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PubMed1992

Phase I trial of thiotepa in combination with recombinant human granulocyte-macrophage colony-stimulating factor.

PURPOSE: The ability of growth factors to stimulate marrow recovery suggests their potential for use in dose intensification of cytotoxic drugs. We performed a phase I study of the alkylating agent thiotepa in combination with granulocyte-macrophage colony-stimulating factor (GM-CSF), with the goal of dose-escalation of thiotepa. Thiotepa was selected based on its capacity for dose escalation to more than 1 g/m2 in the marrow transplantation setting. PATIENTS AND METHODS: The starting dose of thiotepa (75 mg/m2) was the highest dose evaluated in our previous phase I trial. Thirteen patients received 22 courses of thiotepa and GM-CSF. The dose of GM-CSF was 10 micrograms/kg subcutaneously daily in six patients and 5 micrograms/kg in seven patients. RESULTS: Three patients (23%) developed grade 3 to 4 neutropenia on the first course, with a recovery to more than 1000/mm3 in 4.7 days (mean). Recovery was as rapid with the 5 micrograms/kg as it was with the 10 micrograms/kg GM-CSF dose. Thrombocytopenia grade 3 to 4 affected seven of 13 (54%) patients in the first course; counts recovered to more than 50,000/mm3 in a median of 15 days. GM-CSF at either dose did not influence markedly the severity or duration of thrombocytopenia, and did not permit dose escalation of thiotepa. Among the seven patients who received a second cycle of treatment, six of seven experienced grade 3 or 4 thrombocytopenia that lasted a median of 15.5 days. Five had thrombocytopenia that lasted more than 35 days after one to three cycles of treatment. Plasma concentrations of thiotepa and tepa were measured by gas chromatography in eight patients. The plasma elimination of thiotepa fit a two-compartment open model with a harmonic mean terminal half-life of 2.44 hours. The mean total body clearance was 217.9 mL/min/m2, and the mean steady-state volume of distribution (Vdss) was 36.8 L/m2. The half-life of tepa was 7.98 hours, and the ratio of the area under the plasma concentration versus time curve (AUC) of tepa to that of thiotepa was 0.79. CONCLUSIONS: These data were consistent with our previous observations at this dose, and indicated that the severity of toxicity in these patients was not explained by aberrant pharmacokinetic indices. We conclude that, independent of effects on neutropenia, severe and cumulative platelet toxicity precludes further escalation of thiotepa dose despite the use of GM-CSF.

Aged↗
PubMed2000

Chemistry, pharmacology and pharmacokinetics of N,N',N" -triethylenethiophosphoramide (ThioTEPA).

N,N',N" -triethylenethiophosphoramide (thioTEPA) is a trifunctional alkylating agent with a broad spectrum of antitumour activity developed in the 1950s. The drug is now experiencing renewed interest as it appears to be one of the most effective anticancer drugs in high dose regimens. Despite many years of experience with thioTEPA, pharmacologic data are incomplete and controversy remains with respect to the dose-dependent pharmacokinetics of thioTEPA. In recent years greater insight has been obtained into the metabolism of thioTEPA, but there is still a gap between the total urinary excretion of thioTEPA and metabolites and the alkylating activity. In vivo and in vitro studies show that alkylation of DNA by thioTEPA can follow two pathways, but it remains unclear which pathway represents the precise mechanism of action. The currently available sensitive analytical methods for thioTEPA and its metabolites can be used to elucidate the many questions that still exist even so many years after its introduction. An overview is given of the chemistry, pharmacology, clinical use and toxicity of thioTEPA as well as its pharmacokinetics and analytical methods for thioTEPA and its metabolites.

Animals↗
PubMed1990

Characterization of nonexchangeable radioactivity in L1210 cells incubated with [14C]thiotepa: labeling of phosphatidylethanolamine.

