Real-World Safety and Efficacy of Biosimilar CT-P13 in Patients with Immune-Mediated Inflammatory Diseases: Integrated Analysis of Three Japanese Prospective Observational Studies.

INTRODUCTION: Biosimilar CT-P13 was approved with limited data from clinical trials compared to the originator infliximab in biologic-naïve patients with rheumatoid arthritis. Three prospective post-marketing surveillance studies have been conducted in Japanese biologic-naïve patients and switched patients from biologics including the originator infliximab. OBJECTIVE: We performed an integrated analysis of final data from three post-marketing studies to provide long-term safety and efficacy data of CT-P13 in a real-world clinical setting. METHODS: A total of 1816 patients consisting of 987 patients with rheumatoid arthritis, 342 patients with Crohn's disease, 322 patients with ulcerative colitis, and 165 patients with psoriasis were evaluated for safety. Efficacy was assessed in 1150 patients whose disease parameter values were serially collected. RESULTS: Adverse drug reactions were reported in 24.2% of all patients. The incidence of adverse drug reactions differed by the prior treatment status with biologics: 30.5% in patients naïve to biologics, 17.0% in patients switched from the originator infliximab, and 33.5% in patients switched from other biologics. Infusion reactions were the most frequent adverse drug reactions (8.2%), and its incidence was significantly higher in patients with ulcerative colitis and an allergy history in a multivariable Cox regression analysis. Infection was the second most frequent (6.1%), but tuberculosis only occurred in four patients (0.2%). The incidence of infection was low in patients with Crohn's disease and psoriasis, and significant risk factors were an allergy history, comorbidities, and concomitant steroid use. Interstitial lung disease occurred in 16 patients (0.9%), including 11 patients with rheumatoid arthritis. With CT-P13 therapy, disease activity parameters decreased similarly in all four diseases, although long-term drug discontinuation rates because of inefficacy varied by disease. In naïve patients, the disease activity parameters decreased rapidly and the proportion of patients in remission increased. Patients switched from infliximab maintained lowered parameter levels with infliximab pretreatment. Decreases were also observed in patients switched from other biologics, but discontinuations were most often because of insufficient efficacy. CONCLUSIONS: The integrated analysis of a large number of patients detected no new safety signals with long-term CT-P13 treatment. Efficacy in rheumatoid arthritis, psoriasis, Crohn's disease, and ulcerative colitis cases was confirmed in biologic-naïve patients and switched patients from the originator infliximab or other biologics.

Safety, efficacy, and drug survival of the infliximab biosimilar CT-P13 in post-marketing surveillance of Japanese patients with psoriasis.

Based on extrapolation of similar clinical outcomes in rheumatoid arthritis to the originator infliximab (IFX) in randomized clinical trials, the first biosimilar antibody CT-P13 was approved for the treatment of psoriasis. To evaluate the safety, efficacy, and drug survival of CT-P13 for psoriasis in real-world clinical practice, prospective post-marketing surveillance was conducted in 165 Japanese psoriasis patients. During a 1-year follow-up period, adverse drug reactions (ADRs) occurred in 29 patients (17.6%). Infusion reaction was the most frequent ADR (6.7%), and mild pneumonia was reported as the only case of infection. Serious ADRs were reported in two patients (1.2%): acute cholecystitis and interstitial pneumonia. The interstitial pneumonia developed after a single infusion of CT-P13 and the patient died of respiratory failure. In naive patients to biologic therapy (n = 44), the Psoriasis Area Severity Index (PASI) decreased rapidly after the start of CT-P13 treatment, and response rate achieving an absolute PASI score <1 was 55% at 30 weeks. The response rate was high (78%) in patients with psoriatic arthritis, and 40% and 20% in those in plaque psoriasis and pustular psoriasis, respectively. Of patients switched from IFX to CT-P13 mainly for nonmedical reasons (n = 105), 57% had already reached PASI <1 by pretreatment with IFX and CT-P13 maintained this status. The incidence of ADRs in this patient group was low and the drug survival rate was as high as 74%, even at 1 year, which was significantly higher than that in the naïve patient group (47%). Patients switched from other biologics for medical reasons (n = 16) responded similarly to biologic-naïve patients, but drug survival was lower (24%). In conclusion, CT-P13 showed excellent effectiveness as a first-line therapy, no clinical difficulties in switching from IFX, and usefulness in patients who failed other biologics. CT-P13 could be a cost-effective alternative to IFX for the treatment of psoriasis.

