Increased Plasma Concentrations of Unbound SN-38, the Active Metabolite of Irinotecan, in Cancer Patients with Severe Renal Failure.

PURPOSE: Delayed plasma concentration profiles of the active irinotecan metabolite SN-38 were observed in cancer patients with severe renal failure (SRF), even though SN-38 is eliminated mainly via the liver. Here, we examined the plasma concentrations of unbound SN-38 in such patients. METHODS: Plasma unbound concentrations were examined by ultrafiltration. Physiologically-based pharmacokinetic (PBPK) models of irinotecan and SN-38 were established to quantitatively assess the principal mechanism for delayed SN-38 elimination. RESULTS: The area under the plasma unbound concentration-time curve (AUC(u)) of SN-38 in SRF patients was 4.38-fold higher than that in normal kidney patients. The unbound fraction of SN-38 was also 2.6-fold higher in such patients, partly because SN-38 protein binding was displaced by the uremic toxin 3-carboxy-4-methyl-5-propyl-2-furanpropionate (CMPF). This result was supported by correlation of the unbound fraction of SN-38 with the plasma CMPF concentration, which negatively correlated with renal function. PBPK modeling indicated substantially reduced influx of SN-38 into hepatocytes and approximately one-third irinotecan dose for SRF patients to produce an unbound concentration profile of SN-38 similar to normal kidney patients. CONCLUSION: The AUC(u) of SN-38 in SRF cancer patients is much greater than that of normal kidney patients primarily because of the reduced hepatic uptake of SN-38.

A clinical pharmacokinetic microdosing study of docetaxel with Japanese patients with cancer.

PURPOSE: Whether microdosing studies can be used to evaluate the human pharmacokinetics of new anticancer drugs remains unclear. The disposition of docetaxel in cancer patients is linear in terms of dose proportionality. We examined whether the pharmacokinetics of docetaxel in a clinically relevant therapeutic dose could be predicted from the pharmacokinetics of a microdose of docetaxel in Japanese patients with cancer. METHODS: A microdose of docetaxel (100 µg/patient) was given by 5-min intravenous infusion on day 1, followed by a therapeutic dose of docetaxel (60-75 mg m(-2)), given by 1-h intravenous infusion on day 8. Plasma docetaxel was analyzed by liquid chromatography-tandem mass spectrometry. A two-compartment pharmacokinetic model was used to calculate the area under the plasma concentration-time curve from time 0 to infinity (AUC0-inf). RESULTS: Nine patients received both a microdose and therapeutic dose of docetaxel. The AUC0-inf after microdosing was 3640 ± 1150 ng h L(-1), while that after therapeutic dosing adjusted to 100 mg/patient was 2230 ± 757 µg h L(-1). The ratio of docetaxel clearance in therapeutic dose to that in microdose was 1.8 (P = 0.0041). Plasma α1-acid glycoprotein concentrations negatively correlated with docetaxel clearance at therapeutic dose, whereas the trend was weak at microdose. CONCLUSION: Docetaxel clearance showed marginal nonlinearity between microdose and therapeutic dose, presumably because of saturation of plasma protein binding; however, the magnitude was within twofold, allowing practically acceptable extrapolation.

No pharmacokinetic alteration of docetaxel following coadministration of aprepitant 3 h before docetaxel infusion.