N,N',N''-Triethylenethiophosphoramide ([14C]thiotepa) accumulation by L1210 cells is a biphasic process. A very rapid initial phase is followed by a much slower second phase that reflects accumulation of radioactivity in a form that is not lost or exchanged when cells are resuspended and incubated in drug-free medium for up to 8 h. In this study we attempted to characterize this nonexchangeable radioactivity. Nuclei (10(7)) isolated from L1210 cells and incubated with [14C]thiotepa did not accumulate 14C during incubations of up to 5 h. Similarly, nuclei isolated from 10(7) L1210 cells that had been shown to accumulate nonexchangeable 14C after incubation with [14C]thiotepa did not show an increase in nuclear-associated 14C. Eighty to 85% of nonexchangeable 14C in L1210 cells incubated with [14C]thiotepa was soluble in ethanol or chloroform:methanol (2:1, v/v), and although most of this cell-associated nonexchangeable 14C was precipitated by trichloroacetic acid, subsequent treatment of that precipitate with methanol solubilized most of the 14C so that only 15 to 20% remained with the final precipitate. When chloroform:methanol-soluble nonexchangeable 14C was analyzed with thin-layer chromatography systems suitable for thiotepa or simple lipids, all radioactivity remained at the origin. In contrast, when analyzed with one- and two-dimensional thin-layer chromatographic systems suitable for complex lipids, all chloroform:methanol-soluble radioactivity was associated with a single lipid spot. This lipid cochromatographed with phosphatidylethanolamine, reacted with ninhydrin but not with 4-(p-nitrobenzyl)pyridine or the Dragendorff choline reagent, and was digested by phospholipases C and D, all of which lead to its identification as phosphatidylethanolamine. This extensive labeling of phosphatidylethanolamine in L1210 cells incubated with [14C]thiotepa can be explained by liberation of [14C]aziridine from [14C]thiotepa, hydrolysis of the [14C]aziridine to [14C]ethanolamine, and incorporation of that radiolabeled material into phosphatidylethanolamine via the normal cellular synthetic pathways for that lipid. This information implies that thiotepa serves, at least in part, as a prodrug for aziridine and has implications as to the mechanism of thiotepa-induced cytotoxicity in that aziridine is a monofunctional alkylating agent incapable of producing interstrand, intrastrand, or protein-DNA cross-links.

Animals↗
PubMed2005

Aprepitant inhibits cyclophosphamide bioactivation and thiotepa metabolism.

BACKGROUND: Patients receiving the highly emetogenic high-dose chemotherapy regimen with cyclophosphamide, thiotepa and carboplatin (CTC) may benefit from the neurokin-1 receptor antagonist aprepitant in addition to standard anti-emetic therapy. As aprepitant has been shown to be a moderate inhibitor of the cytochrome P450 (CYP) 3A4 isoenzyme, its effect on the pharmacokinetics and metabolism of cyclophosphamide and thiotepa was evaluated. Moreover, preliminary results on the clinical efficacy of aprepitant in the CTC regimen are reported. PATIENTS AND METHODS: Six patients were enrolled in a protocol that employed a 4-day course of CTC high-dose chemotherapy with cyclophosphamide (1,500 mg/m2/day), thiotepa (120 mg/m2/day) and carboplatin (AUC 5 mg min/ml/day). Two patients received the tCTC protocol, which comprises two-third of the dose of CTC. In addition to standard anti-emetic therapy, the patients received aprepitant from one day before the start of their course until 3 days after chemotherapy. Blood samples were collected on days one and three of the course and analyzed for cyclophosphamide and its activated metabolite 4-hydroxycyclophosphamide, thiotepa and its main active metabolite tepa. The influence of aprepitant on the pharmacokinetics of cyclophosphamide and thiotepa was analyzed using a population pharmacokinetic analysis including a reference population of 49 patients receiving the same chemotherapy regimen without aprepitant and sampled under the same conditions. The frequency of nausea and vomiting in the six patients receiving CTC was compared with those of the last 22 consecutive patients receiving CTC chemotherapy without aprepitant. Inhibitory activity of aprepitant on cyclophosphamide and thiotepa metabolism was also tested in human liver microsomes. RESULTS: In our patient population, the rate of autoinduction of cyclophosphamide (P=0.040) and the formation clearance of tepa (P<0.001) were reduced with 23% and 33% when aprepitant was co-administered, respectively. Exposures to the active metabolite 4-hydroxycyclophosphamide and tepa were therefore reduced (5% and 20%, respectively) in the presence of aprepitant. In human liver microsomes, the 50% inhibitory concentrations (IC50) of aprepitant for inhibition of cyclophosphamide (IC50=1.3 microg/ml) and thiotepa (IC50=0.27 microg/ml) metabolism were within the therapeutic range. Patients receiving aprepitant experienced less frequently CINV both during and after the CTC course compared with the reference population (nausea 3.7 days vs. 5.8 days, P=0.052; vomiting 0.5 days vs. 4.8 days, P<0.001). CONCLUSION: Aprepitant inhibited both cyclophosphamide and thiotepa metabolism, most probably due to inhibition of the CYP 3A4 and/or 2B6 isoenzymes. The effects of this interaction are, however, small compared to the total variability. Addition of aprepitant may provide superior protection against vomiting in patients receiving the highly emetogenic high-dose CTC chemotherapy.

