Toshimichi Miya

Pharmacogenetic impact of polymorphisms in the coding region of the UGT1A1 gene on SN‐38 glucuronidation in Japanese patients with cancer

Pharmacogenetic testing for UDP‐glucuronosyltransferase (UGT) 1A1*28, a promoter variant of the UGT1A1 gene, is now carried out clinically to estimate the risk of irinotecan‐associated toxicity. We studied the clinical significance of UGT1A1*6 and UGT1A1*27, two variants in exon 1 of the UGT1A1 gene that are found mainly in Asians. The study group comprised 46 Japanese patients who received various regimens of chemotherapy including irinotecan at doses from 50 to 180 mg/m2. Pharmacogenetic relationships were explored between the UGT1A1 genotype and the ratio of the area under the plasma concentration–time curve (AUC) of the active metabolite of irinotecan (SN‐38) to that of SN‐38 glucuronide (SN‐38G), used as a surrogate for UGT1A1 activity (AUCSN‐38/AUCSN‐38G). No patient was homozygous for UGT1A1*28, and none had UGT1A1*27. Two were heterozygous for UGT1A1*28. Two were homozygous and 15 heterozygous for UGT1A1*6, all of whom were wild type with respect to UGT1A1*28. Two patients were simultaneously heterozygous for UGT1A1*28 and UGT1A1*6, present on different chromosomes. The other 25 patients had none of the variants studied. The two patients simultaneously heterozygous for UGT1A1*28 and UGT1A1*6 and the two patients homozygous for UGT1A1*6 had significantly higher AUCSN‐38/AUCSN‐38G ratios than the others (P = 0.0039). Concurrence of UGT1A1*28 and UGT1A1*6, even when heterozygous, altered the disposition of irinotecan remarkably, potentially increasing susceptibility to toxicity. Patients homozygous for UGT1A1*6 should also be carefully monitored. UGT1A1 polymorphisms in the coding region of the UGT1A1 gene should be genotyped in addition to testing for UGT1A1*28 to more accurately predict irinotecan‐related toxicity, at least in Asian patients. (Cancer Sci 2006; 97: 1255–1259)

A pharmacokinetic and pharmacodynamic analysis of CPT-11 and its active metabolite SN-38.

In the present study, an attempt was made to determine the precise pharmacokinetics of 7‐ethyl‐10‐[4‐(1‐piperidino)‐1‐piperidino]carbonyloxycamptothecin (CPT‐11) and its active metabolite, 7‐ethyl‐10‐hydroxycamptothecin (SN‐38). The relationship between pharmacokinetic parameters and pharmacodynamic effects was also investigated to elucidate the cause of interpatient variation in side effects. Thirty‐six patients entered the study. CPT‐11, 100 mg/m2, was administered by IV infusion over 90 min weekly for four consecutive weeks. The major dose‐limiting toxicities were leukopenia and diarrhea. There was a positive correlation between the area under the concentration‐time curve (AUC) of CPT‐11 and percent decrease of WBC (r=0.559). On the other hand, episodes of diarrhea had a better correlation with the AUC of SN‐38 (r=0.606) than that of CPT‐11 (r=0.408). Multivariate analysis revealed that the AUC of SN‐38, AUC of CPT‐11 and indocyanine green retention test were significant variables for the incidence of diarrhea and that both performance status and AUC of CPT‐11 were significant variables for percent decrease of WBC. The large interpatient variability of the degree of leukopenia and diarrhea is due to a great plasma pharmacokinetic variation in CPT‐11 or SN‐38. The AUCs of CPT‐11 and SN‐38 obtained from the first administration of CPT‐11 correlate with toxicities, but it is impossible to predict severe side effects before the administration of CPT‐11 at the present time.

A prognostic-factor risk index in advanced non-small-cell lung cancer treated with cisplatin-containing combination chemotherapy

SummaryPrognostic factors for response and survival were retrospectively evaluated in 192 previously untreated patients with advanced non-small-cell lung cancer (NSCLC) who had received either vindesine plus cisplatin or mitomycin plus vindesine plus cisplatin as initial treatment. Univariate analysis demonstrated that squamous-cell histology, early stage, and a small number of metastatic sites were favorable prognostic factors for response to chemotherapy. Multivariate analysis using Coxs proportional hazard model indicated that the number of metastatic sites was the only significant pretreatment factor for response (P=0.0005). Multivariate regression analysis revealed that the number of metastatic sites (P=0.0002), sex (P=0.0009), serum albumen levels (P=0.0018), performance status (P=0.0026) and lactic dehydrogenase values (P=0.0026) contributed independently to survival. On the basis of these five prognostic factors, a prognostic index for survival was used to define three prognostic groupings (good, intermediate, and poor) for survival (median survival, 16.5 vs 9.4 vs 4.6 months;P=0.0001). This particular regression model should aid in the design and analysis of new treatment strategies and may be useful for indirect comparisons of different studies carried out in similar patient populations.