PURPOSE: Aprepitant, a CYP3A4 substrate, effectively prevents chemotherapy-induced nausea and vomiting. Oral aprepitant 1 h before intravenous infusion of docetaxel does not change the pharmacokinetics of docetaxel. In practical combination chemotherapy, oral aprepitant is given 3 h before docetaxel infusion. We examined effects of this treatment schedule on the pharmacokinetics of docetaxel. METHODS: Inhibition constant (K(i)) of aprepitant for CYP3A-mediated docetaxel hydroxylation was estimated with human liver microsomes. A prospective, open-label, triple-crossover study was performed in balanced groups of cancer patients who received three consecutive cycles of docetaxel, consisting of docetaxel alone (A), docetaxel plus aprepitant given 3 h before docetaxel (B1), and docetaxel plus aprepitant given 1 h before docetaxel (B2). Three treatment arms were studied: Arm I, B1 followed by A and B2, respectively; Arm II, B2 followed by A and B1, respectively; and Arm III, A followed by B2 and B1, respectively. Pharmacokinetics of docetaxel and aprepitant were evaluated on day 1. RESULTS: The K(i) value was estimated to be 9.82 µM. Eligible patients (20) were allocated to Arm I (8), Arm II (7), or Arm III (5). On combined analysis of data from all patients assigned to Arms I-III, there were no significant differences among cycles A, B1, and B2 in the area under the plasma concentration-time curve (AUC) of docetaxel or the docetaxel AUC divided by actual dose. Pharmacokinetics of aprepitant showed large interindividual variability. CONCLUSION: Administration of aprepitant 3 h before docetaxel infusion did not alter the pharmacokinetics of docetaxel.

Direct inhibition and down-regulation by uremic plasma components of hepatic uptake transporter for SN-38, an active metabolite of irinotecan, in humans.

PURPOSE: Clinical study has previously revealed that plasma concentration of 7-ethyl-10-hydroxycamptothecin (SN-38), an active metabolite of irinotecan, was higher in patients with end-stage renal failure than those with normal kidney function although SN-38 is mainly eliminated in the liver. Here, we focused on inhibition by uremic toxins of hepatic SN-38 uptake and down-regulation of uptake transporter(s) by uremic plasma in humans. METHODS: We evaluated SN-38 uptake and its inhibition by uremic toxins, 3-carboxy-4-methyl-5-propyl-2-furanpropionate (CMPF), indoxyl sulfate (Indox), hippuric acid (HA) and indole acetate (IA), with cryopreserved human hepatocytes and HEK293 cells stably expressing hepatic uptake transporters, organic anion transporting polypeptides (OATPs). We also collected plasma samples from patients with severe renal failure to examine their effects on mRNA level of OATPs in primary cultured human hepatocytes. RESULTS: SN-38 was taken up by hepatocytes, which showed biphasic saturation patterns. The SN-38 uptake by hepatocytes was significantly inhibited by a uremic toxin mixture including clinically relevant concentrations of CMPF, Indox, HA and IA. Kinetic analyses for OATP-mediated transport revealed that the uptake of SN-38 by OATP1B1 was the highest, followed by OATP1B3. Among the uremic toxins, CMPF exhibited most potent inhibition of OATP1B1-mediated SN-38 uptake and directly inhibited the uptake of SN-38 also in hepatocytes. In addition, gene expression of OATP1B1 and OATP1B3 in hepatocytes was significantly down-regulated by the treatment with the uremic plasma. CONCLUSIONS: OATP1B1-mediated hepatic uptake of SN-38 was inhibited by uremic toxins, and gene expression of OATP1B1 was down-regulated by uremic plasma.

A phase I study of infusional 5-fluorouracil, leucovorin, oxaliplatin and irinotecan in Japanese patients with advanced colorectal cancer who harbor UGT1A1*1/*1,*1/*6 or *1/*28.

OBJECTIVE: To evaluate the safety and efficacy of combination chemotherapy with 5-fluorouracil (5-FU), leucovorin, irinotecan and oxaliplatin (FOLFOXIRI) in Japanese patients with advanced colorectal cancer. METHODS: This phase I dose-finding study was designed to determine the maximum tolerated dose (MTD), recommended dose (RD) or both of FOLFOXIRI. Patients with UDP-glucuronosyltransferase (UGT) 1A1*6/*6, *28/*28 and *6/*28 genotypes were excluded, because these UGT1A1 genotypes are linked to severe neutropenia in Japanese. RESULTS: A total of 10 Japanese patients with advanced colorectal cancer were studied. The MTD of FOLFOXIRI in these Japanese patients was 165 mg/m(2) irinotecan, 85 mg/m(2) oxaliplatin and 2,400 mg/m(2) 5-FU. Accordingly, the RD of FOLFOXIRI was determined to be 150 mg/m(2) irinotecan, 85 mg/m(2) oxaliplatin and 2,400 mg/m(2) 5-FU. Toxic effects, evaluated until the completion of 4 cycles, were manageable. Grade 3-4 neutropenia occurred in 27% of cycles, but there was no febrile neutropenia. Among the 9 assessable patients, the objective response rate was 89%. CONCLUSIONS: We thus determined the RD of FOLFOXIRI in Japanese patients with advanced colorectal cancer who do not have UGT1A1*28/*28, *6/*6 or *6/*28 genotypes. Our results indicate that FOLFOXIRI is a well-tolerated regimen for these Japanese patients.

