- Email: [email protected]
Human pharmacokinetics of WR-2721
036C-3016/86 $3.00 + .Ofl Copyight 0 1986 Petgamon Journals Ltd.
hf. J. Radiarion OncdogyBio/. Phys.. Vol. 12, pp. 1501-1504 Printed in the U.S.A. All rights reserved.
??Session VII
HUMAN
PHARMACOKINETICS
OF WR-2721
LESLIE M. SHAW, PH.D., ANDREW T. TURRISI, M.D., DONNA J. GLOVER, M.D., HEATHER S. BONNER, B.S., A. LORRAINE NORFLEET, B.S., CLARE WEILER, R.N. AND MORTON M. KLIGERMAN, M.D. Departments
of Pathology and Laboratory Medicine, Radiation Therapy, Medicine and the Cancer Center of the University of Pennsylvania, Philadelphia, PA 19 104
The pharmacohinetic properties of WR2721 were investigated in 13 cancer patients given a 150 mg/M* intravenous bolus dose of the drug. An average plasma clearance value of 2.17 L/min was obtained. Very little of the drug or the two metabofites, WR1065 and WR33278, were excreted in urine obtained after the blood collection schedule. Plasma concentrations of WR2721 decreased by 94% within 6 minutes of drug administration. The mean value of 6.44 L obtained for the steady-state volume of distribution indicates that the extravascular space occupied by the drug is small. These observations suggest that in human cancer patients, WR2721 is rapidly taken up by tissues and converted to metabolites. WR2721, WR1065, WR33278, Pharmacohinetics, Human, Cancer, Patients.
INTRODUCTION
nique, recoveries of WR-1065 and WR-33278 from blood, average 104 and 98%, respectively. Recoveries of WR1065 and WR-33278 from mouse liver are 98 and 95%, respectively. I3 This report presents the pharmacokinetics of WR272 1 using the newly developed electrochemical HPLC methods in 13 patients given a 150 mg/M* intravenous bolus dose of WR272 1.
WR2721 is undergoing clinical trials as a radio- and chemoprotective agent and as a hypocalcemic agent in the treatment of patients with hypercalcemia associated with malignancy. 3,4s*7Until recently, there were no reliable methods for measurement of the parent drug and its metabolites, WR 1065, the free sulthydryl metabolite, and WR33278, the symmetrical disulfide of WR1065. We developed electrochemical high pressure liquid chromatography (HPLC) methods for the measurement of WR-2721,” WR-106512 and WR-3327813 in blood and tissues. Similar to other sulfhydryl and disulfide compounds, WR1065 and WR33278 decrease rapidly in concentration when added to bloodI or plasma.2 This rapid fall in drug concentration is presumably caused by the formation of mixed disulfides with other sullhydryl-contaming substances. Based on the kinetics of WR2721 hydrolysis” and the stability of sulthydryl and disulfide compounds in acidic solution,’ we developed a sample preparation technique to quantitate WR1065 and WR33278 in biological fluids and tissues. With this tech-
The electrochemical HPLC method used to measure WR-272 1 concentration in patient’s plasma, prepared from ice-cold blood collected in EDTA blood collection tubes, has been described elsewhere.’ ’WR- 1065 and WR33278 concentrations were determined in whole blood collected in EDTA blood tubes* and immediately processed at 0°C as described elsewhere.12 Urine specimens were stored frozen at -70°C until analyzed for all three compounds. Pharmacokinetic modelling and parameter estimations were determined using the DRUGMODEL method of Holford.6
Presented at the Chemical Modifiers of Cancer Treatment Conference, Clearwater, FL, 20-24 October 1985. Reprint requests to: Leslie M. Shaw, Ph.D., Department of Pathology Laboratory Medicine, Hospital of the University of Pennsylvania, Philadelphia, PA 19 104. Acknowledgements-This work was supported in part by National Cancer Institute grants CA-30100, CA-l,6520, CA-40522
and CA-07 153. Dr. Glover is the recipient of an American Cancer Society Junior Faculty Clinical Fellowship Award. We thank Drs. John Glick and John Gambertoglio for helpful discussions of these studies. Accepted for publication 25 February 1986. * EDTA Vacutainer tubes, Becton Dickinson, Rutherford, NJ.