Real-world safety and efficacy of CT-P13, an infliximab biosimilar, in Japanese rheumatoid arthritis patients naïve to or switched from biologics.

OBJECTIVES: The aim of this post-marketing surveillance (PMS) study is to evaluate the real-world safety and efficacy of CT-P13, the first biosimilar of infliximab (IFX). METHODS: Japanese patients with rheumatoid arthritis were prospectively registered from November 2014 and followed up for 1 year. RESULTS: Of 794 patients in the analysis set, 318 patients naïve to biological disease-modifying antirheumatic drugs (bDMARDs) showed an immediate decrease in Disease Activity Score in 28 joints with C-reactive protein (DAS28-CRP) and increased remission rate (DAS28-CRP < 2.6). In patients who switched from IFX to CT-P13 for non-medical reasons (n = 374), the low DAS28-CRP due to previous IFX treatment decreased further with continued CT-P13 therapy. As in naïve patients, patients who switched from other bDMARDs, mainly for medical reasons (n = 102), responded similarly to CT-P13. CT-P13 in this PMS and IFX in a previous PMS had similar adverse reaction profiles, although the incidence rate in naïve patients in this current PMS was lower due to earlier initiation of CT-P13 therapy. CONCLUSIONS: CT-P13 showed excellent effectiveness as first-line therapy, no clinical difficulties in switching from IFX, and clinical improvement in patients who failed other bDMARDs. CT-P13 could be a cost-effective alternative to IFX in the treatment of rheumatoid arthritis.

Post-marketing analysis for biosimilar CT-P13 in inflammatory bowel disease compared with external data of originator infliximab in Japan.

BACKGROUND AND AIM: CT-P13, an infliximab (IFX) biosimilar, was approved for treatment of inflammatory bowel disease. However, no comparison with the originator IFX in this indication has been conducted in Japan where endemic levels of tuberculosis and hepatitis virus infection are not low. We evaluated the safety and efficacy in real-world data of CT-P13 and compared with originator IFX data in Japan. METHODS: In a prospective post-marketing surveillance (PMS) study, patients who received CT-P13 in a 28-month period from January 2015 were followed up for 2 years. By conducting Japanese administrative database search (DBS) for the same period of PMS, data of the originator IFX including treatment persistence, tuberculosis incidence, and liver injury were analyzed retrospectively and compared with the corresponding PMS data of CT-P13. RESULTS: CT-P13 persistence in PMS (n = 640) and IFX persistence in DBS (n = 4113) were almost similar between patients who switched from the originator and patients who continued on the originator, and also between the biologics-naïve patient groups. There were no differences in the incidences of tuberculosis and hepatic injury (Tuberculosis: 2 patients [0.31%] with CT-P13, 10 patients [0.24%] with the originator, P = 0.75; Hepatic injury: 18.5% with CT-P13, 15.4% with the originator, P = 0.22). Most of the patients with hepatic injury continued treatment in PMS and DBS at similar rates (80.8% vs 83.6%, P = 0.65). CONCLUSION: The results of long-term PMS of CT-P13 compared with external reference data from an administrative database suggested that the biosimilar and its originator were comparably useful in real-world clinical practice.

Infliximab biosimilar CT-P13 is interchangeable with its originator for patients with inflammatory bowel disease in real world practice.

