A prospective audit on the use of prophylactic antiemetics and rates of CINV in patients receiving carboplatin AUC≥4 or combination anthracycline-cyclophosphamide

BACKGROUND

Chemotherapy-induced nausea and vomiting (CINV) are two of the most frequently experienced and distressing side effects of cancer treatment. Recent updates by ESMO/MASCC and ASCO on guidelines for prevention of CINV have recommended the addition of a neurokinin-1 receptor antagonist to antiemetic regimens for patients receiving carboplatin-based chemotherapy area under the curve (AUC) ≥4 mg/mL per minute, and an addition of olanzapine for those receiving combination anthracycline/cyclophosphamide chemotherapy.

AIMS

To assess current use of prophylactic antiemetics and rates of CINV in patients under the care of MidCentral Regional Cancer Treatment Service (MRCTS) receiving carboplatin AUC≥4 or combination anthracycline/cyclophosphamide.

METHODS

Data was prospectively collected on patients under the care of MRCTS receiving carboplatin AUC≥4 or combination anthracycline/cyclophosphamide chemotherapy, including breast cancer patients receiving 5-fluorouracil, epirubicin and cyclophosphamide (FEC) and lymphoma patients receiving rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone (R-CHOP). Questionnaires were given to eligible patients to be completed daily from day two to day six of first cycle of chemotherapy only. Data on each patient's gender, age, types of chemotherapies, types of malignancies, presence of nausea or vomiting, number of dry retching or vomiting episodes and anti-emetics were recorded.

RESULTS

From 15 September 2018 to 10 August 2019, a total of 44 patients receiving carboplatin-based chemotherapy AUC≥4 and 30 patients receiving combination anthracycline/cyclophosphamide were included. Twenty-two patients (50%) had either emesis or significant nausea in the overall and delayed phase when treated with carboplatin AUC≥4, and only three (7%) in the acute phase. Fourteen patients (56%) had either emesis or significant nausea in the overall phase when treated with FEC chemotherapy, mostly in the acute phase (13 patients) rather than in the delayed phase (9 patients).

CONCLUSION

The rates of CINV are high with the existing antiemetic regimens used at MidCentral Regional Cancer Treatment Service. Therefore, in accordance with international guidelines, we will add a neurokinin-1 antagonist to the antiemetic regimens for patients receiving carboplatin-based chemotherapy AUC≥4, and olanzapine for those receiving combination anthracycline/cyclophosphamide chemotherapy, in an attempt to improve the rates of CINV in these groups. Repeating this audit post-implementation of above recommendations will be important to assess for any improvement.

Pharmacokinetics of polatuzumab vedotin in combination with R/G-CHP in patients with B-cell non-Hodgkin lymphoma

Purpose

The phase Ib/II open-label study (NCT01992653) evaluated the antibody-drug conjugate polatuzumab vedotin (pola) plus rituximab/obinutuzumab, cyclophosphamide, doxorubicin, and prednisone (R/G-CHP) as first-line therapy for B-cell non-Hodgkin lymphoma (B-NHL). We report the pharmacokinetics (PK) and drug–drug interaction (DDI) for pola.

Methods

Six or eight cycles of pola 1.0–1.8 mg/kg were administered intravenously every 3 weeks (q3w) with R/G-CHP. Exposures of pola [including antibody-conjugated monomethyl auristatin E (acMMAE) and unconjugated MMAE] and R/G-CHP were assessed by non-compartmental analysis and/or descriptive statistics with cross-cycle comparisons to cycle 1 and/or after multiple cycles. Pola was evaluated as a potential victim and perpetrator of a PK drug–drug interaction with R/G-CHP. Population PK (popPK) analysis assessed the impact of prior treatment status (naïve vs. relapsed/refractory) on pola PK.

Results

Pola PK was similar between treatment arms and independent of line of therapy. Pola PK was dose proportional from 1.0 to 1.8 mg/kg with R/G-CHP. Geometric mean volume of distribution and clearance of acMMAE ranged from 57.3 to 95.6 mL/kg and 12.7 to 18.2 mL/kg/day, respectively. acMMAE exhibited multi-exponential decay (elimination half-life ~ 1 week). Unconjugated MMAE exhibited formation rate-limited kinetics. Exposures of pola with R/G-CHP were similar to those in the absence of CHP; exposures of R/G-CHP in the presence of pola were comparable to those in the absence of pola.

Conclusions

Pola PK was well characterized with no clinically meaningful DDIs with R/G-CHP. Findings are consistent with previous studies of pola + R/G, and support pola + R/G-CHP use in previously untreated diffuse large B-cell lymphoma.

Electronic supplementary material

The online version of this article (10.1007/s00280-020-04054-8) contains supplementary material, which is available to authorized users.

Exposure-Toxicity Association of Cyclophosphamide and Its Metabolites in Infants and Young Children with Primary Brain Tumors: Implications for Dosing

PURPOSE

To characterize the population pharmacokinetics of cyclophosphamide, active 4-hydroxy-cyclophosphamide (4OH-CTX), and inactive carboxyethylphosphoramide mustard (CEPM), and their associations with hematologic toxicities in infants and young children with brain tumors. To use this information to provide cyclophosphamide dosing recommendations in this population.

PATIENTS AND METHODS

Patients received four cycles of a 1-hour infusion of 1.5 g/m² cyclophosphamide. Serial samples were collected to measure cyclophosphamide, 4OH-CTX, and CEPM plasma concentrations. Population pharmacokinetic modeling was performed to identify the patient characteristics influencing drug disposition. Associations between drug exposures and metrics reflecting drug-induced neutropenia, erythropenia, and thrombocytopenia were investigated. A Bayesian approach was developed to predict 4OH-CTX exposure using only cyclophosphamide and CEPM plasma concentrations.

RESULTS

Data from 171 patients (0.07-4.9 years) were adequately fitted by a two-compartment (cyclophosphamide) and one-compartment model (metabolites). Young infants (<6 months) exhibited higher mean 4OH-CTX exposure than did young children (138.4 vs. 107.2 μmol/L·h, P < 0.0001). No genotypes exhibited clinically significant influence on drug exposures. Worse toxicity metrics were significantly associated with higher 4OH-CTX exposures. Dosing simulations suggested decreased cyclophosphamide dosage to 1.2 g/m² for young infants versus 1.5 g/m² for children to attain similar 4OH-CTX exposure. Bayesian-modeled 4OH-CTX exposure predictions were precise (mean absolute prediction error 14.8% ± 4.2%) and had low bias (mean prediction error 4.9% ± 5.1%).

CONCLUSIONS

A 4OH-CTX exposure-toxicity association was established, and a decreased cyclophosphamide dosage for young infants was suggested to reduce toxicity in this population. Bayesian modeling to predict 4OH-CTX exposure may reduce clinical processing-related costs and provide insights into further exposure-response associations.

Kinetics of Cyclophosphamide Metabolism in Humans, Dogs, Cats, and Mice and Relationship to Cytotoxic Activity and Pharmacokinetics

Cyclophosphamide (CP), a prodrug that is enzymatically converted to the cytotoxic 4-hydroxycyclophosphamide (4OHCP) by hepatic enzymes, is commonly used in both human and veterinary medicine to treat cancers and modulate the immune system. We investigated the metabolism of CP in humans, dogs, cats, and mice using liver microsomes; apparent K M, V max, and intrinsic clearance (V max/K M) parameters were estimated. The interspecies and intraspecies variations in kinetics were vast. Dog microsomes were, on average, 55-fold more efficient than human microsomes, 2.8-fold more efficient than cat microsomes, and 1.2-fold more efficient than mouse microsomes at catalyzing CP bioactivation. These differences translated to cell-based systems. Breast cancer cells exposed to 4OHCP via CP bioactivation by microsomes resulted in a stratification of cytotoxicity that was dependent on the species of microsomes measured by IC50: dog (31.65 μM), mouse (44.95 μM), cat (272.6 μM), and human (1857 μM). The contributions of cytochrome P450s, specifically, CYP2B, CYP2C, and CYP3A, to CP bioactivation were examined: CYP3A inhibition resulted in no change in 4OHCP formation; CYP2B inhibition slightly reduced 4OHCP in humans, cats, and mice; and CYP2C inhibition drastically reduced 4OHCP formation in each species. Semiphysiologic modeling of CP metabolism using scaled metabolic parameters resulted in simulated data that closely matched published pharmacokinetic profiles, determined by noncompartmental analysis. The results highlight differential CP metabolism delineated by species and demonstrate the importance of metabolism on CP clearance.

Kinetics of Cyclophosphamide Metabolism in Humans, Dogs, Cats, and Mice and Relationship to Cytotoxic Activity and Pharmacokinetics

Cyclophosphamide (CP), a prodrug that is enzymatically converted to the cytotoxic 4-hydroxycyclophosphamide (4OHCP) by hepatic enzymes, is commonly used in both human and veterinary medicine to treat cancers and modulate the immune system. We investigated the metabolism of CP in humans, dogs, cats, and mice using liver microsomes; apparent K _M, V _max, and intrinsic clearance (V _max/K _M) parameters were estimated. The interspecies and intraspecies variations in kinetics were vast. Dog microsomes were, on average, 55-fold more efficient than human microsomes, 2.8-fold more efficient than cat microsomes, and 1.2-fold more efficient than mouse microsomes at catalyzing CP bioactivation. These differences translated to cell-based systems. Breast cancer cells exposed to 4OHCP via CP bioactivation by microsomes resulted in a stratification of cytotoxicity that was dependent on the species of microsomes measured by IC₅₀: dog (31.65 μM), mouse (44.95 μM), cat (272.6 μM), and human (1857 μM). The contributions of cytochrome P450s, specifically, CYP2B, CYP2C, and CYP3A, to CP bioactivation were examined: CYP3A inhibition resulted in no change in 4OHCP formation; CYP2B inhibition slightly reduced 4OHCP in humans, cats, and mice; and CYP2C inhibition drastically reduced 4OHCP formation in each species. Semiphysiologic modeling of CP metabolism using scaled metabolic parameters resulted in simulated data that closely matched published pharmacokinetic profiles, determined by noncompartmental analysis. The results highlight differential CP metabolism delineated by species and demonstrate the importance of metabolism on CP clearance.