Association of ABCC2 genotype with efficacy of first-line FOLFIRI in Japanese patients with advanced colorectal cancer.

This exploratory retrospective study examined the effects of polymorphisms in transporter genes related to irinotecan pharmacokinetics and those in genes related to irinotecan pharmacodynamics on the efficacy of first-line combination chemotherapy with irinotecan, 5-fluorouracil, and folinic acid (leucovorin) (FOLFIRI) in Japanese patients with advanced colorectal cancer. All patients harbored UDP-glucuronosyltransferase (UGT) 1A1*1/*1, *1/*6, or *1/*28 genotypes, which are associated with similar irinotecan pharmacokinetics and responses to FOLFIRI. Genetic polymorphisms were analyzed by direct sequencing. Overall response rate and median progression-free survival in a total of 61 patients were 43% and 7.5 months, respectively. The overall response rate was higher in patients with the CC genotype at -24 in ATP-binding cassette, subfamily C, and member 2 (ABCC2) than in the others (p = 0.0313). Median progression-free survival was the longest in patients with CC at -24 in ABCC2, followed by those with CT and TT (p = 0.00910). A clear gene-dose effect was seen between -24C>T and median progression-free survival. No other polymorphisms tested were related to the efficacy of FOLFIRI. We thus found that the -24C>T polymorphism in the ABCC2 gene was significantly associated with the efficacy of first-line FOLFIRI in Japanese patients with advanced colorectal cancer.

Regimen selection for first-line FOLFIRI and FOLFOX based on UGT1A1 genotype and physical background is feasible in Japanese patients with advanced colorectal cancer.

OBJECTIVE: We examined the feasibility of regimen selection for first-line irinotecan, 5-fluorouracil and leucovorin or oxaliplatin, 5-fluorouracil and leucovorin in Japanese patients with advanced colorectal cancer based on UDP-glucuronosyltransferase 1A1 genotype as well as physical status of patients related to diarrhea. METHODS: As first-line irinotecan, 5-fluorouracil and leucovorin is a little bit superior to oxaliplatin, 5-fluorouracil and leucovorin with respect to efficacy and toxicity, patients without risk factors of irinotecan-induced toxicity were first assigned to irinotecan, 5-fluorouracil and leucovorin. Patients with UDP-glucuronosyltransferase 1A1 28/ 28, 6/ 6, 28/ 6 or 28/ 27 and those with ascites, peritoneal dissemination or diarrhea first received oxaliplatin, 5-fluorouracil and leucovorin to avoid the irinotecan-induced neutropenia and diarrhea, respectively. We retrospectively evaluated the feasibility of this strategy by assessing toxicity and total progression-free survival in first- and subsequent second-line therapies in all patients studied. RESULTS: In the first-line irinotecan, 5-fluorouracil and leucovorin (n = 61), Grade 4 neutropenia, febrile neutropenia and Grade 3 diarrhea occurred in 8.2, 3.3 and 3.3% of patients, respectively. In the first-line oxaliplatin, 5-fluorouracil and leucovorin (n = 26), Grade 4 neutropenia, febrile neutropenia, Grade 3 thrombocytopenia and Grade 3 neuropathy were observed in 11.5, 3.8, 3.8 and 7.7% of patients, respectively. In the second-line oxaliplatin, 5-fluorouracil and leucovorin (n = 38), Grade 3 diarrhea occurred in 2.6% of patients. In the second-line irinotecan monotherapy (n = 11), Grade 4 or febrile neutropenia occurred in 18% of patients and Grade 3 diarrhea in 9.1% of patients. In second-line S-1 (n = 9), Grade 3 anemia occurred in 2 patients. Median total progression-free survival in all 87 patients was 11.5 months. CONCLUSIONS: Present regimen selection strategy would be feasible, since it causes less toxicity and similar efficacy comparing to previous studies. Determination of appropriate reduced dose in the second-line irinotecan monotherapy or other standard second-line therapy for patients with high-risk to irinotecan-induced toxicity might make this strategy more effective.

