STAT3-EphA7 axis contributes to the progression of esophageal squamous cell carcinoma.

BACKGROUND: Our previous study has revealed that EphA7 was upregulated in patient-derived esophageal squamous cell carcinoma (ESCC) xenografts with hyper-activated STAT3, but its mechanism was still unclear. MATERIALS AND METHODS: To assess the association between EphA7 and STAT3, western blotting, immunofluorescence, ChIP assay, and qRT-PCR were conducted. Truncated mutation and luciferase assay were performed to examine the promoter activity of EphA7. CCK-8 assay and colony formation were performed to assess the proliferation of ESCC. Cell-derived xenograft models were established to evaluate the effects of EphA7 on ESCC tumor growth. RNA-seq analyses were used to assess the effects of EphA7 on related signals. RESULTS: In this study, EphA7 was found upregulated in ESCC cell lines with high STAT3 activation, and immunofluorescence also showed that EphA7 was co-localized with phospho-STAT3 in ESCC cells. Interestingly, suppressing STAT3 activation by the STAT3 inhibitor Stattic markedly inhibited the protein expression of EphA7 in ESCC cells, in contrast, activation of STAT3 by IL-6 obviously upregulated the protein expression of EphA7. Moreover, the transcription of EphA7 was also mediated by the activation of STAT3 in ESCC cells, and the -2000∼-1500 region was identified as the key promoter of EphA7. Our results also indicated that EphA7 enhanced the cell proliferation of ESCC, and silence of EphA7 significantly suppressed ESCC tumor growth. Moreover, EphA7 silence markedly abolished STAT3 activation-derived cell proliferation of ESCC. Additionally, RNA-seq analyses indicated that several tumor-related signaling pathways were significantly changed after EphA7 downregulation in ESCC cells. CONCLUSION: Our results showed that the transcriptional expression of EphA7 was increased by activated STAT3, and the STAT3 signaling may act through EphA7 to promote the development of ESCC.

Ethanol Extract of Citrus grandis 'Tomentosa' Exerts Anticancer Effects by Targeting Skp2/p27 Pathway in Non-Small Cell Lung Cancer.

SCOPE: This study aims to investigate the anticancer properties of Citrus grandis 'Tomentosa' (CGT) in non-small cell lung cancer (NSCLC). METHODS AND RESULTS: The ethanol extract of CGT (CGTE) is prepared by using anhydrous ethanol and analyzed by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), revealing that the main chemical components in CGTE are flavonoids and coumarins, such as naringin, rhoifolin, apigenin, bergaptol, and osthole. CGTE at concentrations without inducing cell death significantly inhibits cell proliferation via inducing cell cycle G1 phase arrest by MTT, colony formation, and flow cytometry assays, implying that CGT has anticancer potential. CGTE markedly inhibits the activity of Skp2-SCF E3 ubiquitin ligase, decreases the protein level of Skp2, and promotes the accumulation of p27 by co-immunoprecipitation (co-IP) and in vivo ubiquitination assay; whereas Skp2 overexpression rescues the effects of CGTE in NSCLC cells. In subcutaneous LLC allograft and A549 xenograft mouse models, CGTE, without causing obvious side effects in mice, significantly inhibits lung tumor growth by targeting the Skp2/p27 signaling pathway. CONCLUSION: These findings demonstrate that CGTE efficiently inhibits NSCLC proliferation both in vitro and in vivo by targeting the Skp2/p27 signaling pathway, suggesting that CGTE may serve as a therapeutic candidate for NSCLC treatment.

Molecular characterization and expression analysis of tumor necrosis factor receptor-associated factor 6 (traf6) like gene involved in antibacterial innate immune of fresh water crayfish, Procambarus clarkii.