METHODS
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AND MATERIALS
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I. J. Radiation Oncology 0 Biology 0 Physics
August 1986, Volume 12, Number 8
Table 1. Single bolus dose (150 mg/M*) WR-272 1 pharmacokinetic Patient 1
2 3 4 5 6* 7 8 9* 10 11 12 13
Ht (cm)
Cancer Lung-oat
173.8 152.5 160.0 165.0 162.0 162.0 177.0 178.0 152.0 160.0 182.0 165.0 180.3
cell
Breast-bone mets Lung Bladder Pancreas Rectum Parathyroid Colon Parathyroid Prostate Lung Chest wall nodules Prostate
88.2 65.5 70.0 58.4 59.0 54.3 70.9 70.4 67.0 56.4 100.0 74.0 85.9
(Z)
study in cancer patients
V, (L)
Cl (L/min)
Tfa (min)
T48 (min)
2.71 2.14 3.79 32.4 2.14 10.3 0.66 4.59 0.52 4.21 1.32 0.68 8.00
1.54 1.oo 2.56 28.02 3.21 2.33 0.85 2.23 0.69 4.57 1.33 1.48 4.23
0.94 1.25 0.91 0.67 0.39 2.77 0.52 1.05 0.52 0.61 0.58 0.30 0.78
20.8 20.3 3.0 2.7 9.4
7.5 3.3 10.3 4.3
12.8 6.4 4.6 44.7 9.0 10.3 0.77 7.55 0.52 6.08 2.03 1.85 15.4
3.50 (0.90)
2.17 (0.39)
0.88 (0.12)
8.76 (2.03)
6.44 (1.46)
V, (L)
3.8 4.9
* A two compartment model gave the best fit to the pharmacokinetic data for eleven patients. For patients 6 and 9 the best fit was given by a single compartment model. t The parameter values for patient 4 were excluded from the calculated it and SE values since that patient’s V,, Cl and V, values were unusually high in comparison with the respective values for the other 12 patients.
The 13 patients included in this study were drawn from those accessed into the Phase I study of WR-272 1 before radiotherapy and the Phase I/II studies of WR-2721, alkylating agents, and cisplatinum. After administration of a 10 second 150 mg/M2 infusion of WR-2721, blood specimens were obtained at the following times: 0,0.5, 1, 2, 2.5, 3, 4, 6, 8, 12, 15, 20, 30, and 45 minutes. Urine specimens were collected from six of the patients at the completion of the blood collection schedule and stored at -70°C until analyzed.
RESULTS Summarized in Table 1 are the pharmacokinetic parameters for each of the 13 patients. The mean value for V,, the volume of distribution at steady-state, is 6.44 L. This indicates low value for volume of distribution that the unmetabolized drug is largely confined to the intravascular system, probably primarily in plasma, and to a small volume of extravascular space. WR-272 1 is rapidly
cleared from the plasma compartment as indicated by the high average clearance value of 2.17 L/minute. The short average distribution half-life, T$cy, value of 0.88 min, taken together with the observation that < 10% of the drug remains in the plasma compartment 6 min after the bolus injection are further indications of how rapidly WR-272 1 is removed from the plasma of human patients. Pharmacokinetic curves for patients 6, 12,2, and 11 are shown in Figure 1. Selection of the pharmacokinetic model that fits the data best for each patient was based on a comparison of the “goodness of fit” standard deviation (SD) values and the relative standard error (SE) values for V, the central compartment volume of distribution and p the terminal disposition rate constant for the one, two, and three compartment models (Table 2). For example, the WR-2721 concentration data of patients 11 and 12 was fit better by the two compartment model than either the one or three compartment models. This conclusion was drawn from (a) the observed lowest goodness of fit SD for the two compartment model, (b) the lowest SE relative to the re-
Table 2. Statistical basis for model selection Goodness of fit SD Patient
17
2
3
6 9$ 11 12
4.2 4.8 11.1 9.5
3.9 6.8 4.4 1.1
5.0 9.1 2.2
p* +- SE
V,* + SE 1 10.3 0.5 8.85 0.91
f 1.5 + 0.07 +- 3.1 + 0.6
2 8.2 0.5 1.32 0.68
k 2.3 kO.15 !I 0.41 + 0.06
3 8.3 f 3.3 1.61 + 1.9 0.43 f 0.32
1 0.25 1.34 0.37 1.97
zk 0.018 k 0.04 Ik 0.05 + 0.37
2 0.08 0.12 0.21 0.067
* V, is the central compartment volume of distribution; p is the terminal disposition rate constant. t The numbers 1, 2, and 3 refer to the number of compartments in the pharmacokinetic model. $ We were unable to fit the WR-272 1 concentration data from patient 9 to 3 compartment model.
III 0.36 kO.15 * 0.03 zk 0.007
3 0.1
4 0.32 -
0.11 kO.22 0.006 k 0.01
Human pharmacokinetics of WR-272 1 0 L. M. SHAWet al. PATIENT 6
I
2
1000
5
6 8 Time (min)
IO
12
15
PATIENT 12
B 3
4
. IL
100
c
2
IO
E
!