Antiemetics↗
PubMed1996

A phase I/II study of high-dose cyclophosphamide, cisplatin, and thioTEPA followed by autologous bone marrow and granulocyte colony-stimulating factor-primed peripheral-blood progenitor cells in patients with advanced malignancies.

The purpose of the present study was to determine the maximally tolerated dose of thioTEPA given with fixed high-dose cyclophosphamide (CPA) and cisplatin (cDDP) followed by autologous bone marrow (ABM) with or without granulocyte colony-stimulating factor (G-CSF)-primed peripheral-blood progenitor cells (PBPCs) in patients with advanced malignancies. Patients were required to have histologically documented malignancies and adequate renal, hepatic, pulmonary, and cardiac function. CPA was given at 1,875 mg/m2 per day as a 1-h i.v. infusion for 3 consecutive days, and cDDP was given at 55 mg/m2 per day as a 24-h continuous i.v infusion over 3 days concurrently with CPA. ThioTEPA was given once as a 1-h i.v. infusion (300-900 mg/m2) either following (the first 13 patients) or prior to CPA and cDDP. In all, 31 patients received PBPCs. A total of 46 patients were treated. There were 6 deaths among the 15 patients who did not receive PBPCs (13 received thioTEPA following CPA and cDDP). Among the other 31 patients who received PBPCs (all of whom also received thioTEPA prior to CPA and cDDP), there were 4 deaths, all involving patients with refractory ovarian carcinoma. The main toxicities were mucositis, esophagitis, hepatotoxicity, and nephrotoxicity. The median time required to achieve an absolute neutrophil count of 500 microliter was 10 days (range, 9-12 days) for those who received PBPCs and 15 days (range, 15-34 days) for those who did not receive PBPCs. Altogether, 47% of the major organ toxicities (grades 3 and 4 renal, hepatic, and cardiac toxicities) occurred among the 15 patients who did not receive PBPCs, although these patients received thioTEPA at the lowest 2 dose levels. There were 3 complete responses and 22 partial responses among 35 evaluable patients (overall response rate, 71%), with the median duration of response being 3.5 months (range, 2-17 months). The maximally tolerated dose of thioTEPA was 600 mg/m2 given as a 1-h i.v. infusion on the day prior to CPA and cDDP administration, The combination of high-dose CPA, cDDP, and thioTEPA is a well-tolerated regimen when thioTEPA is given prior to CPA and cDDP and when the combination also includes PBPCs in addition to ABM. This regimen is active in a variety of malignancies.

Adult↗
PubMed1988

Intravesical thiotepa versus mitomycin C in patients with Ta, T1 and TIS transitional cell carcinoma of the bladder: a phase III prospective randomized study.

A prospective randomized clinical trial was conducted by the National Bladder Cancer Group to compare thiotepa and mitomycin C in ablating residual Ta, T1 and TIS transitional cell carcinoma of the bladder. Eight weekly instillations were given followed by cystoscopy 4 weeks after the treatment was stopped. The over-all complete response rate based on cystoscopy and either biopsy or cytology was 26 per cent for thiotepa versus 39 per cent for mitomycin C (p equals 0.08). The greatest efficacy was seen in the Ta group with mitomycin C demonstrating superiority over thiotepa. Patients with negative cystoscopy and biopsy but who had positive cytology were considered to be partial responders. When partial and complete responders were combined the over-all response rate was 53 per cent for thiotepa and 63 per cent for mitomycin C (p equals 0.23). Patients with TIS appeared to respond equally to thiotepa and mitomycin C. Toxicity included urinary frequency in 22 of the 73 patients in the thiotepa arm and 31 of the 76 patients receiving mitomycin C. A rash was observed in 2 of the thiotepa group versus 14 of the mitomycin C group. Bone marrow depression occurred in 15 patients receiving thiotepa and in 12 receiving mitomycin C.

