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Background: Osimertinib demonstrated promising efficacy for refractory leptomeningeal metastases (LM) in preclinical data and a clinical study at 160 mg, but there is limited data for the standard 80 mg dose., Methods: T790M-positive patients with suspected LM after classical epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) failure were enroled., Results: We investigated 13 patients (5 definitive and 8 possible LM cases). In two of the five definitive cases with T790M in and outside the central nervous system (CNS), osimertinib was effective for both lesions, with cerebrospinal fluid (CSF) clearance of cancer cells and sensitive/T790M mutations. In three definitive cases with extra-CNS T790M without CSF T790M, cancer cells and sensitive mutations in the CSF persisted after osimertinib initiation. The median progression-free survival of all 13 patients was 7.2 months. Osimertinib was generally well-tolerated despite poor performance status, but interstitial lung disease (grade 2) was confirmed in one patient. Based on 25 samples from 13 patients, the osimertinib CSF penetration rate was 2.5±0.3%., Conclusions: Osimertinib 80 mg is a useful therapeutic option for refractory LM after classical EGFR-TKI failure. It appears more effective in CSF T790M-positive cases.

Imatinib mesylate (STI571) is a very effective treatment option for Ph(+) chronic myeloid leukemia (CML) in chronic phase. Secondary treatment failures have mostly been observed in patients with advanced stages of disease. We report the case of a patient who unexpectedly experienced blast crisis of the central nervous system although having achieved complete cytogenetic remission in the bone marrow. The levels of STI571 and its metabolite N-desmethyl STI were 40-fold lower in the cerebral spine fluid than in plasma. The risk of CNS disease has to be kept in mind when patients with CML in chronic phase who are at an increased risk for blastic transformation are treated with imatinib mesylate.

Purpose: Imatinib mesylate (Gleevec, Glivec, STI571, imatinib) is a potent tyrosine kinase inhibitor approved for the treatment of chronic myelogenous leukemia and gastrointestinal stromal tumors. The role of imatinib in the treatment of malignant gliomas and other solid tumors is being evaluated. We used a nonhuman primate model that is highly predictive of the cerebrospinal fluid penetration of drugs in humans to study the pharmacokinetics of imatinib in plasma and cerebrospinal fluid (CSF) after i.v. and p.o. administration., Experimental Design: Imatinib, 15 mg/kg i.v. over 30 min (n = 3) or 30 mg/kg p.o. (n = 3), was administered to nonhuman primates. Imatinib was measured in serial samples of plasma and CSF using high-pressure liquid chromatography with UV absorbance or mass spectroscopic detection. Pharmacokinetic parameters were estimated using model-independent methods., Results: Peak plasma imatinib concentrations ranged from 6.4 to 9.5 microM after i.v. dosing and 0.8 to 2.8 microM after p.o. dosing. The mean +/-SD area under the plasma concentration versus time curve was 2480 +/-1340 microM.min and 1191 +/-146 microM.min after i.v. and p.o. dosing, respectively. The terminal half-life was 529 +/-167 min after i.v. dosing and 266 +/-88 min after p.o. dosing. After i.v. dosing the steady state volume of distribution was 5.9 +/-2.8 liter/kg, and the total body clearance was 12 +/-5 ml/min/kg. The mean peak CSF concentration was 0.25 +/-0.07 microM after i.v. dosing and 0.07 +/-0.04 microM after p.o. dosing. The mean CSF:plasma area under the plasma concentration versus time curve ratio for all of the animals was 5% +/-2%., Conclusions: There is limited penetration of imatinib into the CSF of nonhuman primates after i.v. and p.o. administration.