E
s 2
.I
0
2
4
C
6 8 IO 12 I4 Time (min)
16 I8 20
PATIENT 2 1000
1
,I& 0
5
1503
the goodness of fit SD values suggest that the two compartment model is slightly better than the one compartment model. However, the relative SE values for V, and p for the one compartment model are much lower than the respective relative SE values for the two compartment model. Thus, the pharmacokinetic parameters were much better defined by the single compartment model for this patient. Moreover, for both patients 6 and 9, the one compartment best fit line went through the points best (patient 6, Fig. 1A). WR- 1065 concentrations were measured in the blood of patients 11, 12, and 13. Maximal concentrations of 22, 7.2, and 8.4 umol/L were obtained at 1, 1 and 4 minutes, respectively, after administration of the WR-272 1 bolus dose. The concentration of WR-33278 was measured in the blood of patients 12 and 13. Maximal blood concentrations of 11 umol/L and 7 umol/L were obtained in these two patients at 3 minutes and 1 minute after WR272 1 administration, respectively. The excretion of WR2721, WR-1065, and WR-33278 was measured in the urine of patients 6, 8, 10, 11, 12, and 13 obtained after the blood collection schedule. These results are summarized in Table 3. Very little of WR-2721 or the two metabolites were found in the urine. The mean percent urinary excretion of WR-2721, WR-1065, and WR-33278 were 0.69,2.64, and 2.22% of the administered WR-272 1 dose, respectively.
DISCUSSION
IO 15 20 25 30 35 40 45 Time (min)
PATIENT 11
Time (min)
Fig. 1. WR272 1 pharrnacokinetic curves for 4 patients. Each point is the average of duplicate WR2721 concentrations. The lines are the best-fit lines determined by nonlinear least squares analysis.6 spective value of V, and p for the two compartment
model, and (c) the fact that on visual inspection, the two compartment model best fit line goes through the points better than the line generated by the other two models (patient 12, Fig. IB). We were able to draw the same conclusion for nine additional patients. However, for patients 6 and 9 the best fit was obtained with a one compartment model. For patient 9 the one compartment model goodness of fit SD value was lowest, as were the SE values relative to the respective V, and @parameter values. For patient 6
This pharmacokinetic study shows that WR-2721 is cleared rapidly from patients’ plasma after administration of a 150 mg/M’ bolus dose. Based on inspection of each patient’s pharmacokinetic curves, the distribution (a) phase of WR-272 l’s removal from plasma predominates and is complete within 6 min after drug administration. During this time period plasma WR-272 1 concentrations decreased by 94%. The elimination (p) phase of the pharmacokinetic curves is thus much less important and, in fact, not present in two of the patients. Renal excretion of WR-2721 and two metabolites, WR-1065 and WR33278, during the time of observation was low averaging 0.69%, 2.64%, and 2.22% of the administered WR-272 1 dose, respectively. The latter finding taken together with (a) the observed rapid plasma clearance of WR-272 1, (b) the minimal elimination phase and, (c) the small steady state volume of distribution suggest that the drug exits the bloodstream rapidly and enters normal tissues where it presumably exerts its protective effects and is rapidly converted to metabolites. These observations are consistent with the data of Utley, et al. I4 showing that WR- 1065 appears rapidly in mouse tissues after WR-2721 administration and that mouse tissue concentrations of WR2721 are generally much lower than the corresponding WR-1065 values after WR-2721 administration (L.M. Shaw, unpublished data, June, 1985).
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I. J. Radiation Oncology 0 Biology0 Physics
August 1986, Volume 12, Number 8
Table 3. Urinary excretion of WR-272 1, WR-1065 and WR-33278 WR-272 1
Urinary excretion WR-1065
Patient 6 8 10 11 12 13
WR-272 1 dose (umoles)
(umoles)
1,092 1,307 1,106 1,540 1,260 1,470
15.6 7.34 7.87 5.73 2.96 12.1 (&
(umoles)
(%) 1.43 0.56 0.71 0.37 0.23 0.82
106 21.9 9.14 45.4 3.12 6.32
(%) 9.72 1.67 0.83 2.95 0.25 0.43 2.64 (1.18)
0.69 (0.31)
The clearance, central compartment volume of distribution and the steady-state volume of distribution values obtained for patient 4 were 12.9, 9.3 and 6.9-fold higher than the respective values for these parameters for the other patients. This patient was noted, at the time of the study, to have a very high leukocyte cell count of 40,400/ uL. Leukocytes are known to contain considerable alkaline phosphatase activity.8 This fact, taken together with the observation that alkaline phosphatase catalyzes the hydrolysis of WR-272 1 to produce WR- 1065,9,’’suggests that the patient’s high clearance value might be due to leukocyte-mediated WR-272 1 hydrolysis. This patient’s
WR-33278 @moles) 87.4 28.1 15.0 7.40 5.88 13.1
(%) 8.0 2.15 1.36 0.48 0.47 0.89 2.22 (0.99)
central compartment volume of distribution value (32.4L) and steady state volume of distribution (44.7L) were much higher than the other patients. It is interesting to consider WR-272 I’s pharmacokinetic behavior in light of the hypothesis that alkaline phosphatase is responsible for the catalytic hydrolysis of WR-272 1 to produce WR-1065. Because one prominant location of alkaline phosphatase in many tissues is in the plasma membrane of capillary and arteriolar endothelial cells, WR-272 1 could be hydrolyzed at the endothelial surface to produce WR- 1065 before passage out of the bloodstream into tissues.
