[GANN,65, 153~161; April, 1974]
`DISTRIBUTION AND EXCRETION OF CYCLOCYTIDINE IN MONKEYS, DOGS,
`AND RATS
`
`Hachihiko Hirayama, Taisuke Sucmara, Fukusaburoh Hamapa, Tadashi Kanal, Juhtaroh
`Hrrra,*? Yasuo Araxt,*? Kazuo Kuretant,*? and Akio Hosui**
`Research Laboratories, Kohjin Co., Ltd.,*! and National Cancer Center Research Institute**
`
`The distribution in tissues and excretion of cyclocytidine (2,2’-anhydro-1-8-p-arabino-
`furanosylcytosine hydrochloride) and its metabolites in urine and feces of macaca monkeys
`(Macaca irus, Macacafuscata, and Macaca mulata) and in beagle dogs wereexamined by the
`spectrophotometric assay. Distribution of cyclocytidine in plasma and tissues of rats was
`also examined.
`The administered cyclocytidine showed a half-life of 22 min in plasma of dogs and
`monkeys, whereas the half-life of aracytidine (1-8-p-arabinofuranosylcytosine hydrochlor-
`ide) was 47 min in plasma of dogs and less than 5 min in plasma of monkeys, because of
`rapid deamination of the compound to arauridine (1-f-p-arabinofuranosyluracil) in the
`latter species. Cyclocytidine exhibited maximum concentration in tissues of rats and monkeys
`at 20 to 40 min after the administration, but its metabolites, aracytidine and arauridine,
`were not detected in these tissues. Cyclocytidine levels in tissues diminished thereafter
`but were detected within the next 40 to 80 min. Neither cyclocytidine nor its metabolites
`could be detected in the brain. When cyclocytidine was administered intravenously in dogs
`and monkeys, 65~85% of it was excreted in urine, almost all as intact cyclocytidine, and
`small amounts of aracytidine and arauridine were detected. On the other hand, the ad-
`ministered aracytidine was excreted only as arauridine in urine of monkeys, and aracyt-
`idine and arauridine in dogs. Cyclocytidine and its metabolites were not detected in feces
`of both species.
`It might be suggested that the distribution and elimination rate of cyclocytidine after its
`intravenous administration is not affected by the presence of cytidine deaminase in plasma
`andtissues.
`
`The remarkable antitumor activity of cyclocytidine (2,2’-anhydro-1-§-p-arabinofuranosyl-
`cytosine hydrochloride) against L-1210 leukemia and a variety of mouse tumors was found by
`Hoshiet al,1°:!? and by other workers.1*28) Furthermore, cyclocytidine was found to be effective
`in leukemia patients at phase I study.?” Pharmacological and toxicological properties of the
`compound in mice, rats, monkeys, and dogs were examined by Hirayamaet al.’~® Theside
`effect of cyclocytidine is rare and its cumulative toxicity is extremely low in laboratory animal
`species, when compared with other antitumor agents such as aracytidine (1-8-p-arabino-
`furanosyleytosine hydrochloride).’~” It was reported that aracytidine was inactivated by
`cytidine deaminase through its deaminationto arauridine (1-8-p-arabinofuranosyluracil) when
`used clinically.* °°1%? Cytidine deaminase activity in macaca monkey organs as well as in
`human organsis in a relatively high level, whereas that in dog and rat organsis considerably
`low or none.*:*: #1Cyclocytidine was foundto beresistant against cytidine deaminase.}219)
`It is, therefore, importantin the clinical application of cyclocytidine to investigate the distribu-
`tion and excretion in experimental animals having a high deaminase activity.
`The presentstudy deals with the distribution and excretion of cyclocytidine and its metab-
`olites after intravenous administration of cyclocytidine in macaca monkeys, beagle dogs, and
`also distribution in rat tissues.
`
`i).
`* 51 Komiya-cho, Hachiohji, Tokyo 192 (FHIUAB, BRAM, RAREBS, Sit
`*? Present address: Division of Fermentation and Chemical Products, Kohjin Co., Ltd., Saiki, Oita
`876 GER RABS, FAH).
`.
`;
`,
`>
`*8 Tsukiji 5-1-1, Chuo-ku, Tokyo 104 (S418,
`AG).
`
`e5(2)
`
`1974
`:
`
`(cid:38)(cid:40)(cid:47)(cid:42)(cid:40)(cid:49)(cid:40)(cid:3)(cid:21)(cid:20)(cid:23)(cid:22)
`CELGENE 2143
`uss
`(cid:36)(cid:51)(cid:50)(cid:55)(cid:40)(cid:59)(cid:3)(cid:89)(cid:17)(cid:3)(cid:38)(cid:40)(cid:47)(cid:42)(cid:40)(cid:49)(cid:40)
`APOTEX v. CELGENE
`(cid:44)(cid:51)(cid:53)(cid:21)(cid:19)(cid:21)(cid:22)(cid:16)(cid:19)(cid:19)(cid:24)(cid:20)(cid:21)
`IPR2023-00512
`
`

