Condensation products of Dihydrofuran-2,5-dione, mono-alkenyl derivs. with polyethylene amine and acetic anhydride

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

9 January 2014 to 11 July 2014

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2014

Report date:

2015

Materials and methods

Objective of study:

absorption

distribution

excretion

metabolism

toxicokinetics

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 417 (Toxicokinetics)

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Details on test material:

- Physical state: extremely viscous amber liquid
- Analytical purity:
- Lot/batch No.: E00031-68-1
- Expiration date of the lot/batch: 16 October 2010
- Storage condition of test material:room temperature in the dark, under nitrogen

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Lot/batch No.of test material: E00031-633
- Expiration date of the lot/batch: 12/2014
- Purity: >/= 99%

RADIOLABELLING INFORMATION (if applicable)
- Specific activity: 44.9 µCi/mg (1.66 MBq/mg)

Radiolabelling:

yes

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on species / strain selection:

Male and female Sprague Dawley rats were used in this study. On receipt, from Charles River UK Ltd. (Margate, Kent, UK), the animals were subjected to health examination prior to acceptance onto the study.

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River UK Ltd, Margate, Kent, UK.
- Age at study initiation: 7-13 weeks old
- Weight at study initiation: 212-369 g
- Housing: polypropylene cages
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 +/- 2 °C
- Humidity (%): 55 +/- 10 %
- Photoperiod (hrs dark / hrs light): 12 hours light/12 hours dark

IN-LIFE DATES: From: Febuary 2014 To: April 2014

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

peanut oil

Details on exposure:

Dose formulations were prepared by combining appropriate amounts of [14C]-labelled EXP0700332 with EXP0700332 and diluting with peanut oil to obtain the required dose level of 7.5 or 75 mg/mL. The homogeneity and concentration of each formulation was determined both before and after dose administration by removing triplicate aliquots of each dose formulation for dilution, prior to determination of radioactive content by direct quantitative radiochemical analysis. For dosing performed on 7th February, it was observed that the pre-dose formulation checks were lower than expected therefore additional post-dose checks were performed. For clarity, the formulation concentration was therefore calculated using post-dose checks only.
The dose formulation was stored at ca. 2-8°C when not in use.
A qualitative assessment of the radioactivity of each formulation was performed before and after dose administration by High Performance Liquid Chromatography (HPLC).
Dose administration was performed orally via a syringe and gavage tube. Prior to dosing, animals were weighed. Individual doses were calculated based on body weight, and a dose volume of 4 mL/kg. The syringe was primed with an excess of formulation, the gavage tube was attached and any trapped air/excess formulation was expelled through the gavage tube. The gavage tube was fed down the oesophagus of the appropriate animal, the dose was administered as a single pulse directly into the stomach and the gavage retracted.
Where dose calculation was to be performed by weight dose utensils were weighed empty, pre-dosing and post-dosing. The actual radioactive dose administered to each animal was calculated by the weight of the formulation dispensed (determined by the weight difference between dose apparatus weights recorded pre- and post-dosing) and the radioactive concentration of the dose formulation.
Where dose calculation was to be performed by volume the actual radioactive dose administered to each animal was calculated by the volume of formulation dispensed from the dose apparatus and the radioactive concentration of the dose formulation.

Duration and frequency of treatment / exposure:

Single oral administration to male and female rats at 30 mg/kg and 300 mg/kg. Repeated oral administration at 30mg/kg/day to male rats once a day for 7 consecutive days.