Administration, Intravesical↗
PubMed1991

Phase I/pharmacokinetic reevaluation of thioTEPA.

Because the initial evaluation of N,N',N''-triethylenethiophosphoramide (thioTEPA) preceded the standardized approach to the Phase I trials, uncertainty surrounds the recommended dose. Since it has recently been demonstrated that an almost 100-fold increase in dose can be administered in bone marrow transplant regimens, we conducted a Phase I reevaluation of thioTEPA. ThioTEPA was administered i.v. in 50 ml 5% dextrose in water over 10 min. Twenty-seven patients were entered at doses ranging from 30 to 75 mg/m2. The major toxic effect was myelosuppression; thrombocytopenia greater than or equal to grade 3 occurred in four of seven patients, and leukopenia greater than or equal to grade 3 in two of seven patients at 75 mg/m2. Among eight patients at 65 mg/m2 only two had greater than or equal to grade 3 myelosuppression making this the recommended new phase II dose for the majority of patients. Moderate (grade 2) easily controlled nausea and vomiting was the only other major side effect. There was no alopecia or mucosal or neurological toxicity. Three partial remissions were observed among nine previously treated ovarian cancer patients. Plasma concentrations of thioTEPA and its major active metabolite triethylenephosphoramide (TEPA) were measured by gas chromatography. The half-life of thioTEPA ranged from 51.6 to 211.8 min, and its pharmacokinetics was dose dependent; total body thioTEPA clearance decreased with increasing dose. The half-life of TEPA was considerably longer than that of the parent compound (3.0 to 21.1 h); as a result, the area under the plasma concentration-time curve (AUC) of TEPA was severalfold greater than that of the parent compound. The ratio of TEPA AUC to thioTEPA AUC decreased with increasing dose, suggesting that formation of TEPA is a saturable step in elimination. The AUC and total body clearance of thioTEPA, but not of TEPA, were closely correlated with neutrophil but not platelet toxicity.

Dose-Response Relationship, Drug↗
PubMed1995

Modulation of thiotepa antitumor activity in vivo by alteration of liver cytochrome P450-catalyzed drug metabolism.

The anticancer drug and alkylating agent thiotepa is metabolized by oxidative desulfuration to yield the alkylating metabolite N,N',N"-triethylenephosphoramide (TEPA) in a reaction that is catalyzed by specific liver cytochrome P450 (CYP) enzymes, including CYP2B1, the major phenobarbital-inducible P450 of rat liver, and CYP2C11, a constitutively expressed, male-specific form. The present study investigates the potential for modulating the cytotoxicity and antitumor activity of thiotepa by prior treatment of tumor-bearing rats with the CYP2B1 inducer phenobarbital or the CYP2C11 inhibitor 2-diethylaminoethyl-2,2-diphenylvalerate hydrochloride (SKF-525A) and examines the role of TEPA in the cytotoxicity of thiotepa in vivo. Administration of thiotepa to adult male rats bearing 9L gliosarcoma, grown s.c., resulted in dose-dependent cytotoxicity (ED90 approximately 12 mg/kg i.v., single dose), as determined by a tumor excision/in vitro colony formation assay carried out 24 hr after drug treatment. Tumor growth delay experiments revealed that thiotepa (5 mg/kg) inhibited 9L tumor growth over a 5- to 7-day period after alkylating agent treatment and this effect was accompanied by moderate body weight loss. Pretreatment with phenobarbital, under conditions in which liver CYP2B1 levels and liver microsomal thiotepa desulfuration to yield TEPA are both markedly increased, did not alter thiotepa's short-term (24-hr) cytotoxicity, as judged by a tumor excision assay, nor did it affect the extent of bone marrow toxicity associated with drug treatment. However, phenobarbital did block the tumor growth delay effect of thiotepa and it also attenuated the body weight loss that occurred during the first 5 days after drug treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1999

Differential catalytic efficiency of allelic variants of human glutathione S-transferase Pi in catalyzing the glutathione conjugation of thiotepa.