`

`H. HIRAYAMA, ET AL.
`
`MatTeErRiIats AND MretTHopDs
`Chemicals Cyclocytidine was synthesized by the method of Kanaief al’? and of Kikugawa et al.’® The
`compoundoccurs as white needles of mp 255-257°, easily soluble in water but slightly soluble in ethanol,
`methanol, and acetone, and almost insoluble in ether, chloroform, and benzene. Chemical structure of
`cyclocytidine and aracytidine are shownin Fig. 1.
`
`oo
`tJ
`\
`
`0
`
`NH2-HCl
`N
`om
`
`HOW
`
`9
`
`OH
`
`Ho5_
`
`0
`HO
`
`OH
`
`0
`HN
`ON
`
`9
`HO
`
`OH
`
`Ho
`
`Cyclocytidine
`C,H,,N,0,-HCl
`mol. wt.=261.67
`
`Aracytidine
`(Cytidine arabinoside)
` CyHygNsOs-HCl
`mol. wt,=278.72
`
`Arauridine
`{uridine arabinoside)
`CoH,2N,O,
`mol, wt. = 242.28
`
`Fig. 1. Chemical structures
`
`Animals Macaca monkeys (Macaca irus, Macaca mulata, and Macaca fuscaia), weighing 2~7 kg (Kyudoh
`Co., Kumamoto), beagle dogs weighing 8~14kg (Laboratory for Experimental Beagle Dog, Nippon
`Dog Center Co., Kagoshima), and rats of Wistar strain weighing 180~200 g (Kyudoh Co., Kumamoto)
`were divided into 3 to 6 groups. Both males and females of monkeys and dogs were kept in individual
`cages fed on a commercial diet; Type AF (Oriental Yeast Co., Tokyo) for monkeys and Vita-One (CLEA
`Japan Inc., Osaka) for dogs twice a day, with vegetables to monkeys and meat to dogs. Water was given
`freely from bottles. Rats were allowed free access to a commercial diet, Type MF (Oriental Yeast Co.,
`Tokyo) and fresh water. All the animals were kept in air-conditioned rooms at 24°+1° and 55+5%
`
`relative humidity, and kept for 4~6 weeks before each experiment.
`Cyclocytidine and aracytidine were dissolved in physiological saline and intravenously administered to
`monkeys via the median antebrachial vein and to dogs via the saphenous vein. Control animals received
`physiological saline alone.
`Collection and Preparation of Samples Blood samples were collected from 12 monkeys via the median ante-
`brachia vein, from 13 dogs via the saphenous vein, and from rats via the femoral vein 20, 40, 80, or 160
`rnin after the administration of cyclocytidine. Visceral specimens were also obtained from the same animals
`at the above described time. Urine samples were collected 10, 20, 80, 160, or 320 min and 12, 24, 48,
`or 72 hr after the administration, and stools spontaneously evacuated for 4 days were also collected. These
`blood, organ, urine, and fecal samples were treated as described below and subjected to spectrophotome-
`tric assay.1”
`Plasma Plasma was separated from the heparinized blood by centrifugation (3,000g, 4°, 15 min) and
`deproteinized with trichloroacetic acid at the final concentration of 4%.
`Organs Monkeys and rats were sacrificed by bleeding under ether anesthesia and vascular perfusion with
`Ringer solution was carried out with a peristal pump (Taiyo Rika Kikai Co., Tokyo) to removeresidual
`blood. The abdomen was immediately opened, and brain, salivary gland, muscle, liver, kidneys, spleen,
`and other visceral organs were removed and weighed individually. A portion of these tissues was minced
`and homogenized with 3-~~4 volumes of 4% cold trichleroacetic acid by the Potter-Elvehjem type Teflon
`homogenizer or a cutting-blade homogenizer in ice-cold bath and the supernatant was separated by cen-
`trifugation.
`Urine and Feces From monkeys and dogs housed individually in metabolism cages, urine samples were
`collected in plastic containers containing acetic acid and spontaneously evacuated stools obtained as de-
`scribed above. Both urine and feces were also treated with 4% trichloroacetic acid solution.
`Separation af Cyclocytidine, Aracytidine, and Arauridine The samples were fractionated according to the pro-
`cedure of Kanai ¢ ai.’” into three fractions; A (arauridine), B (aracytidine), and C (cyclocytidine), as
`shown in Fig. 2. Each 2 ml of the sample was applied on a column (1.4 x 3.4.cm) of Dowex 50W x4
`(NH, form) with a Chromacord-UV Analyzer (Model UV-254, Shibata Chemical Apparatus Mfg. Co.,
`Osaka). The first fraction-A was eluted with water, concentrated im vacuo at 40°, and chromatographed
`
`154
`
`GANN
`
`

