Plasma concentration, distribution, metabolism and excretion of ¹²⁵I-KW-2228, a mutant of human granulocyte colony stimulating factor, were studied in rats after single intravenous or subcutaneous administration.
1. After intravenous administration of ¹²⁵I-KW-2228, total radioactivity and trichroloacetic acid(TCA)-insoluble radioactivity in the plasma were eliminated biexponentially. TCA-insoluble radioactivity showed a rapid elimination as compared with total radioactivity. Maximum concentrations of total and TCA-insoluble radioactivity were reached at 2hr after subcutaneous administration. After that, TCA-insoluble radioactivity was eliminated more rapidly than total radioactivity in a case of intravenous administration. The results of SD S-PAGE suggested that most of antibody-bound able radioactivity in the plasma were unchanged KW-2228 in both administration routes.
2. TCA-insoluble radioactivity was distributed to the kidney at the highest concentration, suggesting that the kidney might play the major role in metabolism and elimination of ¹²⁵I-KW-2228. Other tissues showed a difference in the distribution pattern of ¹²⁵I-KW-2228 after intravenous and subcutaneous administrations. In the bone marrow, the target organ of KW-2228, the elimination of radioactivity was slower after subcutaneous administration, which was thought to contribute to higher WBC increasing effect. A high level of radioactivity was observed in the thyroid gland, stomach and skin, which might be related to the ¹²⁵I released from ¹²⁵I-KW-2228.
3. The major excretion route of ¹²⁵I-KW-2228 was urine and there was no difference between administration routes. Most of radioactivity in the urine consisted of low molecular weight metabolites or free ¹²⁵I.

View full abstract

Plasma concentration, distribution, metabolism and excretion of KW-2228 following multiple subcutaneous administrations for 10 days were studied in rats using ¹²⁵I-labelled KW-2228 in rats, and the obtained results were compared with those after single administration.
50μg/kg/day of KW-2228 were given to rats for 9 days and ¹²⁵I-KW-2228 on the 10th day only, and then concentration of radioactivity was determined. C_max, AUC, T_1/2 and Cl_tot calculated from TCA-insoluble radioactivity after multiple administrations did not differ from those obtained following single administration. The highest concentration of radioactivity was found in the kidney, same as observed by single administration.
The distribution and elimination in other tissues, including the target organ, bone marrow, were also similar to those after single administration, indicating no cumulative effect, Most of radioactive substances were, like after single administration, excreted in urine, which were TCA-soluble and a low molecular weight metabolites such as ¹²⁵I.
These results show that none of plasma pharmacokinetics, distribution, metabolism and excretion differ from those obtained after single administration and that the pharmacokinetics of KW-2228 is not affected by multiple subcutaneous administration.

View full abstract

Pharmacokinetics of Marograstim (KW-2228) was studied in rats. Plasma levels of KW-2228 were measured by the enzyme linked immunosorbent assay (ELISA).
1. After intravenous administration of KW-2228 at doses of 5 ?? 150μg/kg to rats, the KW-2228 was biexponentially eliminated from plasma. However, the elimination half-lifa of KW-2228 that was 0.79hr at dose level of 5μg/kg was prolonged to 2.16hr at 150μg/kg, clearly showing dose-dependency. Then it is thought that the saturable metabolic process might play a role in the disappearance of KW-2228. Plasma levels of KW-2228 were fitted to the compartment model with a Michaelis-Menten type of elimination. The Michaelis constant and maximum elimination rate of KW-2228 in rat were calculated to be 2.3ng/ml and 19.27ng/ml/hr, respectively.
2. After a single subcutaneous administration of KW-2228 to rats, plasma level of KW-2228 reached C_max at 1.5 ?? 2.Ohr and was mono-exponentially eliminated. The elimination half-lives of KW-2228 were about 1.5hr at 50 and 150μg/kg. Non-linearities of C_max and AUC versus doses were recognized.
3. After repeated subcutaneous administration of KW-2228 at 50μg/kg/day for 10 days, plasma levels of KW-2228 at 6hr after last administration and elimination half-lives were significantly lower than that of the single administration.
4. Pharmacokinetics of rhG-CSF after intravenous or subcutaneous administration at 50μg/kg was almost equal to that of KW-2228.