In invertebrates, innate immunity was the crucial defending pattern against pathogenic microorganisms. For the past few years, Toll or Toll like receptors (TLRs) signaling pathway was studied extensively in crustaceans. Among the components of Toll or Toll like receptors (TLRs) signaling pathway, tumor necrosis factor receptor-associated factor 6 (TRAF6) acted as an important cytoplasmic adaptor, which was conserved from Drosophila to human. In this study, a new traf6 like gene was cloned from hepatopancreas of P. clarkii. After challenged respectively by S. aureus or E. ictaluri, the expression profiles were studied. And the results showed that the mRNA transcript of Pc-traf6 like gene was up-regulated significantly in the hemocytes, hepatopancreas, gills, and intestine of crayfish. After Pc-traf6 like gene was knocked down, the expression levels of transcription factor (Dorsal) and some crucial immunity effectors (ALF 3, Lysozyme 1, Lectin 1, and Crustin 2) in TLRs signaling pathway were dramatically suppressed. Simultaneously, the survival rate of crayfish challenged respectively by S. aureus or E. ictaluri was significantly decreased in RNAi assay. All these results indicated that Pc-traf6 like gene played an important role in regulating the expression of downstream effectors in the TLRs signaling pathway of crayfish.

Quantification of Radiation Injury on Neutropenia and the Link between Absolute Neutrophil Count Time Course and Overall Survival in Nonhuman Primates Treated with G-CSF.

PURPOSE: To model absolute neutrophil count (ANC) suppression in response to acute radiation (AR) exposure and evaluate ANC time course as a predictor of overall survival (OS) in response to AR exposure with or without treatment with granulocyte colony-stimulating factor in nonhuman primates. METHODS: Source data were obtained from two pivotal studies conducted in rhesus macaques exposed to 750 cGy of whole body irradiation on day 0 that received either placebo, daily filgrastim, or pegfilgrastim (days 1 and 8 after irradiation). Animals were observed for 60 days with ANC measured every 1 to 2 days. The population model of ANC response to AR and the link between observed ANC time course and OS consisted of three submodels characterizing injury due to radiation, granulopoiesis, and a time-to-event model of OS. RESULTS: The ANC response model accurately described the effects of AR exposure on the duration of neutropenia. ANC was a valid surrogate for survival because it explained 76% (95% CI, 41%-97%) and 73.2% (95% CI, 38.7%-99.9%) of the treatment effect for filgrastim and pegfilgrastim, respectively. CONCLUSION: The current model linking radiation injury to neutropenia and ANC time course to OS can be used as a basis for translating these effects to humans.

Vitamin D Deficiency Attenuates Acute Alcohol-Induced Hepatic Lipid Accumulation in Mice.

Vitamin D deficiency has been frequently reported in chronic liver disease. However, its influence on hepatic lipid accumulation in alcoholic liver disease remains unclear. The present study investigated the effects of vitamin D deficiency on acute alcohol-induced hepatic lipid metabolism in mice. Mice were fed with vitamin D deficient diet, in which vitamin D was depleted for 12 weeks to establish an animal model of vitamin D deficiency. Some mice were administered a single gavage of alcohol (4 g/kg bodyweight) before they were euthanized. Results show that feeding mice with vitamin D deficient diet did not induce hepatic lipid accumulation. In contrast, vitamin D deficiency markedly reduced alcohol-induced triacylglycerol (TAG) content and prevented hepatic lipid accumulation. Moreover, vitamin D deficiency significantly attenuated alcohol-induced sterol-regulated element-binding protein (SREBP)-1c activation, which regulates genes for hepatic fatty acid (FA) and TAG synthesis, and the expression of its target genes fatty acid synthase (Fasn) and acetyl-coenzyme- A carboxylase (Acc). In addition, vitamin D deficiency alleviated alcohol-induced downregulation of hepatic nuclear peroxisome proliferator-activated receptor (PPAR)α, which governs FA transport and ß-oxidation, and the expression of Carnitine palmitoyltransferase (Cpt)-1α, cytochrome P450, family 4, subfamily a, polypeptide (Cyp4a)10, and Cyp4a14, which are key enzymes for hepatic fatty acids ß-oxidation and ω-oxidation. Taken together, these results suggest that vitamin D deficiency is not a direct risk factor for hepatic lipid accumulation. Vitamin D deficiency alleviates acute alcohol-induced hepatic lipid accumulation through inhibiting hepatic de novo fatty acid syntheses and promoting fatty acid ß-oxidation and ω-oxidation.

Pharmacokinetics of Anakinra in Subjects of Heavier vs. Lighter Body Weights.