`

`DISTRIBUTION AND EXCRETION OF CYCLOCYTIDINE
`on Toyo Roshi No. 51Afilter paper for 10~12 hr, using a solvent system of ethyl acetate: isopropanol :
`water=65:17.5:17.5 (v/v). The UV-absorbing spot was identified with authentic arauridine. After
`elution with water, amountof arauridine was determined by spectrophotometry at 263 nm. The second
`fraction-B was eluted from the column with 0.444 ammonium acetate. After concentration in vacuo at
`40°, aracytidine was separated by an ascending paper chromatography with a solvent system of 5M am-
`monium acetate: water-saturated sodium borate: ethanol:0.544 EDTA disodium salt = 20:80 :220:0.5
`(v/v). The amountof aracytidine was determined by UV absorption in 0.1N HCl at 280 nm. Finally,
`fraction-C containing cyclocytidine was eluted with 0.4M ammonium acetate andits quantity was assayed
`by UV absorption in 0.4! ammonium acetate at 263 nm.
`
`Sample, 2 ml (treated with trichloroacetic acid)
`Column (1.4 x 3.4 em).of Dowex 50W x4,
`washed with water
`
`
`
`| eluted with 0.444 ammonium acetate
`
`A-fraction
`concentrated .
`{at 40~-50°
`in vacuum)
`PPC AcOEt-iso-PrOH-H,O
`(65:17.5:17.5)
`Rf = 0.45
`(Arauridine)
`
`Keauiline
`Engg (€ = 10.5 x 10°)
`
`B-fraction
`concentrated
`(at 40~50° in vacuum)
`
`PPC 5M AcONH,sat. Na,B,O,-
`EtOH-0.5M EDTA
`(20 :80:220:0.5)
`Rf = 0.6 (Aracytidine)
`
`C-fraction
`
`Cyclocytidine
`Eng (E = 10.6 x 10%)
`
`Aracytidine
`Eggo (€ = 13.3 x 10%)
`Fig. 2. Fractionation procedure for cyclocytidine, aracytidine, and arauridine
`
`REsuLts
`
`Half-lives of Administered Cyclocytidine and Aracytidine in Plasma of Monkeys, Dogs, and Rats
`Monkeys: As shown in Fig. 3, expected metabolites were not detected in plasma of monkeys
`after the intravenous administration of 100 mg/kg of cyclocytidine. The plasma cyclocytidine
`levels in monkeys is shown in Fig.3. Cyclocytidine was present in approximately 170 pg/ml
`in plasma immediately after the injection, and it fell rapidly and disappeared within 80 min.
`The half-life of cyclocytidine was,
`therefore, determined as 22 min. This value was not
`different among the three simian species, cynomolgus, rhesus, and fuscata.
`The plasma of monkeys contained 50 ug/mlof aracytidine immediately after receiving 100
`mg/kg of aracytidine, but a drastic increase of its metabolite, 100~400 pg/ml of arauridine,
`in plasma occurred already 5 min later. Aracytidine disappeared completely from the plasma
`within 10 min and arauridine alone was detected. Arauridine diminished gradually as shown in
`Fig. 4, The half-life of aracytidine was therefore considered to be less than 5 min in the three
`simian species.
`Dogs: As shown in Fig.5, only cyclocytidine was detected in plasma after the administration
`of 100 mg/kg of cyclocytidine, and its concentration in plasma was about 200 pg/mlafter 10
`min and disappeared within 80 min,the half-life of cyclocytidine being 22 min. At 10 min after
`injection of the same dose of aracytidine, plasma level of aracytidine was 100 pg/ml and it
`decreased gradually. Arauridine was not detected in plasma (Fig. 5). The half-life of aracyt-
`idine was 47 min in dogs. These findings indicate that the disappearance of aracytidine from
`plasma was gradual in the animals having low or no cytidine deaminase activity.
`
`65(2)
`
`1974
`
`/
`
`155
`
`