Alkylating agents are extensively used in the treatment of cancer. The clinical usefulness of this class of anticancer drugs, however, is often limited by the emergence of drug-resistant tumor cells. Increased glutathione (GSH) conjugation through catalysis by GSH S-transferases (GSTs) is believed to be an important mechanism in tumor cell resistance to alkylating agents. In the present study, we report that the allelic variants of human Pi class GST (hGSTP1-1), which differ in their primary structures at amino acids in positions 104 and/or 113, exhibit significant differences in their activity in the GSH conjugation of alkylating anticancer drug thiotepa. Mass spectrometry revealed that the major product of the reaction between thiotepa and GSH was the monoglutathionyl-thiotepa conjugate. While nonenzymatic formation of monoglutathionyl-thiotepa was negligible, the formation of this conjugate was increased significantly in the presence of hGSTP1-1 protein. The hGSTP1-1-catalyzed GSH conjugation of thiotepa was time and protein dependent and followed Michaelis-Menten kinetics. The catalytic efficiency of hGSTP1-1(I104, A113) variant was approximately 1.9- and 2.6-fold higher compared with hGSTP1-1(V104,A113) and hGSTP1-1(V104,V113) isoforms, respectively. The results of the present study indicate that the hGSTP1-1 polymorphism may be an important factor in GST-mediated tumor cell resistance to thiotepa, and that subjects homozygous for the hGSTP1-1(I104,A113) allele, which is most frequent in human populations, are likely to be at a greater risk for developing GST-mediated resistance to thiotepa than heterozygotes or homozygotes with valine 104 background.

Alleles↗
PubMed1990

ThioTEPA pharmacokinetics during intravesical chemotherapy and the influence of Tween 80.

A pharmacokinetic study of randomised crossover design was carried out in which eight patients with recurrent stage pTa or pT1 transitional cell carcinoma of the bladder were given thioTEPA (30 mg) in distilled water or in 10% (v/v) Tween 80 (30 ml) intravesically for 2 h, followed 3 months later by the alternative treatment. ThioTEPA and its primary metabolite, TEPA, were measured in plasma and urine using a sensitive and specific chromatographic assay. Large differences between patients were observed in the proportion of thioTEPA absorbed, ranging from 20%-78%. Peak plasma levels of thioTEPA were observed within 1 h of intravesical administration. By 2 h after administration the plasma levels of TEPA were similar to those of thioTEPA and, in contrast to those of the parent compound, remained at a similar level over the next 4 h. The rate of absorption of thioTEPA was not influenced by Tween 80, but it did cause statistically significant increases in mean peak plasma levels (from 101 to 154 ng/ml) and mean AUC values (from 0.376 to 0.496 micrograms h per ml) and a decrease in the mean half-life (from 1.83 to 1.25 h). To obtain plasma levels similar to those achieved after instillation with thioTEPA alone, the dose should be reduced with Tween 80.

Absorption↗
PubMed1996

Stability of thiotepa (lyophilized) in 5% dextrose injection at 4 and 23 degrees C.

The stability of thiotepa (lyophilized) 0.5 and 5 mg/mL in 5% dextrose injection was studied. Vials of lyophilized thiotepa were reconstituted with sterile water for injection to yield a solution with a nominal 10-mg/mL drug concentration. The reconstituted solution was filtered and diluted in 5% dextrose injection in polyvinyl chloride and polyolefin bags to nominal thiotepa concentrations of 0.5 and 5 mg/mL. Triplicate test admixtures were prepared and stored at 4 or 23 degrees C in normal fluorescent light. Initially and after four and eight hours and 1, 3, 7, and 14 days, samples were removed for visual evaluation, turbidimetry, and stability-indicating high-performance liquid chromatography. No incompatibilities were observed. Admixtures containing thiotepa 0.5 mg/mL retained at least 90% of the initial drug concentration for eight hours at either temperature in either type of container; after 24 hours, losses ranged from 10% to 17%. Thiotepa in the 5-mg/mL admixtures was stable for 3 days at 23 degrees C and 14 days at 4 degrees C in both container types. Thiotepa (lyophilized) 0.5 mg/mL in 5% dextrose injection was stable for eight hours at 4 or 23 degrees C. Thiotepa (lyophilized) 5 mg/mL in 5% dextrose injection was stable for 3 days at 23 degrees C and 14 days at 4 degrees C.

Antineoplastic Agents, Alkylating↗
PubMed1996

Compatibility of thiotepa (lyophilized) with selected drugs during simulated Y-site administration.