Delayed elimination of SN-38 in cancer patients with severe renal failure.

This prospective study is designed to examine the effects of severe renal failure on the pharmacokinetics of irinotecan. The pharmacokinetics of irinotecan, 7-ethyl-10-hydroxycamptothecin (SN-38), and SN-38 glucuronide (SN-38G) in three cancer patients with severe renal failure [creatinine clearance (Ccr) ≤ 20 ml/min] who were undergoing dialysis and received 100 mg/m(2) irinotecan as monotherapy were prospectively compared with those in five cancer patients with normal renal function (Ccr ≥ 60 ml/min). To ensure that the subjects had similar genetic backgrounds of UDP-glucuronosyltransferase (UGT) 1A1, patients with UGT1A1*1/*1, *1/*6, or *1/*28 were enrolled. The estimated terminal elimination rate constant of SN-38 in patients undergoing dialysis was approximately one tenth of that in patients with normal renal function (P = 0.025). Approximately 50% of SN-38 was dialyzed with a 2.1-m(2) dialysis membrane, whereas 27% was dialyzed with a 1.5-m(2) membrane. Our results showed that the elimination of SN-38 was significantly delayed in patients with severe renal failure compared with patients with normal renal function. We demonstrated that SN-38 was partly dialyzed.

Phase I/II study of FOLFIRI in Japanese patients with advanced colorectal cancer.

OBJECTIVE: This phase I/II study determined the recommended dose of FOLFIRI (irinotecan, infusional 5-fluorouracil and leucovorin) for Japanese patients with advanced colorectal cancer, and evaluated safety at the recommended dose in patients without the UDP-glucuronosyltransferase 1A1*28 allele which caused reduced enzyme expression. METHODS: The phase I part assessed the maximum tolerated dose of FOLFIRI to determine the recommended doses of irinotecan and infusional 5-fluorouracil. The doses were escalated from 150 to 180 mg/m(2) (irinotecan) and 2000 to 2400 mg/m(2) (5-fluorouracil). UDP-glucuronosyltransferase 1A1*6 and *28, and pharmacokinetics of irinotecan were observationally examined. In the phase II part, patients without the UDP-glucuronosyltransferase 1A1*28 allele received FOLFIRI at the recommended dose to evaluate safety. RESULTS: Among 15 patients in the phase I part, dose-limiting toxicity (diarrhea) occurred in one patient who received 150 mg/m(2) irinotecan and 2400 mg/m(2) infusional 5-fluorouracil. The respective recommended doses were 180 and 2400 mg/m(2) for irinotecan and infusional 5-fluorouracil, without reaching the maximum tolerated dose. Twenty-five patients received FOLFIRI at the recommended doses. Grade 3 or 4 neutropenia occurred in 44%, and Grade 3 diarrhea in 4%. CONCLUSIONS: This phase I/II study demonstrates that the recommended doses of irinotecan and infusional 5-fluorouracil in FOLFIRI for Japanese patients with advanced colorectal cancer who do not possess the UDP-glucuronosyltransferase 1A1*28 allele are 180 and 2400 mg/m(2), respectively. Toxicities occurring at the recommended doses are manageable in these patients.

UGT1A1*1/*28 and *1/*6 genotypes have no effects on the efficacy and toxicity of FOLFIRI in Japanese patients with advanced colorectal cancer.

