A pharmacometrics model to define docetaxel target in early breast cancer

Aims: We aimed to study the relation between pharmacokinetics (PK) and pharmacodynamics (PD) of docetaxel in early breast cancer and recommend a target exposure. Methods: A PK/PD study was performed in 27 early breast cancer patients treated with doxorubicin and cyclophosphamide for 4 cycles followed by 4 cycles of docetaxel 75–100 mg/m2 infused every 21 days. Individual Bayesian estimates of docetaxel PK parameters were obtained using a nonparametric population PK model developed with data from patients with metastatic breast cancer who received dose-intensified docetaxel (300–350 mg/m2). Docetaxel area under the curve (AUC) and maximum concentration (Cmax) in each cycle and total cumulative AUC (AUCcum) were calculated and related to the incidence of adverse effects and tumour recurrence. Results: Docetaxel clearance showed no change over the 4 treatment cycles, but a gradual increase in the volume of distribution was observed. One third of the patients had at least 1 dose reduction of docetaxel due to toxicity. The mean AUC, AUCcum and Cmax in patients showing docetaxel-associated adverse events were significantly higher than in patients free of toxicity (P 4.5 mg*h/L and 3.5 mg/L, respectively, were risk factors for docetaxel toxicity, while an AUC <4.5 mg*h/L was associated with tumour recurrence. Conclusion: We report for the first time a relation between docetaxel exposure and toxicity and recommend specific targets of drug exposure with implications for the clinical management of early breast cancer patients.Fil: Aldaz, Azucena. Universidad de Navarra; EspañaFil: Schaiquevich, Paula Susana. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Aramendía, José Manuel. Universidad de Navarra; Españ

Importancia de la excrecion biliar en la farmacocinetica del paracetamol en la rata

El presente trabajo reporta el estudio de la farmacocinética del paracetamol en ratas (100 mg/kg, p.o) con flujo biliar modificado, interrumpido por canulación del conducto biliar o estimulado por acción farmacológica con ácido ursodesoxicólico. A pesar de que el paracetamol sufre recirculación enterohepática y que la excreción biliar de la droga es una vía importante de eliminación en la rata, la alteración del flujo biliar no provocó diferencias estadísticamente significativas en el tiempo de vida medio de eliminación de la droga. Por el contrario, se observó una modificación de los parámetros farmacocinéticos relacionados con la biodisponibilidad del paracetamol.Importance of Biliary Excretion in Paracetamol Pharmacokinetics in the Rat”. The present work reports the study of paracetamol pharmacokinetics in the rat (100 mg/kg, p.o) with modified bile flow, interrupted by bile duct cannulation or pharmacologically stimulated by ursodeoxycholic acid. Even if paracetamol undergoes enterohepatic recycling and the biliary excretion has been reported to be an important pathway of drug elimination in the rat, the modification of the bile flow lead to no statistical significant difference in the elimination half life time of the drug. On the contrary, it was observed a change in the pharmacokinetic parameters related to the bioavailability of paracetamolFil: Schaiquevich, Paula Susana. ININFA; Argentina. ININFA; ArgentinaFil: Viviana Niselman. ININFA; ArgentinaFil: Rubio, Modesto Carlos. ININFA; Argentin

Pharmacovigilance of calcineurin inhibitors in pediatric kidney and liver transplantation

