Cerebrospinal Fluid Penetration Research Articles

Population pharmacokinetic modeling of ceftriaxone in cerebrospinal fluid in children: should we be using once- or twice-daily dosing for meningitis?

Guidelines for bacterial meningitis in children recommend intravenous ceftriaxone 50 mg/kg (max 2 g) twice daily (BD) or 100 mg/kg (max 4 g) once daily (OD), leaving the decision regarding the dose frequency to the prescriber. We investigated the cerebrospinal fluid (CSF) penetration of ceftriaxone to evaluate whether one dosing regimen is superior. Unbound ceftriaxone concentrations were measured in serum and CSF samples from children aged 0-18 years treated with ceftriaxone if there was a sample remaining after clinical tests were performed. A serum-CSF population pharmacokinetic model was developed using non-linear mixed-effects modeling. The once- and twice-daily dosing regimens were simulated, and the probability of target attainment (PTA) was determined for maintaining a CSF concentration above a minimum inhibitory concentration (MIC) of 1 mg/L for common meningitis pathogens and 4 mg/L for Staphylococcus aureus for 100% of the dosing interval. Sixteen serum and 87 CSF samples were collected from 98 children (age range 0.1-18.5 years). The final two-compartment serum-CSF model included a renal maturation function with weight scaling on clearance and volume of distribution. The estimated serum:CSF uptake was 20.1%. For MIC 1 mg/L, the 24 h PTA was higher for OD (88%) compared with BD (53%) dosing, although both achieved a 100% PTA at steady state. For S. aureus (MIC 4 mg/L), neither dosing regimen was sufficient. Our findings support the use of a 100 mg/kg once daily regimen for empirical treatment of bacterial meningitis due to earlier achievement of the pharmacodynamic target. Neither dosing regimen was adequate for S. aureus meningitis.

Lazertinib in EGFR-Variant Non–Small Cell Lung Cancer With CNS Failure to Prior EGFR Tyrosine Kinase Inhibitors

EGFR-variant non-small cell lung cancer (NSCLC) is associated with a high rate of central nervous system (CNS) metastases, even with treatment with first-generation or second-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs). To investigate CNS activity with lazertinib, a third-generation EGFR TKI. This multicenter single-arm, phase 2 nonrandomized controlled trial was conducted in South Korea and included patients with EGFR-variant NSCLC who had asymptomatic or mildly symptomatic brain metastases after unsuccessful treatment with first-generation or second-generation EGFR TKIs. Data were collected from June 2021 to April 2022, with a data cutoff date of December 15, 2022. Lazertinib, 240 mg, once daily. The primary end point was intracranial objective response rate (iORR) in the evaluable population according to the Response Evaluation Criteria in Solid Tumours version 1.1 assessed by the investigators. Secondary end points included intracranial progression-free survival (iPFS) and iORR in patients with T790M-negative disease and isolated CNS progression as well as overall ORR, duration of response, intracranial duration of response, disease control rate, overall survival, cerebrospinal fluid penetration of lazertinib, and safety. Among 40 included patients, 25 (63%) were women, and the median (range) age was 63 (29-85) years. A total of 38 patients were evaluable for tumor response, including 12 patients with leptomeningeal metastases. At data cutoff, the median (range) follow-up was 13.6 (2.9-17.7) months. The iORR for the evaluable population was 55% (21 of 38; 95% CI, 38.3-71.4); for patients with T790M-positive disease, 80% (4 of 5; 95% CI, 28.4-99.5); for patients with T790M-negative disease, 43% (9 of 21; 95% CI, 21.8-66.0); and for patients with T790M-unknown disease, 67% (8 of 12; 95% CI, 34.9-90.1). The median iPFS was 15.8 months (95% CI, 15.2-not reached) for the evaluable population, 15.2 months (95% CI, 4.2-not reached) for the T790M-positive subgroup, 15.4 months (95% CI, 7.9-not reached) for the T790M-negative subgroup, and 18.0 months (95% CI, 3.9-not reached) for the T790M-unknown subgroup. The cerebrospinal fluid penetration rate of lazertinib was 46.2% (95% CI, 10.0-49.6), providing further support for its mechanism of intracranial response. Most adverse events were grade 1 or 2. In this study, lazertinib had substantial CNS activity, regardless of T790M status, against the progression of intracranial metastases with or without leptomeningeal metastases after unsuccessful treatment with first-generation or second-generation EGFR TKIs in patients with metastatic EGFR-variant NSCLC. These results suggest that using lazertinib instead of brain local treatment could be a potential strategy in patients with EGFR-variant NSCLC whose CNS metastases progressed after prior EGFR TKI treatment. ClinicalTrials.gov Identifier: NCT05326425.

