 ppm and 45% at 1000 ppm.  Food consumption during lactation was increased 7% at 500 ppm and 8% at 1000 ppm.  The combination of body weight decrease and increase food consumption resulted in a decrease in food efficiency or 33% at 500 ppm and 49% at 1000 ppm. The maternal LOAEL is 500 ppm (39 mg/kg/day) based primarily on decreased feed efficiency (combination of decreased body weight gain and increased feed consumption) during lactation.   The maternal NOAEL is 100 ppm (8 mg/kg/day).

      Offspring Toxicity.  Treatment-related effects for offspring were also limited to decreased body weight and body weight gain at 500 ppm and above.  At birth, the average body weight of treated offspring was not different from controls at any dose level.  By PND 11, body weight was decreased 7-8% (p<0.05) for high-dose male and female offspring, this decrease averaged 11-12% (p<0.01) by weaning on PND 21.  Body weight gain was decreased in males and females in the 500 (8-13 %; p<0.05 or p<0.01) and 1000 ppm (11-21 %; p<0.05 or p<0.01) groups.  Offspring in the 500 ppm group had recovered by termination; however, decreased body weight gain persisted to study termination in high-dose animals. The offspring LOAEL is 500 ppm (91 mg/kg/day) based on decreased body weight gain.  The offspring NOAEL is 39 mg/kg/day.

      This study is classified as Acceptable/guideline and satisfies the guideline requirement (OPPTS 870.6300) for a developmental neurotoxicity study in the rat.

A.4.8	Metabolism

	870.7485	Metabolism - Rat

   (1) In a rat metabolism study (MRID 45121701), [triazolinone-3-[14]C] MKH 3586 (amicarbazone; Vial No.: C-710A; radiochemical purity >99%) in water, was administered to 4 male Fischer rats as a single gavage dose at 5.25-5.99 mg/kg.  Samples were collected from these animals to determine elimination kinetics and to quantify metabolites.

      Overall recovery of the radioactive dose was 95% by 72 hours following administration.  The majority of the dose was recovered in the urine within 24 hours (64% dose), indicating substantial absorption.  Fecal excretion accounted for 27% dose within 24 hours post-dose.  Only 2% dose was recovered in the excreta after 24 hours.  At 72 hours following administration, <=1% dose was found in each of the following fractions: carcass and selected tissues, CO2 trap, volatile organic trap, urine trap wash, and cage and feces trap wash.  Concentrations of radioactivity in the selected tissues at 72 hours post-dose were low (0.004-0.073 ug/g).

      HPLC and LC-MS/MS analyses were used to identify the parent and 9 metabolites in excreta from male rats following oral dosing with [triazolinone-3-[14]C] MKH 3586.  Identified compounds in excreta accounted for 74% of the dose.  Unidentified peaks in urine and fecal extracts each accounted for <1% dose, and unanalyzed fractions from urine and feces each accounted for <2% dose.  Overall accountability of the administered dose was ~84%, with minor fractions and unknowns being reported at accounting for "<1% dose".

      Minor amounts of parent were detected in both  urine (~2% dose) and feces (<1% dose).  The major metabolite in excreta was a hydroxylated, deanimated derivative of the parent, iPr-2-OH DA (34% dose), mainly found in the urine (32% dose).  Other hydroxylated deanimated derivatives were also identified: tBu-OH DA (11% dose in urine and 4% dose in feces), and iPr-1,2-diOH DA (6% dose in urine and <1% dose in feces).  The glucuronic acid conjugate of the parent, MKH 3586 GA, accounted for 11% dose, mainly in the feces (10% dose).  Other minor metabolites (each <=3% dose) identified in excreta included:  tBu-1,2-di-iPr-tri-OH DA; tBu-iPr-di-OH DA; iPR-1,3-di-OH DA; tBu-OH-iPr-ene and DA.  Based on the metabolite profile, the metabolism of MKH 3586 in males rats primarily involves deamination followed by hydroxylation with elimination in the urine. Parent also undergoes glucuronic acid conjugation and elimination in the feces.