BACKGROUND/AIMS: An interim analysis of post-marketing surveillance of CT-P13, an infliximab biosimilar, was performed to evaluate its safety and efficacy in Japanese patients with inflammatory bowel disease. METHODS: Patients were prospectively enrolled between November 2014 and March 2017, after the launch of CT-P13 in Japan, and case report forms of patients followed for at least 4 months were analyzed as of July 2018. RESULTS: Of 523 patients in the analysis set, 372 remained on CT-P13 therapy, while 54 (20.2%) of 267 patients with Crohn's disease, and 97 (37.9%) of 256 patients with ulcerative colitis were withdrawn during follow-up. A total of 144 adverse drug reactions (ADRs) were reported in 106 patients (20.3%). Infusion reaction was the most frequent ADR observed in 49 patients (9.4%). Efficacy parameters decreased immediately after the start of treatment in naïve patients to anti-tumor necrosis factor-α antibody. In the patients switched from originator infliximab for nonmedical reasons, the decreased parameters due to proceeded treatment with the originator were maintained in low ranges, and the treatment continuation rate was high with low ADR incidence. In contrast, in patients switched for medical reasons such as adverse event or loss of response, the incidence of ADRs was high. However, the efficacy parameters were improved, and the treatment continuation rate was not significantly different from that of the naïve patient group. CONCLUSIONS: In this interim analysis, CT-P13 was comparable to the originator infliximab with respect to ADRs and efficacy, and is therefore considered to be a cost-efficient interchangeable biosimilar for Japanese patients with inflammatory bowel disease.

Clinical safety and efficacy of "filgrastim biosimilar 2" in Japanese patients in a post-marketing surveillance study.

We conducted a post-marketing surveillance to evaluate the safety and efficacy of TKN732, approved as "filgrastim biosimilar 2", in Japanese patients who developed neutropenia in the course of cancer chemotherapy or hematopoietic stem cell transplantation. A total of 653 patients were registered during the 2-year enrollment period starting from May 2013, and 627 and 614 patients were eligible for safety and efficacy analyses of the G-CSF biosimilar, respectively. Forty-three adverse drug reactions were reported in 33 patients (5.26%). Back pain was most frequently observed and reported in 20 patients (3.19%), followed by pyrexia (1.28%) and bone pain (0.96%). Risk factors for adverse reactions identified by logistic regression analyses were younger age, presence of past medical history, and lower total dose at the onset of adverse reactions. Among the 576 cancer patients who developed Grade 2-4 neutropenia after chemotherapy, recovery to Grade 1/0 was reported in 553 patients (96%) following filgrastim biosimilar 2 treatment. The median duration of neutrophil counts below 1500/µL was 5 days. In addition, all 11 patients who underwent hematopoietic stem cell transplantation had good responses to filgrastim biosimilar 2. In conclusion, this study showed that filgrastim biosimilar 2 has a similar safety profile and comparable effects to the original G-CSF product in the real world clinical setting.

A novel compound, NK150460, exhibits selective antitumor activity against breast cancer cell lines through activation of aryl hydrocarbon receptor.

Antiestrogen agents are commonly used to treat patients with estrogen receptor (ER)-positive breast cancer. Tamoxifen has been the mainstay of endocrine treatment for patients with early and advanced breast cancer for many years. Following tamoxifen treatment failure, however, there are still limited options for subsequent hormonal therapy. We discovered a novel compound, NK150460, that inhibits 17ß-estradiol (E2)-dependent transcription without affecting binding of E2 to ER. Against our expectations, NK150460 inhibited growth of not only most ER-positive, but also some ER-negative breast cancer cell lines, while never inhibiting growth of non-breast cancer cell lines. Cell-based screening using a random shRNA library, identified aryl hydrocarbon receptor nuclear translocator (ARNT) as a key gene involved in NK150460's antitumor mechanism. siRNAs against not only ARNT but also its counterpart aryl hydrocarbon receptor (AhR) and their target protein, CYP1A1, dramatically abrogated NK150460's growth-inhibitory activity. This suggests that the molecular cascade of AhR/ARNT plays an essential role in NK150460's antitumor mechanism. Expression of ERα was decreased by NK150460 treatment, and this was inhibited by an AhR antagonist. Unlike two other AhR agonists now undergoing clinical developmental stage, NK150460 did not induce histone H2AX phosphorylation or p53 expression, suggesting that it did not induce a DNA damage response in treated cells. Cell lines expressing epithelial markers were more sensitive to NK150460 than mesenchymal marker-expressing cells. These data indicate that NK150460 is a novel AhR agonist with selective antitumor activity against breast cancer cell lines, and its features differ from those of the other two AhR agonists.