Role of Cefiderocol in Multidrug-Resistant Gram-Negative Central Nervous System Infections: Real Life Experience and State-of-the-Art.

Cefiderocol is a new molecule effective against multidrug-resistant (MDR) Gram-negative pathogens. Currently, there is limited evidence regarding the use of cefiderocol in central nervous system (CNS) infections. Data on the cerebrospinal fluid penetration rate of cefiderocol are limited and heterogeneous, and there is no consensus on the dosing scheme of cefiderocol to penetrate the blood-brain barrier. We present a case series and a literature review of CNS infections caused by MDR pathogens that were treated with cefiderocol: some of these patients were treated with different dose schemes of cefiderocol and underwent therapeutic drug monitoring both on plasma and cerebrospinal fluid (CSF). The CSF penetration rates and the clinical outcomes were evaluated.

Successful Treatment of Carbapenem-Resistant Acinetobacter baumannii Meningitis With Sulbactam-Durlobactam.

The treatment of carbapenem-resistant Acinetobacter baumannii/calcoaceticus complex (CRAB) presents significant treatment challenges. We report the case of a 42-year-old woman with CRAB meningitis who experienced persistently positive cerebrospinal fluid (CSF) cultures for 13 days despite treatment with high-dose ampicillin-sulbactam and cefiderocol. On day 13, she was transitioned to sulbactam-durlobactam and meropenem; 4 subsequent CSF cultures remained negative. After 14 days of sulbactam-durlobactam, she was cured of infection. Whole genome sequencing investigations identified putative mechanisms that contributed to the reduced cefiderocol susceptibility observed during cefiderocol therapy. Blood and CSF samples were collected pre-dose and 3-hours post initiation of a sulbactam-durlobactam infusion. The CRAB isolate belonged to sequence type 2. An acquired blaOXA-23 and an intrinsic blaOXA-51-like (ie, blaOXA-66) carbapenemase gene were identified. The paradoxical effect (ie, no growth at lower cefiderocol dilutions but growth at higher dilutions) was observed by broth microdilution after 8 days of cefiderocol exposure but not by disk diffusion. Potential markers of resistance to cefiderocol included mutations in the start codon of piuA and piuC iron transport genes and an A515V substitution in PBP3, the primary target of cefiderocol. Sulbactam and durlobactam were detected in CSF at both timepoints, indicating CSF penetration. This case describes successful treatment of refractory CRAB meningitis with the administration of sulbactam-durlobactam and meropenem and highlights the need to be cognizant of the paradoxical effect that can be observed with broth microdilution testing of CRAB isolates with cefiderocol.

Impact of Fenebrutinib Treatment on MRI Outcomes and Cerebrospinal Fluid Penetrance in Multiple Sclerosis: Results from the Phase II FENopta Study (S31.004)

Impact of Fenebrutinib Treatment on MRI Outcomes and Cerebrospinal Fluid Penetrance in Multiple Sclerosis: Results from the Phase II FENopta Study (S31.004)

Distribution of Bevacizumab into the Cerebrospinal Fluid of Children and Adolescents with Recurrent Brain Tumors.