Schisandra chinensis extract decreases chloroacetaldehyde production in rats and attenuates cyclophosphamide toxicity in liver, kidney and brain

ETHNOPHARMACOLOGICAL RELEVANCE

Schisandra chinensis (Turcz.) Baill (S. chinensis) has been used for thousands years in China, and is usually applied in treatment of urinary tract disorders and liver injury. S. chinensis extract (SCE) has board protective effects on liver, kidney and nervous system. Schisandra lignans are generally considered as the bioactive components of SCE.

AIM OF THE STUDY

To investigate the pharmacokinetic herb-drug interactions (HDIs) between SCE and cyclophosphamide (CTX). To evaluate the protective effects of SCE against CTX induced damage in rat liver, kidney and brain.

MATERIALS AND METHODS

The pharmacokinetic HDIs between SCE and CTX were investigated by determining plasma concentrations of CTX and three metabolites, namely 4-ketocyclophosphamide (4-Keto), 2-dechloroethylcyclophosphamide (DCCTX) and carboxyphosphamide (CPM) using a previously developed UPLC-MS/MS method. To evaluate the protective effects of SCE pretreatment, toxicity and oxidation stress assessments along with histology investigations were carried out in rat liver, kidney and brain.

RESULTS

The equimolar produced metabolite DCCTX was chosen to reflect chloroacetaldehyde (CAA, a toxic metabolite of CTX) production in rats. Single-dose pretreatment of SCE significantly reduced CAA production and decreased the C_max and AUC_0-24h of DCCTX by 69% and 49% respectively (P < 0.05). After pretreated with SCE for 7 consecutive days, the C_max and AUC_0-24h of DCCTX were still decreased (-25% and -37%, P < 0.05) when compared with CTX alone group. Parallel toxicity and oxidation stress investigations showed that single-dose SCE pretreatment significantly decreased plasma BUN and Cr levels (-12% and -46%, respectively) and reduced liver AST activity (-32%). Moreover, SCE pretreatment potently increased the brain GSH content by 7.8-fold, and reduced MDA levels in rat liver, kidney and brain by 39%, 28% and 31%, respectively (compared with CTX alone group). The protective effects of SCE were also supported by histological observations.

CONCLUSION

Our experiment results suggest that S. chinensis may find use as a complementary medicine in CTX treatment.

Pharmacokinetics of cyclophosphamide and 4-hydroxycyclophosphamide in cats after oral, intravenous, and intraperitoneal administration of cyclophosphamide

OBJECTIVE To characterize pharmacokinetics of cyclophosphamide and 4-hydoxycyclophosphamide (4-OHCP) in the plasma of healthy cats after oral, IV, and IP administration of cyclophosphamide. ANIMALS 6 healthy adult cats. PROCEDURES Cats were randomly assigned to receive cyclophosphamide (200 mg/m²) via each of 3 routes of administration (oral, IV, and IP); there was a 30-day washout period between successive treatments. Plasma samples were obtained at various time points for up to 8 hours after administration. Samples were treated with semicarbazide hydrochloride to trap the 4-OHCP in stable form, which allowed for cyclophosphamide and trapped 4-OHCP to be simultaneously measured by use of tandem mass spectrometry. Pharmacokinetic parameters were determined from drug concentration-versus-time data for both cyclophosphamide and 4-OHCP. RESULTS Cyclophosphamide was tolerated well regardless of route of administration. Pharmacokinetic parameters for 4-OHCP were similar after oral, IV, and IP administration. Area under the concentration-time curve for cyclophosphamide was lower after oral administration than after IV or IP administration. CONCLUSIONS AND CLINICAL RELEVANCE Cyclophosphamide can be administered interchangeably to cats as oral, IV, and IP formulations, which should provide benefits with regard to cost and ease of administration to certain feline patients.

Soy-Based Multiple Amino Acid Oral Supplementation Increases the Anti-Sarcoma Effect of Cyclophosphamide

The use of a mixture of amino acids caused a selective apoptosis induction against a variety of tumor cell lines, reduced the adverse effects of anti-cancer drugs and increased the sensitivity of tumor cells to chemotherapeutic agents. We evaluated the effects and underlying mechanisms of soy-derived multiple amino acids' oral supplementation on the therapeutic efficacy of low-dose cyclophosphamide (CTX) and on tumor growth, apoptosis, and autophagy in severe combined immunodeficiency (SCID) mice that were injected with sarcoma-180 (S-180) cells. 3-methyladenine or siRNA knockdown of Atg5 was used to evaluate its effect on sarcoma growth. A comparison of mice with implanted sarcoma cells, CTX, and oral saline and mice with implanted sarcoma cells, CTX, and an oral soy-derived multiple amino acid supplement indicated that the soy-derived multiple amino acid supplement significantly decreased overall sarcoma growth, increased the Bax/Bcl-2 ratio, caspase 3 expression, and apoptosis, and depressed LC3 II-mediated autophagy. Treatment with 3-methyladenine or Atg5 siRNA elicited similar responses as CTX plus soy-derived multiple amino acid in downregulating autophagy and upregulating apoptosis. A low dose of CTX combined with an oral soy-derived multiple amino acid supplement had a potent anti-tumor effect mediated through downregulation of autophagy and upregulation of apoptosis.

Ecotoxicity and genotoxicity of cyclophosphamide, ifosfamide, their metabolites/transformation products and their mixtures

Cyclophosphamide (CP) and ifosfamide (IF) are commonly used cytostatic drugs that repress cell division by interaction with DNA. The present study investigates the ecotoxicity and genotoxicity of CP, IF, their human metabolites/transformation products (TPs) carboxy-cyclophosphamide (CPCOOH), keto-cyclophosphamide (ketoCP) and N-dechloroethyl-cyclophosphamide (NdCP) as individual compounds and as mixture. The two parent compounds (CP and IF), at concentrations up to 320 mg L(-1), were non-toxic towards the alga Pseudokirchneriella subcapitata and cyanobacterium Synecococcus leopoliensis. Further ecotoxicity studies of metabolites/TPs and a mixture of parent compounds and metabolites/TPs performed in cyanobacteria S. leopoliensis, showed that only CPCOOH (EC50 = 17.1 mg L(-1)) was toxic. The measured toxicity (EC50 = 11.5 mg L(-1)) of the mixture was lower from the toxicity predicted by concentration addition model (EC50 = 21.1 mg L(-1)) indicating potentiating effects of the CPCOOH toxicity. The SOS/umuC assay with Salmonella typhimurium revealed genotoxic activity of CP, CPCOOH and the mixture in the presence of S9 metabolic activation. Only CPCOOH was genotoxic also in the absence of metabolic activation indicating that this compound is a direct acting genotoxin. This finding is of particular importance as in the environment such compounds can directly affect DNA of non-target organisms and also explains toxicity of CPCOOH against cyanobacteria S. leopoliensis. The degradation study with UV irradiation of samples containing CP and IF showed efficient degradation of both compounds and remained non-toxic towards S. leopoliensis, suggesting that no stable TPs with adverse effects were formed. To our knowledge, this is the first study describing the ecotoxicity and genotoxicity of the commonly used cytostatics CP and IF, their known metabolites/TPs and their mixture. The results indicate the importance of toxicological evaluation and monitoring of drug metabolites as they may be for certain aquatic species more hazardous than parent compounds.

[Chemotherapy for Malignancy During Pregnancy - Literature Review.]

In today's dynamic development of modern life, we can unfortunately see more and more often cases of malignant diseases during pregnancy. Therapy of these conditions in pregnant women is a challenge to the doctors, due to concerns for the mother's health, but also the possible risks for the foetus. An additional difficulty is the fact that there are no common algorithms for the treatment. Of great importance is the ges'tation period, because in its different parts, the risks vary in grade. It is believed that up to 10-12th ges.tation week chemotherapy should not be included. The optimal time for the last course is 35th gestation week or three weeks to the due date. The purpose of this review is to examine the benefits and risks of the treatment of malignant diseases during pregnancy for both the mother and the fetus.

Mechanisms of Fatal Cardiotoxicity following High-Dose Cyclophosphamide Therapy and a Method for Its Prevention

Observed only after administration of high doses, cardiotoxicity is the dose-limiting effect of cyclophosphamide (CY). We investigated the poorly understood cardiotoxic mechanisms of high-dose CY. A rat cardiac myocardial cell line, H9c2, was exposed to CY metabolized by S9 fraction of rat liver homogenate mixed with co-factors (CYS9). Cytotoxicity was then evaluated by 3-(4,5-dimethyl-2-thiazolyl)¬2,5-diphenyl¬2H-tetrazolium bromide (MTT) assay, lactate dehydrogenase release, production of reactive oxygen species (ROS), and incidence of apoptosis. We also investigated how the myocardial cellular effects of CYS9 were modified by acrolein scavenger N-acetylcysteine (NAC), antioxidant isorhamnetin (ISO), and CYP inhibitor β-ionone (BIO). Quantifying CY and CY metabolites by means of liquid chromatography coupled with electrospray tandem mass spectrometry, we assayed culture supernatants of CYS9 with and without candidate cardioprotectant agents. Assay results for MTT showed that treatment with CY (125-500 μM) did not induce cytotoxicity. CYS9, however, exhibited myocardial cytotoxicity when CY concentration was 250 μM or more. After 250 μM of CY was metabolized in S9 mix for 2 h, the concentration of CY was 73.6 ± 8.0 μM, 4-hydroxy-cyclophosphamide (HCY) 17.6 ± 4.3, o-carboxyethyl-phosphoramide (CEPM) 26.6 ± 5.3 μM, and acrolein 26.7 ± 2.5 μM. Inhibition of CYS9-induced cytotoxicity occurred with NAC, ISO, and BIO. When treated with ISO or BIO, metabolism of CY was significantly inhibited. Pre-treatment with NAC, however, did not inhibit the metabolism of CY: compared to control samples, we observed no difference in HCY, a significant increase of CEPM, and a significant decrease of acrolein. Furthermore, NAC pre-treatment did not affect intracellular amounts of ROS produced by CYS9. Since acrolein seems to be heavily implicated in the onset of cardiotoxicity, any competitive metabolic processing of CY that reduces its transformation to acrolein is likely to be an important mechanism for preventing cardiotoxicity.