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. (Cancer Sci 2008; 99: 1049–1054)

Genetic testing for UGT1A1*28 and *6 in Japanese patients who receive irinotecan chemotherapy

Polymorphisms of the UDP-glucuronosyltransferase (UGT) 1A1 gene, such as UGT1A1*28 and UGT1A1*6, can cause severe neutropenia and diarrhea in patients who receive irinotecan [1, 2]. Homozygosity for UGT1A1*28 is associated with less efficient glucuronidation of SN-38, the active metabolite of irinotecan, resulting in increased plasma SN-38 concentrations. Four pharmacogenetic trials have demonstrated an association between UGT1A1*28 genotype and irinotecan-induced hematologic toxicity, diarrhea, or both [3]. In response to these findings, the United States Food and Drug Administration has approved genetic testing for UGT1A1*28 and recommends that the initial dose of irinotecan is reduced by at least one level in patients who are homozygous for UGT1A1*28, albeit the effectiveness of such testing remains to be confirmed prospectively. UGT1A1*6 is also associated with severe irinotecan-related toxicity [4]. Given that the area under the time versus concentration curve ratio (SN-38 glucuronide/SN-38) seen in patients homozygous for UGT1A1*28 and *6 are almost equal [4], the impact of these variants on glucuronidation capacity of UGT1A1 for SN-38 is almost the same. The distribution of genotypes associated with these polymorphisms varies considerably among ethnic groups. UGT1A1*28 is found in Japanese and whites, but the allele frequency in Japanese is lower than that in whites [2, 4]. UGT1A1*6 is found in Japanese, but not in whites [4]. Homozygosity for UGT1A1*28 or UGT1A1*6 and heterozygosity for both UGT1A1*6 and UGT1A1*28 are associated with severe irinotecan-related neutropenia in Japanese patients [1, 4]. The Ministry of Health, Labour and Welfare in Japan has therefore recently approved genetic testing for UGT1A1*28 and *6. The value of genetic testing for UGT1A1 depends on genotype frequency and the association of genetic variants with irinotecan-induced toxicity. The higher the frequency of toxicity-related polymorphisms, the greater is the number of patients who would benefit from genetic testing. Large prospective studies are needed to accurately estimate the distribution of UGT1A1 polymorphisms in a given population. We have carried out the largest prospective study to date, examining the distributions of UGT1A1*28 and UGT1A1*6 genotypes in 300 Japanese patients (male/female, 172 of 128) with various solid tumors (200 colorectal, 43 gastric, 15 ovarian, 14 breast, 10 lung, and 18 others). All patients gave written informed consent, and the study protocol was approved by the Institutional Review Board of Saitama Medical University. Genotyping was carried out as described elsewhere [5]. UGT1A1*28 and UGT1A1*6 were in Hardy–Weinberg equilibrium (P > 0.05). Only 2 of 300 patients were UGT1A1*28 homozygotes (0.7%) (Table 1). The frequency of homozygosity for UGT1A1*28 was much lower than that in other prospective studies in Japan (2.3%, 4 of 176) [4]. The frequency of UGT1A1*6 homozygosity was 5.7% (Table 1), higher than that reported previously (2.8%) [4]. Eleven patients were both heterozygous for UGT1A1*6 and UGT1A1*28 (3.7%). The combined frequency of patients with two ‘risk alleles’ (i.e. *28/*28, *6/*6, and *6/*28) was 10.1% (95% confidence interval, 6.8% to 14.0%). Such patients might be at increased risk for irinotecan-related neutropenia. Given the genotype frequencies of UGT1A1*28 and UGT1A1*6, genetic testing for UGT1A1 might not be essential for identifying homozygotes for UGT1A1*28, but useful for identifying homozygotes for UGT1A1*6 as well as heterozygotes for UGT1A1*6 and UGT1A1*28, thereby avoiding severe irinotecan-induced toxicity in Japanese patients. The present results and considerations are likely to have application across East Asia. Prospective evaluations of genetic testing for UGT1A1 polymorphisms, encompassing both medical aspects and cost effectiveness, appear to be warranted, especially in East Asian countries including Japan. Table 1. Genotype frequencies of UGT1A1*28 and UGT1A1*6 in Japanese

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/m2 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-m2 dialysis membrane, whereas 27% was dialyzed with a 1.5-m2 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.