Objetivo: Desarrollar un programa de farmacovigilancia de pacientes pediátricos trasplantados hepáticos y renales centrado en inmunosupresores calcineurínicos del Hospital de Pediatría JP Garrahan de Argentina. Métodos: Se evaluaron las reacciones adversas a medicamentos (RAM) de los pacientes pediátricos trasplantados renales y hepáticos de nuestro hospital tratados con inhibidores de calcineurina (ciclosporina y tacrolimus) por revisión retrospectiva de historias clínicas de pacientes trasplantados en 2010-2011, y análisis prospectivo por farmacovigilancia activa de trasplantados fuera de dicho período, cuyas complicaciones se hayan presentado en los ateneos semanales del Servicio de Trasplante desde marzo de 2011. Las RAM se notificaron a la autoridad sanitaria nacional. Resultados: Se analizaron un total de 59 pacientes, 28 trasplantados renales y 31 hepáticos. Se notificaron, en ambos trasplantes, 60 RAM a ciclosporina destacándose (número de casos) hipertensión arterial (19) y nefrotoxicidad (6). Asimismo, se registraron 46 RAM a tacrolimus, incluyendo hipomagnesemia (25), hipertensión (7) y nefrotoxicidad (5). El 95% y 96% de los eventos adversos a ciclosporina y a tacrolimus, respectivamente, han sido agrupados como probables o definitivos. El 70% y 98% de los eventos adversos a ciclosporina y a tacrolimus respectivamente, han sido de severidad moderada o grave. Conclusiones: Este es el primer proyecto en América Latina que propone y desarrolla el estudio cuali-cuantitativo intensivo de RAM a inhibidores de calcineurina en trasplante pediátrico renal y hepático. Es necesario estimular la notificación espontánea así como continuar el seguimiento de RAM a mediano y largo plazo para mejorar la calidad de vida del paciente trasplantado.Aim: To develop a pharmacovigilance program of calcineurin inhibitors used in pediatric renal and liver transplant patients at Hospital de Pediatría JP Garrahan, Argentina. Methods: Adverse drug reactions (ADRs) of pediatric patients with kidney and liver transplantation treated with calcineurin inhibitors (cyclosporine and tacrolimus) were evaluated by retrospective review of medical records of patients transplanted between 2010 and 2011. In addition, we carried out active pharmacovigilance since March, 2011. ADRs were reported to the National Health Authority. Results: A total of 59 patients, 28 kidney transplant and 31 liver tarnsplant patients were analyzed. In both transplants, 60 ADRs to cyclosporine were reported including (number of cases), hypertension (19) and nephrotoxicity (6). In addition, 46 ADRs to tacrolimus were registered as hypomagnesemia (25), hypertension (7) and nephrotoxicity (5). A total of 95% and 96% of the adverse events to cyclosporine and tacrolimus, respectively, were defined as probable or definitive. Lastly, 70% and 98% of the events to cyclosporine and tacrolimus respectively, have been moderately severe or severe. Conclusions: This is the first study in Latin America that developed an intensive qualitative and quantitative analysis of the ADRs to calcineruin inhibitors in pediatric kidney and liver transplant patients. Spontaneous reporting should be motivated as well as monitoring ADRs should continue in the medium and long term for improving patient's quality of life.Fil: Riva, Natalia. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Caceres Guido, Paulo Arturo. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Rousseau, Marcela. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Dip, Marcelo. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Monteverde, Marta. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Imventarza, Oscar. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Mato, Gabriel. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Schaiquevich, Paula Susana. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Pharmacokinetic analysis of topotecan after superselective ophthalmic artery infusion and periocular administration in a porcine mode

Purpose: To characterize the vitreous and plasma pharmacokinetics of topotecan after ophthalmic artery infusion (OAI) subsequent to superselective artery catheterization and to compare it with periocular injection (POI). Methods: The ophthalmic artery of 4 pigs was catheterized and 1 mg of topotecan infused over a period of 30 minutes. The contralateral eye was subsequently used for administering topotecan by POI. Serial vitreous specimens were obtained by microdialysis and plasma samples collected and assayed for total and lactone topotecan. Results: Maximum total topotecan concentration in the vitreous (median, range) was significantly higher after OAI compared with POI (131.8 ng/mL [112.9–138.7] vs. 13.6 ng/mL [5.5–15.3], respectively; P , 0.005). Median vitreous exposure calculated as area under the curve for total topotecan attained after OAI was significantly higher than after POI (299.8 nghour/mL [247.6–347.2] and 48.9 nghour/mL [11.8–63.4], respectively; P , 0.05). The vitreous to plasma exposure ratio was 29 after OAI and 3.4 after POI. Systemic exposure for total topotecan was low after both modalities of administration, with a trend to be lower after OAI compared with POI (10.6 nghour/mL [6.8–13.4] vs. 18.7 nghour/mL [6.3–21.7]; P = 0.54). Conclusion: Superselective OAI resulted in significantly higher vitreous concentrations and exposure and a trend toward lower systemic exposure than POI.Fil: Schaiquevich, Paula Susana. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Buitrago, Emiliano. Universidad de Buenos Aires; ArgentinaFil: Ceciliano, Alejandro. No especifíca;Fil: Fandino, Adriana C.. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Asprea, Marcelo. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Sierre, Sergio. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Abramson, David H.. No especifíca;Fil: Bramuglia, Guillermo Federico. Universidad de Buenos Aires; ArgentinaFil: Chantada, Guillermo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; Argentin