Combination of letrozole, metronomic cyclophosphamide and sorafenib is well-tolerated and shows activity in patients with primary breast cancer

PURPOSE

To assess whether the combination of letrozole, metronomic cyclophosphamide and sorafenib (LCS) is well tolerated and shows activity in primary breast cancer (BC).

METHODS

Thirteen oestrogen receptor-positive, postmenopausal, T2-4, N0-1 BC patients received the LCS combination for 6 months. In these patients we examined the pharmacokinetics of sorafenib and cyclophosphamide, toxicity of the regimen, the clinical response to therapy and changes in the levels of biologically relevant biomarkers.

RESULTS

Adequate plasma concentrations of sorafenib were achieved in patients when it was dosed in combination with L+C. The mean plasma concentrations of C were consistently lower following administration of LCS, compared with administration of L+C only. The most common drug-related grade 3/4 adverse events were skin rash (69.3%), hand-foot skin reaction (69.3%) and diarrhoea (46.1%). According to RECIST Criteria, a clinical complete response was observed in 6 of 13 patients. A significant reduction in tumour size, evaluated with MRI, was also observed between baseline and 14 days of treatment in all 13 patients (P=0.005). A significant reduction in SUV uptake, measured by (18)FDG-PET/CT, was observed in all patients between baseline and 30 days of treatment (P=0.015) and between baseline and definitive surgery (P=0.0002). Using modified CT Criteria, a response was demonstrated in 8 out of 10 evaluable patients at 30 days and in 11 out of 13 evaluable patients at the definitive surgery. A significant reduction in Ki67 expression was observed in all patients at day 14 compared with baseline (P<0.00001) and in 9 out of 13 patients at the definitive surgery compared with baseline (P<0.03). There was also a significant suppression of CD31 and VEGF-A expression in response to treatment (P=0.01 and P=0.007, respectively).

CONCLUSIONS

The LCS combination is feasible and tolerable. The tumour response and target biomarker modulation indicate that the combination is clinically and biologically active.

Involvement of a volatile metabolite during phosphoramide mustard-induced ovotoxicity

The finite ovarian follicle reserve can be negatively impacted by exposure to chemicals including the anti-neoplastic agent, cyclophosphamide (CPA). CPA requires bioactivation to phosphoramide mustard (PM) to elicit its therapeutic effects however; in addition to being the tumor-targeting metabolite, PM is also ovotoxic. In addition, PM can break down to a cytotoxic, volatile metabolite, chloroethylaziridine (CEZ). The aim of this study was initially to characterize PM-induced ovotoxicity in growing follicles. Using PND4 Fisher 344 rats, ovaries were cultured for 4 days before being exposed once to PM (10 or 30 μM). Following eight additional days in culture, relative to control (1% DMSO), PM had no impact on primordial, small primary or large primary follicle number, but both PM concentrations induced secondary follicle depletion (P<0.05). Interestingly, a reduction in follicle number in the control-treated ovaries was observed. Thus, the involvement of a volatile, cytotoxic PM metabolite (VC) in PM-induced ovotoxicity was explored in cultured rat ovaries, with control ovaries physically separated from PM-treated ovaries during culture. Direct PM (60 μM) exposure destroyed all stage follicles after 4 days (P<0.05). VC from nearby wells depleted primordial follicles after 4 days (P<0.05), temporarily reduced secondary follicle number after 2 days, and did not impact other stage follicles at any other time point. VC was determined to spontaneously liberate from PM, which could contribute to degradation of PM during storage. Taken together, this study demonstrates that PM and VC are ovotoxicants, with different follicular targets, and that the VC may be a major player during PM-induced ovotoxicity observed in cancer survivors.

A pilot pharmacologic biomarker study in HLA-haploidentical hematopoietic cell transplant recipients

PURPOSE

Eleven patients diagnosed with various hematologic malignancies receiving an HLA-haploidentical hematopoietic cell transplant (HCT) participated in an ancillary biomarker trial. The goal of the trial was to evaluate potential pharmacologic biomarkers pertinent to the conditioning regimen [fludarabine monophosphate (fludarabine) and cyclophosphamide (CY)] or postgrafting immunosuppression [CY and mycophenolate mofetil (MMF)] in these patients.

METHODS

We characterized the interpatient variability of nine pharmacologic biomarkers. The biomarkers evaluated were relevant to fludarabine (i.e., area under the curve (AUC) of 2-fluoro-ara-A or F-ara-A), CY (i.e., AUCs of CY and four of its metabolites), and MMF (i.e., total mycophenolic acid (MPA) AUC, unbound MPA AUC, and inosine monophosphate dehydrogenase (IMPDH) activity).

RESULTS

Interpatient variability in the pharmacologic biomarkers was high. Among those related to HCT conditioning, the interpatient variability ranged from 1.5-fold (CY AUC) to 4.0-fold (AUC of carboxyethylphosphoramide mustard, a metabolite of CY). Among biomarkers evaluated as part of postgrafting immunosuppression, the interpatient variability ranged from 1.7-fold (CY AUC) to 4.9-fold (IMPDH area under the effect curve). There was a moderate correlation (R (2) = 0.441) of within-patient 4-hydroxycyclophosphamide formation clearance.

CONCLUSIONS

Considerable interpatient variability exists in the pharmacokinetic and drug-specific biomarkers potentially relevant to clinical outcomes in HLA-haploidentical HCT recipients. Pharmacodynamic studies are warranted to optimize the conditioning regimen and postgrafting immunosuppression administered to HLA-haploidentical HCT recipients.

Cyclophosphamide followed by intravenous targeted busulfan for allogeneic hematopoietic cell transplantation: pharmacokinetics and clinical outcomes

Targeted busulfan ((T)BU) and cyclophosphamide (CY) for allogeneic hematopoietic cell transplantation carries a high risk of sinusoidal obstruction syndrome (SOS) in patients undergoing transplantation for myelofibrosis. We tested the hypothesis that reversing the sequence of administration (from (T)BU/CY to CY/(T)BU) would reduce SOS and day +100 nonrelapse mortality. We enrolled 51 patients with myelofibrosis (n = 20), acute myelogenous leukemia (n = 20), or myelodysplastic syndrome (n = 11) in a prospective trial of CY/(T)BU conditioning for allogeneic hematopoietic cell transplantation. CY 60 mg/kg/day i.v. for 2 days was followed by daily i.v. BU for 4 days, targeted to a concentration at steady state (Css) of 800-900 ng/mL. Compared with (T)BU/CY-conditioned patients, CY/(T)BU-conditioned patients had greater exposure to CY (P < .0001) and less exposure to 4-hydroxycyclophosphamide (P < .0001). Clinical outcomes were compared between cases and controls (n = 271) conditioned with (T)BU/CY for the same indications. In patients with myelofibrosis, CY/(T)BU conditioning was associated with a significantly reduced incidence of SOS (0% versus 30% after (T)BU/CY; P = .006), whereas the incidence of SOS was low in both cohorts with acute myelogenous leukemia/myelodysplastic syndrome. Day +100 mortality was significantly lower in the CY/(T)BU cohort (2% versus 13%; P = .01). CY/(T)BU conditioning had a marked affect on the pharmacokinetics of CY and was associated with significantly lower incidence of SOS and day +100 mortality, suggesting that CY/(T)BU is superior to (T)BU/CY as conditioning for patients with myelofibrosis.

Obesity effects on cyclophosphamide-induced DNA damage in hematopoietic cell transplant recipients

BACKGROUND

Cyclophosphamide, an alkylating agent, is metabolically activated to phosphoramide mustard, to form toxic DNA-DNA (G-NOR-G) crosslinks. Increased exposure to cyclophosphamide metabolites has been associated with treatment-related toxicity. The effect of obesity on exposure to cyclophosphamide-induced G-NOR-G crosslinks is not known. Therefore we sought to determine whether obesity affects the formation of cyclophosphamide-specific G-NOR-G crosslinks.

PATIENTS AND METHODS

Plasma cyclophosphamide concentrations and blood cell G-NOR-G amounts were measured.

RESULTS

Overweight/obese patients received a significantly higher daily cyclophosphamide dose (median 3000 vs. 4450 mg, p<0.01). Despite the higher doses, overweight/obese patients had lower exposure to cyclophosphamide compared to lean patients with an area under the curve (AUC(0-∞)) =529.24 vs. 867.99 μcg/ml*h respectively, p<0.01. G-NOR-G amounts were similar in overweight/obese and lean subjects, AUC(0-∞)=142.8 vs. 147.0 adducts/10(6) nucleotides*h, respectively, p=0.59.

CONCLUSION

Overweight/obese patients have altered metabolism and disposition of cyclophosphamide. This altered exposure may be an important determinant of efficacy and may play a role in treatment-related mortality.

Biological monitoring of occupational exposure to antineoplastic drugs in hospital settings

BACKGROUND

In view of the evidence of cytotoxicity of chemotherapic antineoplastic drugs (AD), current guidelines recommend the evaluation of the health risks of hospital personnel exposed to these compounds. Biological monitoring is the main tool to evaluate all possible drug intake and measure workers' real risk.