DNA-dependent protein kinase and ataxia telangiectasia mutated (ATM) promote cell survival in response to NK314, a topoisomerase IIα inhibitor.

4-Hydroxy-5-methoxy-2,3-dihydro-1H-[1,3]benzodioxolo[5,6-c]pyrrolo[1,2-f]-phenanthridium chloride (NK314) is a benzo[c] phenanthridine alkaloid that inhibits topoisomerase IIα, leading to the generation of DNA double-strand breaks (DSBs) and activating the G(2) checkpoint pathway. The purpose of the present studies was to investigate the DNA intercalating properties of NK314, to evaluate the DNA repair mechanisms activated in cells that may lead to resistance to NK314, and to develop mechanism-based combination strategies to maximize the antitumor effect of the compound. A DNA unwinding assay indicated that NK314 intercalates in DNA, a property that likely cooperates with its ability to trap topoisomerase IIα in its cleavage complex form. The consequence of this is the formation of DNA DSBs, as demonstrated by pulsed-field gel electrophoresis and H2AX phosphorylation. Clonogenic assays demonstrated a significant sensitization in NK314-treated cells deficient in DNA-dependent protein kinase (DNA-PK) catalytic subunit, Ku80, ataxia telangiectasia mutated (ATM), BRCA2, or XRCC3 compared with wild-type cells, indicating that both nonhomologous end-joining and homologous recombination DNA repair pathways contribute to cell survival. Furthermore, both the DNA-PK inhibitor 8-(4-dibenzothienyl)-2-(4-morpholinyl)-4H-1-benzopyran-4-one (NU7441) and the ATM inhibitor 2-(4-morpholinyl)-6-(1-thianthrenyl)-4H-pyran-4-one (KU55933) significantly sensitized cells to NK314. We conclude that DNA-PK and ATM contribute to cell survival in response to NK314 and could be potential targets for abrogating resistance and maximizing the antitumor effect of NK314.

Comparative study of peripheral neurotoxicity after injection of two different paclitaxel formulations in rats.

Paclitaxel Inj. [NK] (test; paclitaxel, CAS 33069-62-4) is a generic version of the drug from the originator (reference). Both drugs contain the same active ingredient and showed identical pharmacokinetics in patients in the previous study; however, these two drugs may have different safety profiles because they contain different inactive ingredients. Thus, in this study, peripheral neurotoxicity, one of the dose-limiting toxicities of the reference, was compared between the test and the reference in rats electrophysiologically and histopathologically. In a nerve conduction study, the amplitude of the caudal sensory nerve action potential decreased significantly after either the test or the reference administration, compared with the amplitude after saline administration, but no significant differences were observed between the two drugs. Histopathologically, apparent degeneration of the myelinated fibers in the sciatic and the sural nerves was seen after either the test or the reference injection, compared with after saline injection, but no apparent differences were observed between the two formulations. These results suggest that no significant difference in peripheral neurotoxicity exists between the test and the reference in rats.

Suppression of mutant androgen receptors by flutamide.

OBJECTIVES: To examine the effects of flutamide and hydroxyflutamide on the transactivation of mutant androgen receptors. METHODS: Androgen-independent human prostate cancer cell line PC3 was transfected with plasmids expressing wild-type, W741C mutant, T877A mutant or W741C+T877A mutant androgen receptors. The effects of bicalutamide, hydroxyflutamide or flutamide on the basal and dihydrotestosterone-induced transcriptional activities of the wild-type and mutant androgen receptors were evaluated by luciferase assays using a reporter plasmid containing the prostate-specific antigen (PSA) promoter. The effects of the antiandrogens on the transcription and translation of the PSA gene in LNCaP cells expressing a mutant (T877A) androgen receptor were assessed by real-time reverse transcription-polymerase chain reaction and radioimmunoassays. Affinity of the antiandrogens to each androgen receptor construct was evaluated by ligand-binding assay. RESULTS: Flutamide, but not hydroxyflutamide, successfully suppressed the transcription of all of the mutant androgen receptors examined in this study and also showed suppressive effects on PSA secretion by LNCaP cells treated with dihydrotestosterone. These inhibitory effects were probably not the result of competitive inhibition by flutamide given its low affinity to the androgen receptor constructs. CONCLUSIONS: Flutamide, with its suppressive effects on mutant androgen receptors, may be an alternative to conventional antiandrogens for hormone refractory prostate cancer.