`

`H. HIRAYAMA, ET AL.
`
`200
`
`100
`
`50
`
`200 Cyclocytidine
`
`160
`
`50
`
`
`
`
`
`Plasmaconcentration(g/ml)
`
`half-life 22 min
`
`10
`80=:100
`0
`20
`40
`60
`0
`20
`4)
`60
`80
`
`se *
`-e ° he Arauridine
`“$~sSe
`
`Aracytidine half-life <5 min
`
`
`
`Plasmaconcentration(¢g/ml) 10
`
`Time (min)
`
`Time (min)
`
`Fig. 3.
`
`Plasma level of cyclocytidine in ma-
`caca monkeys after intravenous ad-
`ministration of 100 mg/kg of cyclo-
`cytidine
`
`Fig. 4. Plasma level of arauridine in macaca
`monkeys after intravenous adminis-
`tration of 100 mg/kg of aracytidine
`
`
`
`
`
`Plasmaconcentration(g/ml)
`
`
`
`Cyclocytidine
`Ne
`half-life = 22 min
`
`ome
`e ~~~
`
`™
`
`Aracytidine
`
`200
`
`100
`
`50
`
`’ half-life=47 min
`
`60
`40
`Time (min)
`
`80
`
`105
`
`20
`
`
`
`
`
`Plasmaconcentration(#g/ml)
`
`
`
`Cyclocytidine
`half-life =37 min
`
`
` 100
`
` Aracytidine
`
`half-life = 80 min
`
`0
`
`20
`
`46
`
`60
`
`80
`
`100
`
`Time (min)
`
`Fig. 5.
`
`Plasma level of cyclocytidine and
`aracytidine in dogs after intravenous
`administration
`of
`100 mg/kg
`of
`cyclocytidine or aracytidine
`
`Fig. 6. Plasma level of cyclocytidine and
`aracytidine in rats after intravenous
`administration of 100 mg/kg of cyclo-
`cytidine
`
`As shownin Fig. 6, neither aracytidine nor arauridine was detected in plasmaafter the
`Rats:
`administration of 600 mg/kg of cyclocytidine, and intact cyclocytidine alone was detected in
`plasma. Thelevel of cyclocytidine was 1,800 ug/ml in plasma 5 min after the injection, dimin-
`ished to 800 pg/ml within 20 min, and continued to decrease during the next 100 min. Half
`life of cyclocytidinc in plasmaof rats was about 37 min and that of aracytidine, 80 min,
`Distribution in Tissues Monkeys:
`Figs. 7 and 8 illustrate the serial plasma levels and dis-
`tribution of cyclocytidine in tissues of monkeys after the intravenous injection of 600 mg/kg
`ofcyclocytidine. Fig.7 showsthe pattern of plasmalevel, and about 1,000 ug/ml ofcyclocytidine
`
`156
`
`GANN
`
`