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

30 mg/kg bw/day

Remarks:

Pharmacokinetic study: male and female - single oral dose; male - repeat dose

Doses / concentrations 2

Dose / conc.:

300 mg/kg bw/day

Remarks:

Pharmacokinetic study (male and female) - single dose

Doses / concentrations 3

Dose / conc.:

30 mg/kg bw/day

Remarks:

Excretion Balance study: male and female - single dose; male - repeat dose

Doses / concentrations 4

Dose / conc.:

300 mg/kg bw/day

Remarks:

Excretion Balance study: male and female - single dose

Doses / concentrations 5

Dose / conc.:

30 mg/kg bw/day

Remarks:

Biliary Excretion study: male and female - single dose

Doses / concentrations 6

Dose / conc.:

300 mg/kg bw/day

Remarks:

Biliary Excretion study: male and female - single dose

Doses / concentrations 7

Dose / conc.:

30 mg/kg bw/day

Remarks:

Tissue Distribution: male - single dose

No. of animals per sex per dose / concentration:

See "details of study design" below.

Control animals:

no

Positive control reference chemical:

No

Details on study design:

Phase 1: Preliminary studies
- Stage 1 Preliminary pharmacokinetic study
After a single oral dose of [14C]-labelled EXP0700332 (30 mg/kg) to one male and one female rat, serial blood samples (for plasma preparation) were collected from a tail vein at the following times: 30 minutes and 1, 2, 4, 6, 8, 12, 24 and 48 hours. At 48 hours after the dose administration the rats were killed by cervical dislocation.
- Stage 2 Preliminary excretion study
After a single oral dose of [14C]-labelled EXP0700332 (30 mg/kg) to one male and one female rat, urine (collected in a container cooled in solid carbon dioxide), faeces and expired air were collected separately at the following intervals: Urine: Predose, 0 – 6, 6 – 24, and 24 – 48 hours; Faeces: Predose, 0 – 24 and 24 – 48 hours; Expired air: Predose, 0 – 24 and 24 – 48 hours. At 48 hours after dose administration, the rats were killed by cervical dislocation.

Phase 2: Pharmacokinetic study in male and female rats (single oral dose)

After a single oral dose of [14C]-labelled EXP0700332 at a dose level of either 30 mg/kg or 300 mg/kg to two groups of three male and three female rats (one group per dose level), concentrations of radioactivity were measured in whole blood and plasma at pre dose and at the following times after dosing: 30 minutes and 1, 2, 4, 6, 8, 12, 24, 48 and 72 hours.
Blood samples were collected from three male and three female rats (per dose group), either serially via a tail vein or terminally via cardiac puncture under anaesthetic. After the final sampling time, the animals were killed by cervical dislocation and the carcasses discarded. All blood samples were collected into heparinised containers. A portion of each blood sample was retained as whole blood whilst the remainder was centrifuged for harvesting of plasma into clean neutral tubes, blood cells were discarded. Prior to analysis, whole blood samples were stored at ca. 4°C and plasma samples stored at ca. -20°C. After analysis all samples were stored at ca. -20°C.

Phase 3: Pharmacokinetic study in male rats (repeat oral dose)

A single oral dose of [14C]-labelled EXP0700332 was administered once a day for seven consecutive days at a dose level of 30 mg/kg/day to a group of three male rats. Concentrations of radioactivity were measured in whole blood and plasma at pre dose, once a day during dosing and at the following times after the dosing period: 30 minutes and 1, 2, 4, 6, 8, 12, 24, 48 and 72 hours.
Blood samples were collected either serially via a tail vein or terminally via cardiac puncture under anaesthetic. After the final sampling time, the animals were killed by cervical dislocation and the carcasses discarded. All blood samples were collected into heparinised containers. A portion of each blood sample was retained as whole blood whilst the remainder was centrifuged for harvesting of plasma into clean neutral tubes, blood cells were discarded. Prior to analysis, whole blood samples were stored at ca. 4°C and plasma samples stored at ca. -20°C. After analysis all samples were stored at ca. -20°C.