REFERENCES 1. Akerboom, T.P.M., Sies, H.: Assay of glutathione, glutathione disulfide, and ghttathione mixed disulfides in biological samples. In Methods in Enzymology, Vol. 77, Jakoby, W.B. (Ed.). NY, Acad. Press. 1981, pp. 373-382. 2. Fahey, R.C., Newton, G.L.: Measurements of WR2721, WR1065, and WR33278 in plasma. Int. J Radiat. Oncol. Biol. Phys. 11: 1193-l 197, 1985. 3. Glick, J.H., Glover, D., Weiler, C., NorfIeet, L., Yuhas, J., Khgerman, M.M.: Phase I controlled trials of WR272 1 and cyclophosphamide. Int. J. Radiat. Oncol. Biol. Phys. 10: 1777-1780, 1984. 4. Glover, D., Glick, J.H., Weiler, C., Yuhas, J., Kligerman, M.M.: Phase I trials of WR2721 and cis-platinum. Znt. J Radiat. Oncol. Biol. Phys. 10: 1781-1784, 1984. 5. Glover, D.J., Shaw, L.M., Glick, J.H., Slatopulsky, E., Weiler, C., Attie, M., Goldfarb, S.: Treatment of hypercalcemia in parathyroid cancer with WR272 1, S-Z(3-aminopropylamino)ethylphosphorothioate: a unique hypocalcemic agent and inhibitor of parathyroid hormone secretion. Ann. Intern. Med. 103: 55-57, 1985. 6. Holford, N.H.G.: DRUGMODEL. In Public Procedures Notebook, (Suppl. l), Perry, H.M. (Ed.). Cambridge, MA, Bolt, Beranek and Newman Inc., 1982. 7. Kligerman, M.M., Glover, D.J., Turrisi, A.T., Nor&et, A.L., Yuhas, J.M., Goia, L.R., Simone, C., Glick, J.H., Goodman, R.L.: Toxicity of WR272 1 administered in single and mul-
8. 9.
10.
11.
12.
13.
14.
tiple doses. Int. J. Radiat. Oncol. Biol. Phys. 10: 1773-1776, 1984. McComb, R.B., Bowers, G.N., Posen, S.: Alkaline Phosphatase, NY, Plenum Press. 1979, pp. 556-557. Mori, T., Nikaido, O., Sugahara, T.: Dephosphorylation of WR2721 with mouse tissue homogenates. Int. J. Radiat. Oncol. Biol. Phys. 10: 1529-1531, 1984. Risley, J.M., Van Etten, R.L., Shaw, L.M., Bonner, H.S.: Hydrolysis of S-2-(3-aminopropylamino)ethylphosphorothioate (WR2721). Biochem. Pharmacol, 35: 1453-1458, 1986. Shaw, L.M., Bonner, H., Turrisi, A., Norfleet, A.L., Glover, D.J.: A liquid chromatographic electrochemical assay for S-2-(3-aminopropylamino)ethylphosphorothioate (WR2721) in human plasma. J. Liq. Chromatography 1: 2447-2465, 1984. Shaw, L.M., Bonner, H., Turrisi, A., NorfIeet, A.L., Kliget-man, M.M.: Measurement of S-2-(3-aminopropylamino)ethanethiol (WR1065) in blood and tissues. J. Liq. Chromatography 9: 845-859, 1986. Shaw, L.M., Bonner, H.S.: Detection and measurement of the disulfide WR-33278 [NHz(CH&NHCH2CH$S-12 in blood and tissues. J. Liq. Chromatog. (In press). Utley, J.F., Seaver, N., Newton, G.L., Fahey, R.C.: Pharmacokinetics of WR1065 in mouse tissue following treatment with WR2721. Int. J. Radiat. Oncol. Biol. Phys. 10: 1525-1528, 1984.
hf. J. Radiarion OncdogyBio/. Phys.. Vol. 12, pp. 1501-1504 Printed in the U.S.A. All rights reserved.