A molecular biology and phase II trial of lapatinib in children with refractory CNS malignancies: a pediatric brain tumor consortium study.

High expression of ERBB2 has been reported in medulloblastoma and ependymoma; EGFR is amplified and over-expressed in brainstem glioma suggesting these proteins as potential therapeutic targets. We conducted a molecular biology (MB) and phase II study to estimate inhibition of tumor ERBB signaling and sustained responses by lapatinib in children with recurrent CNS malignancies. In the MB study, patients with recurrent medulloblastoma, ependymoma, and high-grade glioma (HGG) undergoing resection were stratified and randomized to pre-resection treatment with lapatinib 900 mg/m(2) dose bid for 7-14 days or no treatment. Western blot analysis of ERBB expression and pathway activity in fresh tumor obtained at surgery estimated ERBB receptor signaling inhibition in vivo. Drug concentration was simultaneously assessed in tumor and plasma. In the phase II study, patients, stratified by histology, received lapatinib continuously, to assess sustained response. Eight patients, on the MB trial (four medulloblastomas, four ependymomas), received a median of two courses (range 1-6+). No intratumoral target inhibition by lapatinib was noted in any patient. Tumor-to-plasma ratios of lapatinib were 10-20 %. In the 34 patients (14 MB, 10 HGG, 10 ependymoma) in the phase II study, lapatinib was well-tolerated at 900 mg/m(2) dose bid. The median number of courses in the phase II trial was two (range 1-12). Seven patients (three medulloblastoma, four ependymoma) remained on therapy for at least four courses range (4-26). Lapatinib was well-tolerated in children with recurrent or CNS malignancies, but did not inhibit target in tumor and had little single agent activity.Fil: Fouladi, Maryam. St. Jude Children’s Research Hospital; Estados UnidosFil: Stewart, Clinton F.. St. Jude Children’s Research Hospital; Estados UnidosFil: Blaney, Susan M.. Baylor College of Medicine. Texas Children’s Cancer Center; Estados UnidosFil: Onar Thomas, Arzu. St. Jude Children’s Research Hospital; Estados UnidosFil: Schaiquevich, Paula Susana. St. Jude Children’s Research Hospital; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Packer, Roger J.. Children’s National Medical Center; Estados UnidosFil: Goldman, Stewart. Anne and Robert H. Lurie Children’s Hospital of Chicago; Estados UnidosFil: Geyer, J. Rusell. Children’s Hospital and Regional Medical Center; Estados UnidosFil: Gajjar, Amar. St. Jude Children’s Research Hospital; Estados UnidosFil: Kun, Larry E.. St. Jude Children’s Research Hospital; Estados UnidosFil: Boyett, James M.. St. Jude Children’s Research Hospital; Estados UnidosFil: Gilbertson, Richard J.. St. Jude Children’s Research Hospital; Estados Unido

Pharmacokinetics, Safety, and Efficacy of Intravitreal Digoxin in Preclinical Models for Retinoblastoma