Phase 4: Excretion Balance study in male and female rats (single oral dose)

Two groups of four male and four female rats (one group per dose level) were administered a single oral dose of [14C]-labelled EXP0700332 at a dose level of either 30 mg/kg or 300 mg/kg. Urine and faeces were collected separately as described below.
At 168 hours animals were killed by cervical dislocation and the carcasses retained at approximately –20°C prior to analysis.
The radioactivity associated with each sample was determined by quantitative radiochemical analysis (QRA).
- Urine
Urine, cooled by solid carbon dioxide, was collected into individual, pre-weighed containers at the following intervals: Pre-dose, 0 – 6, 6-12, 12 - 24, 24 - 48, 48 - 72, 72 - 96, 96 - 120, 120 - 144, and 144 -168 hours. The weight of each urine sample was recorded and duplicate weighed aliquots were taken for direct QRA. Prior to and following analysis, urine samples were retained at approximately -20°C.
- Faeces
Faeces were collected into individual pre-weighed containers at the following intervals: Pre-dose, 0 – 24, 24 – 48, 48 – 72, 72 - 96, 96 - 120, 120 – 144 and 144 – 168 hours. The weight of each faeces sample was recorded and an appropriate volume of water was added prior to homogenisation. Each homogenate weight was recorded and duplicate weighed aliquots of each homogenate were taken for oxidation prior to QRA. Prior to and following analysis, faeces samples were retained at approximately -20°C.
- Carcasses
Carcasses were solubilised individually, in ca. 1L of 2M NaOH in Water:Methanol:Triton X-405 (6:3:1, v:v:v) at ca. 55°C for ca. 24-48 hours. The total weight of each solubilised carcass was recorded and duplicate weighed aliquots of each sample were taken for direct QRA. Prior to solubilisation, carcasses were stored at approximately -20°C. After solubilisation digests were retained at room temperature.
- Cage washes
The washings (water followed by methanol) from each metabolism cage were separately collected into pre-weighed plastic containers. The weight of each cage wash sample was recorded and duplicate weighed aliquots were taken for direct QRA. Cage wash samples were retained at room temperature.

Phase 5: Excretion Balance study in male rats (repeated oral dose)

A single oral dose of [14C]-labelled EXP0700332 was administered once a day for seven consecutive days at a dose level of 30 mg/kg/day to a group of four male rats. Urine and faeces were collected separately at 24 hour intervals for days 1-6. On day 7 samples were collected.

Phase 6: Biliary Excretion study in male and female rats (single oral dose)

After a single oral dose of [14C]-labelled EXP0700332 to two groups of three male and three female rats with cannulated bile ducts (one group per dose level of either 30 mg/kg or 300 mg/kg), bile, urine and faeces were collected separately as described below.
At 48 hours animals were killed by cervical dislocation and the carcasses retained at approximately -20°C prior to analysis.
- Bile
Collection intervals were as follows: Pre-dose, 0-1, 1-2, 2-3, 3-4, 4-5, 5-6, 6-24 and 24-48 hours.
Bile was collected into individual pre-weighed plastic containers (cooled in solid carbon dioxide), and the mass of each sample recorded. Samples were retained at approximately –20°C pending analysis.
- Urine
Collection intervals were as follows: Pre-dose, 0–6, 6-24 and 24-48 hours.
Urine was collected into individual pre-weighed plastic containers (cooled in solid carbon dioxide), and the mass of each sample recorded. Samples were retained at approximately –20°C pending analysis.
- Faeces
Collection intervals were as follows: Pre-dose, 0–24 and 24-48 hours.
Faeces were collected into individual pre-weighed plastic containers and the mass of each sample recorded. Prior to analysis each faeces sample was homogenised to a paste in water and the homogenate weight recorded. Samples were retained at approximately –20°C pending analysis.
- Carcasses
Carcasses were weighed and solubilised at about 55°C for about 24 – 48 hours in a solution of NaOH (80g) and Triton X-405 (100 mL) in distilled water (600 mL) diluted to 1 litre with methanol. Aliquots of the digests were mixed with HionicFluor scintillant prior to determination of radioactive content by LSC. Carcass digests were retained at room temperature.
- Cage washes
At 48 hours, metabolism cages were thoroughly rinsed with water followed by methanol and the washings and cage debris collected separately into a pre-weighed plastic container. The mass determined. Cage washings were retained at room temperature.