To date, evidence has been lacking regarding bevacizumab pharmacokinetics in the cerebrospinal fluid (CSF). This study assessed the penetration of bevacizumab, as part of a metronomic antiangiogenic treatment regimen, into the CSF of children, adolescents, and young adults with recurrent brain tumors. Serum and CSF concentrations, malignant cells, and vascular endothelial growth factor A (VEGF-A) were analyzed in 12 patients (5-27 years) following 10 mg/kg bevacizumab intravenous biweekly administration (EudraCT number 2009-013024-23). A population pharmacokinetic model including body weight, albumin, and tumor type as influential factors was extended to quantify the CSF penetration of bevacizumab. Apart from in serum (minimum concentration/maximum concentration [Cmin/Cmax] 77.0-305/267-612 mg/L, median 144/417mg/L), bevacizumab could be quantified in the CSF (0.01-2.26mg/L, median 0.35 mg/L). The CSF/serum ratio was 0.16 and highly variable between patients. Malignant cells could be detected in CSF before initiation of treatment in five of 12 patients; after treatment, the CSF was cleared in all patients. VEGF-A was detected in three patients before treatment (mean ± SD: 20 ± 11 pg/mL), and was still measurable in one of these patients despite treatment (16 pg/mL). This pharmacokinetic pilot study indicated penetration of bevacizumab into the CSF in a population of children, adolescents, and young adults with recurrent brain tumors.

A phase I trial assessing the safety, pharmacokinetics, cerebrospinal fluid penetrance, and food effect of BTK inhibitor tolebrutinib in healthy volunteers

AbstractTolebrutinib is an oral, brain‐penetrant, covalent Bruton's tyrosine kinase inhibitor in development to treat multiple sclerosis at 60 mg/day with food. A phase I trial was conducted in healthy volunteers to assess the safety and pharmacokinetics of tolebrutinib at oral doses higher than 60 mg with food and during fasting, and to determine cerebrospinal fluid (CSF) exposure after a single dose of 60 or 120 mg with food. The trial included double‐blind, placebo‐controlled single ascending dose (120, 240, and 300 mg; fed and fasted) and multiple ascending dose (120, 180, and 240 mg) arms. Additional open‐label cohorts received a single 60 mg dose with a high‐fat meal and during fasting using a crossover design or a single 60 or 120 mg dose with food and lumbar puncture to obtain CSF. Tolebrutinib was rapidly absorbed and converted to an active metabolite (designated “M2”), both of which had a terminal half‐life of ~5 h. Tolebrutinib and M2 exposures increased following administration with food versus fasting, and plasma levels were generally dose proportional. For up to 4 h (the last measurement timepoint) after a 60 mg dose, CSF concentrations of tolebrutinib exceeded its in vitro cellular potency (half‐maximal inhibitory concentration [IC50]) for microglia, and tolebrutinib and M2 surpassed their biochemical IC50. Tolebrutinib was well‐tolerated, and treatment‐emergent adverse events were generally mild. Concentration‐QTc modeling showed no effects on QT/QTc intervals for any tolebrutinib dose or fed status. In conclusion, tolebrutinib has an acceptable safety profile at supratherapeutic doses and achieved bioactive CSF exposures at the phase III dose.

Magnetic Resonance Imaging-Guided Frameless Stereotactic Injections of the Bilateral Cerebellar Dentate Nuclei in Nonhuman Primates: Technical Note.

