[1,2,4]Triazolo[1,5-a]pyrimidine-2-sulfonamide, N-(2,6-difluorophenyl)-5-methyl-

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 5 December 1986 to 28 April 1988

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study conducted in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1988

Report date:

1988

Materials and methods

Objective of study:

other: adsorption, distribution, metabolism, and excretion

Test guideline

Qualifier:

according to guideline

Guideline:

EPA OPP 85-1 (Metabolism and Pharmacokinetics)

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

N-(2,6-difluorophenyl)-5-methyl-[1,2,4]triazolo[1,5-a]pyrimidine-2-sulfonamide

EC Number:

619-383-6

Cas Number:

98967-40-9

Molecular formula:

C12H9F2N5O2S

IUPAC Name:

N-(2,6-difluorophenyl)-5-methyl-[1,2,4]triazolo[1,5-a]pyrimidine-2-sulfonamide

Constituent 2

Reference substance name:

N-(2',6'-difluorophenyl)-5-methyl[1,2,4]triazolo[1,5-a]pyrimidine-2-sulfonamide

IUPAC Name:

N-(2',6'-difluorophenyl)-5-methyl[1,2,4]triazolo[1,5-a]pyrimidine-2-sulfonamide

Details on test material:

See confidential details

Radiolabelling:

yes

Test animals

Species:

other: mice and rats

Strain:

other: B6C3F1 and Fischer 344 rats

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles RIver Breeding Laboratories, Kingston NY and Portage, MI
- Age at study initiation:
- Weight at study initiation: rats = 200 to 250 grams; mice = 20-30 grams
- Fasting period before study: yes - 12 hours for rats, and 3 hours for mice
- Housing: rats and mice were assigned to glass Roth -type metabolism cages, and additional mice were assigned to stainless steel cages with wire mesh bottoms
- Individual metabolism cages: yes
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: one week; and then 2-3 days after rats were fitted with indwelling jugular vein cannula via surgery


ENVIRONMENTAL CONDITIONS

- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

other: some groups were intravenous, others were oral

Vehicle:

other: plasma obtained from stock male rats for intravenous administration

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:

VEHICLE
- Justification for use and choice of vehicle (if other than water): due to insolubility of XRD-498 in aqueous mediums, the dose solution was prepared in plasma obtained from stock male rats for intravenous administration. The vehicle for oral gavage was 0.5% methylcellulose.

Duration and frequency of treatment / exposure:

Rats
Group 1: single intravenous administration of 14C-XRD-498 at dose of 0.75 mg/kg body weight
Group 2 and 3: Single oral dose at 1000 and 5 mg/kg, respectively

Mice
Group 1: Oral 1000 mg/kg dose of 14C-XRD-498

Doses / concentrations

Remarks:

Doses / Concentrations:
Rats
Group 1: single intravenous administration of 14C-XRD-498 at dose of 0.75 mg/kg body weight
Group 2 and 3: Single oral dose at 1000 and 5 mg/kg, respectively

Mice
Group 1: Oral 1000 mg/kg dose of 14C-XRD-498

No. of animals per sex per dose / concentration:

Rats
Group 1: single intravenous administration of 14C-XRD-498 at dose of 0.75 mg/kg body weight (4 male rats)
Group 2: Single oral dose at 1000 (4 male rats)
Group 3: 5 mg/kg, respectively (4 male rats)
Mice: 4 males
Group 1: Oral 1000 mg/kg dose of 14C-XRD-498

Control animals:

not specified

Positive control reference chemical:

no information

Details on study design:

Three groups containing four male rats per group were used to study the absorption, metabolism, excretion, and tissue distribution of 14C-CRD-498. The first group received a single IV administration of 14C-XRD-498 at a dose of approximately 0.75 mg/kg body weight. The secon and third gropus were given 14C-XRD-498 as a single oral dose at 1000 and 5 mg/kg, respectively. Rats from the three groups were housed in glass Roth-type metabolism cages and blood, urine and feces were collected at specified intervals up of 72 hours post-dosing. In addition, expired organics and 14 CO2 were trapped from the 0-12 and 12-24 hr post-dosing periods for the 0.75 mg/kg (IV) group, and the 0-12 hour interval for the 1000 mg/kg (oral) group. Rats were sacrificed at either 54 or 72 hr post dosing and samples of liver, kidney, fat, small, and large intestines, skin and remaining carcass were analyzed for radioactivity.