      This metabolism study in the rat is classified acceptable/guideline and satisfies the guideline requirement for a Tier 1 metabolism study [OPPTS 870.7485, OPP 85-1] in rats.

   (2) In a rat metabolism study (MRID 45121634), [triazolinone-3-[14]C] 4-methyl MKH 3586 (soil metabolite of amicarbazone; Vial No.: C-803; radiochemical purity >99%) in water, was administered to 4 male Fischer rats as a single gavage dose at 4.86-5.22 mg/kg. Samples were collected from these animals to determine elimination kinetics and to identify and quantify metabolites.

      Overall recovery of the radioactive dose was 91% by 96 hours following administration.  The majority of the dose was recovered in the urine within 12 hours (70% dose), with total urinary excretion accounting for 80% dose, indicating substantial absorption.  Fecal excretion (0-24 hours post-dose) accounted for 8% dose.  Approximately 3% dose was recovered in the excreta after 24 hours.  At 96 hours following administration, 2% dose was found in the urine trap wash and <1% dose was found in each of the following fractions: CO2 trap, volatile organics trap, cage and feces trap wash, carcass and selected tissues.  At 96 hours post-dose, the concentration of radioactivity in the tissues was low (0.002-0.028 ug/g), with <0.1% dose in each tissue.

      HPLC, [1]H-NMR, and LC-MS/MS analyses identified 12 components in excreta from rats following oral dosing with [triazolinone-3-[14]C] 4-methyl MKH 3586.  Four of these compounds were present as chiral pairs.  Identified compounds accounted for 75% of the dose.  All unidentified peaks each accounted for <=1% of the dose, and individual unanalyzed fractions each accounted for <2% dose.  The overall accountability of the administered dose was ~82%.  The proposed pathway for biotransformation of [triazolinone-3-[14]C] 4-methyl MKH 3586 in rats is presented in the Appendix to this DER.

      The test substance was not detected in the urine or feces.  Hydroxylation of the soil metabolite at the isopropyl moiety formed the major metabolite, 4-Me-i-Pr-2-OH DA MKH 3586 (29% dose), which was found primarily in urine (28% dose).  Further hydroxylation at the tertiary butyl group resulted in the formation of 4-Me-t-Bu-iPr-2-di-OH DA MKH 3586, which accounted for 12% dose.  Alternatively, additional hydroxylation of the isopropyl moiety formed 4-Me-iPr-1,2-di-OH DA MKH 3586, which constituted 9% dose in urine.  Desmethylation of the parent formed DA MKH 3586 (<1% dose), which was then hydroxylated at the isopropyl moiety to form iPr-2-OH DA MKH 3586 (8% dose).  The parent was also be hydroxylated at the tertiary butyl moiety to form 4-Me-tBu-OH DA MKH 3586 (9% dose), which was only detected urine.  The other minor identified metabolites occurred resulted from further oxidation, usually hydroxylation.  The pathway for the metabolism of 4-methyl DA MKH 3586 in rats primarily involves a series of hydroxylation reaction.  No conjugates were detected.

      This metabolism study in the rat is classified acceptable/guideline and satisfies the guideline requirement for a Tier 1 metabolism study [OPPTS 870.7485, OPP 85-1] in rats.
	870.7600	Dermal Absorption - Rat

      Not Submitted.

