A descriptive analysis of real-world oncology biosimilar use in Japan.

Aim: To describe patient and treatment characteristics associated with bevacizumab BS-Pfizer, rituximab BS-Pfizer and trastuzumab BS-Pfizer and their reference products in Japan. Methods: This retrospective observational study used an administrative claims database to identify patients with ≥1 biosimilar or reference product prescription from 2019 to 2022 for approved indications. Descriptive statistics were calculated. Results: Overall, 14-39% of biosimilar-prescribed patients initiated therapy with reference products. Biosimilar utilization significantly increased from 2019 to 2022. The most-commonly prescribed concomitant class of therapy with biosimilars was antineoplastic therapy. Conclusion: Reference products were most frequently prescribed among the Japanese cohorts, but substantial and increasing proportions received biosimilars over time. Future studies should extend our initial insights to assess biosimilar clinical outcomes in Japanese settings.

This study examines the adoption of cancer biosimilar therapies in Japan from 2019 to 2022. Cancer biosimilars are complex treatments that closely resemble established cancer therapies already available in Japan. We looked into the characteristics of patients receiving three specific biosimilars ­ bevacizumab BS-Pfizer, rituximab BS-Pfizer and trastuzumab BS-Pfizer. We also investigated where patients received biosimilar treatment, other therapies they received alongside biosimilars and the proportion of patients using these therapies each year during the study. Our analysis utilized data from the 'Medical Data Vision' database, which records care provided in hospitals across Japan. We analyzed patient demographics and treatment patterns, and compared different groups using statistics to identify significant differences. Notably, we observed that between 14 and 39% of patients initially started treatment with the original version of the drug on the market, known as the 'reference product,' before switching to the biosimilar. Furthermore, our findings revealed a significant increase in the use of biosimilars each year during the study period. Biosimilars were most-commonly used alongside chemotherapy drugs. These initial findings shed light on the patient population using cancer biosimilars in Japan and the treatment contexts in which they are utilized. Future research should delve deeper into aspects such as cost of care, patient survival, side effects and other pertinent factors related to the use of biosimilars in cancer care in Japan.

Bosutinib in Japanese patients with newly diagnosed chronic-phase chronic myeloid leukemia: final 3-year follow-up results of a phase 2 study.

Bosutinib has been evaluated for treatment of chronic-phase chronic myeloid leukemia (CP-CML) in several clinical studies, including in Japan. This open-label, single-arm, phase 2 study evaluated the efficacy and safety of bosutinib at a starting dose of 400 mg once daily in Japanese patients (n = 60) with newly diagnosed CP-CML. The minimum follow-up period was 3 years and median duration of treatment was 35.9 months. At study completion, 60% of patients were still on treatment. Cumulative rates of major molecular response (MMR), molecular response4 (MR4), and MR4.5 at any time were 70.0%, 53.3%, and 48.3%, respectively. No patient who achieved MMR or MR4 had a confirmed loss of response. No patient experienced on-treatment transformation to accelerated/blast phase or died within 28 days of the last bosutinib dose. Any-grade treatment-emergent adverse events (TEAEs) occurred in 100% (grade ≥ 3: 81.7%) of patients. The most common TEAEs were diarrhea (86.7%), increased alanine aminotransferase (55.0%), and increased aspartate aminotransferase (46.7%). No new safety signals emerged during the follow-up period. Bosutinib continues to demonstrate a favorable benefit/risk profile and is an important treatment option for Japanese patients with newly diagnosed CP-CML. Optimal management of TEAEs during initial treatment with bosutinib should be prioritized.Trial Registration: ClinicalTrials.gov ID: NCT03128411.

Safety profile of bosutinib in Japanese versus non-Japanese patients with chronic myeloid leukemia: a pooled analysis.