OBJECTIVES

The aim of this study was to assess occupational exposure toAD in a large hospital in Northern Italy in order to verify the effectiveness of the structural and procedural improvements carried out over the last decade.

METHODS

Three biological monitoring campaigns were performed using LC-MS/MS analysis of cyclophosphamide (CP) and metotrexate (MTX) as biomarkers of internal dose in the urine of hospital workers. In the first two campaigns, 50 and 81 workers respectively were monitored during AD preparation operations. The last campaign, concerning AD administration activity, was performed after a centralized preparation unit had been set up. Two environmental monitoring campaigns were carried out as well, to complete AD exposure assessment.

RESULTS

During the first monitoring campaign we found positive urinary samples in all the wards studied (total positivity 36%), whereas in the second campaign 11% of the samples were positive and four departments showed negative results in all urine samples. The last campaign showed all urinary CP and MTX levels below the detection limit of the analytical method

CONCLUSION

Exposure of oncology ward nurses considerably decreased due to the centralization of AD preparation operations together with training and education of workers. The last biological monitoring results were reassuring; nevertheless, surface contamination still occurred and safety measures should be further improved in order to achieve the lowest reasonably possible contamination levels.

Pharmacokinetics of 5-fluorouracil and cyclophosphamide in depression rats

OBJECTIVES

Efficacy and toxicity of the drug are mainly determined by physicochemical properties and pharmacological effects of its own. In addition, they are also affected by other factors, such as gender, age, genetic character, pathophysiological status, mood states and so on. The paper aims to study whether mood disorder alters drug metabolism process through the pharmacokinetic research on some clinically important anticancer drugs in depression model rats.

MATERIALS AND METHODS

The depression model rats were built by exposing to chronic unpredicted mild stresses (CUMS) for 8 weeks. 36 female Sprague-Dawley (SD) rats were randomized into model group and control group. In each group, 18 rats were randomized into 2 subgroups: 5-fluorouracil (5-FU) subgroup and cyclophosphamide (CP) subgroup which were given a certain doses of 5-FU and CP. The blood samples were collected at different time points and plasma drug concentration were respectively assayed by high performance liquid chromatography (HPLC) for 5-FU and high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) for CP. Pharmacokinetic parameters were processed with DAS software.

RESULTS

There were significant differences in the pharmacokinetic parameters of 5-FU and CP between in depression model rats group and in the normal control group (p < 0.05), except t1/2alpha (p > 0.05) for CP pharmacokinetics in depression model rats group and in the normal control rats group, with the value of those was 0.07 and 0.09 h.

CONCLUSIONS

Depression mood disorder might alter drug metabolism process.

Xenobiotic metabolomics: major impact on the metabolome

Xenobiotics are encountered by humans on a daily basis and include drugs, environmental pollutants, cosmetics, and even components of the diet. These chemicals undergo metabolism and detoxication to produce numerous metabolites, some of which have the potential to cause unintended effects such as toxicity. They can also block the action of enzymes or receptors used for endogenous metabolism or affect the efficacy and/or bioavailability of a coadministered drug. Therefore, it is essential to determine the full metabolic effects that these chemicals have on the body. Metabolomics, the comprehensive analysis of small molecules in a biofluid, can reveal biologically relevant perturbations that result from xenobiotic exposure. This review discusses the impact that genetic, environmental, and gut microflora variation has on the metabolome, and how these variables may interact, positively and negatively, with xenobiotic metabolism.

Antiangiogenesis enhances intratumoral drug retention

The tumor vasculature delivers nutrients, oxygen, and therapeutic agents to tumor cells. Unfortunately, the delivery of anticancer drugs through tumor blood vessels is often inefficient and can constitute an important barrier for cancer treatment. This barrier can sometimes be circumvented by antiangiogenesis-induced normalization of tumor vasculature. However, such normalizing effects are transient; moreover, they are not always achieved, as shown here, when 9L gliosarcoma xenografts were treated over a range of doses with the VEGF receptor-selective tyrosine kinase inhibitors axitinib and AG-028262. The suppression of tumor blood perfusion by antiangiogenesis agents can be turned to therapeutic advantage, however, through their effects on tumor drug retention. In 9L tumors expressing the cyclophosphamide-activating enzyme P450 2B11, neoadjuvant axitinib treatment combined with intratumoral cyclophosphamide administration significantly increased tumor retention of cyclophosphamide and its active metabolite, 4-hydroxycyclophosphamide. Similar increases were achieved using other angiogenesis inhibitors, indicating that increased drug retention is a general response to antiangiogenesis. This approach can be extended to include systemic delivery of an anticancer prodrug that is activated intratumorally, where antiangiogenesis-enhanced retention of the therapeutic metabolite counterbalances the decrease in drug uptake from systemic circulation, as exemplified for cyclophosphamide. Importantly, the increase in intratumoral drug retention induced by neoadjuvant antiangiogenic drug treatment is shown to increase tumor cell killing and substantially enhance therapeutic activity in vivo. Thus, antiangiogenic agents can be used to increase tumor drug exposure and improve therapeutic activity following intratumoral drug administration, or following systemic drug administration in the case of a therapeutic agent that is activated intratumorally.

In vitro evaluation of the permeation of cytotoxic drugs through reconstructed human epidermis and oral epithelium

BACKGROUNDS

Occupational exposure to antineoplastic agents may represent a risk to health care workers, although the relevance of different exposure routes is not fully understood. The objectives of this study were to determine in vitro permeation of four widely used cytotoxic drugs (cisplatin, cyclophosphamide, doxorubicin, and fluorouracil) through two reconstituted tissue models representing human skin epidermis and oral mucosa.

MATERIALS AND METHODS

Experiments were conducted with reconstructed models of human epidermis and oral epithelium, cultured in a chemically-defined medium under conditions simulating possible exposure scenarios (6 h duration, three concentrations corresponding to commonly used application doses). The amounts of drugs permeated through the tissues into the receptor media were determined using ultra performance liquid chromatography with photospectrometric detection.

RESULTS

The highest epidermis permeations (P = 0.2 x 10(-3) - 1.5 x 10(-3) cm x h(-1)) were observed with three polar drugs (cisplatin, cyclophosphamide and fluorouracil), while permeation by more hydrophobic doxorubicin was minor (P(max) = 0.03 x 10(-3) cm x h(-1)). As expected, more pronounced tissue permeation was observed with the reconstructed oral epithelium having the maximum permeability coefficient (P = 180 x 10(-3) cm x h(-1)) for cisplatin and fluorouracil. Histological evaluation of the exposed tissues revealed cytotoxic effects at higher doses, especially for oral epithelium.

CONCLUSION

Although the skin epidermis with keratinised stratum corneum provided relatively good protection, uptake (of at least some investigated drugs) via both types of tissue should not be underestimated. Our results provide basic experimental data on the skin and oral epithelia permeation for further modelling of exposure and health risk assessment.

Linking genotoxic responses with cytotoxic and behavioural or physiological consequences: differential sensitivity of echinoderms (Asterias rubens) and marine molluscs (Mytilus edulis)

Integrated laboratory studies addressed multiple biomarker responses in the sea star (Asterias rubens) and the blue mussel (Mytilus edulis) exposed to a range of concentrations of direct and indirect acting genotoxins: methyl methane sulfonate (MMS) and cyclophosphamide (CP; an environmentally relevant anti-cancer pharmaceutical), respectively, in order to determine if the expressed genotoxicity has knock-on effects at the higher levels of biological organisation. The experimental design aimed to concurrently evaluate biomarkers of behavioural and physiological conditions (i.e. 'righting time' and 'clearance rate' for sea stars and mussels, respectively) in addition to cytotoxicity (neutral red retention assay), induction of micronuclei (Mn) and DNA strand breaks (as determined by the Comet assay). The protocol also included the determination of the maximum tolerated concentration (MTC), prior to genotoxic evaluation. The 3d MTC, as determined by the survival of the organisms, showed sea stars to be more sensitive than mussels to MMS (18 and 32 mg L(-1), respectively) and CP (56 and 180 mg L(-1), respectively). For both species and chemicals, cytotoxicity was not found to be significantly different compared to controls. Apart from the MMS exposure to sea stars (which showed 100% mortality at higher concentrations after 5d exposure), clear dose-response relationships were observed for both genotoxicity endpoints in each species. Following exposure to CP, good correlations were also found between the behavioural and physiological responses and genetic damage in each species (sea stars-MN vs. RT: R=0.73; Comet vs. RT: R=0.91; mussels-MN vs. CR: R=0.69; Comet vs. CR: R=0.72). This integrated approach, applying non-invasive assays to simultaneously determine the responses at different levels of biological organisation, indicates the potential value of behavioural and physiological measures in determining the toxicity of chemicals to marine organisms and highlights also the relevance of including adult echinoderms in environmental studies.

MRI measurements of tumor size and pharmacokinetic parameters as early predictors of response in breast cancer patients undergoing neoadjuvant anthracycline chemotherapy

PURPOSE

To investigate the value of using changes in three parameters (tumor size, transfer constant (K(trans)), and rate constant (k(ep))) obtained after the first treatment-cycle in predicting the final clinical response after two to four cycles of neoadjuvant anthracycline and cyclophosphamide (AC) chemotherapy.

MATERIALS AND METHODS

Early changes in the three parameters were measured in 29 patients with invasive breast cancer by MRI after one cycle of treatment. Changes were then assessed for their predictive value of final clinical response and compared among patients with four different response patterns, Group 1 = responder (R) after one cycle and also R after four cycles, Group 2 = nonresponder (NR) after one cycle, but eventual R after four cycles, Group 3 = NR after one cycle and still NR after four cycles, and Group 4 = NR after one cycle and determined as NR after two cycles, being switched to the taxane regimen.