A.4.9	Immunotoxicity

	870.7800	Immunotoxicity

      In an immunotoxicity study (MRID 48407504) Amicarbazone (99.3% a.i. batch 0709AMZ120-1) was administered to 10 female Fischer (F344/DuCRL [CDF[(R)]]) rats/dose via diet at dose levels of 0, 250, 1000, or 2500 ppm (0, 20, 81, 195 mg/kg/day) for 28 days.  The positive control group consisted of 10 female Fischer (F344/DuCRL [CDF[(R)]]) rats were administered 50 mg/kg cyclophosphamide via intraperitoneal injection on Days 24-27.  On Day 24 of the study, all animals were immunized via 0.5 mL intravenous injection with 2.0x10[8] sheep red blood cells (SRBCs).  On Day 28, T-cell dependent antibody response (TDAR) was determined with an antibody forming cell (AFC) assay.  Parameters evaluated include mortality, clinical signs of toxicity, body weight, body weight gain, food consumption, water consumption, organ weights (i.e. spleen and thymus), macroscopic pathology, and assay-specific parameters.

In the treated animals there were no unscheduled mortalities; there were no treatment-related effects on body weight, water consumption, or thymus weight; and there were no treatment-related findings for clinical signs of toxicity or macroscopic pathology.  At the 2500 ppm dose, the treatment-related effects were decreased body weight, food consumption, and absolute spleen weight.

      The systemic toxicity NOAEL is 1000 ppm (81 mg/kg/day) and the LOAEL is 2500 ppm (195 mg/kg/day) based on decreased body weight gain, food consumption, and absolute spleen weight.

      The antibody forming cell (AFC) assay results showed that there was decrease in the quantity of spleen cells/spleen in the 2500 ppm dose group with no statistical differences in the quantity of IgM AFC/spleen cells or IgM AFC/spleen in any treatment group when compared with the vehicle controls.  A high inter-individual variability was noted in all the treatment groups as well as in the control group.  Evaluation of individual animal data showed a distribution demonstrating significant suppression of SRBC antibody response at the 2500 ppm dose.

The Natural Killer (NK) cells activity assay was not performed in this study.  Under HED guidance, NK cells activity assay is not required due to a positive response in the TDAR study (i.e. AFC assay).

The immunotoxicity NOAEL is 1000 ppm (81 mg/kg/day) and the LOAEL is 2500 ppm 195 mg/kg/day) based on results of an AFC assay.

      This immunotoxicity study in rats is classified as Acceptable/Guideline and satisfies the guideline requirement for an immunotoxicity study (OPPTS 870.7800).

A.4.9	Special/Other Studies

Nonguideline Mechanistic Studies

Subchronic Mechanistic Feeding Study in Rats

      In a nonguideline mechanistic subchronic oral toxicity study (MRID 45121603), MKH 3586 (Amicarbazone; >=98% a.i., Lot/batch # PT:05362/0005) was administered to 25 Fisher 344 rats/sex/group in the diet at dose levels of 0, 50, 1250 or 2500 ppm (equivalent to 0/0, 0.8/0.6, 19.4/13.5 or 40.0/28.8 mg/kg bw/day in males/females) for 10 weeks.  Additionally, 5 rats/sex/group were fed test diets containing 0 and 2500 ppm for 10 weeks followed by a four-week recovery period.  The purpose of this study was to determine whether thyroid hormone changes (observed in subchronic and chronic toxicity studies with MKH 3586 in the rat) are due to a direct effect of the test substance on the thyroid or to effects on liver enzymes that affect thyroid hormone metabolism.  Thyroid function was assessed using the perchlorate discharge assay and by determining circulating levels of thyroid hormones T3 and T4 (total and free measured for both) and TSH.  Liver function was assessed by determining liver weight and levels of hepatic UDP-glucuronosyltransferase and 5'deiodinase activities.  Additionally, estrous cycle duration and frequency were examined.