GEFITINIB (IRESSA) INHIBITS THE CYP3A4-MEDIATED FORMATION OF 7-ETHYL-10-(4-AMINO-1-PIPERIDINO)CARBONYLOXYCAMPTOTHECIN BUT ACTIVATES THAT OF 7-ETHYL-10-[4-N-(5-AMINOPENTANOIC ACID)-1-PIPERIDINO]CARBONYLOXYCAMPTOTHECIN FROM IRINOTECAN

Gefitinib (Iressa) is an anticancer drug that selectively inhibits tyrosine kinases of epidermal growth factor receptor. Gefitinib might affect CYP3A4-mediated metabolism, since the drug is a substrate of human CYP3A. In this study, we evaluated the effects of gefitinib on drug metabolism catalyzed by human CYP3A4. The effects of gefitinib on the CYP3A4-mediated formation of NPC (7-ethyl-10-(4-amino-1-piperidino)carbonyloxycamptothecin) and that of APC (7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidino]carbonyloxycamptothecin) from irinotecan were examined with the use of human liver and small intestinal microsomes. Gefitinib inhibited the formation of NPC in liver and small intestinal microsomes. The apparent intrinsic metabolic clearance (CLint) in the presence of 40 μM gefitinib was equivalent to about 26% of control in liver microsomes and 45% of control in small intestinal microsomes. Gefitinib stimulated the formation of APC by CYP3A4. CLint in the presence of 20 μM gefitinib with human liver microsomes was about 1.9 times higher than control. In human small intestinal microsomes, APC formation was enhanced by the addition of gefitinib at concentrations 20 μM or higher. CLint in the presence of 40 μM gefitinib was 2.8 times higher than control. Thus, we discovered that gefitinib inhibited the formation of NPC but stimulated the formation of APC from irinotecan.

Pharmacokinetic study of mitomycin C with emphasis on the influence of aging.

Mitomycin C (MMC) at a dose of 8 mg/m2 was administered by short intravenous infusion to 14 cancer patients. All patients had normal renal, hepatic, cardiac and bone marrow functions. The plasma level of MMC, which was determined by high‐performance liquid chromatography over a 24–h period after the infusion, fitted the 2‐compartment model curve except for one patient. There was a significant correlation between the area under the time versus concentration curve (AUC) of MMC and the age of patients (r= 0.558, P < 0.05). Pharmacokinetic parameters in one of the older (a 69‐year‐old male) patients were extremely different from those of the other 13 patients. This patient experienced severe myelosuppression, probably due to the markedly increased AUC of MMC. Our results suggest that a patients age has a significant influence on the pharmacokinetics of MMC in patients with normal major organ functions and that in some patients, MMC pharmacokinetics may be altered, possibly due to interpatient variation in the activation or metabolic pathway of MMC.

Detection and treatment of akathisia in advanced cancer patients during adjuvant analgesic therapy with tricyclic antidepressants: Case reports and review of the literature

OBJECTIVE There is substantial evidence that tricyclic antidepressants are effective in the management of chronic pain, including cancer pain. In oncological settings, these agents are used as adjuvant analgesic drugs. However, cases of akathisia due to tricyclic antidepressants used as adjuvant analgesic therapy have not previously been reported. CASE REPORTS Two cancer patients experiencing chronic pain who were refractory to nonsteroidal anti-inflammatory drugs and opioids were prescribed amoxapine as an adjuvant analgesic therapy for neuropathic pain. These patients developed inner restlessness and restless physical movements after amoxapine was prescribed. Although symptoms were atypical, akathisia was suspected and discontinuation of amoxapine resolved the symptoms. RESULTS AND SIGNIFICANCE OF RESULTS Akathisia should be considered in patients receiving adjuvant analgesic therapy with tricyclic antidepressants. Early detection and appropriate treatment will relieve this distressing symptom. Restless movements involving parts of the body other than the legs may be the clue to the diagnosis.

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.