For cross species comparison, three to four male mice per sampling interval were administered an oral 1000 mg/kg dose of 14C-XRD-498. Plasma 14C concentrations were determined throughout a 48-hour post-dosing period, and the concentration of 14 C in the liver, kidney, and fat were determined at various times throughout the first 8 hr post-dosing interval as well as at 48 hrs post-dosing. The mice assigned to the 48 hr sampling period were housed individually in glass Roth-type metabolism cages and urine and feces were collected at specified intervals. These animals were sacrificed at 48 hr post-dosing and samples of liver, kidney, fat, skin, and the remaining carcass were analyzed for radioactivity.

In order to determine the extent of metabolism of 14C-XRD-498 in the rat and mouse, selected samples of urine were analyzed by high performance liquid chromatgraph (HPLC) and mass spectrometry (MS).

Details on dosing and sampling:

PHARMACOKINETIC STUDY (Absorption, distribution, excretion)

RATS
- Tissues and body fluids sampled (delete / add / specify): blood, urine, feces, expired organics and 14CO2
- Time and frequency of sampling: Feces collected for first 0-24 hour post-dosing and at 12 hour intervals thereafter; blood collected at 0.25, 0.5, 0.75, 1,2,4,6,8,12,24,30,36,48,54 and 72 hours post dosing; urine collected at 12 hr intervals.


MICE
- Tissues and body fluids sampled (delete / add / specify):liver, kidney, fat
- Time and frequency of sampling: 0.25, 0.5, 0.75, 1, 2, 4, 6, 8, 12, 18, 24, 30, 36, and 48 hours post-dosing

Statistics:

A two compartment pharmacokinetic model was used to desribe the time-course of radioactivity in the plasma of rats and mice given 14C-XRD-498 orally. The time-course after IV administration of 14C-XRD-498 also used a two-compartment pharmacokintetic model.

Results and discussion

Preliminary studies:

no information

Toxicokinetic / pharmacokinetic studies

Details on absorption:

In the rat, the absorption half-lives were 0.73 and 0.95 hr in the 5 and 1000 mg/kg groups, respectively, which represented an approximate 1.3-fold faster absorption rate in the low dose group. In comparson, the mouse (1000 mg/kg) absorption half-life was 0.45 hr, which was an approximate 2.1 fold faster rate of absorption when compared to rats administered the same dose.

Details on distribution in tissues:

In the mouse, the 14C analysis in the plasma, liver, kidney, and fat throughout the initial 8-hr post-dosing interval indicated that the plasma and kidneys contained comparable amounts of radioactivity, whereas the liver and fat contained appreciably lower concentrations of 14C. In the rat, 14 C analysis in the major organ systems at the termination of this study (54-72 hour post-dosing) indicated thatthe amount of 14C in the tissues was negligible and/or below the limits of quantitation. These data suggest that 14C-XRD-498 is unlikely to accumulate in rats and mice.

Details on excretion:

In he rat, 14C-XRD-498 was adequately absorbed and the principle excretory route was via the urine. The urinary 14C excretion time-course demonstrated a slightly slower excretion rate in the 0-12 hour interval after oral dosing at 1000 mg/kg. This finding is consistent with the longer plasma 14C elimination half-life at 1000 mg/kg as compared to the 5 mg/kg dose group in the rat. Based on the IV (0.75 mg/kg) data, the feces represented a minor excretory pathway. The larger percentage of the administered dose collected in the feces during the first 24 hour after oral dosing most probably represented non-absorbed 14C-XRD-498.