Phase 7: Tissue distribution

A group of six male Sprague Dawley rats received single oral doses of [14C]-labelled EXP0700332 at 30 mg/kg. One rat was killed by overdose of CO2 at 1, 6, 12, 24, 72 and 168 hours post dose. All carcasses were immediately snap frozen in a hexane/solid CO2 mixture and retained.
Each carcass was subjected to whole-body autoradiography using procedures based on the work of Ullberg (Acta. Radiol. Suppl 118, 22-31, 1954).
Sections were presented at up to five different levels of the rat body to include as many tissues as possible.
Level A: exorbital lachrymal gland
Level B: intra-orbital lachrymal gland
Level C: Harderian gland/adrenal gland
Level D: thyroid
Level E: brain and spinal cord
Note: The section levels quoted above are for reference and may not occur in the quoted order.
Distribution of radioactivity was determined and quantified using a Fuji FLA-5100 fluorescent image analyser and associated Tina and SeeScan Software. Tissue concentrations of radioactivity were determined using calibrated autoradiographic microscales produced by Amersham International. A standard curve was produced using the microscales from which tissue concentrations of radioactivity were determined (nCi/g). For calculation of the weight equivalent/g data, the nCi/g data was divided by the relevant specific activity (nCi/µg).
Prior to analysis, samples were stored at approximately -20°C (carcass) or ambient temperature (sections after freeze drying). After analysis carcass remains were disposed of, sections were stored at ambient temperature.

Phase 8: Chromatographic Analysis Experiment

Chromatographic analysis was performed using selected faeces samples obtained in the study. A method was established at Quotient Bioresearch (Rushden) Limited for the extraction and recovery of radioactivity from selected samples of faeces. Extracts were analysed by HPLC for the separation and qualitative evaluation of the radiolabelled test compound using on-line radiodetection.

Details on dosing and sampling:

See "Details on study design"

Results and discussion

Preliminary studies:

The pharmacokinetic results showed a maximum concentration of 0.644 µg/g of plasma at hours, and 0.792 µg/g of plasma at hours post dose for males and females respectively. The phase 4 (excretion balance) experimental procedures showed that EXP0700332 was excreted predominantly via the faecal route. The majority of radioactivity was recovered during 0 – 24 hours, with a sub-total recovery of 104.52% and 102.02% for males and females respectively. Smaller proportions of the test item were removed in the urine, with a total of 1.18% at 0-6 hours for males and a total of 1.19% at 6-24 hours for females. Less than 2% of radioactivity was detected in expired air and cage wash. The total radioactivity recovery after 48 hours was 107.14% (males) and 103.32% (females).

Main ADME results

Main ADME results 1

Type:

absorption

Results:

At 30 mg/kg, single dose administration, the maximum plasma concentration was 0.48 µg/mL (males) and 0.58 µg/mL (females) at 4 hours. The AUC from the time of dosing to 72 hours post-dose was 11.80 µg.h/mL (males) and 15.16 µg.h/mL (females).

Main ADME results 2

Type:

distribution

Results:

Single oral dose at 30 mg/kg was confined to the gatro-intestinal tract, with the highet concentrations observed in the stomach and small intestine.

Main ADME results 3

Type:

excretion

Results:

At 30 mg/kg and 300 mg/kg, single and repeat dose oral administration, the faecal route was the predominant route for radioactivty excretion, with the majority of this radioactivity recovered within the first 24 hours after dosing.