PURPOSE:To assess in vitro cytotoxic activity and antiangiogenic effect, ocular and systemic disposition, and toxicity of digoxin in rabbits after intravitreal injection as a potential candidate for retinoblastoma treatment.METHODS:A panel of two retinoblastoma and three endothelial cell types were exposed to increasing concentrations of digoxin in a conventional (72-hour exposure) and metronomic (daily exposure) treatment scheme. Cytotoxicity was defined as the digoxin concentration that killed 50% of the cells (IC50) and was assessed with a vital dye in all cell types. Induction of apoptosis and cell-cycle status were evaluated by flow cytometry after both treatment schemes. Ocular and systemic disposition after intravitreal injection as well as toxicity was assessed in rabbits. Electroretinograms (ERGs) were recorded before and after digoxin doses and histopathological examinations were performed after enucleation.RESULTS:Digoxin was cytotoxic to retinoblastoma and endothelial cells under conventional and metronomic treatment. IC50 was comparable between both schedules and induced apoptosis in all cell lines. Calculated vitreous digoxin Cmax was 8.5 μg/mL and the levels remained above the IC50 for at least 24 hours after intravitreal injection. Plasma digoxin concentration was below 0.5 ng/ml. Retinal toxicity was evident after the third intravitreal dose with considerable changes in the ERG and histologic damage to the retina.CONCLUSIONS:Digoxin has antitumor activity for retinoblastoma while exerting antiangiogenic activity in vitro at similar concentrations. Metronomic treatment showed no advantage in terms of dose for cytotoxic effect. Four biweekly injections of digoxin led to local toxicity to the retina but no systemic toxicity in rabbits.Fil: Winter, Ursula Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Buitrago, Emiliano. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Mena, Hebe Agustina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: del Sole, Maria Jose. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Veterinarias. Departamento de Fisiopatología. Laboratorio de Farmacología; ArgentinaFil: Laurent, Viviana Eunice. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Negrotto, Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Francis, Jasmine. Memorial Sloan-Kettering Cancer Center; Estados UnidosFil: Arana, Eloisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Inmunología, Genética y Metabolismo. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Inmunología, Genética y Metabolismo; ArgentinaFil: Sgroi, Mariana. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Croxatto, Juan Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Fundación Oftalmología Argentina "J. Malbrán"; ArgentinaFil: Djaballah, Hakim. Core Facility Memorial Sloan-Kettering Cancer Center; Estados UnidosFil: Chantada, Guillermo Luis. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Abramson, David. Memorial Sloan-Kettering Cancer Center; Estados UnidosFil: Schaiquevich, Paula Susana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; Argentin

P-glycoprotein, but not multidrug resistance protein 4, plays a role in the systemic clearance of irinotecan and SN-38 in mice

The ATP-binding cassette transporters P-glycoprotein (ABCB1, MDR1) and multidrug resistance protein 4 (MRP4) efflux irinotecan and its active metabolite SN-38 in vitro, and thus may contribute to system clearance of these compounds. Mdr1a/b(-/-), Mrp4(-/-), and wild-type mice were administered 20 or 40 mg/kg irinotecan, and plasma samples were collected for 6 hours. Irinotecan and SN-38 lactone and carboxylate were quantitated and data were analyzed with nonlinear mixed-effects modeling. Mdr1a/b genotype was a significant covariate for the clearance of both irinotecan lactone and SN-38 lactone. Exposures to irinotecan lactone and SN-38 lactone after a 40 mg/kg dose were 1.6-fold higher in Mdr1a/b(-/-) mice compared to wild-type mice. Plasma concentrations of irinotecan lactone, irinotecan carboxylate, and SN-38 lactone in Mrp4(-/-) mice were similar to the wild-type controls. These results suggest that P-gp plays a role in irinotecan and SN-38 elimination, but Mrp4 does not affect irinotecan or SN-38 plasma pharmacokinetics.Fil: Tagen, Michael. St. Jude Children's Research Hospital; Estados UnidosFil: Zhuang, Yanli. St. Jude Children's Research Hospital; Estados UnidosFil: Zhang, Fan. St. Jude Children's Research Hospital; Estados UnidosFil: Harstead, K. Elaine. St. Jude Children's Research Hospital; Estados UnidosFil: Shen, Jun. St. Jude Children's Research Hospital; Estados UnidosFil: Schaiquevich, Paula Susana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. St. Jude Children's Research Hospital; Estados UnidosFil: Fraga, Charles H.. St. Jude Children's Research Hospital; Estados UnidosFil: Panetta, John C.. St. Jude Children's Research Hospital; Estados UnidosFil: Waters, Christopher M.. St. Jude Children's Research Hospital; Estados UnidosFil: Stewart, Clinton F.. St. Jude Children's Research Hospital; Estados Unido