RESULTS

Pearson's correlation analysis revealed significant correlation between early changes in tumor size and both pharmacokinetic parameters (r = 0.49 and P < 0.01 for K(trans), r = 0.66 and P < 0.001 for k(ep)). The areas under the receiver operating characteristic (ROC) curve differentiating between R (Groups 1+2) and NR (Groups 3+4) groups using changes in tumor size, K(trans), and k(ep) were 0.88 (standard error [SE] = 0.06, P < 0.0001), 0.63 (SE = 0.11, P = 0.11), and 0.77 (SE = 0.09, P = 0.001), respectively.

CONCLUSION

Early tumor size change in MRI after one cycle is better response predictor than that of either K(trans) or k(ep) in breast cancer undergoing neoadjuvant chemotherapy using an AC regimen.

Enhancement of intratumoral cyclophosphamide pharmacokinetics and antitumor activity in a P450 2B11-based cancer gene therapy model

The therapeutic utility of cytochrome P450-based enzyme prodrug therapy is well established by preclinical studies and in initial clinical trials. The underlying premise of this gene therapy is that intratumoral P450 expression leads to in situ activation of anticancer P450 prodrugs, such as cyclophosphamide (CPA), with intratumoral accumulation of its activated 4-OH metabolite. In mice bearing 9L gliosarcomas expressing the CPA 4-hydroxylase P450 2B6, enhanced tumor apoptosis was observed 48 h after CPA treatment; however, intratumoral 4-OH-CPA levels were indistinguishable from those of P450-deficient tumors, indicating that the bulk of activated CPA is derived from hepatic metabolism. In contrast, in 9L tumors expressing P450 2B11, a low K(m) CPA 4-hydroxylase, intratumoral 4-OH-CPA levels were higher than in blood, liver and P450-deficient tumors. Intratumoral 4-OH-CPA increased dose-dependently, without saturation at 140 mg kg(-1) CPA, suggesting restricted tumor cell permeation of the parent drug. To circumvent this problem, CPA was administered by direct intratumoral injection, which increased the maximum concentration and area under the curve of drug concentration x time (AUC) of intratumoral 4-OH-CPA by 1.8- and 2.7-fold, respectively. An overall 3.9-fold increase in intratumoral 4-OH-CPA AUC, and in antitumor activity, was obtained when CPA release to systemic circulation was delayed using the slow-release polymer poloxamer 407 as vehicle for intratumoral CPA delivery. These findings highlight the advantage of gene therapy strategies that combine low K(m) P450 prodrug activation enzymes with slow, localized release of P450 prodrug substrates.

Pharmacodynamic and pharmacokinetic study of chronic low-dose metronomic cyclophosphamide therapy in mice

Prolonged, frequently administered low-dose metronomic chemotherapy (LDM) is being explored (pre)clinically as a promising antiangiogenic antitumor strategy. Although appealing because of a favorable side effect profile and mostly oral dosing, LDM involves new challenges different from conventional maximum tolerated dose chemotherapy. These include possible altered pharmacokinetic characteristics due to long-term drug exposure potentially resulting in acquired resistance and increased risk of unfavorable drug interactions. We therefore compared the antitumor and antivascular effects of LDM cyclophosphamide (CPA) given to mice that had been pretreated with either LDM CPA or normal saline, obtained blood 4-hydroxy-CPA (activated CPA) concentrations using either gas chromatography/mass spectrometry or liquid chromatography/tandem mass spectrometry in mice treated with LDM CPA, and measured hepatic and intratumoral activity of enzymes involved in the biotransformation of CPA and many other drugs [i.e., cytochrome P450 3A4 (CYP3A4) and aldehyde dehydrogenase]. Exposure of mice to LDM CPA for >or=8 weeks did not compromise subsequent activity of LDM CPA therapy, and biologically active 4-hydroxy-CPA levels were maintained during long-term LDM CPA administration. Whereas the effects on CYP3A4 were complex, aldehyde dehydrogenase activity was not affected. In summary, our findings suggest that acquired resistance to LDM CPA is unlikely accounted for by altered CPA biotransformation. In the absence of reliable pharmacodynamic surrogate markers, pharmacokinetic parameters might become helpful to individualize/optimize LDM CPA therapy. LDM CPA-associated changes of CYP3A4 activity point to a potential risk of unfavorable drug interactions when compounds that are metabolized by CYP3A4 are coadministered with LDM CPA.

Validation of urinary excretion of cyclophosphamide as a biomarker of exposure by studying its renal clearance at high and low plasma concentrations in cancer patients

OBJECTIVES

Cyclophosphamide (CP) is an alkylating agent classified as a human carcinogen. Health care workers handling this drug may be exposed during, e.g., preparation or administration. Cyclophosphamide is readily absorbed by inhalation and by dermal uptake. A biomarker, CP in urine, has frequently been used to assess the occupational exposure to CP, but has not been fully validated. The aim of this study was to investigate if the proportion of the CP dose that is excreted in urine (renal clearance) is constant over different plasma drug concentrations and other pharmacokinetic parameters, e.g., urine flow.

METHODS

Pharmacokinetics of CP were studied in 16 breast cancer patients that were treated with postoperative adjuvant chemotherapy including CP. Plasma and urine from the patients were collected at different occasions up to 12 days after the dose. Urine was collected during 4-h periods and blood was sampled at the end of each period. Analysis of CP was performed by liquid chromatography tandem mass spectrometry. The limit of detection for CP in urine and plasma was 0.01 and 0.02 ng/ml, respectively. The precisions of the developed methods were determined to < or =8%.

RESULTS

The administered doses of CP in absolute amounts ranged between 800 and 2,240 mg. Mean renal clearance of CP was 8.6 (confidence interval 6.5-10.7) ml/min and was not significantly dependent of the plasma drug concentration. However, a significant correlation between renal clearance and urine flow was observed. There was a large inter-individual variation in the plasma and urine concentrations even when the same doses were given.

CONCLUSIONS

Cyclophosphamide in urine can be continued to be used as a biomarker to monitor occupational exposure to CP, however the inter-individual variability of excretion of CP in urine, and its dependency on urine flow must be taken into consideration in future applications.

Genetic polymorphisms of CYP2B6 affect the pharmacokinetics/pharmacodynamics of cyclophosphamide in Japanese cancer patients

OBJECTIVE

To evaluate the effects of genetic polymorphisms of drug metabolizing enzymes on the pharmacokinetics of cyclophosphamide and its active metabolite, 4-hydroxycyclophosphamide, and on the pharmacodynamics.

EXPERIMENTAL DESIGN

One hundred and three Japanese patients with malignant lymphoma or breast cancer treated with cyclophosphamide (500-750 mg/m) participated in this study. The plasma concentrations of cyclophosphamide and 4-hydroxycyclophosphamide were determined by high-performance liquid chromatography, and pharmacokinetic parameters were calculated. The genotypes of CYP2B6, CYP2C19, CYP3A4, CYP3A5, ALDH1A1, GST genes were determined by allele-specific polymerase chain reaction or polymerase chain reaction-restriction-fragment length polymorphism.

RESULTS

A large interindividual difference (54-fold) was observed in the area under the curve ratio of 4-hydroxycyclophosphamide/cyclophosphamide calculated as the metabolic index. We first proved that leukocytopenia and neutropenia were significantly (P<0.01) related to the area under the curve of 4-hydroxycyclophosphamide. We found that the homozygotes of CYP2B6*6 (Q172H and K262R) showed significantly (P<0.05) higher clearance and shorter half-life of cyclophosphamide than heterozygotes and homozygotes of CYP2B6*1. The small sample size, however, limited the impact. On the other hand, it was clearly demonstrated that the patients possessing the single nucleotide polymorphisms of the CYP2B6 gene, g.-2320T>C, g.-750T>C (5'-flanking region), g.15582C>T (intron 3), or g.18492T>C (intron 5), had significantly lower area under the curve ratios of 4-hydroxycyclophosphamide/cyclophosphamide, indicating a decreased cyclophosphamide 4-hydroxylation. Of particular importance was the finding that leukocytopenia was significantly related to the single nucleotide polymorphisms g.-2320T>C, g.-750T>C, and g.18492T>C in CYP2B6 gene, which are highly linked. No relationship was observed between the pharmacokinetics of cyclophosphamide or 4-hydroxycyclophosphamide and genetic polymorphisms of the other enzymes.

CONCLUSIONS

We clarified that the single nucleotide polymorphisms in the promoter region or introns in the CYP2B6 affect the potency of cyclophosphamide activation to 4-hydroxycyclophosphamide. This information would be valuable for predicting adverse reactions and the clinical efficacy of cyclophosphamide.

Simultaneous analysis of cyclophosphamide, doxorubicin and doxorubicinol by liquid chromatography coupled to tandem mass spectrometry

A method for the simultaneous determination of cyclophosphamide (CP), doxorubicin (dox), and doxorubicinol (dol) was developed and validated to analyze 400 microL of plasma from patients receiving chemotherapeutic treatment with CP and dox. Final calibration ranges for the analytes were 0.440-60.0 microg/mL for cyclophosphamide, 7.20-984 ng/mL for dox and 3.04-104 ng/mL for dol. The samples were prepared using solid phase extraction and analyzed using a gradient separation over a Waters Symmetry C18, 2.1 by 30 mm (Milford, MA) column. Detection was achieved in positive mixed reaction monitoring mode on a triple quadrupole mass spectrometer.