Pharmacokinetic analysis of a combined chemoendocrine treatment with paclitaxel and toremifene for metastatic breast cancer.

BACKGROUND: Multidrug resistance protein could be a target for improving the efficacy of paclitaxel (PXL). Toremifene (TOR) may moderate P-gp-related drug resistance in vitro. Some P-gp moderators may change the pharmacokinetic parameters of PXL in vivo. A pharmacokinetic (PK) study in metastatic breast cancer patients (MBC) was conducted to determine the safety and efficacy of PXL and TOR. METHOD AND PATIENTS: Fifteen patients received 80 mg/m(2) PXL (i.v.) weekly and 120 mg/body TOR (p.o.) daily. For the pharmacokinetic study, PXL was administered on days 1, 8, 15, 32, and 39; TOR was given from day 18 to the end of study. On days 1, 8, 15, 18, 32, and 39, blood samples were collected from the patients who received either PXL alone or PXL + TOR, and these were analyzed by high-performance liquid chromatography. RESULTS: Among the 15 patients enrolled in the study, one showed a partial response, and eight had a stable disease. TOR caused no specific adverse events that were greater than grade 3, and its toxicity profile in combination with PXL was similar to that of PXL monotherapy. The PK profile of PXL was similar with or without TOR. The PK parameters of PXL indicated no inter- or intra-patient variability in previously treated patients with MBC. No increased PXL toxicity was observed. CONCLUSION: The PK profile of combined PXL and TOR was similar to that of PXL monotherapy. The addition of TOR to PXL in previously treated patients with MBC appears safe.

NK314, a topoisomerase II inhibitor that specifically targets the alpha isoform.

Topoisomerase II (Top2) is a ubiquitous nuclear enzyme that relieves torsional stress in chromosomal DNA during various cellular processes. Agents that target Top2, involving etoposide, doxorubicin, and mitoxantrone, are among the most effective anticancer drugs used in the clinic. Mammalian cells possess two genetically distinct Top2 isoforms, both of which are the target of these agents. Top2alpha is essential for cell proliferation and is highly expressed in vigorously growing cells, whereas Top2beta is nonessential for growth and has recently been implicated in treatment-associated secondary malignancies, highlighting the validity of a Top2alpha-specific drug for future cancer treatment; however, no such agent has been hitherto reported. Here we show that NK314, a novel synthetic benzo[c]phenanthridine alkaloid, targets Top2alpha and not Top2beta in vivo. Unlike other Top2 inhibitors, NK314 induces Top2-DNA complexes and double-strand breaks (DSBs) in an alpha isoform-specific manner. Heterozygous disruption of the human TOP2alpha gene confers increased NK314 resistance, whereas TOP2beta homozygous knock-out cells display increased NK314 sensitivity, indicating that the alpha isoform is the cellular target. We further show that the absence of Top2beta does not alleviate NK314 hypersensitivity of cells deficient in non-homologous end-joining, a critical pathway for repairing Top2-mediated DSBs. Our results indicate that NK314 acts as a Top2alpha-specific poison in mammalian cells, with excellent potential as an efficacious and safe chemotherapeutic agent. We also suggest that a series of human knock-out cell lines are useful in assessing DNA damage and repair induced by potential topoisomerase-targeting agents.

Azaspirene, a fungal product, inhibits angiogenesis by blocking Raf-1 activation.