Nonhuman primates (NHPs) are important preclinical models for evaluating therapeutics because of their anatomophysiological similarities to humans, and can be especially useful for testing new delivery targets. With the growing promise of cell and gene therapies for the treatment of neurological diseases, it is important to ensure the accurate and safe delivery of these agents to target structures in the brain. However, a standard guideline or method has not been developed for stereotactic targeting in NHPs. In this article, we describe the safe use of a magnetic resonance imaging-guided frameless stereotactic system to target bilateral cerebellar dentate nuclei for accurate, real-time delivery of viral vector in NHPs. Seventeen rhesus macaques (Macaca mulatta) underwent stereotactic surgery under real-time MRI guidance using the ClearPoint® system. Bilateral cerebellar dentate nuclei were targeted through a single parietal entry point with a transtentorial approach. Fifty microliters of contrast-impregnated infusate was delivered to each dentate nucleus, and adjustments were made as necessary according to real-time MRI monitoring of delivery. Perioperative clinical outcomes and postoperative volumes of distribution were recorded. All macaques underwent bilateral surgery successfully. Superficial pin site infection occurred in 4/17 (23.5%) subjects, which resolved with antibiotics. Two episodes of transient neurological deficit (anisocoria and unilateral weakness) were recorded, which did not require additional postoperative treatment and resolved over time. Volume of distribution of infusate achieved satisfactory coverage of target dentate nuclei, and only 1 incidence (2.9%) of cerebrospinal fluid penetration was recorded. Mean volume of distribution was 161.22 ± 39.61 mm3 (left, 173.65 ± 48.29; right, 148.80 ± 23.98). MRI-guided frameless stereotactic injection of bilateral cerebellar dentate nuclei in NHPs is safe and feasible. The use of this technique enables real-time modification of the surgical plan to achieve adequate target coverage and can be readily translated to clinical use.

Linezolid does not improve bactericidal activity of rifampin-containing first-line regimens in animal models of TB meningitis

Tuberculous meningitis (TB meningitis) is the most devastating form of tuberculosis (TB) and there is a critical need to optimize treatment. Linezolid is approved for multidrug resistant TB and has shown encouraging results in retrospective TB meningitis studies, with several clinical trials underway assessing its additive effects on high-dose (35 mg/kg/day) or standard-dose (10 mg/kg/day) rifampin-containing regimens. However, the efficacy of adjunctive linezolid to rifampin-containing first-line TB meningitis regimens and the tissue pharmacokinetics (PK) in the central nervous system (CNS) are not known. We therefore conducted cross-species studies in two mammalian (rabbits and mice) models of TB meningitis to test the efficacy of linezolid when added to the first-line TB regimen and measure detailed tissue PK (multicompartmental positron emission tomography [PET] imaging and mass spectrometry). Addition of linezolid did not improve the bactericidal activity of the high-dose rifampin-containing regimen in either animal model. Moreover, the addition of linezolid to standard-dose rifampin in mice also did not improve its efficacy. Linezolid penetration (tissue/plasma) into the CNS was compartmentalized with lower than previously reported brain and cerebrospinal fluid (CSF) penetration, which decreased further two weeks after initiation of treatment. These results provide important data regarding the addition of linezolid for the treatment of TB meningitis.

