Toxicity Study of DC-D3T in Rats

Toxicity Study of DC-D3T in Rats

PRE-CLINICAL TOXICOLOGICAL EVALUATION OF 5,6-DIHYDRO-4H-CYCLOPENTA-1,2-DITHIOLE-3-THIONE, A POTENTIAL CANCER CHEMOPREVENTIVE DRUG, IN RATS
Rajabather Krishnaraj1, Izet M. Kapetanovic2, Robert L. Morrissey3, Thomas Kensler4, James Crowell2, Barry S. Levine1
1Toxicology Research Laboratory, University of Illinois at Chicago, Chicago, IL; 2NCI, Bethesda, MD; 3Pathology Associates, Chicago, IL; 4Johns Hopkins University, Baltimore, MD.

ABSTRACT

The purpose of this study was to examine the in vivo toxicity of 5,6-dihydro-4H-cyclopenta-1,2-dithiole-3-thione (DC-D3T), a potential cancer chemopreventive drug that may act primarily as a phase II enzyme inducer, in normal CD rats. Based on a 14-day range finding study, DC-D3T was administered daily by oral gavage (20/group/sex) for 28 days at 0, 3,12 and 50 mg/kg bwt/day. Endpoints included daily clinical signs, weekly body weight and food consumption, week 4 clinical chemistry, hematology, coagulation, ophthalmology, and necropsy at week 5 and histopathology. The mean plasma DC-D3T levels (measured 2 hours post-dosing in week 4) in the 3 (low), 12 (mid) and 50 (high) mg/kg/day dose groups were 0.28, 0.77 and 1.83 μg/mL for males and 0.24, 0.70 and 2.05 μg/mL for females, respectively. No mortalities or clinical signs of toxicity were seen. Reduced body weight gains and food consumption occurred in the high dose group males. At the high dose, hepatic effects were seen: elevated serum ALT, bilirubin (in the high and mid dose group females), protein, albumin, globulin, cholesterol and decreased triglycerides, and hepatomegaly. Mild renal injury was inferred from hypochloremia in the high dose group and creatininemia in high and mid dose group males. Decreased weights of heart and thyroid/parathyroids noted in the high dose group rats were unaccompanied by histologic changes. Splenomegaly (high dose), dose-dependent increases in the incidence and severity of follicular center hyperplasia of spleen and mesenteric lymph node (at low, mid and high doses), mild monocytosis and reticulocytosis (high dose group females) were also observed. Chronic perivascular inflammation (presence of lymphocytes around small arteries) of epididymis and kidney was noted at 3, 12 and 50 mg/kg/day of DC-D3T. The preliminary data on the effect of DC-D3T on lymphoid tissues could be interpreted as either general immunomodulation or toxicity of DC-D3T. Additional studies are needed to define the threshold for the tissue inflammatory reactions and possible direct immunologic effects of DC-D3T. Under the conditions of this study, a NOEL was not found for DC-D3T in male and female rats. (Supported by NCI contract No.N01-CN-0512).

CONCLUSIONS

* Toxicity of 5,6-dihydro-4H-cyclopenta[1,2]-dithiole-3-thione (DC-D3T) was tested in CD® rats after 28 days of daily gavage administration at 0, 3 (low dose), 12 (mid dose) and 50 (high dose) mg/kg/day.
* Neither mortalities nor drug-related clinical signs were seen at any dose.

* Reductions in weekly body weight gains accompanied by reduced food consumption occurred in the high dose group males, culminating in 25% decrease in total body weight gain.
* Elevated serum total bilirubin levels (high & mid dose group females) and elevated %reticulocytes (high & mid dose group males) were noted. There was no unequivocal evidence for mild hemolytic anemia.
* Mild hepatic injury was evident from the raised serum ALT levels (high dose group), hepatomegaly (high & mid dose group), and a dose-dependent increase in the incidence & severity of centrilobular hypertrophy in males. Hyperproteinemia, hypercholesterolemia and hypotriglyceridemia were also noted at high dose.
* Mild renal injury was suggested by elevated serum creatinine (at high dose), and chloride levels (in high and mid dose group males).
* Mean plasma drug levels in the low, mid and high dose groups were 0.284, 0.767 and 1.831 µg/mL (males) and 0.239, 0.700 and 2.045 µg/mL (females).
* Hyperglobulinemia, splenomegaly (high dose group), dose-dependent increase in the incidence and severity of follicular center hyperplasia of spleen (all DC-D3T treated groups) and mesenteric lymph node (low, mid and high dose group females) were also noted. These effects were accompanied by dose-dependent chronic perivascular inflammation of epididymis and kidney in all dose groups. These findings could be interpreted as either immunostimulatory or toxic effect of DC-D3T. A comprehensive evaluation of the immunomodulatory effect of this chemopreventive agent is needed.

* Under the conditions of this study, a No-Observed-Effect-Level was not found for DC-D3T.

Summary of Treatment-Related Lesions
* Incidence (severity range)
LYMPH NODE, MESENTERIC

-Hyperplasia, follicular center
-Inflammation, chronic, perivascular
-Hyperplasia, follicular center
-Hypertrophy, centrilobular
-Vacuolation, centrilobular

ORGAN - lesion
Dose (mg/kg/day DC-D3T)
Summary Of DC-D3T-Treatment Related Changes
Hematology
Clinical Chemistry
Food Consumption
Total Body Weight Gain
EXPERIMENTAL DESIGN

During the quarantine/pretest period, 80 male and 80 female rats were randomized using a computer-generated randomization program, stratified on the basis of body weight, and animals were assigned to 4 treatment groups of 20 males and 20 females per group. The study was stagger-started over two consecutive days beginning with the males.
Dose Concentration
Dose Volume
LIST OF ORGANS AND TISSUES EVALUATED FOR LESIONS

Abnormal lymph nodes Pancreas
*Adrenal glands Pituitary
Aorta (thoracic) Prostate
*Brain (fore-, mid-, hind-) Salivary gland (mandibular)
Cecum Sciatic nerve
Colon Seminal vesicles
Duodenum Skeletal muscle
Epididymides Skin
Esophagus Spinal cord (cervical and Eyes thoracolumbar segments)
Femur (with marrow) *Spleen
Gross lesions Sternum (with marrow)
*Heart Stomach
Ileum *Testes
Jejunum Thymus
*Kidneys *Thyroid/parathyroids
*Liver *Tissue masses
*Lungs/Bronchi Trachea
Lymph node (mesenteric) Urinary bladder
Mammary gland Uterus (corpus and cervix)
*Ovaries/Fallopian tubes Vagina
* Organs weighed.

Toxicity Study of DC-D3T in Rats.ppt