Purpose: In patients with acute leukemias, a lymphoid phenotype, the presence of a Philadelphia chromosome (Ph), and inadequate central nervous system (CNS)-directed prophylactic therapy are risk factors for CNS involvement. Imatinib mesylate has promising single-agent antileukemic activity in patients with advanced Ph(+) acute leukemias. It was the aim of this analysis to determine the incidence of, and risk factors associated with, meningeal leukemia during imatinib monotherapy., Study Design: We analyzed 107 consecutive patients with relapsed or refractory Ph(+) acute lymphoid leukemia (ALL; n = 65) or chronic myeloid leukemia blast crisis (n = 42) who were enrolled in successive Phase II trials of single-agent imatinib and who did not receive routine prophylactic intrathecal chemotherapy., Results: CNS leukemia developed in 13 of 107 patients (12%) and was associated primarily with a lymphoid or bilineage phenotype (12 of 78; 15%) and with imatinib refractory Ph(+) ALL (5 of 19; 26%). Meningeal leukemia did not occur among patients who received prior prophylactic cranial irradiation. The median survival with combined CNS and systemic disease was 108 days (range, 58-141), with no patient surviving long term. In contrast, two of three patients with exclusively meningeal leukemia achieved prolonged molecular remissions with intrathecal chemotherapy, cranial irradiation, and continued imatinib., Conclusions: Patients with Ph(+) ALL are at considerable risk of meningeal leukemia during imatinib monotherapy and should routinely receive CNS prophylaxis. Although the prognosis with combined meningeal and systemic relapse is dismal, patients with an isolated meningeal relapse may still achieve sustained remissions. The optimal type of CNS-directed treatment and the extent of protection afforded by prophylactic cranial irradiation remain to be defined.

The chronic myelogenous leukemia (CML)-like myeloproliferative disorder observed in the BCR/ABL murine bone marrow transduction and transplantation model shares several features with the human disease, including a high response rate to the tyrosine kinase inhibitor imatinib mesylate (STI571). To study the impact of chronic imatinib mesylate treatment on the CML-like illness, mice were maintained on therapeutic doses of this drug and serially monitored. Unexpectedly, despite excellent systemic control of the CML-like illness, many of the mice developed progressive neurologic deficits after 2 to 4 months of imatinib mesylate therapy because of central nervous system (CNS) leukemia. Analysis of imatinib mesylate cerebral spinal fluid concentrations revealed levels 155- fold lower than in plasma. Thus, in the mouse, the limited ability of imatinib mesylate to cross the blood-brain barrier allowed the CNS to become a sanctuary for Bcr/Abl-induced leukemia. This model will be a useful tool for the future study of novel anti-CML drugs and in better defining the mechanisms for limited imatinib mesylate penetration into the CNS.

The goals of the present study were to model the population kinetics of in vivo influx and efflux processes of grepafloxacin at the serum-cerebrospinal fluid (CSF) barrier and to propose a simulation-based approach to optimize the design of dose-finding trials in the meningitis rabbit model. Twenty-nine rabbits with pneumococcal meningitis receiving grepafloxacin at 15 mg/kg of body weight (intravenous administration at 0 h), 30 mg/kg (at 0 h), or 50 mg/kg twice (at 0 and 4 h) were studied. A three-compartment population pharmacokinetic model was fit to the data with the program NONMEM (Nonlinear Mixed Effects Modeling). Passive diffusion clearance (CL(diff)) and active efflux clearance (CL(active)) are transfer kinetic modeling parameters. Influx clearance is assumed to be equal to CL(diff), and efflux clearance is the sum of CL(diff), CL(active), and bulk flow clearance (CL(bulk)). The average influx clearance for the population was 0.0055 ml/min (interindividual variability, 17%). Passive diffusion clearance was greater in rabbits receiving grepafloxacin at 15 mg/kg than in those treated with higher doses (0.0088 versus 0.0034 ml/min). Assuming a CL(bulk) of 0.01 ml/min, CL(active) was estimated to be 0.017 ml/min (11%), and clearance by total efflux was estimated to be 0.032 ml/min. The population kinetic model allows not only to quantify in vivo efflux and influx mechanisms at the serum-CSF barrier but also to analyze the effects of different dose regimens on transfer kinetic parameters in the rabbit meningitis model. The modeling-based approach also provides a tool for the simulation and prediction of various outcomes in which researchers might be interested, which is of great potential in designing dose-finding trials.