Pharmacokinetic considerations in the treatment of CNS tumours

Despite aggressive therapy, the majority of primary and metastatic brain tumour patients have a poor prognosis with brief survival periods. This is because of the different pharmacokinetic parameters of systemically administered chemotherapeutic agents between the brain and the rest of the body. Specifically, before systemically administered drugs can distribute into the CNS, they must cross two membrane barriers, the blood-brain barrier (BBB) and blood-cerebrospinal fluid (CSF) barrier (BCB). To some extent, these structures function to exclude xenobiotics, such as anticancer drugs, from the brain. An understanding of these unique barriers is essential to predict when and how systemically administered drugs will be transported to the brain. Specifically, factors such as physiological variables (e.g. blood flow), physicochemical properties of the drug (e.g. molecular weight), as well as influx and efflux transporter expression at the BBB and BCB (e.g. adenosine triphosphate-binding cassette transporters) determine what compounds reach the CNS. A large body of preclinical and clinical research exists regarding brain penetration of anticancer agents. In most cases, a surrogate endpoint (i.e. CSF to plasma area under the concentration-time curve [AUC] ratio) is used to describe how effectively agents can be transported into the CNS. Some agents, such as the topoisomerase I inhibitor, topotecan, have high CSF to plasma AUC ratios, making them valid therapeutic options for primary and metastatic brain tumours. In contrast, other agents like the oral tyrosine kinase inhibitor, imatinib, have a low CSF to plasma AUC ratio. Knowledge of these data can have important clinical implications. For example, it is now known that chronic myelogenous leukaemia patients treated with imatinib might need additional CNS prophylaxis. Since most anticancer agents have limited brain penetration, new pharmacological approaches are needed to enhance delivery into the brain. BBB disruption, regional administration of chemotherapy and transporter modulation are all currently being evaluated in an effort to improve therapeutic outcomes. Additionally, since many chemotherapeutic agents are metabolised by the cytochrome P450 3A enzyme system, minimising drug interactions by avoiding concomitant drug therapies that are also metabolised through this system may potentially enhance outcomes. Specifically, the use of non-enzyme-inducing antiepileptic drugs and curtailing nonessential corticosteroid use may have an impact.

Gene signature-based prediction of tumor response to cyclophosphamide

Cyclophosphamide (CY) is a clinically used cytotoxic agent that is effective in a wide range of tumor types including breast and small cell lung cancers. However, by far not all patients benefit from CY therapy. We used patient tumor explants grown in nude mice as an experimental model system to identify a gene signature that, based on a tumor's gene expression profile, predicts its CY response. Forty-nine human tumor xenografts of different histologies were defined as the training set. Correlation of the gene expression profiles of untreated tumors to the sensitivity of the same tumors to CY led to the identification of 129 transcripts as predictive biomarkers for CY response. Interestingly, the products of 12 of these genes were known to interact at least indirectly with CY. A leave-one-out cross-validation approach led to a correct prediction of the CY response of the training set tumors in 15 out of 18 cases (83%) as compared to a response rate of 18 out of 49 (32%), following random testing. For an independent set of 25 previously untested tumors with known gene expression profiles (validation set) CY sensitivity was predicted correctly for 6 out of 8 tumors (75%), and CY resistance for 15 out of 17 tumors (88%). In comparison, random testing of the same tumors resulted in a response rate of 8 out of 25 (32%). For the same 25 tumors, the median minimum T/C value for predicted responders was 1% as compared to 49% for predicted non-responders. Finally, for tumor types considered as CY sensitive such as small cell lung and breast cancers as well as melanoma, the combined real and predicted response rates for 37 tested and 26 untested tumors was 49%. In contrast, for tumor types considered as CY resistant, including colon and renal cancer, the combined real and predicted response rate for 37 tested and 75 untested tumors was only 13%. Taken together, we identified a gene signature that can predict tumor response to CY and warrants clinical validation.

Fluconazole coadministration concurrent with cyclophosphamide conditioning may reduce regimen-related toxicity postmyeloablative hematopoietic cell transplantation

In a previous study comparing fluconazole and itraconazole administered as antifungal prophylaxis in hematopoietic cell transplant (HCT) recipients, we found that fluconazole administration concurrent with cyclophosphamide (CY)-based conditioning was associated with fewer early toxicities compared to itraconazole. Fluconazole inhibits cytochrome P450 2C9, which is involved with the activation of CY, and so might provide protection from CY-related toxicities. To investigate this further, we compared CY and CY-metabolite data from patients who received fluconazole (n = 56) concurrent with CY-containing conditioning and in patients who did not (n = 17). The fluconazole group had greater exposure to CY, and lower peak serum concentration of CY-metabolite 4-hydroxycyclophosphamide. In a separate cohort, we examined outcomes in patients randomized to receive either fluconazole (n = 152) or placebo (n = 147) concurrent with CY-containing conditioning in a prior randomized trial. Patients who received fluconazole experienced less hepatic and renal toxicity, and had lower mortality. No difference in relapsed malignancy was apparent. These data support the hypothesis that fluconazole, when coadministered with CY, decreases CY-related toxicities by inhibiting cytochrome P450 2C9 metabolism.

Simultaneous quantification of cyclophosphamide and its active metabolite 4-hydroxycyclophosphamide in human plasma by high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-MS/MS)

Cyclophosphamide is a cytotoxic prodrug with a very narrow therapeutic index. To study the clinical pharmacology of cyclophosphamide in a large cohort of patients a previously published method for the simultaneous quantitative determination of cyclophosphamide and 4-hydroxycyclophosphamide in human plasma using liquid chromatography tandem mass spectrometry (LC-MS/MS) was optimized. Addition of an isotopically labelled internal standard and adaptation of the gradient resulted in a fast, robust and sensitive assay. Because 4-hydroxycyclophosphamide is not stable in plasma, the compound is derivatized with semicarbazide immediately after sample collection. Sample preparation was carried out by protein precipitation with methanol-acetonitrile (1:1, v/v), containing isotopically labelled cyclophosphamide and hexamethylphosphoramide as internal standards. The LC separation was performed on a Zorbax Extend C18 column (150 mm x 2.1 mm ID, particle size 5 microm) with 1 mM ammonium hydroxide in water-acetonitrile (90:10, v/v) as the starting gradient, at a flow-rate of 0.40 mL/min with a total run time of 6 min. The lower limit of quantification (LLQ, using a 100 microL sample volume) was 200 ng/mL and the linear dynamic range extended to 40,000 ng/mL for cyclophosphamide and 50-5000 ng/mL for 4-hydroxycyclophosphamide. Accuracies as well as precisions were lower than 20% at the LLQ concentration and lower than 15% for all other concentrations. This method has been successfully applied in our institute to support ongoing studies into the pharmacokinetics and pharmacogenetics of cyclophosphamide.

A mouse model with liver-specific deletion and global suppression of the NADPH-cytochrome P450 reductase gene: characterization and utility for in vivo studies of cyclophosphamide disposition

A mouse model combining liver-specific deletion with global suppression of the NADPH-cytochrome P450 reductase gene (Cpr) has been developed and characterized. These mice (designated "Cpr-low and liver-Cpr-null" or CL-LCN) retain the respective phenotypes of the previously reported Cpr-low (CL) and liver-Cpr-null (LCN) mouse strains, but hepatic deletion of the Cpr gene occurs at an earlier age in the CL-LCN mouse than in the LCN mouse. Residual hepatic microsomal CPR activities are very low in both CL-LCN and LCN mice (at 1.5 and 2.5% of wild-type levels, respectively). The utility of CL-LCN mice for in vivo drug metabolism studies was explored using the cytochrome P450 (P450) prodrug cyclophosphamide (CPA). After i.p. injection of CPA at 100 mg/kg, the t1/2 and the area under the concentration-time curve for plasma CPA were significantly increased in mice deficient in liver CPR compared with wild-type controls, indicating a lower rate of metabolism, with the effects greater in CL-LCN mice than in LCN mice. Correspondingly, substantial decreases in Cmax, and increases in Tmax, and t1/2, of 4-hydroxycyclophosphamide (4-OH-CPA) formation were observed in both LCN and CL-LCN mice relative to wild-type controls. In contrast, CPA and 4-OH-CPA pharmacokinetic parameters were essentially unchanged in CL mice, relative to wild-type controls. The slower elimination of CPA in CL-LCN mice compared with LCN mice suggests a role for extrahepatic P450 in the in vivo metabolism of CPA and demonstrates the utility of the CL-LCN model in determining the role of extrahepatic P450 enzymes in drug metabolism and chemical toxicity.

Determination and pharmacokinetic study of norcantharidin in human serum by HPLC-MS/MS method

A sensitive, simple and selective high-performance liquid chromatography-tandem mass spectrometry method was developed and applied to the determination of norcantharidin concentration in human serum. Norcantharidin (NCTD) and cyclophosphamide (IS) in serum were extracted with acetone, separated on a C18 reversed-phase column, gradiently eluted with a mobile phase of acetonitrile-water containing 2 mm ammonium acetate and 0.1% formic acid (pH 3), ionized by positive ion pneumatically assisted electrospray and detected in the multi-reaction monitoring mode using precursor-->product ions of m/z 169.3-->123.1 for NCTD and 261.2-->140.2 for IS, respectively. The linear range of the calibration curve for NCTD was 2.5-50 ng/mL, with a lowest limit of quantification of 2.5 ng/mL, and the intra/inter-day RSD was less than 10%. The method was suitable for determination of low NCTD concentration in human serum after therapeutic oral doses, and has been successfully used for pharmacokinetic studies in healthy Chinese volunteers.

Real-time dose adjustment of cyclophosphamide in a preparative regimen for hematopoietic cell transplant: a Bayesian pharmacokinetic approach

PURPOSE

Dose-related toxicity of cyclophosphamide may be reduced and therapeutic efficacy may be improved by pharmacokinetic sampling and dose adjustment to achieve a target area under the curve (AUC) for two of its metabolites, hydroxycyclophosphamide (HCY) and carboxyethylphosphoramide mustard (CEPM). To facilitate real-time dose adjustment, we developed open-source code within the statistical software R that incorporates individual data into a population pharmacokinetic model.