The compatibility of lyophilized thiotepa injection with selected other drugs during simulated Y-site injection was evaluated. Five-milliliter samples of thiotepa (lyophilized) 1 mg/mL in 5% dextrose injection were combined with 5 mL each of 100 other drugs, including antineoplastics, anti-infectives, and supportive care drugs, in 5% dextrose injection or 0.9% sodium chloride injection. The combinations were stored at room temperature (approximately 23 degrees C) under constant fluorescent light. Visual examinations were performed immediately and at one and four hours with the unaided eye and, if there was no obvious incompatibility, with a high-intensity mono-directional light beam to enhance visualization of small particles and low-level turbidity. The turbidity of each combination was measured as well. Particle sizing and counting were performed on selected solutions. Most of the test drugs were compatible with thiotepa 1 mg/mL during the observation period. Two drugs exhibited incompatibilities with thiotepa. The thiotepa-cisplatin combination developed turbidity in four hours, and the thiotepa-minocycline hydrochloride combination developed a bright yellow-green discoloration in one hour. All the test drugs except cisplatin and minocycline hydrochloride were compatible with thiotepa 1 mg/mL (prepared from the lyophilized formulation) for at least four hours at room temperature.

Alkylating Agents↗
PubMed1997

Stability of thiotepa (lyophilized) in 0.9% sodium chloride injection.

The stability of thiotepa in a new formulation of the drug was studied. Vials of Thioplex (Immunex), a relatively new lyophilized formulation of thiotepa, were reconstituted with sterile water and diluted with 0.9% sodium chloride injection in polyvinyl chloride infusion bags to thiotepa concentrations of 0.5, 1, and 3 mg/mL. The solutions were stored at 8 and 25 degrees C in ambient light and analyzed at 0, 8, 24, and in most cases 48 hours for thiotepa concentration and chloro-adduct formation by stability-indicating high-performance liquid chromatography. Thiotepa 1 and 3 mg/mL was stable for 48 hours at 8 degrees C and for 24 hours at 25 degrees C. Thiotepa 0.5 mg/mL was not stable at either temperature. Storage at 8 degrees C slowed but did not prevent chloro-adduct formation and loss of potency. The pH tended to increase with time; turbidity remained low. Thiotepa (lyophilized) 1 and 3 mg/mL in 0.9% sodium chloride injection was stable for 48 hours at 8 degrees C and for 24 hours at 25 degrees C; the drug was unstable when diluted to 0.5 mg/mL and stored under the same conditions.

Antineoplastic Agents, Alkylating↗
PubMed1999

Hprt mutant frequency and molecular analysis of Hprt mutations in Fischer 344 rats treated with thiotepa.

Thiotepa is a bifunctional alkylating anticancer drug that is a rodent carcinogen and a suspected human carcinogen. In order to determine the sensitivity of mutant induction in the Hprt lymphocyte assay for detecting tumorigenic doses of thiotepa, Fischer 344 rats were treated for 4 weeks with thiotepa using a procedure adapted from a carcinogenesis protocol. At various times after beginning the treatment regimen, rats were killed and the lymphocyte Hprt assay was performed on splenic lymphocytes isolated from the animals. The 6-thioguanine-resistant T lymphocyte mutant frequency increased with time during the period of thiotepa exposure and declined slightly thereafter. Significant dose-dependent increases in mutant frequency were found using concentrations of thiotepa that eventually result in lymphoproliferative tumors. Hprt mRNA from mutant lymphocytes was reverse transcribed to cDNA, amplified by PCR and examined for mutations by DNA sequencing. This analysis indicated that the major type of point mutation was G:C-->T:A transversion and that 33% of the mutants contained simple or complex frameshifts. Also, a multiplex PCR performed on DNA from mutant clones that were expanded in vitro indicated that 34% of the clones had deletions in the Hprt gene. These results indicate that the induction of lymphocyte Hprt mutants is a sensitive biomarker for the carcinogenicity of thiotepa and that the types of mutations found in the lymphocyte Hprt gene reflect the kinds of DNA damage produced by thiotepa.

Adenine↗
PubMed2001

Validation of a therapeutic drug monitoring strategy for thiotepa in a high-dose chemotherapy regimen.