      In the 1250 ppm females, TSH, free T3, T3, free T4 and T4 were increased by 27-61%.  In the 2500 ppm females, levels of these thyroid hormones were increased over controls by 5-24% (not significant [NS]) but to a lesser extent than at 1250 ppm.  Increased T3 (incr. 52%) and free T3 (incr. 31%; NS) were observed in males at 2500 ppm.  At the end of the recovery period, levels of TSH, T3 and T4 in 2500 ppm males and females were comparable to controls.  In the perchlorate assay, thyroid to blood ratio of [125]I in MKH 3586 treated groups were comparable to negative controls in males and females, indicating that the increase in thyroid hormones is not due to increased synthesis.  Thus, an organ or tissue other than the thyroid must be responsible for altered levels of thyroid hormones in rats treated with >=1250 ppm test diets.  There were no treatment-related effects on thyroid weight or microscopic changes in the thyroid at any dose.

      In the liver, UDP-GT activity was increased by 109-241% in the >=1250 ppm males and females and remained increased by 27% in the 2500 ppm females at the end of recovery.  Absolute/relative (to body) liver weights were increased in the main study 1250 ppm males (incr. 9/14%) and females (incr. 5/12%) and in the 2500 ppm males (incr. 25/32%) and females (incr. 18/31%).  Relative liver weights remained increased (incr. 7%) in the 2500 ppm males at the end of the recovery period.  Absolute liver weights in males and absolute and relative liver weights in females were comparable to controls at the end of the recovery period.  Because metabolism of the test substance is primarily via glucuronidation by UDP-GT, it is postulated that MKH 3586 competitively inhibited UDP-GT glucuronidation of T3 and T4 at 1250 ppm, resulting in increased levels of these thyroid hormones in the blood serum.  At 2500 ppm, further induction of UDP-GT began to compensate for this competitive inhibition, allowing T3 and T4 levels to decline.

      In the females, terminal body weights were decreased by 7-10% at >=1250 ppm during the main study and remained decreased by 8% at 2500 ppm at the end of recovery.  An increase in the number of animals spilling food was noted at 2500 ppm.  Food consumption was intermittently decreased on a g/animal/day basis by 3-16% (p<=0.05) in the: (i) main study and recovery group males at 2500 ppm during treatment; (ii) main study and recovery group females at >=1250 ppm during treatment; and (iii) 2500 ppm females at the end of the recovery period.  On a g/kg bw/day basis, food consumption was similar among groups.  Absolute/relative uterine weights were decreased at 1250 ppm (decr. 15/9%) and 2500 ppm (decr. 24/15%).  Decreases in absolute (decr. 20%) and relative (decr. 13%; NS) uterine weights continued in the 2500 ppm recovery group animals.  There were no effects of treatment on the number of estrous cycles.  However, a minor increase of 4% in the duration of the estrous cycle was observed at 2500 ppm.

      In conclusion, thyroid hormones were increased in the >=1200 ppm females and 2500 ppm males.  However, thyroid to blood ratios of [125]I in treated groups were comparable to negative controls, indicating there was no impairment thyroid hormone synthesis.  Thus, the differences in thyroid hormones must be due to metabolism at an extra-thyroidal site.  The liver was implicated as this site based on increased liver weights and UDP-glucuronosyltransferase activity.

	The submitted special mechanistic subchronic oral toxicity study in the rat is classified as 	acceptable/nonguideline and satisfies the purpose for which it was intended.

In vitro Studies on Enzymes of Thyroid Hormone Regulation.  MRID 45121618.

      In a nonguideline study (MRID 45121618), possible interactions of MKH 3586 (Amicarbazone; 98.2% a.i., Lot/batch # 05362/0005, TOX 4490), MKH 3594 (N-desamino metabolite; 99.4% a.i., batch # 200898) and KOK 9422 (putative hydrolysis metabolite; 100% a.i., batch # 130898) with the enzymes involved in the synthesis of thyroid hormones and the regulation of the hypothalmus-pituitary-thyroid axis were investigated using three in vitro systems: (i) thyroid peroxidase (TPO), the key enzyme responsible for organification of iodide and the coupling of iodinated tyrosine residues to both T3 and T4; (ii) iodothyronine deiodinase type I (ID-I), catalyzing the phenolic ring deiodination of T4 to form T3 in peripheral organs like thyroid, liver and kidney; and (iii) iodothyronine deiodinase type II (ID-II), catalyzing the phenolic ring deiodination of T4 to T3 in the hypothalamus and pituitary gland.