EXTH-56. CSF PENETRATION COMPARISON OF TWO ORAL FORMULATIONS OF APL-101 IN A PRE-CLINICAL NON-HUMAN PRIMATE MODEL

Abstract Vebreltinib (APL-101) is a potent c-Met inhibitor which has shown efficacy in murine pre-clinical models and is under clinical trial evaluation for several cancer types, including adult high-grade glioma. The capsule formulation (APL-101-Cap) was reformulated as a pill (APL-101-Pill) with the expectation of increasing bioavailability. We determined and compared the plasma pharmacokinetics (PK) and cerebrospinal fluid (CSF) penetration of APL-101-Cap and APL-101-Pill in a non-human primate (NHP) model. METHODS: Seven animals, previously developed as serial CSF access models, were utilized across all studies. One NHP was studied with both formulations. Both formulations were administered orally as a single drug/single dose in serial studies, followed by serial plasma and CSF sample collections from 0-96 hours. Dosages: APL-101-Cap 3.25 mg/kg (n = 3) or 6.5 mg/kg (n = 4) and APL-101-Pill 5 mg/kg (n = 4). The resulting plasma concentrations from each formulation were quantified by LC-MS/MS. PK parameters were calculated via noncompartmental methods, and results were analyzed to assess CNS penetration (AUCCSF:AUCPlasma) and compare formulations. RESULTS: Mean (range) for plasma and CSF PK exposure [AUCLAST (hr*ng/mL)] reported. APL-101-Cap plasma exposure, regardless of dose, was more variable than APL-101-Pill. APL-101-Pill had lower exposure in both plasma (AUC 1893.0 (841-2865)] and CSF [AUC 27.7 (5.0-65.0)] than APL-101-Cap regardless of dose [(3.25 mg/kg): plasma AUC 9621.0 (1331-23132) and CSF AUC 688.0 (24-1352); 6.5 mg/kg: plasma AUC 6208.0 (1424-19800) and CSF AUC 606.0 (34-1179)]. CNS penetrance was higher with APL-101-Cap (3.2% [0.5-5.8%] at 3.25mg/kg; 4.2% (2.4-6%) at 6.5 mg/kg), but also more variable when compared to APL-101-Pill (1.2% [0.6-2.3%]). For APL-101-Cap, one animal at 3.25 mg/kg and two animals at 6.25 mg/kg had undetectable CSF concentrations. CONCLUSION: In this NHP model, single-dose oral administration of APL-101-Pill resulted in lower, but less variable plasma and CSF exposure compared to APL-101-Cap. APL-101-Cap CSF exposure was unaffected by dose escalation.

Treatment optimization by monitoring vancomycin concentration in the serum and cerebrospinal fluid in a child with cystoperitoneal shunt-related infection caused by methicillin-resistant Staphylococcus aureus: a case report and literature review

BackgroundCerebral ventricular shunt infections caused by methicillin-resistant Staphylococcus aureus (MRSA), especially strains with elevated minimum inhibitory concentration (MIC) values, have a poor prognosis. Monitoring serum vancomycin (VCM) levels with therapeutic drug monitoring and maintaining high VCM concentrations in the cerebrospinal fluid (CSF) are critical to treatment success. However, there have been a few reports about the CSF penetration and the pharmacokinetics of VCM in children.Case presentationHere, we report the case of a pediatric patient with cysto-peritoneal shunt-related meningitis caused by MRSA with an MIC of 2 μg/mL. The adequate VCM concentration was maintained by monitoring the VCM concentration in the CSF via the external ventricular drain, and frequent blood taking was avoided. VCM showed a good CSF penetration in our patient, and she was discharged without complications.DiscussionTherapeutic drug monitoring of VCM concentration in the CSF may result in successful treatment even if MRSA shows a higher MIC. Therapeutic drug monitoring of VCM concentration in the CSF may also reduce the side effects.

Phase II trial of lazertinib in patients with epidermal growth factor receptor (EGFR) mutation-positive (M+), metastatic non-small cell lung cancer (NSCLC) with asymptomatic or mild symptomatic brain metastases after failure of EGFR tyrosine kinase inhibitor (TKI) (KCSG LU20-15).