Thiotepa is an alkylating agent widely used in high-dose chemotherapy. The pharmacokinetics of thiotepa and its main metabolite tepa show a wide interpatient variability, which may be responsible for the interpatient variability in toxicity. The aim of this study was to develop and validate a pharmacokinetically guided dosing strategy with the sum of the thiotepa and tepa area under the concentration-time curve (AUC) as the target parameter. A total of 46 patients received 77 courses of chemotherapy with thiotepa (80-120 mg/m(2) per day) divided into two daily 30-minute infusions in combination with cyclophosphamide and carboplatin. Patients received up to three courses of chemotherapy. The interpatient, course-to-course, day-to-day, and residual variability in the pharmacokinetics of thiotepa and tepa were estimated with a population analysis with the software program NONMEM. The planned strategy consisted of the collection of blood samples on day 1 and either day 3 or day 4 of each 4-day course. The thiotepa dose was planned to be adjusted on day 3 of each course and before the start of a new course on the basis of Bayesian predictions of the pharmacokinetics with data of day 1 and/or the possible previous course. The prediction procedure was validated by dividing the dataset into an index and validation set. The Bayesian predictions of the validation set were compared with true AUC values generated with individual fits of each course. The performance of the complete strategy was tested with a simulation procedure in 1,000 patients. Interpatient variability and course-to-course variability were in the same order (+/-20%); day-to-day variability was less (+/-15%). The sampling strategy resulted in predictions of the AUC without bias with acceptable precision (+/-20%). The simulation showed that variability in exposure was effectively decreased by the dosing strategy. This strategy resulted in a reduction in the variability of the exposure to thiotepa and tepa and can be implemented in a clinical study.

Antineoplastic Agents, Alkylating↗
PubMed2005

Population pharmacokinetics of cyclophosphamide and its metabolites 4-hydroxycyclophosphamide, 2-dechloroethylcyclophosphamide, and phosphoramide mustard in a high-dose combination with Thiotepa and Carboplatin.

The anticancer prodrug cyclophosphamide (CP) is activated by the formation of 4-hydroxycyclophosphamide (4OHCP), which decomposes into phosphoramide mustard (PM). This activation pathway is inhibited by thiotepa. CP is inactivated by formation of 2-dechloroethylcyclophosphamide (2DCECP). The aim of this study was to develop a population pharmacokinetic model describing the complex pharmacokinetics of CP, 4OHCP, 2DCECP, and PM when CP is administered in a high-dose combination with thiotepa and carboplatin. Patients received a combination of CP (1000-1500 mg/m/d), carboplatin (265-400 mg/m/d), and thiotepa (80-120 mg/m/d) administered in short infusions over 4 days. Twenty blood samples were collected per patient per course. Concentrations of CP, 4OHCP, 2DCECP, PM, thiotepa, and tepa were determined in plasma. Using NONMEM, an integrated population pharmacokinetic model was used to describe the pharmacokinetics of CP, 4OHCP, 2DCECP, and PM, including the already described processes of autoinduction of CP and the interaction with thiotepa. Data were available on 35 patients (70 courses). The pharmacokinetics of CP were described with a 2-compartment model, and those of 4OHCP, 2DCECP, and PM with 1-compartment models. Before onset of autoinduction, it was assumed that CP is eliminated through a noninducible pathway accounting for 20% of total CP clearance, whereas 2 inducible pathways resulted in formation of 4OHCP (75%) and 2DCECP (5%). It was assumed that 4OHCP was fully converted to PM. Induction of CP metabolism was mediated by 2 hypothetical amounts of enzyme whose quantities increased in time in the presence of CP (kenz=0.0223 and 0.0198 hours). Induction resulted in an increased formation of 4OHCP (approximately 50%), PM (approximately 50%), and 2DCECP (approximately 35%) during the 4-day course, and concomitant decreased exposure to CP (approximately 50%). The formation of 2DCECP was not inhibited by thiotepa. Apparent volumes of distribution of CP, PM, and 2DCECP could be estimated being 43.7, 55.5, and 18.5 L, respectively. Exposure to metabolites varied up to 9-fold. The complex population pharmacokinetics of CP, 4OHCP, 2DCECP, and PM in combination with thiotepa and carboplatin has been established and may form the basis for further treatment optimization with this combination.

Adolescent↗
PubMed2001

Retrovirus-mediated expression of the base excision repair proteins, formamidopyrimidine DNA glycosylase or human oxoguanine DNA glycosylase, protects hematopoietic cells from N,N',N"-triethylenethiophosphoramide (thioTEPA)-induced toxicity in vitro and in vivo.