Bosutinib has been investigated in multiple clinical trials globally, including Japan, for treatment of chronic myeloid leukemia (CML). A pooled analysis of seven Pfizer-sponsored clinical trials evaluated the safety of bosutinib in Japanese (n = 138) vs non-Japanese (n = 1210) patients with CML. First-line bosutinib was administered in 54.3% vs 41.4% of patients, and second-line or later bosutinib in the remainder. Median treatment duration was 1.4 vs 2.3 years, and median relative dose intensity 78.1% vs 90.0%. Any-grade treatment-emergent adverse events (TEAEs) occurred in 100.0% vs 98.9% (grade ≥ 3: 81.9% vs 75.2%). In both groups, the most common TEAEs relevant to bosutinib were gastrointestinal (92.8% vs 84.7%), liver function (72.5% vs 34.8%), rash (63.8% vs 37.4%), and myelosuppression (55.1% vs 50.7%). TEAEs led to dose reduction in 65.2% vs 50.6%, dose interruption in 78.3% vs 68.8%, and permanent treatment discontinuation in 30.4% vs 25.4% of patients. The safety profile of bosutinib in Japanese patients was generally consistent with that in non-Japanese patients, despite a higher incidence of gastrointestinal, liver function, and rash events. TEAEs were largely manageable with dose modifications and supportive care in both groups. These data may help optimize TEAE management and outcomes in Japanese patients receiving bosutinib for CML. Trial registration ClinicalTrials.gov: NCT02130557, NCT03128411, NCT00574873, NCT00261846, NCT01903733, NCT00811070, NCT02228382.

Efficacy and safety of bosutinib versus imatinib for newly diagnosed chronic myeloid leukemia in the Asian subpopulation of the phase 3 BFORE trial.

Bosutinib is approved in the United States, Europe, Japan, and other countries for treatment of newly diagnosed chronic phase (CP) chronic myeloid leukemia (CML), and CML resistant/intolerant to prior therapy. In the phase 3 BFORE trial (Clinicaltrials.gov, NCT02130557), patients were randomized 1:1 to first-line bosutinib or imatinib 400 mg once daily. We examined efficacy, safety, and patient-reported outcomes of bosutinib vs imatinib and pharmacokinetics of bosutinib in the Asian (n = 33 vs 34) and non-Asian (n = 235 vs 234) subpopulations of BFORE followed for at least 24 months. At the data cutoff date, 72.7 vs 66.7% of Asian and 70.6 vs 66.4% of non-Asian patients remained on treatment. The major molecular response rate at 24 months favored bosutinib vs imatinib among Asian (63.6 vs 38.2%) and non-Asian (60.9 vs 52.6%) patients, as did the complete cytogenetic response rate by 24 months (86.7 vs 76.7%, 81.5 vs 76.3%). Treatment-emergent adverse events in both subpopulations were consistent with the primary BFORE results. Trough bosutinib concentration levels tended to be higher in Asian patients. Health-related quality of life was maintained after 12 months of bosutinib in both subpopulations. These results support bosutinib as a first-line treatment option in Asian patients with CP CML.

Inotuzumab ozogamicin versus standard of care in Asian patients with relapsed/refractory acute lymphoblastic leukemia.

Inotuzumab ozogamicin (InO) is a targeted treatment for adults with relapsed or refractory B-cell acute lymphoblastic leukemia (ALL). InO was previously studied in INO-VATE, an international, open-label, randomized phase 3 trial comparing InO against standard of care (SoC). In the present subgroup analysis, we evaluated outcomes in the 55 Asian patients who were randomized in INO-VATE (31 InO and 24 SoC). Complete remission (CR) or CR with incomplete hematologic recovery (CRi) was achieved in 22/31 patients treated with InO versus 5/24 treated with SoC. In the InO arm, more of the patients achieving CR/CRi were minimal residual disease (MRD)-negative (17/22 versus 1/5), and more patients proceeded directly to hematopoietic stem cell transplantation (15/31 versus 3/24). Median overall survival for the respective arms was 5.8 versus 3.9 months (hazard ratio 0.67; 97.5% CI 0.28, 1.62). In the safety analysis (n = 51), the most common adverse events were hematologic. Sinusoidal obstruction syndrome was reported in five InO patients and one SoC patient. In conclusion, Asian patients with relapsed or refractory B-cell ALL experienced improved efficacy with InO versus SoC, with an efficacy and safety profile consistent with results of the overall INO-VATE population.Clinical trial registration: ClinicalTrials.gov identifier: NCT01564784.

Phase I study of glasdegib (PF-04449913), an oral smoothened inhibitor, in Japanese patients with select hematologic malignancies.