??Session VII
HUMAN
PHARMACOKINETICS
OF WR-2721
LESLIE M. SHAW, PH.D., ANDREW T. TURRISI, M.D., DONNA J. GLOVER, M.D., HEATHER S. BONNER, B.S., A. LORRAINE NORFLEET, B.S., CLARE WEILER, R.N. AND MORTON M. KLIGERMAN, M.D. Departments
of Pathology and Laboratory Medicine, Radiation Therapy, Medicine and the Cancer Center of the University of Pennsylvania, Philadelphia, PA 19 104
The pharmacohinetic properties of WR2721 were investigated in 13 cancer patients given a 150 mg/M* intravenous bolus dose of the drug. An average plasma clearance value of 2.17 L/min was obtained. Very little of the drug or the two metabofites, WR1065 and WR33278, were excreted in urine obtained after the blood collection schedule. Plasma concentrations of WR2721 decreased by 94% within 6 minutes of drug administration. The mean value of 6.44 L obtained for the steady-state volume of distribution indicates that the extravascular space occupied by the drug is small. These observations suggest that in human cancer patients, WR2721 is rapidly taken up by tissues and converted to metabolites. WR2721, WR1065, WR33278, Pharmacohinetics, Human, Cancer, Patients.
INTRODUCTION
nique, recoveries of WR-1065 and WR-33278 from blood, average 104 and 98%, respectively. Recoveries of WR1065 and WR-33278 from mouse liver are 98 and 95%, respectively. I3 This report presents the pharmacokinetics of WR272 1 using the newly developed electrochemical HPLC methods in 13 patients given a 150 mg/M* intravenous bolus dose of WR272 1.
WR2721 is undergoing clinical trials as a radio- and chemoprotective agent and as a hypocalcemic agent in the treatment of patients with hypercalcemia associated with malignancy. 3,4s*7Until recently, there were no reliable methods for measurement of the parent drug and its metabolites, WR 1065, the free sulthydryl metabolite, and WR33278, the symmetrical disulfide of WR1065. We developed electrochemical high pressure liquid chromatography (HPLC) methods for the measurement of WR-2721,” WR-106512 and WR-3327813 in blood and tissues. Similar to other sulfhydryl and disulfide compounds, WR1065 and WR33278 decrease rapidly in concentration when added to bloodI or plasma.2 This rapid fall in drug concentration is presumably caused by the formation of mixed disulfides with other sullhydryl-contaming substances. Based on the kinetics of WR2721 hydrolysis” and the stability of sulthydryl and disulfide compounds in acidic solution,’ we developed a sample preparation technique to quantitate WR1065 and WR33278 in biological fluids and tissues. With this tech-
The electrochemical HPLC method used to measure WR-272 1 concentration in patient’s plasma, prepared from ice-cold blood collected in EDTA blood collection tubes, has been described elsewhere.’ ’WR- 1065 and WR33278 concentrations were determined in whole blood collected in EDTA blood tubes* and immediately processed at 0°C as described elsewhere.12 Urine specimens were stored frozen at -70°C until analyzed for all three compounds. Pharmacokinetic modelling and parameter estimations were determined using the DRUGMODEL method of Holford.6
Presented at the Chemical Modifiers of Cancer Treatment Conference, Clearwater, FL, 20-24 October 1985. Reprint requests to: Leslie M. Shaw, Ph.D., Department of Pathology Laboratory Medicine, Hospital of the University of Pennsylvania, Philadelphia, PA 19 104. Acknowledgements-This work was supported in part by National Cancer Institute grants CA-30100, CA-l,6520, CA-40522
and CA-07 153. Dr. Glover is the recipient of an American Cancer Society Junior Faculty Clinical Fellowship Award. We thank Drs. John Glick and John Gambertoglio for helpful discussions of these studies. Accepted for publication 25 February 1986. * EDTA Vacutainer tubes, Becton Dickinson, Rutherford, NJ.