EXPERIMENTAL DESIGN

Dosage prediction performance was compared to that obtained with nonlinear mixed-effects modeling using NONMEM in 20 cancer patients receiving cyclophosphamide. Bayesian estimation of individual pharmacokinetic parameters was accomplished from limited (i.e., five samples over 0-16 hours) sampling of plasma HCY and CEPM after the initial cyclophosphamide dose. Conditional on individual pharmacokinetics, simulations of the AUC of both HCY and CEPM were provided for a range of second doses (i.e., 0-100 mg/kg cyclophosphamide).

RESULTS

The results compared favorably with NONMEM and returned accurate predictions for AUCs of HCY and CEPM with comparable mean absolute prediction error and root mean square prediction error. With our method, the mean absolute prediction error and root mean square prediction error of AUC CEPM were 11.0% and 12.8% and AUC HCY were 31.7% and 44.8%, respectively.

CONCLUSIONS

We developed dose adjustment software that potentially can be used to adjust cyclophosphamide dosing in a clinical setting, thus expanding the opportunity for pharmacokinetic individualization of cyclophosphamide. The software is simple to use (requiring no programming experience), reads individual patient data directly from an Excel spreadsheet, and runs in less than 5 minutes on a desktop PC.

A Phase I Study of Pemetrexed (ALIMTA) and Cyclophosphamide in Patients with Locally Advanced or Metastatic Breast Cancer

PURPOSE

Determine the maximum tolerated dose (MTD) of pemetrexed and cyclophosphamide combination therapy for patients with locally advanced or metastatic breast cancer.

EXPERIMENTAL DESIGN

Patients with locally advanced or metastatic breast cancer and WHO performance status 0 to 2 were eligible. Pemetrexed (range, 400-2,400 mg/m(2)) was administered on day 1 of a 21-day schedule followed by cyclophosphamide (range, 400-800 mg/m(2)). Folic acid and vitamin B(12) supplementation began 1 to 2 weeks before the first pemetrexed dose.

RESULTS

Fifty-seven pretreated patients were enrolled and received 342 cycles (median, 4 cycles; range, 1-26) through 14 dose levels. The MTD of pemetrexed was 2,400 mg/m(2) (combined with cyclophosphamide, 600 mg/m(2)) with dose-limiting toxicities of grade 4 neutropenia with grade 4 infection and grade 3 diarrhea. Other grade 3 or 4 toxicities included (febrile) neutropenia, thrombocytopenia, anemia, elevated alanine aminotransferase/aspartate aminotransferase, and diarrhea. Pharmacokinetic analysis indicated that pemetrexed clearance and central volume of distribution were 40% lower than single-agent reference data, yielding a 68% increase in total systemic exposure and a 56% increase in maximal plasma concentration. Among the 50 patients evaluable for efficacy, 13 (26%) patients had a partial response and 17 (34%) patients had stable disease.

CONCLUSIONS

Pemetrexed was generally well tolerated. The observed toxicities were consistent with the known toxicity profiles of pemetrexed and cyclophosphamide. Considering the MTD and the toxicity and efficacy results in this and prior studies, a low (600 mg/m(2)) and a high (1,800 mg/m(2)) dose of pemetrexed with cyclophosphamide (600 mg/m(2)) will be evaluated in the consecutive prospective randomized phase II study.

Ex vivo expansion of mafosfamide-purged PBPC products

BACKGROUND

Multiple studies have demonstrated that 'purging' of autografts with 4-hydroperoxycyclophosphamide (4HC) or the related compound mafosfamide (Mf), to eradicate residual leukemia, produces the best results associated with autologous blood and marrow transplantation for AML. However, 4HC purging results in prolonged aplasia. Therefore, we evaluated the potential of ex vivo expansion of Mf-treated CD34+ cells from mobilized PBPC.

METHODS

CD34+ cells were isolated from PBPC products and treated with 30 microg/mL Mf. The Mf-treated CD34+ cells were washed and cultured for 14 days in StemLine II-defined media containing recombinant human (rh) SCF, G-CSF and thrombopoietin (Tpo).

RESULTS

Treatment with Mf resulted in 90% killing of progenitor cells (GM-CFC) but maintenance of SCID-repopulating cells (SRC). Ex vivo culture of the Mf-treated CD34+ cells resulted in decreased cell numbers (10-20% of the starting cell dose) during the first week. Nevertheless, in the second week of culture the total cell numbers expanded to approximately 20-fold above starting cell numbers and progenitor cells returned to approximately pre-treatment levels.

DISCUSSION

These studies demonstrate the potential of ex vivo culture to expand both total cell numbers and progenitor cells following treatment of PBPC CD34+ cells with Mf. Clinical studies are currently being initiated to evaluate the engraftment potential of these purged and expanded products.

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.

High exposures to bioactivated cyclophosphamide are related to the occurrence of veno-occlusive disease of the liver following high-dose chemotherapy

We investigated whether the occurrence of veno-occlusive disease of the liver (VOD) may be associated with individual variations in the pharmacokinetics of high-dose cyclophosphamide. Patients received single or multiple courses of cyclophosphamide (1000 or 1500 mg m-2 day-1), thiotepa (80 or 120 mg m-2 day-1) and carboplatin (265-400 mg m-2 day-1) (CTC) for 4 consecutive days. The area under the plasma concentration-time curves (AUCs) were calculated for cyclophosphamide and its activated metabolites 4-hydroxycyclophosphamide and phosphoramide mustard based on multiple blood samples. Possible relationships between the AUCs and the occurrence of VOD were studied. A total of 59 patients (115 courses) were included. Four patients experienced VOD after a second CTC course. The first-course AUC of 4-hydroxycyclophosphamide (P=0.003) but not of phosphoramide mustard (P=0.101) appeared to be predictive of the occurrence of VOD after multiple courses. High exposures to bioactivated cyclophosphamide may lead to increased organ toxicity.

Effects of polysaccharide peptide (PSP) from Coriolus versicolor on the pharmacokinetics of cyclophosphamide in the rat and cytotoxicity in HepG2 cells

Polysaccharide peptide (PSP), isolated from Coriolus versicolor COV-1, has been shown to restore the immunological effects against cyclophosphamide-induced immuno-suppression, although the mechanism(s) involved remain uncertain. This study investigated the PSP-cyclophosphamide interaction by studying the effects of PSP on the pharmacokinetic of cyclophosphamide in the rat and the effect of PSP on the cytotoxic effects of cyclophosphamide on a cancer cell line (HepG2 cells). In the pharmacokinetic studies in the rat, acute pre-treatment of PSP (4 micromol/kg/day, i.p.) decreased the clearance (CL) of cyclophosphamide by 31%, with a concomitant increase in the area under concentration-time curve (AUC) by 44%, and prolongation of the plasma half-life (T(1/2)) by 43%. Sub-chronic pre-treatment of PSP (2 micromol/kg/day, i.p., 3 days) decreased the CL of cyclophosphamide by 33%, with a concomitant increase in the AUC by 50%, and prolongation of the plasma T(1/2) by 34%. In cytotoxicity studies using HepG2 cells, non-toxic dose of PSP (1-10 microM) enhanced the cytotoxicity of cyclophosphamide. PSP at 10 microM further decreased HepG2 cell viability by 22% compared to when cyclophosphamide was present alone. In summary, PSP enhanced the cytotoxic effect of cyclophosphamide on a cancer cell line in vitro and altered the pharmacokinetics of cyclophosphamide in vivo in the rat. Both of these effects may be beneficial in the use of PSP as an adjunct to cyclophosphamide treatment.

Activation of oxazaphosphorines by cytochrome P450: Application to gene-directed enzyme prodrug therapy for cancer

Cancer chemotherapeutic prodrugs, such as the oxazaphosphorines cyclophosphamide and ifosfamide, are metabolized by liver cytochrome P450 enzymes to yield therapeutically active, cytotoxic metabolites. The effective use of these prodrugs is limited by host toxicity associated with the systemic distribution of cytotoxic metabolites formed in the liver. This problem can, in part, be circumvented by implementation of cytochrome P450 gene-directed enzyme prodrug therapy (P450 GDEPT), a prodrug activation strategy for cancer treatment that augments tumor cell exposure to cytotoxic drug metabolites generated locally by a prodrug-activating cytochrome P450 enzyme. P450 GDEPT has been exemplified in preclinical rodent and human tumor models, where chemosensitivity to a P450 prodrug can be greatly increased by introduction of a prodrug-activating P450 gene. Further enhancement of the efficacy of P450-based gene therapy can be achieved: by co-expression of P450 with the flavoenzyme NADPH-P450 reductase, which provides electrons required for P450 metabolic activity; by metronomic (anti-angiogenic) scheduling of the prodrug; by localized delivery of the prodrug to the tumor; and by combination with anti-apoptotic factors, which slow the death of the P450 'factory' cells and thereby enhance the bystander cytotoxic response. P450 GDEPT has several important features that make it a clinically attractive strategy for cancer treatment. These include: the substantial bystander cytotoxicity of P450 prodrugs such as cyclophosphamide and ifosfamide; the ability to use human P450 genes and thereby avoid an immune response to the therapeutic gene; the use of well-established conventional chemotherapeutic prodrugs, as well as bioreductive drugs activated by P450/P450 reductase in a hypoxic tumor environment; and the potential to decrease systemic exposure to active drug metabolites by selective inhibition of hepatic P450 activity. Recent advances in this area of research are reviewed, and two proof-of-concept clinical trials that highlight the utility of this strategy are discussed.

Population analysis of the pharmacokinetics and the haematological toxicity of the fluorouracil-epirubicin-cyclophosphamide regimen in breast cancer patients

PURPOSE

The aims of the study were (a) to characterise the pharmacokinetics (PK), including inter-individual variability (IIV) and inter-occasion variability (IOV) as well as covariate relationships and (b) to characterise the relationship between the PK and the haematological toxicity of the component drugs of the fluorouracil (5-FU)-epirubicin (EPI)-cyclophosphamide (CP) regimen in breast cancer patients.