`

`DISTRIBUTION AND EXCRETION. OF CYCLOCYTIDINE
`
`1000
`
`500
`
`100
`
`©6450
`
`10
`
`Qo
`
`Plasma
`
`120
`
`240
`
`360
`
`2 ao
`
`o i 2
`
`5000 “oe=}
`
`5s
`
`2S
`
`Ce
`,
`
`sg
`
`Set
`3
`
`=88
`
`Fig. 7. Distribution of cyclocytidine in plasma, liver, and kidney of monkeys
`after intravenous administration of 600 mg/kg of cyclocytidine
`
`Time (min)
`
`et
`g
`ul
`
`Submaxillary
`gland
`
`Heart
`
`Lung
`
`Stomach
`
`Spleen
`
`Pancreas
`
`Intestinal
`mucosa
`
`= 1000
`oo
`y=
`ac
`
`S 2a >
`
`‘3
`
`<2=i E°§
`
`oO
`
`40
`
`80
`
`40
`
`80
`
`0
`
`40
`
`80
`
`O
`
`40
`
`80
`
`O
`
`40
`
`80
`
`40
`
`80
`
`40
`
`80
`
`Time (min)
`
`Fig, 8. Distribution of cyclocytidine in monkey tissues after intravenous administration of
`600 mg/kg of cyclocytidine
`
`was demonstrated 5 min after the injection of cyclocytidine, but arauridine and aracytidine
`were not detected. Cyclocytidine decreased gradually and was detected even 240 min later.
`Maxium concentrations of cyclocytidine in liver and kidney were 5,000 and 2,500 pg/g, re-
`spectively, after 80 min, and concentration decrease was like that in plasma. Fig. 8 shows the
`distribution patterns in othertissues and significant amount ofcyclocytidine was found during
`the initial 20 to 40 min in pulmonarytissue and intestinal mucosa (300~400 g/g). Spleen and
`cardiac tissues exhibited a notable uptake (100~200 g/g) in the first 20min and a rapid
`uptake (100 s#g/g) also occurred in pancreasand salivary gland. The compound disappeared
`from the tissue progressively in the subsequent period of 80 min. Brain tissues failed to show
`any significant detectable level of cyclocytidine.
`
`65(2)
`
`1974
`
`157
`
`

`

`H. HIRAYAMA, ET AL.
`
`Rat: The metabolites, aracytidine and arauridine, were not found in any tissues and plasma
`of rats after 600 mg/kg of cyclocytidine was given intravenously. As seen in Fig. 9, the maximum
`concentration of cyclocytidine in plasma was 1,000 wg/g during theinitial 80 min. Renal tis-
`sue maintained a high concentration of over 1,000 ug/g of cyclocytidine in the first 40 min,
`which declined slowly in parallel with the plasma concentration. The compound in lung and
`salivary gland increased in the first 20 min and then it disappeared completely during the fol-
`lowing 40 to 100 min. Maximum concentration of 300~500 g/g of cyclocytidine was seen in
`the stomach, intestine, and pancreas immediately after its administration and subsequently
`disappeared within 80 to 100 min. Cyclocytidine was not detected in brain throughoutthis
`experimental period.
`
`Plasma
`
`»
`
`Liver
`
`Kidney
`
`Submaxillary
`gland
`
`Heart
`
`1090
`
`500
`
`b
`
`Lung
`
`i
`
`0
`
`40 80
`
`
`50
`
`
`
`Concentrationofcyclocytidine(g/gtissue)
`
`100
`
`50
`
`10
`
`1000
`
`500
`
`100
`
`0
`
`40
`
`80
`
`0
`
`40
`
`80
`
`1 L
`40
`80
`
`Q
`
`Time (min)
`
`G0
`
`40
`
`80
`
`0
`
`40
`
`80
`
`Stomach
`
`Spleen
`
`Pancreas
`
`Large
`intestine
`
`Small
`intestine
`
`|
`
`10
`
`0
`
`I
`40
`
`i
`80
`
`Jose
`40
`80
`
`0
`
`0
`
`40
`
`80
`
`0
`
`!
`40
`
`|
`80
`
`LL
`80
`
`0
`
`40
`
`Time (min)
`
`Fig. 9, Distribution of cyclocytidine in rat tissues after intravenous administration of
`600 mg/kg of cyclocytidine
`
`Urinary Excretion of Cyclocytidine, Aracytidine, and Arauridine in Dogs and Monkeys Monkeys: Table I
`shows the urinary excretion pattern after the administration of 100 mg/kg of cyclocytidine
`in monkeys. The amount of excreted material was 40.9~64.5% as cyclocytidine, 0~0.3%
`as aracytidine, and 1.9~2.0% as arauridine during 4 hr after the injection.Moreovecr, 7.1~
`9.3% was excreted as cyclocytidine, 0O~1.3% as aracytidine, and 1.8~1.9% as arauridine
`within the following 24 hr, and they were not detected after that time. On the other hand,
`the injected aracytidine was excreted very rapidly as arauridine which was the sole metabolite
`detected at the rate of 34.7% and 13.2% in 4-hr and 8-hr urine, respectively (Table I).
`
`158
`
`GANN
`
`