      Positive controls adequately demonstrated the sensitivity of each of these in vitro assays through strong, concentration-dependent inhibition of the enzyme of concern.  Amitrole inhibited TPO-catalyzed guaiacol oxidation and iodine formation.  Ethylenethiourea (ETU) temporarily inhibited iodine formation, not by inhibiting TPO itself but instead by reducing iodinating species (i.e., trapping).  Propylthiouracil (PTU) inhibited ID-I, and iopanoic acid inhibited ID-II.

      Neither MKH 3586, MKH 3594, nor KOK 9422 inhibited TPO, ID-I or ID-II at concentrations up to 1 mM, suggesting that MKH 3586 does not affect the iodide organification step of thyroid hormone synthesis (via either inhibition of TPO or trapping of iodine) or the peripheral metabolism of thyroid hormones via Type I or Type II deiodinases in vivo.  These findings support the conclusion that MKH 3586 does not affect the major enzymes involved in the synthesis or regulation of thyroid hormones and are consistent with the findings of the nonguideline subchronic mechanistic study in rats (MRID 45121603) which indicate that upregulation of UDP-glucuronosyl transferase in the liver may account for alterations in the thyroid hormone profile.

      The submitted special in vitro mechanistic study is classified as acceptable/nonguideline and satisfies the purpose for which it was intended, to investigate the possible inhibition of enzyme regulation of thyroid hormone synthesis and metabolism.

Nonguideline Behavioral Study in Rats.  MRID 45121511, 45121521, 45121629.

      In three special studies (MRIDs 45121511, 45121521 and 45121629),  BAY 31-4666 (amicarbazone, 98.4% a.i., Batch #: 05362/0005) was administered in a single gavage dose in 0.5% aqueous tylose suspension (w/v) plus 0.4% TWEEN 80 (5 mL/kg) to 6-10 male HsdCbp WU rats/dose at 0, 1.0, 2.5, 5, 10, 20 or 100 mg/kg bw.  The purpose of the studies was to assess central nervous system (CNS) effects in rats dosed with BAY 31-4666 and to determine a LOAEL.  In the first two studies, rats were dosed with 0, 1,0, 20.0 or 100.0 mg/kg BAY 31-4666.  In (1) MRID 45121529, 6 rats/dose were evaluated for behavioral or physiological changes by the modified Irwin test every 15 minutes for 3 hrs post-dosing, then at 24 hrs post-dosing.  In (2) MRID 45121521, 5 rats/dose were evaluated for catalepsy (5 rats/dose) and 6 rats/dose for body temperature (both assessed every 30 minutes post-dosing up to 240 minutes; pre-dosing body temperature measurements also taken), and 10 rats/dose were evaluated for psychomotoric activity (traveling distance, resting time and rearing) at 30, 60 and 120 minutes post-dosing.  In the third study (MRID 45121511), 6 rats/dose were administered BAY 31-4666 at 0, 2.5, 5.0 or 10.0 mg/kg and evaluated by the modified Irwin test every 15 minutes for 3 hrs post-dosing, then at 24 hrs post-dosing.

      No treatment-related effect was observed in the 1 mg/kg group, nor on clinical signs at 2.5 and 5 mg/kg.  No treatment-related effect was observed during the catalepsy test.  A treatment-related decrease in body temperature was observed in the 100 mg/kg males; however, the minor decreases (<=0.6̊C) were considered not to be biologically adverse.

      The following clinical signs (# rats) were observed: (i) sedation at 10 (1), 20 (3) and 100 (6) mg/kg; (ii) ptosis at 10 (1), 20 (3) and 100 (6) mg/kg; and (iii) salivation at 10 (2), 20 (2) and 100 (6).  Additionally, piloerection (2), Straub phenomenon (4), and prone position (2) were observed in the 100 mg/kg group.  The effects were first observed at 30 minutes post-dose, and no effect was observed in any animal after 150 minutes post-dose, with the higher dose groups showing greater persistence of effects.