Main ADME results 4

Type:

metabolism

Results:

HPLC radiochromatograms showed minimal change

Toxicokinetic / pharmacokinetic studies

Details on absorption:

Following single oral doses (30 mg/kg) of [14C]-labelled EXP0700332 to male and female Sprague Dawley rats, mean maximum concentrations of 0.48 and 0.58 µg equivalents/mL respectively, were measured in plasma at 4 hours post dose. Following single oral doses (300 mg/kg) of [14C]-labelled EXP0700332 to male and female Sprague Dawley rats, mean maximum concentrations of 5.76 and 6.45 µg equivalents/mL respectively, were measured in plasma at 1 and 6 hours post dose. For both dose levels, the radioactivity declined rapidly at subsequent time points. The apparent terminal half-life was estimated at 22.5 and 27.5 hours for 30 mg/kg dose levels, and at 24.5 and 23.9 hours for 300 mg/kg dose levels for male and female rats respectively. Similar rates of elimination were observed in both sexes, showing no gender differences. This data suggests that there was a low rate of absorption and/or rapid rate of clearance of the test material.
Following seven oral doses (30 mg/kg/day) of [14C]-labelled EXP0700332 to male Sprague Dawley rats, a mean maximum concentration of 0.77 µg equivalents/mL was measured in plasma at 4 hours post last dose. Radioactivity declined rapidly at subsequent time points. The apparent terminal half-life was estimated at 32.76 hours post last dose.

Details on distribution in tissues:

The lower limit of accurate quantification (LLOQ) was 0.172 µg equivalents/g. Values below this limit are described as ‘BLQ’ (below limit of quantification) in the following text and associated tables. The upper limit of accurate quantification was 296 equivalents/g.
Following single oral doses (30 mg/kg) of [14C]-labelled EXP0700332 to male Sprague Dawley rats, radioactivity at 1 hour post dose was not widely distributed and was generally confined to components of the gastro-intestinal tract. Highest concentrations were observed in the stomach and small intestine contents, (387 and 249 µg equivalents/g respectively), with notable concentrations measured in the urinary bladder contents (7.95 µg equiv./g), kidney (2.06 µg equiv./g) and liver (0.384 µg equiv./g). Concentrations in all remaining tissues were at levels below the limit of detection (BLQ).
Small increases in radioactive concentration were observed at 6 hours post dose in the adrenal glands (0.180 µg equiv./g), heart blood (0.197 µg equiv./g), liver (0.460 µg equiv./g), pancreas (0.381 µg equiv./g) and skin (1.60 µg equiv./g), however the majority of radioactivity remained associated with components of the gastro-intestinal tract. Radioactivity in the kidney had decreased from 1 hour after dosing, and concentrations in all remaining tissues were below the limit of detection (BLQ).
At 12 hours post, radioactive concentrations in the liver and adrenal glands were similar to those observed at 6 hours (0.483 and 0.196 µg equivalents/g respectively). Excluding components of the gastro-intestinal tract (BLQ – 166 µg equiv./g), concentrations in all remaining tissues were at levels below the limit of detection (BLQ).
A similar distribution of radioactivity was observed at 24 hours post dose, with radioactivity detectable only in the adrenal gland (0.460 µg equiv./g), liver (0.397 µg equiv./g) and components of the gastro-intestinal tract (BLQ – 22.7 µg equivalents/g). Concentrations in all remaining tissues were below the limit of detection (BLQ).
By 72 hours post dose, radioactivity was detectable only in the small intestine mucosa (0.290 µg equivalents/g), lymph node (0.223 µg equivalents/g) and adrenal gland (0.188 µg equivalents/g).
At 168 hours after dosing, radioactivity was at levels below the limit of detection (BLQ) in all tissues analysed.

Details on excretion:

Excretion of administered radioactivity in the 168 hours after both single and repeated oral administration of [14C]-labelled EXP0700332 was almost exclusively via the faecal route in both sexes. Urine accounted for a smaller proportion of radioactivity (ca. 1 % for each animal) with remaining concentrations of radioactivity measured in the cage washings and carcass. The mean total recovery of radioactivity ranged from 83 - 106% (n = 19 animals). Although greater than 90% recovery of radioactivity has not been achieved for all animals in this study, this can potentially be explained by the fact that the majority of the faecal radioactivity is eliminated in one sample and therefore obtaining a truly homogeneous sample for determination of radioactive content is challenging. In order to perform the quantitative radiochemical analysis on the faeces sample, small replicate subsamples were taken (ca. 0.2g) which contained very high levels of radioactivity. It is assumed that any small analytical/experimental error in either value could produce an artificially low recovery of radioactivity.