`

`DISTRIBUTION AND EXCRETION OF CYCLOCYTIDINE
`
`Table I. Excretion Ratio of Cyclocytidine and Its Metabolites in Urine of Macaca
`Monkeys after Intravenous Administration of 100 mg/kg of Cyclocytidine
`
`Case 1 (female, 2.8 kg)
`Case 2 (female, 3.4 kg)
`Time
`
`(hr) Cyclocytidine
`Aracytidine
`Arauridine
`-Cyclocytidine Aracytidine Arauridine
`
`(%)
`(%)
`(%)}
`(%)
`(%)
`(%)
`64.5
`0
`1.9
`40.9
`0.3
`2.0
`4
`—
`_
`— :
`3.4
`0.3
`14
`8
`9.3
`0
`1.9
`3.7
`1.0
`0.4
`24
`48
`0
`0
`0
`0
`0
`0
`
`73.8
`0
`3.8
`48.0
`1.6
`3.8
`
`77.6
`53.4
`
`
`Total
`
`In urine of dogs collected for 56 hr after the
`Dogs:
`intravenous administration of 100 mg/kg of cyclocyti-
`dine, about 80% was excreted, 65% as clcyocytidine,
`15% as aracytidine, and 1.5% as arauridine (Table
`III). In urine of dogs administered with aracytidine,
`24.2% was excreted as
`aracytidine and 5% as
`arauridine (Table IV).
`These results indicated that in macaca monkeys
`and. dogs, cyclocytidine was excreted in urine mainly
`within 24 hr after the administration at 67 and 74%,
`as cyclocytidine, 0 and 18% as aracytidine, and 2 and
`4% as arauridine, respectively. ‘There was a difference
`between these two species after aracytidine administra-
`tion, and administered aracytidine was excreted 48%
`as arauridine in monkeys, and 6% as arauridine and
`24% as aracytidine in dogs.
`*
`
`Percent of dose
`
`Table II. Excretion Ratio of Aracyt-
`idine and Arauridine in Urine of
`Macaca Monkey after
`Intravenous
`Administration of 100 mg/kg
`of
`Aracytidine
`
`Time
`Case I (female, 3.2 kg)
`(br) Aracytidine Arauridine
`(%)
`(%)
`0
`34.7
`4
`0
`13.2
`8
`24
`0
`0
`48
`0
`0
`
`
`0
`
`47.9
`
`Total
`47.9
`
`
`50
`
`100
`
`i —S
`
`|]
`
`0
`
`T o
`
`o]
`
`Cyclocytidine, 100 mg/kg,i-v.
`
`50100 0
`
`
`
`| Arauridine
`
`Aracytidine
`
`Cyclocytidine
`
`Aracytidine, 100 mg/kg,i.v.
`
` oo r T rT
`
`| Arauridine
`
`Aracytidine
`
`
`
`Dog
`
`Monkey
`Fig. 10. Cumulative urinary exerction in dogs and monkeys as percentage of dose at 56 hr
`after single intravenous administration of 100 mg/kg of cyclocytidine
`
`65(2)
`
`1974
`
`159
`
`