METHODS
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AND MATERIALS
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I. J. Radiation Oncology 0 Biology 0 Physics
August 1986, Volume 12, Number 8
Table 1. Single bolus dose (150 mg/M*) WR-272 1 pharmacokinetic Patient 1
2 3 4 5 6* 7 8 9* 10 11 12 13
Ht (cm)
Cancer Lung-oat
173.8 152.5 160.0 165.0 162.0 162.0 177.0 178.0 152.0 160.0 182.0 165.0 180.3
cell
Breast-bone mets Lung Bladder Pancreas Rectum Parathyroid Colon Parathyroid Prostate Lung Chest wall nodules Prostate
88.2 65.5 70.0 58.4 59.0 54.3 70.9 70.4 67.0 56.4 100.0 74.0 85.9
(Z)
study in cancer patients
V, (L)
Cl (L/min)
Tfa (min)
T48 (min)
2.71 2.14 3.79 32.4 2.14 10.3 0.66 4.59 0.52 4.21 1.32 0.68 8.00
1.54 1.oo 2.56 28.02 3.21 2.33 0.85 2.23 0.69 4.57 1.33 1.48 4.23
0.94 1.25 0.91 0.67 0.39 2.77 0.52 1.05 0.52 0.61 0.58 0.30 0.78
20.8 20.3 3.0 2.7 9.4
7.5 3.3 10.3 4.3
12.8 6.4 4.6 44.7 9.0 10.3 0.77 7.55 0.52 6.08 2.03 1.85 15.4
3.50 (0.90)
2.17 (0.39)
0.88 (0.12)
8.76 (2.03)
6.44 (1.46)
V, (L)
3.8 4.9
* A two compartment model gave the best fit to the pharmacokinetic data for eleven patients. For patients 6 and 9 the best fit was given by a single compartment model. t The parameter values for patient 4 were excluded from the calculated it and SE values since that patient’s V,, Cl and V, values were unusually high in comparison with the respective values for the other 12 patients.
The 13 patients included in this study were drawn from those accessed into the Phase I study of WR-272 1 before radiotherapy and the Phase I/II studies of WR-2721, alkylating agents, and cisplatinum. After administration of a 10 second 150 mg/M2 infusion of WR-2721, blood specimens were obtained at the following times: 0,0.5, 1, 2, 2.5, 3, 4, 6, 8, 12, 15, 20, 30, and 45 minutes. Urine specimens were collected from six of the patients at the completion of the blood collection schedule and stored at -70°C until analyzed.
RESULTS Summarized in Table 1 are the pharmacokinetic parameters for each of the 13 patients. The mean value for V,, the volume of distribution at steady-state, is 6.44 L. This indicates low value for volume of distribution that the unmetabolized drug is largely confined to the intravascular system, probably primarily in plasma, and to a small volume of extravascular space. WR-272 1 is rapidly
cleared from the plasma compartment as indicated by the high average clearance value of 2.17 L/minute. The short average distribution half-life, T$cy, value of 0.88 min, taken together with the observation that < 10% of the drug remains in the plasma compartment 6 min after the bolus injection are further indications of how rapidly WR-272 1 is removed from the plasma of human patients. Pharmacokinetic curves for patients 6, 12,2, and 11 are shown in Figure 1. Selection of the pharmacokinetic model that fits the data best for each patient was based on a comparison of the “goodness of fit” standard deviation (SD) values and the relative standard error (SE) values for V, the central compartment volume of distribution and p the terminal disposition rate constant for the one, two, and three compartment models (Table 2). For example, the WR-2721 concentration data of patients 11 and 12 was fit better by the two compartment model than either the one or three compartment models. This conclusion was drawn from (a) the observed lowest goodness of fit SD for the two compartment model, (b) the lowest SE relative to the re-
Table 2. Statistical basis for model selection Goodness of fit SD Patient
17
2
3
6 9$ 11 12
4.2 4.8 11.1 9.5
3.9 6.8 4.4 1.1
5.0 9.1 2.2
p* +- SE
V,* + SE 1 10.3 0.5 8.85 0.91
f 1.5 + 0.07 +- 3.1 + 0.6
2 8.2 0.5 1.32 0.68
k 2.3 kO.15 !I 0.41 + 0.06
3 8.3 f 3.3 1.61 + 1.9 0.43 f 0.32
1 0.25 1.34 0.37 1.97
zk 0.018 k 0.04 Ik 0.05 + 0.37
2 0.08 0.12 0.21 0.067
* V, is the central compartment volume of distribution; p is the terminal disposition rate constant. t The numbers 1, 2, and 3 refer to the number of compartments in the pharmacokinetic model. $ We were unable to fit the WR-272 1 concentration data from patient 9 to 3 compartment model.
III 0.36 kO.15 * 0.03 zk 0.007
3 0.1
4 0.32 -
0.11 kO.22 0.006 k 0.01
Human pharmacokinetics of WR-272 1 0 L. M. SHAWet al. PATIENT 6
I
2
1000
5
6 8 Time (min)
IO
12
15
PATIENT 12
B 3
4
. IL
100
c
2
IO
E
!