The hedgehog signaling pathway regulates multiple morphogenetic processes during embryogenesis. Aberrant activation of the hedgehog pathway signal transduction in adult tissues is associated with the pathogenesis of hematologic malignancies and solid tumors. We report findings from an open-label, multicenter phase I trial of the selective, small-molecule hedgehog signaling inhibitor glasdegib (PF-04449913) in Japanese patients with select advanced hematologic malignancies. Glasdegib was administered as once-daily oral doses (25, 50 and 100 mg) in 28-day cycles after a lead-in dose on Day -5. The primary objectives were to determine first-cycle dose-limiting toxicities, safety, vital signs and laboratory test abnormalities. Secondary objectives included evaluation of pharmacokinetics, pharmacodynamics and preliminary evidence of clinical activity of glasdegib. No dose-limiting toxicities were noted in the 13 patients in the present study. All patients experienced at least one treatment-emergent, all-causality adverse event. The most frequent treatment-related adverse events (observed in ≥3 patients) were dysgeusia (n = 9), muscle spasms (n = 5), alopecia, decreased appetite (n = 4 each), and increased blood creatinine phosphokinase, constipation and diarrhea (n = 3 each). Two deaths occurred during the study and were deemed not to be treatment-related due to disease progression. Glasdegib demonstrated dose-proportional pharmacokinetics, marked downregulation of the glioma-associated transcriptional regulator GLI1 expression in normal skin, and evidence of preliminary clinical activity, although data are limited. Glasdegib was safe and well tolerated across the dose levels tested. It is confirmed that the 100-mg dose is safe and tolerable in Japanese patients, and this dose level will be examined in the future clinical trial.

Long-term treatment with bosutinib in a phase 1/2 study in Japanese chronic myeloid leukemia patients resistant/intolerant to prior tyrosine kinase inhibitor treatment.

This long-term follow-up of a completed phase 1/2 study assessed the safety and efficacy of bosutinib in Japanese Philadelphia chromosome-positive, chronic phase (CP) or advanced phase (ADV) chronic myeloid leukemia patients who were resistant/refractory or intolerant to prior tyrosine kinase inhibitor treatment. This analysis included 63 patients with a median bosutinib follow-up of 132 weeks (range 3‒372). In the CP second-line (2L) cohort, the cumulative major cytogenetic response (MCyR) and major molecular response (MMR) rates throughout the study were 73 and 53%, respectively. In the CP third-line (3L) cohort, the cumulative MCyR and MMR rates throughout the study were 70 and 40%, respectively. Of the eight ADV patients, MCyR was attained or maintained by 50% of patients, and complete hematologic response was attained or maintained by 25% of patients. Progression-free survival rate and overall survival rate at 96 weeks were, respectively, 91 and 98% in CP2L, 88 and 100% in CP3L, and 33 and 50% in ADV patients. The most common adverse events (>50%) reported were diarrhea (95%), nasopharyngitis (57%), and rash (57%). Bosutinib demonstrated durable efficacy and a manageable tolerability profile over long-term use in Japanese patients.ClinicalTrials.gov: NCT00811070.

Application of Physiologically Based Pharmacokinetic Modeling to the Understanding of Bosutinib Pharmacokinetics: Prediction of Drug-Drug and Drug-Disease Interactions.

Bosutinib is an orally available Src/Abl tyrosine kinase inhibitor indicated for the treatment of patients with Philadelphia chromosome-positive chronic myelogenous leukemia. Bosutinib is predominantly metabolized by CYP3A4 as the primary clearance mechanism. The main objectives of this study were to 1) develop physiologically based pharmacokinetic (PBPK) models of bosutinib; 2) verify and refine the PBPK models based on clinical study results of bosutinib single-dose drug-drug interaction (DDI) with ketoconazole and rifampin, as well as single-dose drug-disease interaction (DDZI) in patients with renal and hepatic impairment; 3) apply the PBPK models to predict DDI outcomes in patients with weak and moderate CYP3A inhibitors; and 4) apply the PBPK models to predict DDZI outcomes in renally and hepatically impaired patients after multiple-dose administration. Results showed that the PBPK models adequately predicted bosutinib oral exposures in patients after single- and multiple-dose administrations. The PBPK models also reasonably predicted changes in bosutinib exposures in the single-dose DDI and DDZI results, suggesting that the PBPK models were sufficiently developed and verified based on the currently available data. Finally, the PBPK models predicted 2- to 4-fold increases in bosutinib exposures by moderate CYP3A inhibitors, as well as comparable increases in bosutinib exposures in renally and hepatically impaired patients between single- and multiple-dose administrations. Given the challenges in conducting numerous DDI and DDZI studies of anticancer drugs in patients, we believe that the PBPK models verified in our study would be valuable to reasonably predict bosutinib exposures under various scenarios that have not been tested clinically.