PURPOSE: Differences in efficacy and toxicity between UDP-glucuronosyltransferase (UGT) 1A1*1/*1 and *1/*6 or *1/*28 genotypes remain unclear in Japanese patients. METHODS: Patients with advanced colorectal cancer who received irinotecan combined with 5-fluorouracil plus l-leucovorin (FOLFIRI) as first-line therapy were divided into two groups: those with UGT1A1*1/*1 genotype and those with UGT1A1*1/*6 or *1/*28 genotype. Efficacy and toxicity were compared between these groups retrospectively. RESULTS: Forty-two patients (24 *1/*1 and 18 *1/*6 or *1/*28) were evaluated. The response rate was 48% in *1/*1 group and 56% in *1/*6 or *1/*28 group (P = 0.847). Median progression-free survival was 8.6 months in *1/*1 group and 8.5 months in *1/*6 or *1/*28 group (P = 0.888). No hematologic or non-hematologic toxic effects were clearly related to UGT1A1*1/*6 or *1/*28 during the first cycle or throughout the entire course of chemotherapy. CONCLUSIONS: There were no significant differences in the efficacy or toxicity of FOLFIRI between patients with UGT1A1*1/*1 genotype and those with UGT1A1*1/*6 or *1/*28 genotype. Our results suggest that patients with the latter genotypes can receive FOLFIRI at the same dose of irinotecan as those with the UGT1A1*1/*1 genotype receive.

Clinical and economic evaluation of first-line therapy with FOLFIRI or modified FOLFOX6 for metastatic colorectal cancer.

OBJECTIVE: Recently, significant progress in treatment of metastatic colorectal cancer has been achieved. Either FOLFIRI (fluorouracil, leucovorin and irinotecan) or modified FOLFOX6 (fluorouracil, leucovorin and oxaliplatin, oxaliplatin dose 85 mg/m(2)) is selected as first-line therapy in clinical practice in Japan. However, economic burden of colorectal cancer is considerable. METHODS: Analysis was made for all patients who were treated with FOLFIRI or modified FOLFOX6 for metastatic colorectal cancer. Regimen of FOLFIRI was compared with modified FOLFOX6 under consideration from clinical and economic standpoints. Progression free survival, response, toxicity and cancer care cost in patients with metastatic colorectal cancer was analyzed. Direct costs based on the fee schedule of the Japanese national health insurance were calculated. RESULTS: Median progression free survival was 7.7 months for FOLFIRI versus 8.4 months for modified FOLFOX6 (P = 0.48). Overall cost for first four cycles was yen756 284 for FOLFIRI and yen1 081 162 for modified FOLFOX6 (P < 0.0001). All grade alopecia was significantly more frequent with FOLFIRI than with modified FOLFOX6 (P = 0.04). All grade neuropathy was more observed with modified FOLFOX6 than FOLFIRI (P = 0.0002). CONCLUSIONS: FOLFIRI is inexpensive in the initial stage of treatment which a number of patients can receive chemotherapy than modified FOLFOX6 as first-line therapy for metastatic colorectal cancer in Japanese national insurance system.

Association of UGT2B7 and ABCB1 genotypes with morphine-induced adverse drug reactions in Japanese patients with cancer.

PURPOSE: To investigate the effects of genetic polymorphisms on morphine-induced adverse events in cancer patients. METHODS: We examined the relation of morphine-related adverse events to polymorphisms in UDP-glucuronosyltransferase (UGT) 2B7, ATP-binding cassette, sub-family B, number 1 (ABCB1), and µ-opioid receptor 1 genes in 32 Japanese cancer patients receiving oral controlled-release morphine sulfate tablets. RESULTS: The T/T genotype at 1236 or TT/TT diplotype at 2677 and 3435 in ABCB1 was associated with significantly lower frequency of fatigue (grades 1-3) (P = 0.012 or 0.011, Fisher's exact test). The UGT2B7*2 genotype was associated with the frequency of nausea (grades 1-3) (P = 0.023). The frequency of nausea was higher in patients without UGT2B7*2 allele than others. The diplotype at 2677 and 3435 in ABCB1 was associated with the frequency of vomiting (grades 1-3) (P = 0.011). No patient whose diplotype was consisted of no GC allele at 2677 and 3435 suffered from vomiting. CONCLUSION: Our findings suggest that pharmacogenetics can be used to predict the risk of morphine-induced adverse events.