The absence of the potassium channel KCNQ4 affects the visual function

Voltage-gated KCNQ potassium channel subunits are responsible for the M-current that regulates neuronal excitability. We found expression of KCNQ4 in the retinal pigmented epithelium (RPE) and in the ciliary body (CB) of mouse eyes, suggesting that it could participate in visual processing and aqueous humor formation. Using Kcnq4 knockout (KO) and wild-type (WT) mice we studied the role of KCNQ4 in vision. First, we analyzed Kcnq gene expression by qPCR. We found that in KO mice, the expression of Kcnq3 and -5 in the RPE/retina did not change. On the other hand, in CB the expression of Kcnq3 increased 2.5-fold while the expression of Kcnq5 decreased 30%. Then, we tested light perception by testing the innate aversion of rodents to it. We did not find any differences between the KO and WT in the test performance. To analyze the function of the neuronal visual pathway, we recorded electroretinogram (ERG) in both genotypes. We observed no differences in a- and b-wave peaks and latency times between WT and KO in young animals, whereas in 50 weeks-old mice we observed a reduction trend in b-wave peak in KO while a-wave showed no differences. We also measured intraocular pressure (IOP) in young animals to evaluate CB function. We found a slight increase in the IOP in KO mice (13.6±1.0 to 15.8±1.1 mm Hg). In conclusion, the presence of the KCNQ4 subunit is necessary for the proper expression of the other Kcnq subunits and it would contribute to CB and retinal functionFil: Vera, Marcela Sonia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Investigaciones Bioquímicas de Bahía Blanca. Universidad Nacional del Sur. Instituto de Investigaciones Bioquímicas de Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; ArgentinaFil: Stupniki, Sofia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Investigaciones Bioquímicas de Bahía Blanca. Universidad Nacional del Sur. Instituto de Investigaciones Bioquímicas de Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; ArgentinaFil: Bruera, Manuel Gaston. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Química Biológica de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Centro de Investigaciones en Química Biológica de Córdoba; ArgentinaFil: Paz, Maria Constanza. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Química Biológica de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Centro de Investigaciones en Química Biológica de Córdoba; ArgentinaFil: Dionisio, Leonardo Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Investigaciones Bioquímicas de Bahía Blanca. Universidad Nacional del Sur. Instituto de Investigaciones Bioquímicas de Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; ArgentinaFil: Vater, Alan. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Schaiquevich, Paula Susana. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Contin, Maria Ana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Química Biológica de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Centro de Investigaciones en Química Biológica de Córdoba; ArgentinaFil: Spitzmaul, Guillermo Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Investigaciones Bioquímicas de Bahía Blanca. Universidad Nacional del Sur. Instituto de Investigaciones Bioquímicas de Bahía Blanca; Argentina. Universidad Nacional del Sur. Departamento de Biología, Bioquímica y Farmacia; ArgentinaSAN 2022 MeetingBuenos AiresArgentinaSociedad Argentina de Investigación en Neurociencia

Tridimensional Retinoblastoma Cultures as Vitreous Seeds Models for Live-Cell Imaging of Chemotherapy Penetration