Angiogenesis is an inevitable event in tumor progression and metastasis, and thus has been a compelling target for cancer therapy in recent years. Effective inhibition of tumor progression and metastasis could become a promising way to treat tumor-induced angiogenesis. We discovered that a fungus, Neosartorya sp., isolated from a soil sample, produced a new angiogenesis inhibitor, which we designated azaspirene. Azaspirene was previously shown to inhibit human umbilical vein endothelial cell (HUVEC) migration induced by vascular endothelial growth factor (VEGF) at an effective dose, 100% of 27 micromol/L without significant cell toxicity. In the present study, we investigated the antiangiogenic activity of azaspirene in vivo. Azaspirene treatment reduced the number of tumor-induced blood vessels. Administration of azaspirene at 30 microg/egg resulted in inhibition of angiogenesis (23.6-45.3% maximum inhibition relative to the controls) in a chicken chorioallantoic membrane assay. Next, we elucidated the molecular mechanism of antiangiogenesis of azaspirene. We investigated the effects of azaspirene on VEGF-induced activation of the mitogen-activated protein kinase signaling pathway in HUVEC. In vitro experiments indicated that azaspirene suppressed Raf-1 activation induced by VEGF without affecting the activation of kinase insert domain-containing receptor/fetal liver kinase 1 (VEGF receptor 2). Additionally, azaspirene preferentially inhibited the growth of HUVEC but not that of the non-vascular endothelial cells NIH3T3, HeLa, MSS31, and MCF-7. Taken together, these results demonstrate that azaspirene is a novel inhibitor of angiogenesis and Raf-1 activation that contains a unique carbon skeleton in its molecular structure.

Epoxyquinol B shows antiangiogenic and antitumor effects by inhibiting VEGFR2, EGFR, FGFR, and PDGFR.

Angiogenesis is the development of new blood vessels to provide oxygen and nutrients and is indispensable for solid tumor growth. Therefore, the inhibition of angiogenesis is an important modality for cancer chemotherapy. Here we report the antiangiogenic mechanism and antitumor effects of epoxyquinol B (EPQB), which was isolated from fungal metabolites. Short-term treatment of EPQB resulted in the reduction of tumor growth and the number of blood vessels directed to the tumor in a murine xenografts model. Furthermore, EPQB inhibited vascular endothelial growth factor (VEGF)-induced migration and tube formation in human umbilical vein endothelial cells (HUVECs) without cytotoxicity. VEGF-stimulated phosphorylation of VEGF receptor 2 (VEGFR2), phospholipase Cgamma-1 (PLCgamma1), and p44/42 MAP kinases (ERK) was inhibited by EPQB in a dose-dependent manner, and in vitro assay using kinase domain of VEGFR2 showed that EPQB covalently bound and inhibited the VEGFR2 kinase. Its binding site on VEGFR2 was different from SU5614, a well-known VEGFR2 kinase inhibitor. Interestingly, EPQB inhibited growth factor-induced activation of not only VEGFR2 but also epidermal growth factor receptor (EGFR), fibroblast growth factor receptor (FGFR), and platelet-derived growth factor receptor (PDGFR), suggesting that EPQB is a novel multiple kinase inhibitor. These findings suggest that EPQB would be a good lead compound for the development of potent antiangiogenic and antitumor drugs.

Small molecules destabilize cIAP1 by activating auto-ubiquitylation.

Overexpression of an anti-apoptotic protein cIAP1 caused by its genetic amplification was reported in certain cancers, such as hepatocellular carcinoma, esophageal squamous cell carcinoma, cervical cancer, and lung cancer, which confers resistance to chemotherapy and radiotherapy. Here we report cIAP1 to be selectively down-regulated by a class of small molecules ((-)-N-[(2S,3R)-3-amino-2-hydroxy-4-phenyl-butyryl]-l-leucine methyl ester (ME-BS)), resulting in a sensitization of cancer cells to apoptosis. ME-BS directly interacts with the BIR3 domain of cIAP1, promotes auto-ubiquitylation dependent on its RING domain, and facilitates proteasomal degradation of cIAP1. Other IAPs such as XIAP and cIAP2 were not affected by ME-BS. These results suggest targeted destabilization of cIAP1 by small molecules as a novel method to treat cancers expressing cIAP1, which interferes with treatment. Manipulation of the intrinsic ubiquitin-ligase activity could be a novel strategy to develop small molecules for therapeutic purposes.