This trial (20010168) studied how body weight (BW) and body mass index (BMI) influenced the pharmacokinetics (PK) of anakinra. Subjects (n = 32) were assigned to four groups (n = 8) according to BW and BMI. Randomization was according to a four-treatment, four-period, four-sequence crossover design. The four anakinra injections were 100, 150, and 300 mg s.c. and 100 mg i.v. Plasma samples were measured by enzyme-linked immunosorbent assay and noncompartmental PK parameters estimated. BW demonstrated the following effects: after i.v. administration, significant effects (P < 0.05) were observed for exposure (area under the concentration-time curve from zero to infinity (AUC0-∞ )), peak plasma concentration (Cmax ), volume of distribution at steady state, and clearance; whereas after s.c. administration, significant effects (P < 0.05) were observed for Cmax , AUC0-∞ , terminal half-life, and estimated apparent clearance. Mean AUC was reduced 24% and 33% for heavier (BW ≥ 100 kg) vs. lighter subjects (BW ≤ 90 kg) after i.v. and s.c. administration, respectively. BMI increased clearance for heavier subjects. For example, mean (SD) plasma clearance of i.v. anakinra increased from 1.17 ± 0.29 to 1.62 ± 0.24 mL/minute/kg (P < 0.05) for larger (> 100 kg) obese (BMI > 36) vs. larger (> 100 kg) less obese (BMI < 35) subjects, respectively. Similarly, results following s.c. supported those after i.v. administration. Derived half-lives increased with higher BW and higher BMI ranging from 3.63 hour for less obese, lighter-weight subjects to 7.62 hour for obese, heavier-weight subjects. Absolute bioavailability ranged from 80-92% and was unrelated to BW or BMI. Anakinra exposure is statistically significantly related to BW and to a lesser extent BMI.

[Effect of ABO-Incompatibility on Outcome of Allogeneic Hematopoietic Stem Cell Transplantation].

OBJECTIVE: To investigate the effect of ABO-incompatibility on the efficacy and complications of allogeneic hematopoietic stem cell transplantation(HSCT). METHODS: The clinical data of 54 recipients who received ABO-incompatible allo-HSCT were retrospectively analyzed and were compared with 54 ABO-identical recipients as controls. Hematopoietic reconstruction and the blood type conversion time were dynamically observed and compared between 2 groups. RESULTS: The time of erythrocyte reconstitution was prolonged to 24 d in ABO-incompatible group, compared with that of 19 d in ABO-compatible group (P<0.01). The difference of neutrophil and platelet reconstruction was not statistically significant (P>0.05). Major mismatch group and bidirectional mismatch group required more erythrocyte transfusions than that of ABO-compatible group. The surface antigen of erythrocyte change in major mismatch group was earlier than that of minor mismatch group (P<0.05). The incidence of cytomegalovirus (CMV) infection, acute graft versus host disease (aGVHD) and survival were not significantly different between 2 groups. CONCLUSION: ABO-incompatibility can not influence the effect of allo-HSCT, but ABO-incompatibility delayed erythrocyte recovery, and required more RBC and platelet transfusions.

Development of Romiplostim for Treatment of Primary Immune Thrombocytopenia From a Pharmacokinetic and Pharmacodynamic Perspective.

Romiplostim is a novel thrombopoiesis-stimulating peptibody consisting of a carrier Fc domain and a peptide domain that binds to the thrombopoietin receptor (TPOR) on platelets and platelet precursors. Similar to endogenous thrombopoietin, romiplostim activates the TPOR to stimulate the growth and maturation of megakaryocytes, resulting in increased production of platelets in the circulation. Binding of romiplostim to TPOR on the platelets and megakaryocytes presumably triggers subsequent internalization and degradation. Therefore, increased platelet counts following romiplostim treatment results in increased elimination of the drug. The TPOR target-mediated process is saturable, resulting in nonlinear volume of distribution and clearance of romiplostim. Therefore, target-mediated disposition plays a decreasing role in drug elimination with increasing romiplostim serum concentration. Conversely, nonspecific elimination processes such as renal clearance play an increasing role with increasing romiplostim serum concentration. Limited pharmacokinetics data demonstrated that the exposure to romiplostim was lower after multiple dose administrations than after the first dose, although large inter-subject variability was observed. Large inter- and intra-subject variability in the platelet response was also observed at a given dose. These findings suggest considerable heterogeneity of disease in patients with primary immune thrombocytopenia and support the need for individual dose adjustments based on platelet counts.