E
s 2
.I
0
2
4
C
6 8 IO 12 I4 Time (min)
16 I8 20
PATIENT 2 1000
1
,I& 0
5
1503
the goodness of fit SD values suggest that the two compartment model is slightly better than the one compartment model. However, the relative SE values for V, and p for the one compartment model are much lower than the respective relative SE values for the two compartment model. Thus, the pharmacokinetic parameters were much better defined by the single compartment model for this patient. Moreover, for both patients 6 and 9, the one compartment best fit line went through the points best (patient 6, Fig. 1A). WR- 1065 concentrations were measured in the blood of patients 11, 12, and 13. Maximal concentrations of 22, 7.2, and 8.4 umol/L were obtained at 1, 1 and 4 minutes, respectively, after administration of the WR-272 1 bolus dose. The concentration of WR-33278 was measured in the blood of patients 12 and 13. Maximal blood concentrations of 11 umol/L and 7 umol/L were obtained in these two patients at 3 minutes and 1 minute after WR272 1 administration, respectively. The excretion of WR2721, WR-1065, and WR-33278 was measured in the urine of patients 6, 8, 10, 11, 12, and 13 obtained after the blood collection schedule. These results are summarized in Table 3. Very little of WR-2721 or the two metabolites were found in the urine. The mean percent urinary excretion of WR-2721, WR-1065, and WR-33278 were 0.69,2.64, and 2.22% of the administered WR-272 1 dose, respectively.
DISCUSSION
IO 15 20 25 30 35 40 45 Time (min)
PATIENT 11
Time (min)
Fig. 1. WR272 1 pharrnacokinetic curves for 4 patients. Each point is the average of duplicate WR2721 concentrations. The lines are the best-fit lines determined by nonlinear least squares analysis.6 spective value of V, and p for the two compartment
model, and (c) the fact that on visual inspection, the two compartment model best fit line goes through the points better than the line generated by the other two models (patient 12, Fig. IB). We were able to draw the same conclusion for nine additional patients. However, for patients 6 and 9 the best fit was obtained with a one compartment model. For patient 9 the one compartment model goodness of fit SD value was lowest, as were the SE values relative to the respective V, and @parameter values. For patient 6
This pharmacokinetic study shows that WR-2721 is cleared rapidly from patients’ plasma after administration of a 150 mg/M’ bolus dose. Based on inspection of each patient’s pharmacokinetic curves, the distribution (a) phase of WR-272 l’s removal from plasma predominates and is complete within 6 min after drug administration. During this time period plasma WR-272 1 concentrations decreased by 94%. The elimination (p) phase of the pharmacokinetic curves is thus much less important and, in fact, not present in two of the patients. Renal excretion of WR-2721 and two metabolites, WR-1065 and WR33278, during the time of observation was low averaging 0.69%, 2.64%, and 2.22% of the administered WR-272 1 dose, respectively. The latter finding taken together with (a) the observed rapid plasma clearance of WR-272 1, (b) the minimal elimination phase and, (c) the small steady state volume of distribution suggest that the drug exits the bloodstream rapidly and enters normal tissues where it presumably exerts its protective effects and is rapidly converted to metabolites. These observations are consistent with the data of Utley, et al. I4 showing that WR- 1065 appears rapidly in mouse tissues after WR-2721 administration and that mouse tissue concentrations of WR2721 are generally much lower than the corresponding WR-1065 values after WR-2721 administration (L.M. Shaw, unpublished data, June, 1985).
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I. J. Radiation Oncology 0 Biology0 Physics
August 1986, Volume 12, Number 8
Table 3. Urinary excretion of WR-272 1, WR-1065 and WR-33278 WR-272 1
Urinary excretion WR-1065
Patient 6 8 10 11 12 13
WR-272 1 dose (umoles)
(umoles)
1,092 1,307 1,106 1,540 1,260 1,470
15.6 7.34 7.87 5.73 2.96 12.1 (&
(umoles)
(%) 1.43 0.56 0.71 0.37 0.23 0.82
106 21.9 9.14 45.4 3.12 6.32
(%) 9.72 1.67 0.83 2.95 0.25 0.43 2.64 (1.18)
0.69 (0.31)
The clearance, central compartment volume of distribution and the steady-state volume of distribution values obtained for patient 4 were 12.9, 9.3 and 6.9-fold higher than the respective values for these parameters for the other patients. This patient was noted, at the time of the study, to have a very high leukocyte cell count of 40,400/ uL. Leukocytes are known to contain considerable alkaline phosphatase activity.8 This fact, taken together with the observation that alkaline phosphatase catalyzes the hydrolysis of WR-272 1 to produce WR- 1065,9,’’suggests that the patient’s high clearance value might be due to leukocyte-mediated WR-272 1 hydrolysis. This patient’s
WR-33278 @moles) 87.4 28.1 15.0 7.40 5.88 13.1
(%) 8.0 2.15 1.36 0.48 0.47 0.89 2.22 (0.99)
central compartment volume of distribution value (32.4L) and steady state volume of distribution (44.7L) were much higher than the other patients. It is interesting to consider WR-272 I’s pharmacokinetic behavior in light of the hypothesis that alkaline phosphatase is responsible for the catalytic hydrolysis of WR-272 1 to produce WR-1065. Because one prominant location of alkaline phosphatase in many tissues is in the plasma membrane of capillary and arteriolar endothelial cells, WR-272 1 could be hydrolyzed at the endothelial surface to produce WR- 1065 before passage out of the bloodstream into tissues.