NK314, a novel topoisomerase II inhibitor, induces rapid DNA double-strand breaks and exhibits superior antitumor effects against tumors resistant to other topoisomerase II inhibitors.

NK314 is a novel synthetic benzo[c]phenanthridine alkaloid that shows strong antitumor activity. It inhibited topoisomerase II activity and stabilized topoisomerase II-DNA cleavable complexes. The DNA breaks occurred within 1h after treatment with NK314 even without digestion of topoisomerase II by proteinase K, whereas etoposide required digestion of the enzyme protein in cleavable complex to detect DNA breaks. Pretreatment with topoisomerase II catalytic inhibitors, ICRF-193 and suramin, reduced both cleavable complex-mediated DNA breaks and proteinase K-independent DNA breaks, but protease inhibitors and nuclease inhibitors only decreased the latter. These results indicate that NK314 might affect topoisomerase II in the different manner from cleavable complex formation and activate intracellular proteinase and nuclease to produce DNA fragmentation. As a result of this unique mechanism of DNA breakage, NK314 showed substantial growth inhibition of topoisomerase II inhibitor-resistant tumors.

Inhibition of topoisomerase IIalpha and G2 cell cycle arrest by NK314, a novel benzo[c]phenanthridine currently in clinical trials.

NK314 is a novel synthetic benzo[c]phenanthridine alkaloid that has recently entered clinical trials as an antitumor compound, based on impressive activities in preclinical models. The present investigations were directed at determining the mechanism of action of this agent. NK314 induced significant G(2) cell cycle arrest in several cell lines, independent of p53 status, suggesting the existence of a common mechanism of checkpoint activation. The Chk1-Cdc25C-Cdk1 G(2) checkpoint pathway was activated in response to 100 nmol/L NK314 in ML-1 human acute myeloid leukemia cells. This was associated with the phosphorylation of the histone variant H2AX, an action that was predominant in the G(2) population, suggesting that double-strand DNA breaks caused cells to activate the checkpoint pathway. Double-strand DNA breaks were visualized as chromosomal aberrations when the G(2) checkpoint was abrogated by 7-hydroxystaurosporine. In vitro assays showed that NK314 inhibited the ability of topoisomerase IIalpha to relax supercoiled DNA and trapped topoisomerase IIalpha in its cleavage complex intermediate. CEM/VM1 cells, which are resistant to etoposide due to mutations in topoisomerase IIalpha, were cross-resistant to NK314. However, CEM/C2 cells, which are resistant to camptothecin due to mutations in topoisomerase I, retained sensitivity. These findings support the conclusion that the major mechanism of NK314 is to inhibit topoisomerase IIalpha, an action that leads to the generation of double-strand DNA breaks, which activate the G(2) DNA damage checkpoint pathway.

Immunohistochemical expression of aminopeptidase N (CD13) in human lung squamous cell carcinomas, with special reference to Bestatin adjuvant therapy.

Bestatin, a specific inhibitor of aminopeptidase N (CD13), has been reported to prolong survival time in patients with completely resected stage I lung squamous cell carcinoma. Considering the antitumor mechanism of Bestatin, it is interesting to know whether CD13 is expressed in human lung squamous cell carcinoma. The immunohistochemical expression of CD13 was examined in human lung carcinoma and the question of whether CD13 was immunohistochemically expressed in the interstitial tissue was investigated, mainly in the fibroblasts and blood vessels, surrounding the tumor nests of various kinds of non-small cell lung cancers, especially of squamous cell carcinomas. In Japanese squamous cell carcinoma of the lung, 38 (61.3%) out of 62 cancers were positively stained in the same manner on immunohistochemistry for CD13. The area of interstitial tissue positively stained for CD13 varied depending on the case. To confirm the cell nature of the interstitial tissue with CD13 positivity, double immunohistochemistry using CD34 and alpha-smooth muscle actin was performed. Double immunohistochemistry showed that the majority of CD13-positive cells were slender fibroblastic cells around the blood vessels and some endothelial cells.