A preclinical model could aid in understanding retinoblastoma vitreous seeds behavior, drug penetration, and response to chemotherapy to optimize patient treatment. Our aim was to develop a tridimensional in vitro model of retinoblastoma vitreous seeds to assess chemotherapy penetration by means of live-cell imaging. Cell cultures from patients with retinoblastoma who underwent upfront enucleation were established and thoroughly characterized for authentication of human tumor origin. The correlation of the in vitro tridimensional structures resembling human spheres and dusts vitreous seeds was established. Confocal microscopy was used to quantify real-time fluorescence of topotecan as a measure of its penetration into different sizes of spheres. Cell viability was determined after chemotherapy penetration. The in vitro spheres and dusts models were able to recapitulate the morphology, phenotype, and genotype of patient vitreous seeds. The larger the size of the spheres, the longer the time required for the drug to fully penetrate into the core (p < 0.05). Importantly, topotecan penetration correlated with its cytotoxic activity. Therefore, the studied tridimensional cell model recapitulated several characteristics of vitreous seeds observed in patients with retinoblastoma and were successfully used to assess live-cell imaging of chemotherapy penetration for drug distribution studies.Fil: Winter, Ursula Andrea. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Aschero, María del Rosario. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Fuentes, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Medicina Experimental. Academia Nacional de Medicina de Buenos Aires. Instituto de Medicina Experimental; ArgentinaFil: Buontempo, Fabian. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Zugbi, Santiago. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Sgroi, Mariana. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Sampor, Claudia. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Abramson, David H.. Memorial Sloan-kettering Cancer Center; Estados UnidosFil: Carcaboso, Angel M.. Hospital Sant Joan de Deu Barcelona; EspañaFil: Schaiquevich, Paula Susana. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Identification of Factors Affecting Tacrolimus Trough Levels in Latin American Pediatric Liver Transplant Patients

Tacrolimus is the cornerstone in pediatric liver transplant immunosuppression. Despite close monitoring, fluctuations in tacrolimus blood levels affect safety and efficacy of immunosuppressive treatments. Identifying the factors related to the variability in tacrolimus exposure may be helpful in tailoring the dose. The aim of the present study was to characterize the clinical, pharmacological, and genetic variables associated with systemic tacrolimus exposure in pediatric liver transplant patients. De novo transplant patients with a survival of more than 1 month were considered for inclusion and were genotyped for cytochrome P450 3A5 (CYP3A5). Peritransplant clinical factors and laboratory covariates were recorded retrospectively between 1 month and 2 years after transplant, including alanine aminotransferase (ALT), aspartate aminotransferase, hematocrit, and tacrolimus predose steady-state blood concentrations collected 12 hours after tacrolimus dosing. A linear mixed effect (LME) model was used to assess the association of these factors and the log-transformed tacrolimus dose-normalized trough concentration (logC0/D) levels. Bootstrapping was used to internally validate the final model. External validation was performed in an independent group of patients who matched the original population. The developed LME model described that logC0/D increases with increases in time after transplant (β = 0.019, 95% confidence interval [CI], 0.010-0.028) and ALT values (β = 0.00030, 95% CI, 0.00002-0.00056), whereas logC0/D is significantly lower in graft CYP3A5 expressers compared with nonexpressers (β = −0.349, 95% CI, −0.631 to −0.062). In conclusion, donor CYP3A5 genotype, time after transplant, and ALT values are associated with tacrolimus disposition between 1 month and 2 years after transplant. A better understanding of tacrolimus exposure is essential to minimize the occurrence of an out-of-range therapeutic window that may lead to adverse drug reactions or acute rejection.Fil: Riva, Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Woillard, Jean Baptiste. Inserm; FranciaFil: Distefano, Maximiliano. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Moragas, Matías. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Dip, Marcelo Fabian. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Halac, Esteban Tomas. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Cáceres Guido, Paulo. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Licciardone, Nieves. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Mangano, Andrea María Mercedes. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bosaleh, Andrea. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: de Davila, María Teresa. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Schaiquevich, Paula Susana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; ArgentinaFil: Imventarza, Oscar Cesar. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Gobierno de la Ciudad de Buenos Aires. Hospital de Pediatría "Juan P. Garrahan"; Argentin