      A dose- and time-dependent effect was demonstrated on motor activity.  In the 20 and 100 mg/kg groups, decreased (↓17-28%; p<=0.05) distance traveled and increased (↑19-36%; p<=0.05) resting time was observed at 30 minutes post-dose.  Rearing was decreased (↓52-54%; p<=0.05) at 100 mg/kg at 30 and 60 minutes post-dose; a non-significant reduction of ↓34% was also observed at 20 mg/kg at 60 minutes.  The CNS effects LOAEL is 10 mg/kg, based on transient sedation, ptosis and salivation.  The NOAEL is 5 mg/kg.

      This study is classified as acceptable/nonguideline and satisfies the purpose for which it was intended.

Nonguideline Study of Central Nervous System Safety Pharmacology in Mice

      In a nonguideline study (MRID 45121522), a single dose of MKH 3586 (Amicarbazone; Lot/batch # 05362/0005; 98.4% a.i.), in a 0.5% aqueous tylose suspension (w/v) plus 0.4% Tween-80, was administered orally, in a dosing volume of 10 mL/kg, to 40 male HsdWin: NMRI mice/group at dose levels of 0, 1, 20 or 100 mg/kg/day.  Control animals received an appropriate volume of vehicle without test substance.  The following tests were performed (10 animals/test): (1) hot plate test (analgesia), 56̊C at pretreatment, 30, 45, 60 and 120 min post-dosing; (2) traction, balance rod and electroshock test (reduction of traction force, sensorimotor disturbances and anticonvulsive activity at 30, 40 and 50 minutes post-dosing, respectively); (3) pentylenetetrazole test (pro- and anticonvulsive activity at 45 minutes post-dosing; volume of pentylenetetrazole required to induce clonic seizure) and (4) hexobarbital test (potentiation or reduction of narcotic effects at 60 minutes post-dosing, duration of anesthesia measured).  The objective of this study was to assess the effects of a single oral administration of MKH 3586 on the central nervous system of mice.

      At 100 mg/kg, mice showed increased (not significant unless noted) response times compared to controls to a nociceptive stimulus at 30 (incr. 24%), 45 (incr. 45%), 60 (p<=0.05; incr. 67%) and 120 (incr. 32%) minutes after dosing.  2/10 mice were observed to have reduced traction force and impaired motor coordination, compared to 0/10 in the controls and in the 1 and 20 mg/kg groups.  An increased (p<=0.05) mean threshold dose of pentylenetetrazole was noted (incr. 16%) compared to controls, indicating an anticonvulsant effect by the test compound.  Mice also were observed to exhibit sedation and partial ptosis approximately 20 minutes after treatment.

      Following treatment with the test compound, all mice at all doses exhibited tonic convulsions in the electroshock test.  Additionally, no treatment-related effects were observed on the duration of hexobarbital-induced anesthesia.  There were no effects on the CNS of the 1 and 20 mg/kg mice in any test.

      The data indicate that a single oral dose of MKH 3586 at 100 mg/kg causes minimal CNS functional impairment, characterized by increased reaction times to nociceptive stimuli, reduced traction force, impaired motor coordination, sedation, partial ptosis and a mild anticonvulsive effect.

      The submitted study is classified as acceptable/nonguideline and satisfies the intended purpose of assessing the effects of a single oral administration of MKH 3586 on the central nervous system of mice.

Appendix B.  Physical/Chemical Properties and Structures.