Modulation of DNA damage repair activity could lead to new approaches to reduce cytotoxic side effects of chemotherapy. N,N',N"-Triethylenethiophosphoramide (thioTEPA) induces the formation of amino-ethyl adducts of guanine, resulting in imidazole ring opening [formamidopyrimidine (Fapy)] and is associated with significant myelosuppression in dose-intensive therapies. In Escherichia coli, Fapy lesions are repaired by the Fapy-DNA glycosylase (Fpg) protein. We hypothesized that the expression of the Fpg could increase resistance of hematopoietic cells to thioTEPA-induced cytotoxicity. Expression of Fpg in bone marrow (BM) cells via a retrovirus vector was associated with demonstrable 8-oxodeoxyguanosine DNA glycosylase activity. BM cells were infected with a recombinant retrovirus, SF91, containing the Fpg gene and expressing the enhanced green fluorescence protein (EGFP) via an internal ribosomal entry site element. Control mice received BM transduced with the backbone containing IRES-EGFP alone. Fpg-transduced and GFP+ BM hematopoietic cells were resistant in vitro to thioTEPA at multiple concentrations. Mice transplanted with transduced cells were treated with four doses of thioTEPA (10 mg/kg) given over 7 weeks. Despite low transduction efficiency, peripheral blood leukocytes, hemoglobin, and platelet counts of thioTEPA-treated Fpg mice were significantly higher than treated control mice (P < 0.05). In addition, after treatment, the BM, spleen, and thymic cellularity as well as the number of GFP+ progenitor cells in the BM of treated mice were significantly higher than those of control group. Selection of Fpg-transduced cells in vivo was demonstrated by an increase in the mean fluorescence intensity of peripheral mononuclear cells of Fpg mice compared with pretreatment value. In addition, a significant increase in the EGFP-bright cells was demonstrated, suggesting preferential survival of high-expressing hematopoietic cells. Similar results were demonstrated in vitro with primary BM expressing the human functional counterpart of Fpg, OGG1. These results show that expression of the Fpg or hOGG1 protein protects hematopoietic cells from thioTEPA-induced DNA damage and suggest that a high level of expression of these repair proteins is required to establish resistance to this drug. Expression of Fpg and/or OGG1 may provide an novel approach to preventing thioTEPA-induced toxicity of primary hematopoietic cells.

Animals↗
PubMed1990

Effects of ethanolamine and choline on thiotepa cellular accumulation and cytotoxicity in L1210 cells.

The amino alcohols, ethanolamine and choline, were studied for their effects on (a) L1210 cell growth, (b) N,N',N"-triethylenetheiphosphoramide (thiotepa)-induced growth inhibition of L1210 cells, and (c) 14C accumulation by L1210 cells incubated with [14C]thiotepa. Ethanolamine, at concentrations up to 300 microM, had no effect on L1210 cell growth but, at concentrations greater than 300 microM, produced a dose-dependent reduction in cell growth. Choline, at concentrations up to 20 mM, had no effect on L1210 cell growth. Neither ethanolamine, at 250 microM, nor choline, at 10 mM, altered the ability of thiotepa to reduce L1210 cell growth. Neither ethanolamine, at 250 microM, nor choline, at 10 mM, affected the rapid phase of 14C accumulation by L1210 cells incubated with [14C]thiotepa. The slow phase of 14C accumulation by L1210 cells incubated with 5 microM [14C]thiotepa, a process which is 80-85% due to production of [14C]phosphatidylethanolamine, was not affected by 250 microM choline. In contrast, ethanolamine produced a dose-dependent reduction in this slow rate of 14C accumulation. The reduction in the slow rate of 14C accumulation produced by ethanolamine was due almost entirely to a decrease in the accumulation of nonexchangeable 14C. Kinetic analysis of the inhibition of 14C accumulation produced by 25, 100, and 250 microM ethanolamine was compatible with competitive inhibition. Thin layer chromatography of cell extracts showed that the ability of ethanolamine to reduce 14C accumulation by L1210 cells incubated with [14C]thiotepa was due solely to reduction in production of [14C]phosphatidylethanolamine. These results are all compatible with and predicted by our previously described scheme wherein thiotepa enters cells by simple diffusion and serves as a prodrug for aziridine, some of which is hydrolyzed to ethanolamine which is then incorporated into phosphatidylethanolamine via normal metabolic synthetic pathways.

Animals↗