View full abstract

Pharmacokinetics and hematopoietic effects of KW-2228 and recombinant human granulocyte colony stimulating factor (rhG-CSF) in monkeys were studied after a single intravenous, a single subcutaneous and repeated subcutaneous administration at a dose of 10μg/kg or 10μg/kg/day.
1. After a single administration of KW-2228, white blood cell (WBC) count in peripheral blood largely increased. WBC reached a maximum level, about 2 times higher than basal level, at 12hr after administration, and returned to control level at 24hr. WBC count was 4 times higher than basal level, at 12hr after a single subcutaneous administration of KW-2228. After repeated administration for 10 days, the WBC showed 6 times higher level than basal one. It was due to the increase of segmented neutrophils. The same effect was also observed after rhG-CSF administration and there was no differences between the effect of KW-2228 and rhG-CSF. Red blood cell and platelet counts were not changed in this experiments.
2. After a single intravenous administration, KW-2228 and rhG-CSF showed biexponential elimination from the plasma. Half-lives of KW-2228 were 0.43±0.09 (α) and 1.34±0.35hr (β), respectively, which were a little longer than those of rhG-CSF, 0.40±0.04(α) and 1.11±0.05hr (β).
3. After a single subcutaneous administration of KW-2228 or rhG-CSF, both plasma levels reached maximum levels of 13.20±3.76, 8.96±2.81ng/ml respectively, at 2hr, and then were eliminated monoexponentially. Plasma levels of KW-2228 were significantly higher (1.5 ?? 2 times) than those of rhG-CSF, especially in the elimination phase. Elimination half-life of KW-2228 was not different from that of rhG-CSF.
4. After repeated subcutaneous administration for 10 days, C_max of KW-2228 was decreased to about 2/5 of that of a single administration and elimination half-life was about 2/3. Also AUC was decreased to 1/4. The same results were obtained after rhG-CSF administration.
No difference was shown between plasma levels of KW-2228 and rhG-CSF after repeated administration.

View full abstract

It is known that SN-38, a main metabolite of the novel camptothecin derivative CPT-11, shows a more potent anti-proliferative effect than CPT-11, in vitro. Therefore, it is presumed that SN-38 greatly influences the antitumor effect of CPT-11. In this study, we examined the generation of SN-38 from CPT-11 by plasma and tissue homogenates from the rat, dog, and man.
1. In the rat, the plasma, followed by the intestine, showed the highest activity in the generation of SN-38, and activity was also detected in the lung, liver, and kidney.
2. In the dog, the liver showed the highest sustained activity, but little activity was detected in the plasma and intestine.
3. In human subjects, almost the same activity was initially detected in the liver and intestine, but only the liver showed sustained activity. Plasma possessed marginal activity.
4. Comparison of the rat, the dog, and man showed remarkable species differences in the activity of the plasma, but not in that of the liver.
5. Among rat liver cell fractions, microsomes showed the highest activity, and the activity was also detected in the mitochondria. However, the activity of lysosomes was low.
6. The microsomal fraction of rat liver and tissue homogenates (liver, intestine, kidney, and lung) prepared from the rat showed almost equal Michaelis constants, rang from 20 to 26μM, for the generation of SN-38.
7. The activity of the human liver homogenate was inhibited by more than 80% by DFP (1 × 10^-4M), an inhibitor of serine esterases such as carboxylesterases and cholinesterases. However, 40% inhibition was induced by physostigmine (1 × 10^-4M), an inhibitor of cholinesterases, but none by PCMB (1 × 10^-4M), an inhibitor of arylesterases.

View full abstract

The renal excretion mechanism of ME1206, an active form of a novel oral cephalosporin antibiotic ME1207, was studied in rats using the renal clearance method and in rabbits and dogs applying the stop-flow analysis method.
Excretion ratio (ER) was 3.64 in rats when ME1206 was administered alone. In contrast, the ER was 0.932 when the tubular secretion was inhibited by iodopyracet administered concomitantly. These results indicate that ME1206 is excreted into urine not only by the glomerular filtration but also by the tubular secretion in rats.
In dogs, the ME1206 stop-flow pattern showed neither secretion nor reabsorption peak when ME1206 was administered with p-aminohippuric acid(PAH) as a marker substance for proximal tubular function. On the other hand, except for PAH, there was a small peak showing the tubular secretion. These results suggest that ME1206 is mainly excreted in dogs by the glomerular filtration with small contribution of the proximal tubular secretion. PAH inhibite d a weak secretion of ME1206 competing with the transport system for organic anions.
In rabbits, there was an obvious secretion peak of ME1206 even in the presence of PAH. This peak disappeared completely by the coadministration of probenecid. Accordingly, ME1206 is extensively secreted by the proximal tubules in addition to the glomerular filtration in rabbits.
In summary, the mechanism of renal excretion of ME1206 differs among animal species. Moreover, it is suggested that the tubular secretion marker in the stop-flow analysis method should be substances which will be secreted by another transport system from that for the test substance.