Design Rationale and Development Approach for Pegfilgrastim as a Long-Acting Granulocyte Colony-Stimulating Factor.

Filgrastim, a recombinant methionyl human granulocyte colony-stimulating factor (G-CSF) (r-metHuG-CSF), is efficacious in stimulating neutrophil production and maturation to prevent febrile neutropenia (FN) in response to chemotherapy. Because of its relatively short circulating half-life, daily filgrastim injections are required to stimulate neutrophil recovery. In an effort to develop a long-acting form of filgrastim that was as safe and efficacious as filgrastim but had a longer in vivo residence time, a number of strategies were considered. Ultimately, fusion of filgrastim to polyethylene glycol (PEG) was selected. Following extensive analysis of conjugation chemistries as well as in vitro and in vivo characterization of a panel of PEGylated proteins, a construct containing a 20 kDa PEG moiety covalently conjugated to the N-terminus of filgrastim was chosen for advancement as pegfilgrastim. Pegfilgrastim is primarily cleared by neutrophils and neutrophil precursors (rather than the kidneys), meaning that clearance from the circulation is self-regulating and pegfilgrastim is eliminated only after neutrophils start to recover. Importantly, addition of PEG did not alter the mechanism of action and safety profile compared to filgrastim. Clinical evaluation revealed that a single 6 mg dose effectively reduces the duration of neutropenia and risk of FN in patients receiving chemotherapy. This work demonstrates the benefit of using PEGylation to generate pegfilgrastim, which allows for once-per-chemotherapy cycle administration while maintaining similar safety and efficacy profiles as those for multiple daily administration of filgrastim. Approaches that may provide advances for therapeutic agonists of G-CSF receptor are also discussed.

Comparison of pharmacokinetics and safety of pegfilgrastim administered by two delivery methods: on-body injector and manual injection with a prefilled syringe.

PURPOSE: For patients with clinically significant risk of febrile neutropenia, pegfilgrastim administration should occur the day after myelosuppressive chemotherapy; however, a variety of factors may preclude patients from returning to the clinic the next day for pegfilgrastim administration, necessitating other strategies. This study compared the pharmacokinetics and safety of pegfilgrastim administered via an on-body injector applied to the subject's skin versus manual injection using a prefilled syringe. METHODS: Healthy subjects aged 18-50 years were randomized 1:1 to receive a single 6-mg subcutaneous pegfilgrastim dose from an on-body injector or a prefilled syringe. Blood for pharmacokinetic measurements was collected at baseline and prespecified time points after pegfilgrastim administration; safety was assessed throughout the 6-week study. Primary endpoints were maximum concentration (C max) and area under the concentration curve from time 0 to infinity (AUC0-inf). Secondary endpoints included safety, tolerability, and immunogenicity. RESULTS: Pegfilgrastim mean AUC0-inf values for the on-body injector (n = 125) and manual injection (n = 128) were 10,900 and 11,100 h ng/mL, respectively; mean C max values were 248 and 262 ng/mL, respectively. The least squares geometric mean ratios were 0.97 for C max and 1.00 for AUC0-inf; the corresponding 90 % CIs were within the prespecified range (0.80-1.25), indicating comparable pegfilgrastim pharmacokinetics between delivery methods. Treatment-emergent adverse events (AEs) were similar between groups (injector, 86 %; manual, 85 %). Injector- or syringe-related AEs were more prevalent with the injector (13 %; manual, 4 %); none were serious. No pegfilgrastim-neutralizing antibodies were detected. CONCLUSIONS: Pegfilgrastim pharmacokinetics and safety were comparable between the on-body injector and manual injection groups.

Pharmacokinetic and pharmacodynamic interactions between palifermin and heparin.