The N-methyl-D-aspartate (NMDA) receptor complex plays a central role in the modulation of neuronal information in the central nervous system. This study was designed to examine the pharmacokinetics of the NMDA antagonist 3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP) in plasma and cerebrospinal fluid (CSF) and rostral spread in the CSF after lumbar intrathecal, extradural and i.v administration. Anaesthetized pigs were given a lumbar intrathecal, lumbar extradural or an i.v. injection of a mixture of [3H]-labelled and unlabelled CPP. CSF was sampled over 10 h through intrathecal catheters positioned at the L1, T5 and C1 vertebral levels. Blood samples were obtained over the same period. Haemodynamic and arterial blood-gas variables and acid-base balance were monitored during the study. The area under the radioactivity concentration-time curves showed a gradient between cervical and lumbar CSF radioactivity of about 1:2500 after intrathecal administration and about 1:140 after extradural administration, indicating that only small fractions of lumbar administered CPP spread rostrally. About 2% of an extradurally administered dose was found in the CSF. After i.v. administration of [3H]CPP, clearance was mean 122 (SEM 16) ml min-1 and the CSF: serum radioactivity gradient was approximately 1:4. The half-life of [3H]CPP varied little (mean range 94-191 min) irrespective of the route of administration or the level of sampling. Cervical radioactivity after lumbar intrathecal administration probably resulted from rostral transport via CSF bulk flow, whereas after extradural administration, systemic absorption and redistribution via the blood-brain barrier probably contributed.(ABSTRACT TRUNCATED AT 250 WORDS)

The pharmacology of ketoconazole was studied in patients with fungal infections. After administration of 50-, 100-, and 200-mg doses of ketoconazole, there was a linear increase in the area under the curve of serum concentrations; this was not apparent when higher doses of ketoconazole were given. An increase in the area under the curve occurred in patients receiving 200 mg daily who were restudied after 1 to 12 months of therapy. However, normalized area under the curve appeared to decrease after higher doses were administered chronically. The half life ranged from 2.0 to 3.3 h. Peak serum concentrations up to 50 micrograms/ml were detected in this study, and potentially therapeutic concentrations were detectable up to 26 h after high doses. Ketoconazole penetrated the saliva and inflamed joint fluid and meninges, although variably, and could be demonstrated in some other tissue compartments. In the presence of renal failure, ketoconazole disposition was not altered, whereas in the presence of hepatic insufficiency, an alteration in disposition was suggested. The interactions of ketoconazole and other drugs were studied. Of note, antacids did not significantly affect ketoconazole pharmacokinetics (nor did meals), and ketoconazole and warfarin did not appear to affect the pharmacokinetics of the other.

Ketoconazole is a broad-spectrum antifungal agent which appears promising for treatment of a variety of systemic mycoses. Pharmacokinetic studies are limited due to a lack of readily available methods for quantitation of ketoconazole in serum or cerebrospinal fluid. We developed a rapid, simple bioassay for measurement of ketoconazole alone or in the presence of therapeutic levels of amphotericin B, using an agar diffusion assay incorporating Candida pseudotropicalis. Pairs of 8-mm wells cut in the seeded assay medium were filled with four duplicate ketoconazole standards and duplicate patient specimens. Zones of inhibition were visible after 7 to 8 h of incubation, but were most easily measured after overnight growth. The assay allowed determinations of serum ketoconazole levels as low as 0.3 microgram/ml with a 4.4% coefficient of variation. Thirty-five serum samples from patients receiving the drug were assayed by this method, and the results were compared with the Coccidioides immitis endospore assay. The correlation coefficient between the assays was 0.90. This assay allows any microbiology laboratory to easily and safely determine ketoconazole levels in serum or cerebrospinal fluid.