View full abstract

The absorption, distribution, metabolism and excretion of NZ-105 were studied in male rats after a single (10mg/kg) administration of ¹⁴C-NZ-105.
1. Blood levels reached the maximum of 710.8ng eq./ml at 2hr after administration and decreased with half-life of 1.9hr until 11hr.
The absorption of radioactivity was significantly affected by the presence of food in the gastrointestinal tract.
2. The rates of radioactivity excretion in urine and feces within 120hr and bile within 24hr were 2.0, 93.8, and 60.2% of dose, respectively, demonstrating that the major route of excretion was biliary system.
3. The absorption ratio of radioactivity estimated from the sum of biliary and urinary excretions was calculated to be approximately 62%.
4. The radioactivity was high in the gastrointestinal tract and liver, followed by the adrenals. Radioactivity in each tissue was eliminated rapidly, and at 24hr was very low when compared with the maximum value.
5. The unchanged drug in the plasma accounted for 47.7% of total radioactivity at 2hr after administration, suggesting a lower first-pass effect in comparison with other dihydropyridine Ca channel blockers.
6. In plasma, major metabolites of NZ-105 were N-debenzylated compound (DBZ), N-dephenylated compound (DPH), oxidative deaminated compound (AL), AL-corresponding pyridine compound (ALP), unknown metabolite M-1 and M-25. They accounted for 2.5, 5.6, 3.5, 4.9, 3.8 and 14.4% of plasma total radioactivity, respectively, at 2hr after administration.
7. NZ-105 was metabolized by N-debenzylation, N-dephenylation, oxidative deamination, ester hydrolysis and oxidation of 1, 4-dihydropyridine ring to corresponding pyridine.

View full abstract

Transfer of radioactivities into the fetus and milk after oral administration of ¹⁴C-NZ-105 to pregnant or lactating rats were studied. Absorption, distribution, metabolism and excretion of ¹⁴C-NZ-105 were studied in male rats after repeated oral administration (21 times) at the dose of 10mg, /kg/day.
1. On day 13 and 18 of gestation, the autoradiography revealed that the radioactivity in the fetus was very lower than that in the maternal blood. On day 18 of gestation, the radioactivity in the fetal blood and liver was lower than that in the maternal plasma.
2. Radioactivity level in the milk was similar to that of plasma but it disappeared below detection limit at 48hr after oral administration.
3. Blood levels of radioactivity at 24hr after daily dosing increased with the number of doses. Blood concentration at 24hr after the 21-st dose was 8 times higher than blood concentration at 24hr after the first dosing respectively.
4. After repeated administration, the radioactivities in most of tisuues at 24hr reached the steady state after the 14-th administration.
5. The cumulative excretion of radioactivity in urine and feces accounted for 2.8% and 97.5% of the total dose, respectively, within 120hr after the final administration.
6. The ratio of unchanged drug to its metabolites, measured as a fraction of total radioactivity in the plasma at 2hr after the last dosing was similar to that after the single dose.

View full abstract

Absorption, metabolism and excretion of ¹⁴C-NZ-105 were studied in male dogs after oral (10mg/kg) administration. Serum protein binding was investigated in the rat, dog and human.
1. Blood levels of radioactivity reached a peak level (564ng eq./ml) at 2hr after administration and then decreased with the half-life of 3. 1hr until 12hr.
2. The excretion of radioactivity in urine and feces within 120hr after oral administration was 3.1% and 98.5% of dose, respectively.
3. The in vitro binding to rat, dog and human serum proteins was 98% or more at 200, 600 and 2000ng/ml. That observed in vivo was 85.8 ?? 89.7% at 0.5, 2 and 6hr after oral administration in rats and 38.5 ?? 45.6% at 2, 4 and 8hr after dosing in dogs.
4. The unchanged drug and oxidatively deaminated compound (AL) were mainly detected in the plasma.

View full abstract