Oral mucositis, a severe complication during chemo- and/or radiotherapy, is prevented with palifermin treatment, a recombinant human keratinocyte growth factor (KGF/FGF-7). The FGF family belongs to the larger family of heparin-binding growth factors. Because it has been shown that heparin modulates binding of KGF to the KGF receptor and subsequently affects cellular proliferation induced by the KGF mitogenic signal, it is critical to understand the drug-drug interactions between palifermin and heparin, particularly because of heparin's narrow therapeutic margin. Two studies were performed in healthy subjects to characterize the effect of palifermin on the pharmacodynamics of heparin (activated partial thromboplastin time) and evaluate the impact of heparin on the pharmacokinetics and pharmacodynamics (Ki67 staining of buccal mucosal tissue) of palifermin. Results demonstrated a pronounced pharmacokinetic interaction; heparin coadministration increased the palifermin AUC 4- to 5-fold and decreased its half-life by 40%-45%, suggesting an approximate 70%-80% decrease in palifermin clearance and volume of distribution. These changes in the pharmacokinetics of palifermin during coadministration of heparin, however, did not affect the pharmacodynamic effect of palifermin, or the anticoagulant activity of heparin, and did not lead to increased safety findings. Therefore, these results suggest that dose adjustments for heparin and palifermin are not warranted when administered concurrently.

Pharmacokinetics of Irinotecan With and Without Panitumumab Coadministration in Patients With Metastatic Colorectal Cancer.

This study examined the effects of panitumumab, a human monoclonal antibody against epidermal growth factor receptor (EGFR), on irinotecan pharmacokinetics. This phase I, open-label, multicenter, single-arm study enrolled patients with metastatic colorectal cancer (mCRC) without prior exposure to an EGFR inhibitor. In cycle 1, patients received irinotecan (180 mg/m(2) intravenously [IV]) on day 1 and panitumumab (6 mg/kg IV) on Day 4. In cycle 2 (2 weeks after cycle 1 panitumumab administration) and subsequent every-2-week cycles, patients received panitumumab followed immediately by irinotecan until disease progression or intolerability. Primary and secondary endpoints included Cmax and AUC of irinotecan after irinotecan infusion in cycles 1 and 2, and adverse events, respectively. Nineteen of 27 treated patients were eligible for pharmacokinetic analysis. Pharmacokinetic profiles of irinotecan with or without panitumumab coadministration were nearly identical. The 90% confidence intervals for ratios of geometric means for irinotecan Cmax and AUC with or without panitumumab were within the 80-125% interval, indicating that panitumumab had no apparent effects on irinotecan pharmacokinetics. Adverse events were as expected for irinotecan plus panitumumab combination therapy.

Tumor penetration and epidermal growth factor receptor saturation by panitumumab correlate with antitumor activity in a preclinical model of human cancer.

BACKGROUND: Successful treatment of solid tumors relies on the ability of drugs to penetrate into the tumor tissue. METHODS: We examined the correlation of panitumumab (an anti-epidermal growth factor [EGFR] antibody) tumor penetration and EGFR saturation, a potential obstacle in large molecule drug delivery, using pharmacokinetics, pharmacodynamics, and tumor growth rate in an A431 epidermoid carcinoma xenograft model of human cancer. To determine receptor saturation, receptor occupancy, and levels of proliferation markers, immunohistochemical and flow cytometric methods were used. Pharmacokinetic data and modeling were used to calculate growth characteristics of panitumumab-treated tumors. RESULTS: Treatment with panitumumab in vivo inhibited pEGFR, Ki67 and pMAPK levels vs control. Tumor penetration and receptor saturation were dose- and time-dependent, reaching 100% and 78%, respectively. Significant tumor inhibition and eradication (p < 0.05) were observed; plasma concentration associated with tumor eradication was estimated to be 0.2 µg/ml. The tumor inhibition model was able to describe the mean tumor growth and death rates. CONCLUSIONS: These data demonstrate that the antitumor activity of panitumumab correlates with its ability to penetrate into tumor tissue, occupy and inhibit activation of EGFR, and inhibit markers of proliferation and MAPK signaling.

Prevention of chemotherapy-induced neutropenia with pegfilgrastim: pharmacokinetics and patient outcomes.