Toxicokinetic parameters

Toxicokinetic parameters 1

Test no.:

#1

Toxicokinetic parameters:

half-life 1st:

Remarks:

single oral dose at 30 mg/kg (male): 22.5 hours

Toxicokinetic parameters 2

Test no.:

#1

Toxicokinetic parameters:

AUC:

Remarks:

Single oral dose at 30 mg/kg (male): 11.80 µg.h/mL

Toxicokinetic parameters 3

Test no.:

#1

Toxicokinetic parameters:

Cmax:

Remarks:

Single oral dose at 30 mg/kg (male): 0.48 µg/mL

Toxicokinetic parameters 4

Test no.:

#1

Toxicokinetic parameters:

Tmax:

Remarks:

Single oral dose at 30 mg/kg (male): 4 hours

Toxicokinetic parameters 5

Test no.:

#2

Toxicokinetic parameters:

half-life 1st:

Remarks:

Single oral dose at 30 mg/kg (female): 27.5 hours

Toxicokinetic parameters 6

Test no.:

#2

Toxicokinetic parameters:

AUC:

Remarks:

Single oral dose at 30 mg/kg (female): 15.16 µg.h/mL

Toxicokinetic parameters 7

Test no.:

#2

Toxicokinetic parameters:

Cmax:

Remarks:

Single oral dose at 30 mg/kg (female): 0.58 µg/mL

Toxicokinetic parameters 8

Test no.:

#2

Toxicokinetic parameters:

Tmax:

Remarks:

Single oral dose at 30 mg/kg (female): 4 hours

Toxicokinetic parameters 9

Test no.:

#3

Toxicokinetic parameters:

half-life 1st:

Remarks:

Single oral dose at 300 mg/kg (male): 24.52 hours

Toxicokinetic parameters 10

Test no.:

#3

Toxicokinetic parameters:

AUC:

Remarks:

Single oral dose at 300 mg/kg (male): 83.80 µg.h/mL

Toxicokinetic parameters 11

Test no.:

#3

Toxicokinetic parameters:

Cmax:

Remarks:

Single oral dose at 300 mg/kg (male): 5.76 µg/mL

Toxicokinetic parameters 12

Test no.:

#3

Toxicokinetic parameters:

Tmax:

Remarks:

Single oral dose at 300 mg/kg (male): 1 hour

Toxicokinetic parameters 13

Test no.:

#4

Toxicokinetic parameters:

half-life 1st:

Remarks:

Single oral dose at 300 mg/kg (female): 23.88 hours

Toxicokinetic parameters 14

Test no.:

#4

Toxicokinetic parameters:

AUC:

Remarks:

Single oral dose at 300 mg/kg (female): 123.10 µg.h/mL

Toxicokinetic parameters 15

Test no.:

#4

Toxicokinetic parameters:

Cmax:

Remarks:

Single oral dose at 300 mg/kg (female): 6.45 µg/mL

Toxicokinetic parameters 16

Test no.:

#4

Toxicokinetic parameters:

Tmax:

Remarks:

Single oral dose at 300 mg/kg (female): 6 hours

Toxicokinetic parameters 17

Test no.:

#5

Toxicokinetic parameters:

half-life 1st:

Remarks:

Repeat dose at 30 mg/kg (male): 32.76 hours

Toxicokinetic parameters 18

Test no.:

#5

Toxicokinetic parameters:

AUC:

Remarks:

Repeat dose at 30 mg/kg (male): 21.07 µg.h/mL

Toxicokinetic parameters 19

Test no.:

#5

Toxicokinetic parameters:

Cmax:

Remarks:

Repeat dose at 30 mg/kg (male): 0.77 µg/mL

Toxicokinetic parameters 20

Test no.:

#5

Toxicokinetic parameters:

Tmax:

Remarks:

Repeat dose at 30 mg/kg (male): 4 hours

Metabolite characterisation studies

Metabolites identified:

no

Details on metabolites:

HPLC analysis of urine and bile samples were not required due to low recovery of radioactivity in these matrices throughout the conduct of this study. HPLC radiochromatograms obtained showed minimal change in the HPLC profile, compared to that obtained for the dose formulation.