`

`H, HIRAYAMA, ET AL.
`
`Table IIT. Excretion Ratio of Cyclocytidine and Its Metabolites in Urine of Beagle
`Dogs after Intravenous Administration of 100 mg/kg of Cyclocytidine
`
`Fine
`Case 1 (female, 10 kg)
`Case 2 (female, 10.5 kg)
`
`(hr) Cyclocytidine
`Aracytidine
`Arauridine
`Cyclocytidine Aracytidine Arauridine
`(%)
`(%)
`(%)
`(%)
`(%)
`(%)
`—_
`—_
`—
`47.1
`3.3
`0.5
`—
`—_
`a
`17,2
`4.0
`1.0
`59.7
`13.3
`15
`2.9
`2.7
`0
`0
`0
`0
`
`4
`10
`24
`32
`48
`54
`
`2.3 °
`1.8
`
`3.7
`0
`1.8
`0
`
`18.8
`63.8
`Total
`1.5
`67.2
`10.0
`1.5
`
`84.1 78.7
`
`Table IV. Excretion Ratio of Aracytidine and Arauridine in Urine of Beagle
`Dogs after Intravenous Administration of 100 mg/kg of Aracytidine
`Tt
`Case 1 (female, 11.2 kg)
`Case 2 (female, 8.7 kg)
`
`Aracytidine
`Arauridine
`Aracytidine
`Arauridine
`(hr)
`
`
`4
`6
`24
`32
`48
`56
`
`(%)
`13.2
`3.3
`1.7
`21
`3.2
`0.7
`
`(%)
`2.8
`0.7
`0.7
`0.2
`0.3
`0.1
`
`(%)
`22,3
`1.9
`0
`0
`
`(%)
`4.5
`1.0
`0.5
`0.3
`
`
`Total
`24.2
`4.8
`24.2
`6.3
`
`29.0 30.5
`
`Excretion of Cyclocytidine and Aracytidine in Feces of Monkeys Cyciocytidine, aracytidine, and ara-
`uridine were not detected in the feces evacuated within 72 hr after
`the intravenous ad-
`ministration of 100 mg/kg of cyclocytidine or aracytidine.
`
`Discusston
`Present experiments were carried out in monkeys, dogs, and rats to investigate the species
`difference in distribution and metabolism of cyclocytidine in plasma andtissues, and ofits
`excretion in urine and stool.
`After the administration of cyclocytidine, neither aracytidine nor arauridine was detected
`in the circulating plasma and only intact cyclocytidine was detected in monkeys and dogs.
`Cyclocytidine levels in plasma did not differ significantly between these two animal species
`and the biological half-life was 22 min, while it was 37 min in rats, which suggested that
`cyclocytidine is resistant either to cytidine deaminase or other metabolizing enzymes in situ.
`On the other hand, the biological half-life of aracytidine was found to be 47 and 80 min in
`dogs and rats, respectively, whereasit was less than 5 min in monkeys, because ofits metabolism
`to arauridine by cytidine deaminase activity.’:** 74) These results indicated that cyclocytidine
`was scarcely affected by cytidine deaminase in plasma and confirm the results of in vitro ex-
`periments previously reported by Hoshie¢ al.!”) As for metabolites of cyclocytidine in tissues,
`neither aracytidine nor arauridine was detected in liver, kidney, lung,salivary gland, or gastro-
`intestinal mucosa. Cyclocytidine in these tissues diminished in parallel with its reduction in
`plasma. Ofconsiderable interest was the fact that the compounddistributed in high concentra-
`160
`.
`GANN
`
`

`

`DISTRIBUTION AND EXCRETION OF CYCLOCYTIDINE
`
`tion in the salivary gland andgastrointestine. This agreed with our previous findings that cy-
`clocytidine acted pharmacologically to cause hypersalivation and mild inhibitory action on the
`spontaneous gastrointestinal motility.”These data might suggest the clinical applicability
`of cyclocytidine as a chemotherapeutic agent against tumorsof salivary gland and gastrointes-
`tine. Meanwhile, no evidence was obtained for the distribution of cyclocytidine in brain tis-
`sues, with the lack of significant pharmacological effect of the compound on the central
`nervous system.® 2)
`As summarized in Fig. 10, about 65% of intact cyclocytidine was excreted in urine within
`56 hr in monkeys and about 65% within 56 hr in dogs,
`though the deaminase activity in
`plasma andtissues is different in the two animalspecies. A slight excretion of arauridine, which
`is a deaminated metabolite through aracytidine, was greater in monkeys than in dogs. On
`the other hand, in the administration of aracytidine, it was excreted 24.2% as aracytidine
`and 4.8~6.3% as arauridine within 56 hr in dogs, but it was not detected as aracytidine and
`47.9%, of it was excreted as arauridine within 8 hr in monkeys. These data indicated that most
`of administered cyclocytidine was not metabolized rapidly to arauridine through aracytidine.
`It might account for the lower cumulative toxicity of cyclocytidine than that of aracytidine
`in dogs and monkeys.* The distribution and elimination of cylocytidine in mice and macaca
`monkeys have been examined using /‘C- or *H-labeled compounds, andits results will be
`published elsewhere.
`
`(Received November 7, 1973)
`
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`1974.
`
`161
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`