Patients receiving cytotoxic chemotherapy are at risk for developing chemotherapy-induced neutropenia (CIN). Filgrastim, a recombinant granulocyte colony-stimulating factor (G-CSF) that stimulates the proliferation, differentiation and function of neutrophils, is approved for the prevention of CIN. To eliminate the burden of daily filgrastim injection, pegfilgrastim, a long-acting form of filgrastim, was developed by covalently attaching a 20-kDa polyethylene glycol molecule to filgrastim to increase molecular size and thus reduce renal elimination. Consequently, neutrophil-mediated clearance is the primary mechanism for pegfilgrastim elimination. Therefore, after a single pegfilgrastim injection following chemotherapy treatment, pegfilgrastim concentration is sustained during neutropenia and decreases with neutrophil recovery. Pegfilgrastim has received marketing authorization approval from many regions to reduce the incidence of CIN based on the similar efficacy and safety of a single injection of 6 mg of pegfilgrastim administered once per chemotherapy cycle and 10 to 11 daily injections of filgrastim at 5 µg/kg. The efficient self-regulating clearance of pegfilgrastim allows administration once per chemotherapy cycle, thereby providing a more convenient treatment regimen than filgrastim.

Immunogenicity of panitumumab in combination chemotherapy clinical trials.

BACKGROUND: Panitumumab is a fully human antibody against the epidermal growth factor receptor that is indicated for the treatment of metastatic colorectal cancer (mCRC) after disease progression on standard chemotherapy. The purpose of this analysis was to examine the immunogenicity of panitumumab and to evaluate the effect of anti-panitumumab antibodies on pharmacokinetic and safety profiles in patients with mCRC receiving panitumumab in combination with oxaliplatin- or irinotecan-based chemotherapies. METHODS: Three validated assays (two screening immunoassays and a neutralizing antibody bioassay) were used to detect the presence of anti-panitumumab antibodies in serum samples collected from patients enrolled in four panitumumab combination chemotherapy clinical trials. The impact of anti-panitumumab antibodies on pharmacokinetic and safety profiles was analyzed using population pharmacokinetic analysis and descriptive statistics, respectively. RESULTS: Of 1124 patients treated with panitumumab in combination with oxaliplatin- or irinotecan-based chemotherapy with postbaseline samples available for testing, 20 (1.8%) patients developed binding antibodies and 2 (0.2%) developed neutralizing antibodies. The incidence of anti-panitumumab antibodies was similar in patients with tumors expressing wild-type or mutant KRAS and in patients receiving oxaliplatin- or irinotecan-based chemotherapies. No evidence of an altered pharmacokinetic or safety profile was found in patients who tested positive for anti-panitumumab antibodies. CONCLUSIONS: The immunogenicity of panitumumab in the combination chemotherapy setting was infrequent and similar to the immunogenicity observed in the monotherapy setting. Panitumumab immunogenicity did not appear to alter pharmacokinetic or safety profiles. This low rate of immunogenicity may be attributed to the fully human nature of panitumumab.

Pharmacokinetics and pharmacodynamics of pegfilgrastim.

Pegfilgrastim is a sustained-duration form of filgrastim, a recombinant methionyl form of human granulocyte colony-stimulating factor (G-CSF), to which a 20 kDa polyethylene glycol molecule is covalently bound to the N-terminal methionine residue. Similar to filgrastim, pegfilgrastim increases the proliferation and differentiation of neutrophils from committed progenitor cells, induces maturation, and enhances the survival and function of mature neutrophils, resulting in dose-dependent increases in neutrophils. After subcutaneous administration, pegfilgrastim exhibits nonlinear pharmacokinetics and exposure to pegfilgrastim increases in more than a dose-proportional manner, suggesting that the clearance of pegfilgrastim decreases with increased dosing. Filgrastim is primarily eliminated by the kidney and neutrophils/neutrophil precursors; the latter presumably involves binding of the growth factor to the G-CSF receptor on the cell surface, internalization of the growth factor-receptor complexes via endocytosis, and subsequent degradation inside the cells. Pegylation of filgrastim renders renal clearance insignificant, which was demonstrated in bilaterally nephrectomized rats and confirmed in subjects with renal impairment. As a result, the neutrophil-mediated clearance is the predominant elimination pathway for pegfilgrastim. During chemotherapy-induced neutropenia, the clearance of pegfilgrastim is significantly reduced and the concentration of pegfilgrastim is sustained until onset of neutrophil recovery. Pegfilgrastim concentrations are sustained longer in patients with profound neutropenia. Evidence supports the use of a postnadir absolute neutrophil count (ANC) of ≥ 1 × 109/L as a surrogate marker threshold for the clearance of pegfilgrastim to subtherapeutic levels. After repeated administration of pegfilgrastim, the peak concentrations of pegfilgrastim decrease, likely due to increased neutrophil and neutrophil precursor mass. A pharmacokinetic-pharmacodynamic model was developed to describe the pharmacokinetic and ANC profiles of pegfilgrastim; the analysis supported that 100 µg/kg was an adequate weight-based dose of pegfilgrastim and predicted that 6 mg would be an optimal fixed dose of pegfilgrastim to simplify treatment. Data from a pivotal study confirmed that a once-per-chemotherapy-cycle injection of pegfilgrastim at 6 mg was as safe and effective as 11 daily injections of filgrastim at 5 µg/kg in reducing neutropenia and its complications in patients with breast cancer receiving four cycles of doxorubicin/docetaxel chemotherapy. Because of the highly efficient regulation of pegfilgrastim clearance via neutrophils and neutrophil precursors, a single fixed dose of pegfilgrastim can be given once per chemotherapy cycle in conjunction with a variety of myelosuppressive chemotherapy regimens.