Metabolism and hepatic toxicity of flutamide in cytochrome P450 1A2 knockout SV129 mice.

BACKGROUND: Flutamide, a nonsteroidal antiandrogen used for treatment of prostate cancer, causes a temporary increase in transaminase and in some cases severe liver dysfunction. It is dominantly metabolized by cytochrome P450 (CYP) 1A2 into 2-hydroxyflutamide (OH-flutamide), which has stronger antiandrogenic activity without obvious cytotoxicity to cultured hepatocytes. We hypothesized that another subsidiary metabolite might be responsible for induction of hepatotoxicity. METHODS: Flutamide was administered daily to CYP1A2 knockout mice and parental SV129 mice to compare pharmacokinetics and appearance of hepatic toxicity. RESULTS: In the CYP1A2 knockout mice, the plasma concentration of flutamide maintained at a high level and OH-flutamide stayed low; a higher amount of FLU-1, an alternative metabolite of flutamide, was detected in urine. Simple repetitive administration of 800 mg/kg of flutamide for 28 days to CYP1A2 knockout mice did not show abnormal elevation of plasma alanine aminotransferase (ALT). However, after the knockout mice were fed with an amino acid-deficient diet for 2 weeks, which reduced the glutathione (GSH) content to 27% of the initial, administration of 400 mg/kg of flutamide increased ALT to over 200 IU/l and histopathologically moderate hepatitis developed. Since FLU-1 itself did not show cytotoxicity or reduce GSH content in vitro, a further metabolized molecule must cause the hepatotoxicity. CONCLUSIONS: Blockade of CYP1A2 produced an unknown potential hepatotoxic molecule through FLU-1, and GSH might play an important role in diminishing the reactive hepatotoxic metabolite.

Detection of a new N-oxidized metabolite of flutamide, N-[4-nitro-3-(trifluoromethyl)phenyl]hydroxylamine, in human liver microsomes and urine of prostate cancer patients.

Flutamide (2-methyl-N-[4-nitro-3-(trifluoromethyl)phenyl]-propanamide), a nonsteroidal antiandrogen, is used in the treatment of prostate cancer but is occasionally associated with hepatic dysfunction. In the present study, the metabolism of flutamide including the formation of the possible reactive toxic metabolites was investigated using human liver microsomes and 10 isoforms of recombinant human cytochrome P450 (P450). 2-Hydroxyflutamide (OH-flutamide) and 4-nitro-3-(trifluoromethyl)phenylamine (FLU-1) were the main products of flutamide metabolism in human liver microsomes. The formation of OH-flutamide was markedly inhibited by ellipticine, an inhibitor of CYP1A1/1A2, and was mainly catalyzed by the recombinant CYP1A2. FLU-1 was also produced from OH-flutamide, but its metabolic rate was much less than that from flutamide. An inhibitor of carboxylesterase, bis-(p-nitrophenyl)phosphoric acid, completely inhibited the formation of FLU-1 from flutamide in human liver microsomes. A new metabolite, N-[4-nitro-3-(trifluoromethyl)phenyl]hydroxylamine (FLU-1-N-OH), was detected as a product of the reaction of FLU-1 with human liver microsomes and identified by comparison with the synthetic standard. The formation of FLU-1-N-OH was markedly inhibited by the addition of miconazole, an inhibitor of CYP3A4, and was mediated by recombinant CYP3A4. Furthermore, FLU-1-N-OH was detected mostly as the conjugates (glucuronide/sulfate) in the urine of prostate cancer patients collected for 3 h after treatment with flutamide. The formation of FLU-1-N-OH, however, did not differ between patients with and without abnormalities of hepatic functions among a total of 29 patients. The lack of an apparent association of the urinary excretion of FLU-1-N-OH and hepatic disorder may suggest the involvement of an additional unknown factor in the mechanisms of flutamide hepatotoxicity.