Nectrisine Biosynthesis Genes in Thelonectria discophora SANK 18292: Identification and Functional Analysis.

The fungus Thelonectria discophora SANK 18292 produces the iminosugar nectrisine, which has a nitrogen-containing heterocyclic 5-membered ring and acts as a glycosidase inhibitor. In our previous study, an oxidase (designated NecC) that converts 4-amino-4-deoxyarabinitol to nectrisine was purified from T. discophora cultures. However, the genes required for nectrisine biosynthesis remained unclear. In this study, the nectrisine biosynthetic gene cluster in T. discophora was identified from the contiguous genome sequence around the necC gene. Gene disruption and complementation studies and heterologous expression of the gene showed that necA, necB, and necC could be involved in nectrisine biosynthesis, during which amination, dephosphorylation, and oxidation occur. It was also demonstrated that nectrisine could be produced by recombinant Escherichia coli coexpressing the necA, necB, and necC genes. These findings provide the foundation to develop a bacterial production system for nectrisine or its intermediates through genetic engineering. IMPORTANCE: Iminosugars might have great therapeutic potential for treatment of many diseases. However, information on the genes for their biosynthesis is limited. In this study, we report the identification of genes required for biosynthesis of the iminosugar nectrisine in Thelonectria discophora SANK 18292, which was verified by disruption, complementation, and heterologous expression of the genes involved. We also demonstrate heterologous production of nectrisine by recombinant E. coli, toward developing an efficient production system for nectrisine or its intermediates through genetic engineering.

A phase 1/2 study of bosutinib in Japanese adults with Philadelphia chromosome-positive chronic myeloid leukemia.

This phase 1/2 study evaluated the safety and pharmacokinetics (part 1) and efficacy and safety (part 2) of bosutinib in Japanese Philadelphia chromosome-positive (Ph+) chronic-phase (CP) or advanced-phase chronic myeloid leukemia (CML) patients resistant/intolerant to previous imatinib (2L) or imatinib+dasatinib/nilotinib (3L). Based on dose-limiting toxicities and previous studies, the part 2 bosutinib starting dose was 500 mg/day (n = 63). For CP CML 2L (n = 28), the cumulative major cytogenetic response (MCyR) rate by week 24 was 36 % (primary endpoint); the cumulative major molecular response (MMR) rate through the study was 43 %. Transformation to accelerated/blast phase (AP/BP) was observed in one patient. Progression-free survival (PFS) and overall survival (OS) rates at 96 weeks were 94 and 96 %, respectively. Of seven advanced-phase 2L patients, one had confirmed complete hematologic response at week 84, and one had AP/BP transformation. PFS and OS rates at week 96 were 21 and 43 %. For 3L (n = 11), cumulative MCyR rate by week 24 was 18 %; cumulative MMR rate was 18 %; no transformations occurred. Common non-hematologic adverse events (AEs) were diarrhea (95 %), rash (57 %), and nasopharyngitis (51 %). Sixteen patients discontinued due to adverse events; no deaths occurred within 30 days of the last dose. Bosutinib 500 mg/day demonstrated efficacy and manageable toxicity in Japanese Ph+ CML patients resistant/intolerant to imatinib.

Clinical impact of genetic variants of drug transporters in different ethnic groups within and across regions.

Drug transporters, together with drug metabolic enzymes, are major determinants of drug disposition and are known to alter the response to many commonly used drugs. Substantial frequency differences for known variants exist across geographic regions for certain drug transporters. To deliver efficacious medicine with the right dose for each patient, it is important to understand the contribution of genetic variants for drug transporters. Recently, mutual pharmacokinetic data usage among Asian regions, which are thought to be relatively similar in their own genetic background, is expected to accelerate new drug applications and reduce developmental costs. Polymorphisms of drug transporters could be key factors to be considered in implementing multiethnic global clinical trials. This review addresses the current knowledge on genetic variations of major drug transporters affecting drug disposition, efficacy and toxicity, focusing on the east Asian populations, and provides insights into future directions for precision medicine and drug development in east Asia.