Tumor KRAS status predicts responsiveness to panitumumab in Japanese patients with metastatic colorectal cancer.

OBJECTIVE: Mutation status of the KRAS gene in tumors has been shown to be a predictive biomarker of response to anti-epidermal growth factor receptor antibody therapy in patients with metastatic colorectal cancer. This retrospective analysis examined the association between efficacy and safety of the fully human anti-epidermal growth factor receptor antibody panitumumab and KRAS mutation status in Japanese metastatic colorectal cancer patients using data from two clinical trials with adherence to good clinical practices. METHODS: An exploratory, integrated analysis of data from KRAS evaluable patients enrolled in a Phase 1 study (Study 20040192) and a Phase 2 study (Study 20050216) was performed. Paraffin-embedded tumor samples were analyzed for KRAS status. Primary efficacy endpoint of this analysis was objective tumor response per modified response evaluation criteria in solid tumors; a key secondary endpoint was progression-free survival. Safety endpoints included incidence of adverse events. RESULTS: Tumor samples with known KRAS status were available from 8 of 13 (62%) metastatic colorectal cancer patients in the Phase 1 study and 16 of 53 patients (30%) in the Phase 2 study. Overall, 14 (58%) patients had wild-type KRAS tumors and 10 (42%) patients had mutated KRAS tumors. Four (17%) patients had a partial response; all responders had tumors with wild-type KRAS. Results of all secondary efficacy endpoints also favored patients with wild-type KRAS. Treatment-related adverse events were predominantly mild to moderate and skin related, and were similar between patients with tumors with wild-type and mutated KRAS in this small patient population. CONCLUSIONS: Mutated KRAS status in tumors of Japanese patients with metastatic colorectal cancer is associated with lack of response to panitumumab therapy.

Pharmacokinetic and pharmacodynamic perspectives on the clinical drug development of panitumumab.

Panitumumab is a recombinant, fully human IgG2 monoclonal antibody directed against the epidermal growth factor receptor (EGFR). It is indicated for use as monotherapy in the treatment of patients with EGFR-expressing metastatic colorectal cancer after disease progression with standard chemotherapy. The currently indicated dose is 6 mg/kg given every 2 weeks. Panitumumab is mainly distributed into the vascular space and exhibits nonlinear pharmacokinetics that are consistent with target-mediated drug disposition, involving saturable binding to EGFR and subsequent internalization and degradation inside the cells. Panitumumab is also cleared in a linear fashion by the reticuloendothelial system, similarly to other endogenous immunoglobulins. After single-dose administration of panitumumab as a 1-hour intravenous infusion, the area under the serum concentration-time curve increases in a greater-than-dose-proportional manner as the dose increases from 0.75 to 5 mg/kg; however, at doses above 2 mg/kg, the exposure to panitumumab increases in a dose-proportional manner. Panitumumab pharmacokinetics are not meaningfully affected by the tumour type, EGFR membrane expression, tumour KRAS mutation, sex, age, race or renal or hepatic dysfunction. In addition, irinotecan-containing and paclitaxel/carboplatin-containing chemotherapeutic regimens do not appear to affect panitumumab pharmacokinetics. The results of population pharmacokinetic analyses have shown that bodyweight is the most influential covariate on panitumumab exposure, supporting the current use of bodyweight-adjusted doses (mg/kg). The relationship between the weekly dose of panitumumab and skin rash, an on-target pharmacodynamic effect of EGFR inhibition, reaches a plateau at 2.5 mg/kg, indicating that this is the optimal weekly dose. Two less-frequent dosing regimens (6 mg/kg given every 2 weeks and 9 mg/kg given every 3 weeks) achieve steady-state serum trough concentrations similar to those achieved by 2.5 mg/kg given every week, ensuring maximal EGFR coverage. Anti-panitumumab antibody production is uncommon and does not appear to have an impact on the pharmacokinetics of panitumumab.