In the mouse, 14C-XRD-498 was rapidly absorbed, metabolized to a very limited extent, and rapidly eliminated. However, at 48-hour post-dosing, only 82% of the administered dose was recovered. One posible explanation for this recovery was that since the dose solution was administered as a suspension in a small volume (approximately 0.1 ml) an error may have occurred in determining the exact amount of 14C-XRD-498 administered. This hypothesis is supported by the similar recoveries at 0.25 and 48 hour post-dosing. The principle excretory route was via uring (62%) with the feces representing a minor eliminatnoi pathway (17%). Assuming the mouse kinetics are comparable to the rat, the 14C activity collected in the feces most likely also represented non-absorbed XRD-498.

Toxicokinetic parameters

Toxicokinetic parameters 1

Toxicokinetic parameters:

half-life 1st: 0.73 hours in 5 mg/kg group for rat (absorption phase)

Toxicokinetic parameters 2

Toxicokinetic parameters:

half-life 1st: 0.95 hours in 1000 mg/kg group for rat (absorption phase)

Toxicokinetic parameters 3

Toxicokinetic parameters:

half-life 2nd: 2.4 hours in 0.75 mg/kg group for rat (terminal phase)

Toxicokinetic parameters 4

Toxicokinetic parameters:

half-life 2nd: 4.8 hour in 5 mg/kg group for rat (terminal phase)

Toxicokinetic parameters 5

Toxicokinetic parameters:

half-life 2nd: 11.5 hours in 1000 mg/kg group for rat (terminal phase)

Toxicokinetic parameters 6

Toxicokinetic parameters:

half-life 1st: 0.45 hours for mice administered 1000 mg/kg (absorption phase)

Toxicokinetic parameters 7

Toxicokinetic parameters:

half-life 2nd: 4.3 hours for mice administered 1000 mg/kg (terminal phase)

Metabolite characterisation studies

Metabolites identified:

yes

Details on metabolites:

In mice, two minor peaks eluting prior to 14C-XRD-498 were observed in the 0-12 and 12-24 hr urine samples and together represented less than 20% of radioactivity in the urine. No attempt was made to characterize the metabolites in the urine of mice.

Applicant's summary and conclusion

Conclusions:

Interpretation of results (migrated information): no bioaccumulation potential based on study results
No signs of toxicity were observed following intravenous or oral administration of either 0.75, 5, or 1000 mg 14C-XRD-498/kg body weight to male rats or mice (mice 1000 mg/kg only).

Executive summary:

14C-XRD-498 was administered to groups of male rats, intravenously at a dose of 0.75 mg/kg, and orally at doses of 5 and 1000 mg/kg. In addition, groups of male mice were adminstered an oral dose of 1000 mg/kg. In rats, over 92% of the administered doses were excreted by 54 to 72 hours. Following IV administration, 93% of the dose was recovered in the urine. However, after oral administration 14 -C-XRD-498 was only partially absorbed and excreted in the urine (52 - 62%). The feces accounted for 32 to 40% of the oral dose and in all probability was unaborbed XRD-498. In mice, 62 and 17% of the dose was recovered in the urine and feces, respectively by 48 hours. The plasma 14C time-courses in rats and mice were biexponential, indicating a rapidly equilibrating "central" compartment and a more slowly equilibrating "deep" compartment. In rats, the absorption half-lives for the 5 and 1000 mg/kg doses were 0.73 and 0.95 hours, respectively. The terminal phase half-lives for the 0.75, 5, and 1000 mg/kg dose gropus were 2.4, 4.8, and 11.5 hours, respectively. In addition, at the 1000 mg/kg dose, the rats demonstrated an approximate 3 -fold increase in plasa protein binding. In mice, the absorption and terminal phase half-lives were 0.45 and 4.3 hour, respectively. Only a small fraction of the administered radioactivity was detected in the fat and kidneys of mice and the kidneys and large intestines of rats administered the 0.75 mg/kg IV dose. In both rats and mice, XRD-498 was excreted via the urine primarily unchanged, although the mice did form two minor metabolites (<20% of the urinary radioactivity). These data indicate that approximately one-half of an orally administered dose o 14C-XRD-498 was absorbed, and excreted primarily unchanged by the kidneys in both rats and mice. The limited absorption, rapid clearance, and minor metabolism support acute and subchronic findings indicating the lack of significant toxicological effects of XRD-498 in rats and mice.