PATIENTS AND METHODS

Data from 140 breast cancer patients, either within one of different studies or in routine clinical management, were included in the analyses. The patients were all treated with the fluorouracil-epirubicin-cyclophosphamide (FEC) regimen every third week for 3-12 courses, either in standard doses, i.e. 600/60/600 mg/m(2) of 5-FU, EPI and CP, respectively, or according to a dose escalation/reduction protocol (tailored dosing). PK data were available from 84 of the patients, whereas time-courses of haematological toxicity were available from 87 patients. The data analysis was carried out using mixed effects models within the NONMEM program.

RESULTS

The PK of 5-FU, EPI and 4-hydroxy-cyclophosphamide (4-OHCP), the active metabolite of CP, were described with a one-compartment model with saturable elimination, a three-compartment linear model and a two-compartment linear model, respectively. No clinical significant correlation was found between PK across drugs. The unexplained variability in clearance was found to be less within patients, between courses (inter-occasion variability, IOV) than between patients (inter-individual variability, IIV) for EPI and 5-FU. For 4-OHCP, however, the IIV diminished by approximately 45% when significant covariates were included and the final population model predicts an IIV that is equal to IOV. Significant covariates for elimination capacity parameters were serum albumin (5-FU, EPI and 4-OHCP), creatinine clearance (5-FU), bilirubin (EPI) and body surface area (BSA) (4-OHCP). Elimination capacity of 5-FU and EPI was not related to BSA and for none of the studied drugs did body weight explain the PK variability. The time-course of haematological toxicity after treatment was well described by a semi-physiological model that assumes additive haematological toxicity between CP and EPI with negligible contribution from 5-FU. The influence of G-CSF could be incorporated into the model in a mechanistic manner as shortening the maturation time to 43% of the normal duration and increasing the mitotic activity to 269% of normal activity.

CONCLUSIONS

The models presented describe the dose-concentration-toxicity relationships for the FEC therapy and may provide a basis for implementation and comparison of different individualisation strategies based on covariates, therapeutic drug monitoring and/or pharmacodynamic (PD) feedback. The PD model extends on previous semi-mechanistic models in that it also takes G-CSF administration into account.

Clinical pharmacokinetics of cyclophosphamide

Cyclophosphamide is an extensively used anticancer and immunosuppressive agent. It is a prodrug undergoing a complicated process of metabolic activation and inactivation. Technical difficulties in the accurate determination of the cyclophosphamide metabolites have long hampered the assessment of the clinical pharmacology of this drug. As these techniques are becoming increasingly available, adequate description of the pharmacokinetics of cyclophosphamide and its metabolites has become possible. There is incomplete understanding on the role of cyclophosphamide metabolites in the efficacy and toxicity of cyclophosphamide therapy. However, relationships between toxicity (cardiotoxicity, veno-occlusive disease) and exposure to cyclophosphamide and its metabolites have been established. Variations in the balance between metabolic activation and inactivation of cyclophosphamide owing to autoinduction, dose escalation, drug-drug interactions and individual differences have been reported, suggesting possibilities for optimisation of cyclophosphamide therapy. Knowledge of the pharmacokinetics of cyclophosphamide, and possibly monitoring the pharmacokinetics of cyclophosphamide in individuals, may be useful for improving its therapeutic index.

Pharmacogenetics of cyclophosphamide in patients with hematological malignancies

PURPOSE

A high degree of interindividual variation in cyclophosphamide (CPA) pharmacokinetics was reported in certain cancer patient groups. To better understand the mechanisms underlying the variation in CPA metabolism, we have investigated the pharmacokinetics of CPA and its active metabolite 4-hydroxycyclophosphamide (4-OH-CPA) in patients with hematological tumors. The pharmacokinetics of CPA and its active metabolite were related to the genotype of CYP2B6, CYP2C9 and CYP2C19. The influence of liver function on CPA metabolism was also evaluated.

METHODS

Twenty-nine patients with hematological malignancies (MM, ALL or NHL) treated with a conventional CPA dose (1g/m(2)) were recruited to this study. Blood samples were collected before, during and after CPA treatment. HPLC was used to measure plasma concentrations of CPA and 4-OH-CPA. Patients were genotyped for the CYP2B6 G516T, CYP2C9*2, CYP2C9*3, CYP2C19*2 and CYP2C19*3 alleles. Serum bilirubin levels were measured before the treatment. Data was analyzed individually and by population pharmacokinetic methods, using non-linear mixed effect modeling.

RESULTS

The interindividual variability in exposure to CPA, 4-OHCPA and 4-OH-CPA/CPA was 5.8-, 3.3- and 10.3-fold, respectively. A positive correlation between half-lives of CPA and 4-OH-CPA was found while a significant negative correlation between AUCs of CPA and 4-OH-CPA was detected. In the population analysis, the CYP2B6 G516T variant allele contribution to CPA clearance was about twice as the contribution from the wild type gene while the genotype of CYP2C9 and CYP2C19 did not influence clearance. A negative correlation was observed between bilirubin level and CPA bioactivation.

CONCLUSION

This study demonstrates for the first time that the presence of the CYP2B6 G516T mutation increases the rate of 4-OH-CPA formation in patients with hematological malignancies. The liver function prior therapy as assessed by s-bilirubin influences CPA metabolism.

Pharmacokinetics and efficacy of ifosfamide or trofosfamide in patients with intraocular lymphoma

BACKGROUND

The prognosis of intraocular lymphoma (IOL) is poor, and the optimal treatment has not yet been defined. The study assesses ifosfamide (IFO) and trofosfamide (TRO) for treating IOL.

PATIENTS AND METHODS

We prospectively evaluated the efficacy and aqueous penetration of intravenous IFO, oral TRO and their active 4-hydroxy (4-OH) metabolites in 10 patients with IOL. Doses varied from 1500 to 2000 mg/m2/day on days 1-3 for IFO and from 150 to 400 mg/day (continuous or intermittent administration) for TRO. Four patients had newly diagnosed disease, and six had relapsed after pretreatment.

RESULTS

All patients responded to first treatment with IFO or TRO, and both of two patients responded to re-treatment with IFO on ocular relapse. Progression-free survival from the first treatment with IFO or TRO was > or = 6-18 months. In six of six patients, 4-OH metabolites were detected in the aqueous humor at a concentration of 0.32-1.56 microM immediately after IFO infusion with an aqueous/serum ratio of 0.19-0.54. 4-OH metabolites could be detected in one of three patients at a concentration of 7.2 microM 3-16 h after ingestion of TRO.

CONCLUSIONS

IFO and TRO are active in IOL. IOL patients evidence aqueous penetration of 4-OH metabolites after intravenous administration of IFO.

Metabolism-based cyclophosphamide dosing for hematopoietic cell transplant

When cyclophosphamide (120 mg/kg) is used for hematopoietic cell transplant, the increased area under the curve of carboxyethylphosphoramide mustard (AUC(CEPM)) is related to liver toxicity and death. We determined the feasibility of dose-adjusting cyclophosphamide to a preset metabolic endpoint (AUC(CEPM), 325 +/- 25 micromol/L.h). In 20 patients blood sampling was done over a 16-hour period after administration of 45 mg/kg cyclophosphamide; AUC(CEPM) from 0 to 16 hours was calculated by noncompartmental analysis. The expected AUC(CEPM) for 0 to 48 hours was estimated, and the second cyclophosphamide dose was determined. The mean second cyclophosphamide dose was 42 mg/kg, and the mean total cyclophosphamide dose was 86 mg/kg (range, 54-120 mg/kg). The mean AUC(CEPM) for the time from 0 to 48 hours was 296 micromol/L.h (95% confidence interval, 275-317 micromol/L.h). A retrospective analysis indicated that AUC(CEPM) could be more accurately predicted by use of a population pharmacokinetic model. We conclude that metabolism-based dosing of cyclophosphamide is feasible and that a lower cyclophosphamide dose does not affect engraftment.

Associations Between Drug Metabolism Genotype, Chemotherapy Pharmacokinetics, and Overall Survival in Patients With Breast Cancer

Purpose

To evaluate associations between patient survival, pharmacokinetics, and drug metabolism–related genetic polymorphisms in patients receiving a combination chemotherapy regimen for breast cancer.

Patients and Methods

A genotype association study was conducted on 85 chemotherapy-naïve patients with metastatic or inflammatory breast cancer that were evaluated for an extended period after receiving standard-dose chemotherapy followed by high-dose cyclophosphamide, cisplatin, and carmustine. Blood pharmacokinetics were evaluated, and DNA was genotyped for 29 polymorphisms in 17 drug metabolism genes.

Results

Patients with cyclophosphamide plasma exposures above the median (implying slower metabolic activation) had a shorter survival than those below the median (1.8 v 3.8 years, respectively; P = .042). Patients having a variant genotype of cytochrome P450 3A4 displayed higher blood concentrations of parent (inactive) cyclophosphamide with the second and third doses (P = .024 and .028, respectively) in addition to slower cyclophosphamide activation over the three doses (P = .031). Median survival for these patients was 1.3 years compared with 2.7 years for those without the variant (P = .043). Similar results were observed for patients carrying a genetic variant of P450 3A5. Median survival for patients with deletions of glutathione-S-transferase M1 gene was 3.5 v 1.5 years for patients with one or both copies (P = .041). Patients with a polymorphism in a gene regulating metallothionein had lower platinum concentrations and shorter survival (P = .033).

Conclusion

These data suggest that pretreatment evaluation of drug metabolism genes may explain some interindividual differences in both anticancer drug pharmacokinetics and response. The correlations found here may have implications for other commonly used anticancer drugs.