Phase II, randomized, open-label study of pegfilgrastim-supported VDC/IE chemotherapy in pediatric sarcoma patients.

PURPOSE: This multicenter, randomized, open-label study evaluated the efficacy, safety, and pharmacokinetics of a single subcutaneous pegfilgrastim injection with daily subcutaneous filgrastim administration in pediatric patients receiving myelosuppressive chemotherapy for sarcoma. PATIENTS AND METHODS Forty-four patients with previously untreated, biopsy-proven sarcoma stratified into three age groups (0-5, 6-11, and 12-21 years) were randomly assigned in a 6:1 randomization ratio to receive a single pegfilgrastim dose of 100 microg/kg (n = 38) or daily filgrastim doses of 5 microg/kg (n = 6) after chemotherapy (cycles 1 and 3: vincristine-doxorubicin-cyclophosphamide; cycles 2 and 4: ifosfamide-etoposide). The duration of grade 4 neutropenia, time to neutrophil recovery, incidence of febrile neutropenia, and adverse events were recorded. Results Pegfilgrastim and filgrastim were similar for all efficacy and safety end points, and their pharmacokinetic profiles were consistent with those in adults. Younger children experienced more protracted neutropenia and had higher median pegfilgrastim exposure than older children. CONCLUSION A single dose of pegfilgrastim at 100 microg/kg administered once per chemotherapy cycle is comparable to daily injections of filgrastim at 5 microg/kg for pediatric sarcoma patients receiving myelosuppressive chemotherapy.

Population pharmacokinetic analysis of panitumumab in patients with advanced solid tumors.

Panitumumab is a fully human monoclonal antibody targeted to the extracellular domain of human epidermal growth factor receptor (EGFR). A comprehensive population pharmacokinetic model of panitumumab was developed using nonlinear mixed-effects modeling of 1200 patients with advanced solid tumors in 14 clinical studies. The disposition of panitumumab was best described with a 2-compartment model with parallel linear and nonlinear (Michaelis-Menten) elimination pathways. For a typical male patient with colorectal cancer (80 kg, 60 years old), the estimates for the linear clearance (CL), the maximum nonlinear clearance (V(max)/K(m)), the central volume of distribution (V(1)), the peripheral volume of distribution (V(2)), and the Michaelis-Menten constant (K(m)) are 0.273 L/d, 28.4 L/d, 3.95 L, 2.59 L, and 0.426 mcg/mL, respectively. Baseline covariates such as body weight, cancer type, age, sex, and race were studied for their influence on panitumumab pharmacokinetics. Body weight was found to be the most influential covariate on panitumumab exposure, affecting CL, V(max), and V(1). The administration of concomitant chemotherapy (IFL, FOLFIRI, or paclitaxel/carboplatin) or intensity of baseline tumor EGFR expression did not alter the pharmacokinetics of panitumumab. The presence of antipanitumumab antibodies in patients (immunogenicity rate 3.4%) did not appear to affect panitumumab exposure substantially (AUC difference 8%). In support of a new drug application in Japan, the model was used to assess panitumumab pharmacokinetics in Japanese patients compared to other racial groups; there were no significant differences in model-predicted steady-state panitumumab AUC, C(max), or C(min) after accounting for the effect of body weight.