Impact of drug transporter pharmacogenomics on pharmacokinetic and pharmacodynamic variability - considerations for drug development.

INTRODUCTION: Drug transporter proteins are expressed on the cell membrane, regulating substrate exposure in systemic circulation and/or peripheral tissues. Genetic polymorphism of drug transporter genes encoding these proteins could alter the functional activity and/or protein expression, having effects on absorption, distribution, metabolism and excretion (ADME), efficacy and adverse effects. AREAS COVERED: The authors provide the reader with an overview of the pharmacogenetics (PGx) of 12 membrane transporters. The clinical literature is summarized as to the quantitative significance on pharmacokinetics (PK) and implications on pharmacodynamics (PD) and adverse effects, due to transporter influence on intracellular drug concentrations. EXPERT OPINION: Unlike polymorphisms for cytochrome P450s (CYPs) resulting in large magnitude of PK variation, genetic mutations for membrane transporters are typically less than threefold alteration in systemic PK for drugs with a few exceptions. However, substantially greater changes in intracellular drug levels may result. We are aware of 1880 exome variants in 12 of the best-studied transporters to date, and nearly 40% of these change the amino acid. However, the functional consequences of most of these variants remain to be determined, and have only been empirically evaluated for a handful. To the extent that genetic polymorphisms impact ADME, it is a variable that will contribute to ethnic differences due to substantial frequency differences for the known variants.

Phase I study of anti-CD22 immunoconjugate inotuzumab ozogamicin plus rituximab in relapsed/refractory B-cell non-Hodgkin lymphoma.

Inotuzumab ozogamicin (CMC-544), a humanized anti-CD22 antibody conjugated to the potent cytotoxic antibiotic calicheamicin, targets the CD22 antigen expressed on the majority of B-cell non-Hodgkin lymphomas. This phase I study assessed the tolerability, safety, pharmacokinetics, and preliminary efficacy of inotuzumab ozogamicin administered intravenously in combination with rituximab in Japanese patients with relapsed or refractory B-cell non-Hodgkin lymphoma. Ten patients were administered rituximab 375 mg/m(2) followed by inotuzumab ozogamicin at the maximum tolerated dose (1.8 mg/m(2)). Treatment was repeated every 28 days up to eight cycles, or until occurrence of disease progression or intolerable toxicity. The safety profile was similar to that of inotuzumab ozogamicin monotherapy, with hematologic adverse events occurring most frequently. The most common grade three or higher adverse events were thrombocytopenia (70%), neutropenia (50%), leukopenia (30%), and lymphopenia (30%). The overall response rate was 80% (8/10; 95% CI, 44-98%). Drug exposure increased with successive doses, similar to the pharmacokinetic profiles observed in previous phase I monotherapy studies. Efficacy results suggested promising antitumor activity, and the overall findings support the continued clinical development of this therapeutic regimen in patients with relapsed or refractory B-cell non-Hodgkin lymphoma. This trial was registered at www.ClinicalTrials.gov as NCT00724971.

Phase I study of inotuzumab ozogamicin (CMC-544) in Japanese patients with follicular lymphoma pretreated with rituximab-based therapy.