REFERENCES 1. Akerboom, T.P.M., Sies, H.: Assay of glutathione, glutathione disulfide, and ghttathione mixed disulfides in biological samples. In Methods in Enzymology, Vol. 77, Jakoby, W.B. (Ed.). NY, Acad. Press. 1981, pp. 373-382. 2. Fahey, R.C., Newton, G.L.: Measurements of WR2721, WR1065, and WR33278 in plasma. Int. J Radiat. Oncol. Biol. Phys. 11: 1193-l 197, 1985. 3. Glick, J.H., Glover, D., Weiler, C., NorfIeet, L., Yuhas, J., Khgerman, M.M.: Phase I controlled trials of WR272 1 and cyclophosphamide. Int. J. Radiat. Oncol. Biol. Phys. 10: 1777-1780, 1984. 4. Glover, D., Glick, J.H., Weiler, C., Yuhas, J., Kligerman, M.M.: Phase I trials of WR2721 and cis-platinum. Znt. J Radiat. Oncol. Biol. Phys. 10: 1781-1784, 1984. 5. Glover, D.J., Shaw, L.M., Glick, J.H., Slatopulsky, E., Weiler, C., Attie, M., Goldfarb, S.: Treatment of hypercalcemia in parathyroid cancer with WR272 1, S-Z(3-aminopropylamino)ethylphosphorothioate: a unique hypocalcemic agent and inhibitor of parathyroid hormone secretion. Ann. Intern. Med. 103: 55-57, 1985. 6. Holford, N.H.G.: DRUGMODEL. In Public Procedures Notebook, (Suppl. l), Perry, H.M. (Ed.). Cambridge, MA, Bolt, Beranek and Newman Inc., 1982. 7. Kligerman, M.M., Glover, D.J., Turrisi, A.T., Nor&et, A.L., Yuhas, J.M., Goia, L.R., Simone, C., Glick, J.H., Goodman, R.L.: Toxicity of WR272 1 administered in single and mul-
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tiple doses. Int. J. Radiat. Oncol. Biol. Phys. 10: 1773-1776, 1984. McComb, R.B., Bowers, G.N., Posen, S.: Alkaline Phosphatase, NY, Plenum Press. 1979, pp. 556-557. Mori, T., Nikaido, O., Sugahara, T.: Dephosphorylation of WR2721 with mouse tissue homogenates. Int. J. Radiat. Oncol. Biol. Phys. 10: 1529-1531, 1984. Risley, J.M., Van Etten, R.L., Shaw, L.M., Bonner, H.S.: Hydrolysis of S-2-(3-aminopropylamino)ethylphosphorothioate (WR2721). Biochem. Pharmacol, 35: 1453-1458, 1986. Shaw, L.M., Bonner, H., Turrisi, A., Norfleet, A.L., Glover, D.J.: A liquid chromatographic electrochemical assay for S-2-(3-aminopropylamino)ethylphosphorothioate (WR2721) in human plasma. J. Liq. Chromatography 1: 2447-2465, 1984. Shaw, L.M., Bonner, H., Turrisi, A., NorfIeet, A.L., Kliget-man, M.M.: Measurement of S-2-(3-aminopropylamino)ethanethiol (WR1065) in blood and tissues. J. Liq. Chromatography 9: 845-859, 1986. Shaw, L.M., Bonner, H.S.: Detection and measurement of the disulfide WR-33278 [NHz(CH&NHCH2CH$S-12 in blood and tissues. J. Liq. Chromatog. (In press). Utley, J.F., Seaver, N., Newton, G.L., Fahey, R.C.: Pharmacokinetics of WR1065 in mouse tissue following treatment with WR2721. Int. J. Radiat. Oncol. Biol. Phys. 10: 1525-1528, 1984.