Table B1.  Amicarbazone Physico-Chemical Properties
Parameter
                                     Value
                                   Reference
Molecular Weight
                          [C10H19N5O2] = 241.29 g/mol
                                      N/A
pH
                              7.06 (2.5% slurry)
                                 MRID 45121501
Water solubility (20°C)
                                    4.6 g/L
                                 MRID 45121501
Solvent solubility (20°C to 25°C)
                       n-Heptane = 0.07, xylene = 9.2,
                      1-octanol = 43,  2-propanol = 110,
                     ethyl acetate = 140, acetone >250,
polyethylene glycol = 79, acetonitrile >250, dimethylsulfoxide = 250, dichloromethane >250
                                 MRID 45121502
Vapor pressure (25°C)
                   3.00 x 10[-6]Pa @ 25C (=2.3x10[-8] mmHg)
                             1.30 x 10[-6]Pa @ 20C
                                 MRID 45121501
Dissociation constant, pKa
              Does not dissociate. No acidic or basic properties.
                                 MRID 45121501
Octanol/water partition coefficient, log KOW (20°C)
                          log Pow =1.23 @ pH 7 (20C)
                                 MRID 45121502
Soil Half-life (or other relevant information from EFED Drinking water assessment)
                    Aerobic Soil Metabolism t1/2 = 87 days
                            DP Barcode No. D384516

Table B2.  Chemical Structures of Residues of Concern for Tolerance Enforcement Purposes:  Amicarbazone, Desamino amicarbazone and iPr-2-OH desamino amicarbazone.
Amicarbazone

4-amino-N-(1,1-dimethylethyl)-4,5-dihydro-3-(1-methylethyl)-5-oxo-1H-1,2,4-triazole-1-carboxamide
Desamino amicarbazone (metabolite proposed for regulation)

N-(1,1-dimethylethyl)-4,5-dihydro-3-(1-methylethyl)-5-oxo-1H-1,2,4-triazole-1-carboxamide
iPr-2-OH desamino amicarbazone

N-(1,1-dimethylethyl)-4,5-dihydro-3-(1-hydroxy-1-methylethyl)-5-oxo-1H-1,2,4-triazole-1-carboxamide
Appendix C.  Review of Human Research

This risk assessment relies in part on data from studies in which adult human subjects were intentionally exposed to a pesticide or other chemical.  These data, which include studies from the Pesticide Handlers Exposure Database Version 1.1 (PHED 1.1); the Agricultural Handler Exposure Task Force (AHETF) database; and the Outdoor Residential Exposure Task Force (ORETF) database; are subject to ethics review pursuant to 40 CFR 26, have received that review, and are compliant with applicable ethics requirements.  For certain studies that review may have included review by the Human Studies Review Board.  Descriptions of data sources as well as guidance on their use can be found at http://www.epa.gov/pesticides/science/handler-exposure-data.html and http://www.epa.gov/pesticides/science/post-app-exposure-data.html.


[Federal Register Volume 85, Number 171 (Wednesday, September 2, 2020)]
[Notices]
[Pages 54556-54557]
[FR Doc No: 2020-19379]

-----------------------------------------------------------------------

DEPARTMENT OF ENERGY

Federal Energy Regulatory Commission

[Docket No. CP20-511-000]

Gulf South Pipeline Company, LLC; Notice of Request Under Blanket
Authorization

    Take notice that on August 21, 2020, Gulf South Pipeline Company,
LLC (Gulf South), 9 Greenway Plaza, Suite 2800, Houston, Texas 77046,
filed a prior notice application pursuant to sections 157.205 and
157.216(b) of the Federal Energy Regulatory Commission's (Commission)
regulations under the Natural Gas Act, and Gulf South's blanket
certificate issued in Docket No. CP82-430-000. Gulf South proposes to
abandon in-place four, 1,000 horsepower compressor units, various
buildings, yard and station piping, and appurtenant auxiliary