Inotuzumab ozogamicin (CMC-544), an antibody-targeted chemotherapeutic agent composed of an anti-CD22 antibody conjugated to calicheamicin, a potent cytotoxic antibiotic, specifically targets the CD22 antigen present in >90% of B-lymphoid malignancies, rendering it useful for treating patients with B-cell non-Hodgkin lymphoma (B-NHL). This phase I study evaluated the safety, tolerability, efficacy, and pharmacokinetics of inotuzumab ozogamicin in Japanese patients. Eligible patients had relapsed or refractory CD22-positive B-NHL without major organ dysfunction. Inotuzumab ozogamicin was administered intravenously once every 28 days (dose escalation: 1.3 and 1.8 mg/m(2)). All 13 patients had follicular lymphoma, were previously treated with > or =1 rituximab-alone or rituximab-containing chemotherapy, and were enrolled into two dose cohorts (1.3 mg/m(2), three patients; 1.8 mg/m(2), 10 patients). No patient had dose-limiting toxicities, and the maximum tolerated dose, previously determined in non-Japanese patients (1.8 mg/m(2)), was confirmed. Drug-related adverse events (AEs) included thrombocytopenia (100%), leukopenia (92%), lymphopenia (85%), neutropenia (85%), elevated AST (85%), anorexia (85%), and nausea (77%). Grade 3/4 drug-related AEs in > or =15% patients were thrombocytopenia (54%), lymphopenia (31%), neutropenia (31%), and leukopenia (15%). The AUC and C(max) of inotuzumab ozogamicin increased dose-dependently with pharmacokinetic profiles similar to non-Japanese. Seven patients had complete response (CR, 54%) including unconfirmed CR, four patients had partial response (31%), and two patients had stable disease (15%). The overall response rate was 85% (11/13). Inotuzumab ozogamicin was well tolerated at doses up to 1.8 mg/m(2) and showed preliminary evidence of activity in relapsed or refractory follicular lymphoma pretreated with rituximab-containing therapy, warranting further investigations. This trial was registered in ClinicalTrials.gov (NCT00717925).

Metabolism-dependent hepatotoxicity of amodiaquine in glutathione-depleted mice.

We investigated the hepatotoxicity induced by AQ using a glutathione (GSH)-depleted mice model. Although sole administration of either AQ or L-buthionine-S,R-sulfoxinine (BSO), a well-known GSH synthesis inhibitor, produced no significant hepatotoxicity, combined administration of AQ with BSO induced hepatotoxicity characterized by centrilobular necrosis of the hepatocytes and an elevation of plasma alanine aminotransferase activity. Pretreatment of aminobenzotriazole, a nonspecific inhibitor for P450s, completely suppressed the above hepatotoxicity caused by AQ co-treatment with BSO. Administration of radiolabeled AQ in combination with BSO exhibited significantly higher covalent binding to mice liver proteins than that observed after sole dosing of radiolabeled AQ. The results obtained in this GSH-depleted animal model suggest that the reactive metabolite of AQ formed by hepatic P450 binds to liver proteins, and then finally leads to hepatotoxicity. These observations may help to understand the risk factors and the mechanism for idiosyncratic hepatotoxicity of AQ in humans.

Molecular basis of ML-236B production in the high-producing mutant No. 41520 of Penicillium citrinum.

Strain improvement through random mutagenesis, screening and selection has provided us with spontaneous mutants which could produce more ML-236B than the original isolate, Penicillium citrinum SANK18767. The objective of the present study is to clarify how a high-producing mutant No. 41520 acquired the ability to produce 500 times more ML-236B than the original isolate on a molecular basis. Southern blot analysis and sequence comparison revealed that amplification of the ML-236B biosynthetic gene cluster and alteration of nucleotides within the loci had not occurred in the genome of No. 41520. On the other hand, a differential hybridization and Northern blot analysis showed that expression levels of the nine biosynthetic genes mlcA to mlcH and mlcR in No. 41520 increased greatly as compared to those in the original isolate. These data suggested that the increase in ML-236B production was partly due to increased expression of genes involved in ML-236B biosynthesis. Morphological differences and higher consumption of carbon source would also affect ML-236B production in No. 41520. Functional analysis revealed that a gene, orf1 next to mlcR, was not involved in the ML-236B biosynthesis, but it was involved in the transcriptional activation of genes along with the ML-236B gene cluster. Titer enhanced mutations might have occurred in the regulation system for transcription activation of the ML-236B biosynthetic genes in the mutants of P. citrinum.

New highly active taxoids from 9 beta-dihydrobaccatin-9,10-acetals. Part 5.

To improve the metabolic stability of 3, which exhibited both in vitro antitumor activity and in vivo efficacy by both iv and po administration, we designed and synthesized new taxane analogues. Most of the synthetic compounds maintained excellent antitumor activity and were scarcely metabolized by human liver microsomes. And some compounds exhibited potent antitumor effects against B16 melanoma BL6 in vivo by both iv and po administration similarly to 3.