Applicant's summary and conclusion

Executive summary:

The adsorption, distribution, metabolism and excretion of EXP0700332 has been investigated in the rat using [14C]-labelled EXP0700332. Pharmacokinetic, excretion/balance and tissue distribution experiments were conducted on samples generated after a single oral administration of [14C]-labelled EXP0700332 to rats at 30 mg and 300 mg/kg and a repeated oral administration of [14C]-labelled EXP0700332 at 30 mg/kg. Selected samples of faeces were chromatographically analysed to examine the nature of radioactive components.

Maximum mean plasma total radioactivity concentrations were observed at 4 hours post oral dose (30 mg/kg, both sexes) administration and at 1 and 6 hours following oral dose (300 mg/kg, male and female rats, respectively) administration. Concentrations declined rapidly thereafter with apparent half-lives of ca. 25 hours. Systemic exposure to the total radioactivity (AUC0-72) was <16 µg equivalents/g (30 mg/kg dose group) and <123 µg equivalents/g (300 mg/kg dose group). Mean total concentrations of radioactivity were at levels below 0.075 µg equivalents/g (30 mg/kg) and below 0.4 µg equivalents/g (300 mg/kg) at 72 hours dose. The apparently low absorption and rapid elimination of radioactivity is further supported by the excretion balance results obtained.

The mean pharmacokinetic parameters (total radioactivity) obtained in plasma following seven consecutive oral doses of [14C]-labelled EXP0700332 to male rats at a dose level of 30 mg/kg/day showed similar pharmacokinetic parameters to that obtained following single dose administration.

Excretion of administered radioactivity in the 168 hours after both single and repeated oral administration of [14C]-labelled EXP0700332 was almost exclusively via the faecal route in both sexes. Urine accounted for a smaller proportion of radioactivity (ca.1 % for each animal) with remaining concentrations of radioactivity measured in the cage washings and carcass. The mean total recovery of radioactivity ranged from 83 - 106% (n = 19 animals). Although greater than 90% recovery of radioactivity has not been achieved for all animals in this study, this can potentially be explained by the fact that the majority of the faecal radioactivity is eliminated in one sample and therefore obtaining a truly homogeneous sample for determination of radioactive content is challenging. In order to perform the quantitative radiochemical analysis on the faeces sample, small replicate subsamples were taken (ca.0.2g) which contained very high levels of radioactivity. It is assumed that any small analytical/experimental error in either value could produce an artificially low recovery of radioactivity.

The mean proportions of the administered radioactivity recovered from bile cannulated male and female rats during the 48 hour period following a single oral administration of [14C]-labelled EXP0700332 at a dose level of 30 mg/kg show a similar pattern of excretion with =1.2% recovered in the bile.

Although greater than 90% recovery of radioactivity has not been achieved for all animals in this study, this can potentially be explained by the fact that the majority of the faecal radioactivity is eliminated in one sample and therefore obtaining a truly homogeneous sample for determination of radioactive content is challenging.

Following a single oral administration of [14C]-labelled EXP0700332 at a dose level of 30 mg/kg to male Sprague Dawley rats shows limited distribution of radioactivity in tissues. The majority of radioactivity was detectable in components of the gastro-intestinal tract and other tissues associated with elimination. Radioactivity concentrations were at levels below the limit of detection in all tissues at 168 hours post dose, which further supports the data obtained during the excretion balance phase to show that elimination of total radioactivity is essentially complete by this time point.

Qualitative assessment of the HPLC radiochromatograms obtained for all faeces samples analysed showed minimal change in HPLC profile, compared to that obtained for the dose formulation.