facilities located at its Koran Compressor Station in Bossier and
Webster parishes, Louisiana, all as more fully set forth in the
application, which is open to the public for inspection.
    In addition to publishing the full text of this document in the
Federal Register, the Commission provides all interested persons an
opportunity to view and/or print the contents of this document via the
internet through the Commission's Home Page (http://ferc.gov) using the
eLibrary link. Enter the docket number excluding the last three digits
in the docket number field to access the document. At this time, the
Commission has suspended access to the Commission's Public Reference
Room, due to the proclamation declaring a National Emergency concerning
the Novel Coronavirus Disease (COVID-19), issued by the President on
March 13, 2020. For assistance, contact FERC at
<EMAIL_ADDRESS>or call toll-free,<PHONE_NUMBER> or TYY,
(202) 502-8659.
    Any questions regarding this application should be directed to Juan
Eligio, Jr., Supervisor of Regulatory Affairs, Gulf South Pipeline
Company, LLC, 9 Greenway Plaza, Houston, Texas 77046, at<PHONE_NUMBER>
or by email to<EMAIL_ADDRESS>Questions may also be
directed to Payton Barrientos, Sr. Regulatory Analyst, Gulf South
Pipeline Company, LLC, 9 Greenway Plaza, Houston, Texas, 77046, at
(713) 479-8157 or by email to<EMAIL_ADDRESS>    Any person or the Commission's staff may, within 60 days after
issuance of the instant notice by the Commission, file pursuant to Rule
214 of the Commission's Procedural Rules (18 CFR 385.214) a motion to
intervene or notice of intervention and pursuant to Section 157.205 of
the regulations under the NGA (18 CFR 157.205), a protest to the
request. If no protest is filed within the time allowed therefore, the
proposed activity shall be deemed to be authorized effective the day
after the time allowed for filing a protest. If a protest is filed and
not withdrawn within 30 days after the allowed time for filing a
protest, the instant request shall be treated as an application for
authorization pursuant to section 7 of the NGA.
    Pursuant to section 157.9 of the Commission's rules, 18 CFR 157.9,
within 90 days of this Notice the Commission staff will either:
Complete its environmental assessment EA and place it into the
Commission's public record (eLibrary) for this proceeding or issue a
Notice of Schedule for Environmental Review. If a Notice of Schedule
for Environmental Review is issued, it will indicate, among other
milestones, the anticipated date for the Commission staff's issuance of
the environmental assessment (EA) for this proposal. The filing of the
EA in the Commission's public record for this proceeding or the
issuance of a Notice of Schedule for Environmental Review will serve to
notify federal and state agencies of the timing for the completion of
all necessary reviews, and the subsequent need to complete all federal
authorizations within 90 days of the date of issuance of the Commission
staff's EA.
    Persons who wish to comment only on the environmental review of
this project should submit an original and two copies of their comments
to the Secretary of the Commission. Environmental commenters will be
placed on the Commission's environmental mailing list, will receive
copies of the environmental documents, and will be notified of meetings
associated with the Commission's environmental review process.
Environmental commenters will not be required to serve copies of filed
documents on all other parties. However, the non-party commenter will
not receive copies of all documents filed by other parties or issued by
the Commission (except for the mailing of environmental documents
issued by the Commission) and will not have the right to seek court
review of the Commission's final order.
    The Commission strongly encourages electronic filings of comments,
protests and interventions in lieu of paper using the eFile link at
http://www.ferc.gov. In lieu of electronic filing, you may submit a
paper copy. Submissions sent via the U.S. Postal Service must be
addressed to: Kimberly D. Bose, Secretary, Federal Energy Regulatory
Commission, 888 First Street NE, Room 1A, Washington, DC 20426.
Submissions sent via any other carrier must be addressed to: Kimberly
D. Bose, Secretary, Federal Energy Regulatory Commission, 12225 Wilkins
Avenue, Rockville, Maryland 20852.

    Dated: August 27, 2020.
Nathaniel J. Davis, Sr.,
Deputy Secretary.
[FR Doc. 2020-19379 Filed 9-1-20; 8:45 am]
BILLING CODE 6717-01-P