Association of ATP-binding cassette, sub-family C, number 2 (ABCC2) genotype with pharmacokinetics of irinotecan in Japanese patients with metastatic colorectal cancer treated with irinotecan plus infusional 5-fluorouracil/leucovorin (FOLFIRI).

ATP-binding cassette, sub-family C, number 2 (ABCC2) is involved in the biliary excretion of irinotecan and its metabolites, SN-38 and SN-38 glucuronide. Effects of the ABCC2 genotype on the pharmacokinetics (PK) of irinotecan and the metabolites were examined in Japanese patients with metastatic colorectal cancer receiving irinotecan plus infusional 5-fluorouracil/leucovorin (FOLFIRI). ABCC2 genotypes (-1549G>A, -1023G>A, -1019A>G, -24C>T, 1249G>A and 3972C>T) and haplotypes were analyzed for 67 patients with cancer. PK was also examined in a subset of 31 patients receiving FOLFIRI. Relationship between the ABCC2 genotypes or diplotypes and area under the time-concentration curve (AUC) of irinotecan and the metabolites normalized by irinotecan dose was analyzed. The lower AUC of irinotecan was seen in patients with A/A or G/A genotypes at 1249 of the ABCC2 gene than others (p=0.011, Mann-Whitney U teat). AUC of SN-38 in patients with A/A or G/A genotypes at -1023 was significantly lower than that in others (p=0.018). The haplotype I included -1023A (GAACGC) was the most frequent one with the allele frequency of 0.366. The AUC of SN-38 observed in patients with diplotypes harboring at least one haplotype I was lower than that observed in others (p=0.023). The haplotype IV consisted of 1249 (GGACAC) and was the fourth most frequent one with the allele frequency of 0.127. Patients with diplotypes carrying at least one haplotype IV showed lower AUC of irinotecan than others (p=0.011). Thus, ABCC2 genotype is one of the predictors of the variability of irinotecan PK in Japanese patients with metastatic colorectal cancer receiving FOLFIRI.

CYP2A6 and the plasma level of 5-chloro-2, 4-dihydroxypyridine are determinants of the pharmacokinetic variability of tegafur and 5-fluorouracil, respectively, in Japanese patients with cancer given S-1.

S-1 is an oral anticancer agent composed of tegafur (FT), 5-chloro-2,4-dihydroxypyridine (CDHP), and potassium oxonate. CDHP is added to prevent degradation of 5-fluorouracil (5-FU) by inhibiting dihydropyrimidine dehydrogenase. CYP2A6 is involved in the biotransformation of FT to 5-FU. Thus, we prospectively analyzed the effects of the CYP2A6 genotype, plasma level of CDHP, and patient characteristics on the pharmacokinetic (PK) variability of FT and 5-FU. Fifty-four Japanese patients with metastatic or recurrent cancers who received S-1 were enrolled. The CYP2A6 polymorphisms (*4A, *7, and *9) with deficient or reduced activity were analyzed. All subjects were classified into three groups according to their CYP2A6 genotype: wild type (*1/*1), one-variant allele (*1/any), or two-variant alleles (combination other than *1). The PK of FT, 5-FU, and CDHP were measured on day 1 of treatment. Multivariate regression analysis revealed that oral clearance of FT was associated with the CYP2A6 genotype (analysis of variance [ANOVA], P = 0.000838). The oral clearance of FT seen in patients with the two-variant alleles was significantly lower than those in wild type and the one-variant allele (95% confidence intervals 0.75-2.41 and 0.41-1.82, respectively; Tukey-Kramer test). The area under the time-concentration curve (AUC) of 5-FU was significantly correlated with the AUC of CDHP (ANOVA, P = 0.00126). The AUC of 5-FU and CDHP were inversely correlated with creatinine clearance (ANOVA, P = 0.0164 and P = 0.000762, respectively). Although the CYP2A6 variants are the cause of the PK variability of FT, the AUC of CDHP affected by renal function is the key determinant of the variability in the PK of 5-FU.