Absorption, distribution and excretion of 14C-levofloxacin after single oral administration in albino and pigmented rats: binding characteristics of levofloxacin-related radioactivity to melanin in vivo.

After single oral administration of (14)C-levofloxacin at a dose of 20 mg kg(-1) under non-fasting conditions, the absorption, distribution and excretion of radioactivity were studied in albino and pigmented rats. Good penetration of radioactivity into tissues was indicated by higher concentrations in most tissues compared with serum and there were no quantitative differences in the distribution of radioactivity between albino and pigmented rats except for melanin-containing tissues such as the uveal tract of eyes and hair follicles. There was selective and strong binding of drug-related radioactivity to these tissues in pigmented rats. The uveal tract concentrations reached the maximum value (C(max)) of 26.33 +/- 0.75 microg eq. g(-1) at 24 h after dosing and declined slowly with a terminal half-life of 468.1 h (19.5 days). The uveal tract concentration at 12 weeks was 0.73+/- 0.12 microg eq. g(-1), which is c. 1/36 of C(max). The AUC(0- infinity ) for the uveal tract was 12.58 mg h(-1) g(-1). The uveal tracts separated from one eye of each rat were extracted with 0.067 M phosphate buffer (pH 7.4) and 1M HCl/EtOH (30:70), successively. In pigmented rats, approximately 85-48% of radioactivity bound to the uveal tract was released from the tissue by the washing procedures. Most of the eluted radioactivity was released with 1M HCl/EtOH (30:70), indicating that the binding to melanin is reversible, and hydrophobic and electrostatic interactions play an important role in the binding of levofloxacin and/or its metabolites with melanin-containing ocular tissues. Only unchanged drug was detected in the extracts of the uveal tracts. The concentrations and half-life of radioactivity in the uveal tract after dosing of (14)C-levofloxacin were found to be much lower and shorter than those after dosing of (14)C-chloroquine. It is unlikely that levofloxacin causes toxicity because of its much lower affinity to melanin-containing ocular tissues and shorter duration of therapy compared to chloroquine.

Absorption, distribution, and excretion of DJ-927, a novel orally effective taxane, in mice, dogs, and monkeys.

DJ-927, currently undergoing Phase I clinical trial, is a new orally effective taxane with potent antitumor effects. The absorption, tissue distribution, and excretion of DJ-927 were investigated in mice, dogs, and monkeys after a single oral administration. After oral administration of [14C]DJ-927, radioactivity was rapidly absorbed, with the Cmax occurring within 1-2 h in all species. The blood and plasma radioactivity elimination was biphasic and species-dependent. Elimination half-life of plasma in dogs was much longer than those in monkeys or mice. In mice, radioactivity was rapidly distributed to all tissues except for the central nervous system, especially to adrenal glands, liver, pituitary glands, kidneys, lungs, and spleen. In all species, radioactivity was mainly excreted in feces. Following a single oral administration to mice, more than 80% of the radioactivity was excreted within 48 h; in dogs and monkeys, 80% of the radioactivity was excreted within 168 h. Urinary excretion was less than 7% of radioactive dose in all species. In vitro plasma protein binding of [14C]DJ-927 in the mouse, dog, and monkey plasma ranged from 92-98%. These studies showed that, the novel oral taxane DJ-927 was rapidly absorbed in all three species when administered by the oral route. The long biological half-life and slow elimination of radioactivity were distinctive in particular, compared with commercial taxanes. DJ-927 (as parent compound and its metabolites) is widely distributed to tissues except the brain. These preclinical data are useful for the design of clinical trials of DJ-927 and also for their interpretation.

New highly active taxoids from 9beta-dihydrobaccatin-9,10-acetals. Part 4.

It was shown that a new taxane analogue 3, which exhibited both in vitro antitumor activity and in vivo efficacy by both i.v. and p.o. administration, was prone to be metabolized by human liver microsomes. We identified a major metabolite, M-1, generated by human liver microsomes as 20a, a hydroxylated compound at the pyridine ring of 3. To improve the metabolic stability of 3, we designed and synthesized new taxane analogues based on the structure of M-1, and obtained some compounds that maintained excellent antitumor activity and were scarcely metabolized by human liver microsomes.