9054 Background: Central nervous system (CNS) metastases occur not infrequently, ultimately devastating consequences in advanced EGFR M+ NSCLC. Lazertinib, a 3rd-generation (G) EGFR-TKI, has shown potent antitumor activity in EGFR-mutant NSCLC. We conducted a phase II single-arm study of lazertinib in EGFR M+ NSCLC patients (pts) having CNS metastases to evaluate its CNS activity. Methods: The patients exhibiting CNS progression upon 1st or 2nd-G EGFR-TKIs with least one measurable CNS lesion were enrolled. The primary endpoint was intracranial objective response rate (iORR) in evaluable for response set (ERS). Secondary endpoints included iORR without T790M mutation, overall ORR (oORR), disease control rate (DCR), intracranial progression-free survival (iPFS) in ERS. Overall survival (OS) and safety analyses were performed in pts who received at least one dose of lazertinib. Cerebrospinal fluid (CSF) penetration was measured as exploratory biomarker study. Results: Of 40 pts enrolled, 38 were evaluable for tumor response. Nineteen pts harbored exon 19 deletion and 21 pts for exon 21 L858R and 30% of pts had radiologic evidence of leptomeningeal carcinomatosis (LM) with 2 cytological confirmed cases. Forty-five percent of pts received afatinib as first line treatment, followed by 42.5% of gefitinib and 12.5% of erlotinib. Baseline plasma samples of all the 40 patients obtained for liquid-based next-generation sequencing (Guardant360) and T790M was found in 5 pts prior to lazertinib treatment. iORR was 57.9% (22/38). iORR with T790M-negative, oORR, and DCR were 54.5%, 39.5%, and 97.4%, respectively. With median follow-up of 13.6 months, median iPFS and OS were not reached. Treatment-related adverse events (TRAEs) emerged in 85.0% of pts with most common TRAEs being skin rash (50.0%) and paresthesia (42.5%). Grade 3 or 4 TRAEs were reported in 10.0%. The CSF penetration rates of lazertinib and its metabolite (YH26334) were 46.2% and 33.1%, respectively in paired CSF and plasma samples, suggesting high CNS penetration efficacy. Conclusions: Lazertinib has substantial CNS activity regardless of T790M status against the progression of intracranial metastases ± LM during the treatment of 1st or 2nd-G EGFR-TKIs in metastatic EGFR M+ NSCLC pts. These results suggest that using lazertinib instead of brain local treatment would be a potential strategy in EGFR M+ NSCLC, who progressed on CNS metastases after prior EGFR-TKI. Clinical trial information: NCT05326425 . [Table: see text]

Cerebrospinal fluid penetration of fosfomycin in patients with ventriculitis: an observational study

BackgroundFor treatment of ventriculitis, vancomycin and meropenem are frequently used as empiric treatment but cerebrospinal fluid (CSF) penetration is highly variable and may result in subtherapeutic concentrations. Fosfomycin has been suggested for combination antibiotic therapy, but data are sparse, so far. Therefore, we studied CSF penetration of fosfomycin in ventriculitis.MethodsAdult patients receiving a continuous infusion of fosfomycin (1 g/h) for the treatment of ventriculitis were included. Routine therapeutic drug monitoring (TDM) of fosfomycin in serum and CSF was performed with subsequent dose adaptions. Demographic and routine laboratory data including serum and CSF concentrations for fosfomycin were collected. Antibiotic CSF penetration ratio as well as basic pharmacokinetic parameters were investigated.ResultsSeventeen patients with 43 CSF/serum pairs were included. Median fosfomycin serum concentration was 200 [159–289] mg/L and the CSF concentration 99 [66–144] mg/L. Considering only the first measurements in each patient before a possible dose adaption, serum and CSF concentrations were 209 [163–438] mg/L and 104 [65–269] mg/L. Median CSF penetration was 46 [36–59]% resulting in 98% of CSF levels above the susceptibility breakpoint of 32 mg/L.ConclusionPenetration of fosfomycin into the CSF is high, reliably leading to appropriate concentrations for the treatment of gram positive and negative bacteria. Moreover, continuous administration of fosfomycin appears to be a reasonable approach for antibiotic combination therapy in patients suffering from ventriculitis. Further studies are needed to evaluate the impact on outcome parameters.

Determining plasma and cerebrospinal fluid concentrations of EGFR-TKI in lung cancer patients

Epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) are commonly used to treat advanced non-small cell lung cancer (NSCLC). A rapid and reliable method for measuring plasma and cerebrospinal fluid (CSF) concentrations of EGFR-TKIs is needed for therapeutic drug monitoring. By using UHPLC‒MS/MS with multiple reaction monitoring mode, we developed a method for rapidly determining the plasma and CSF concentrations of gefitinib, erlotinib, afatinib, and osimertinib. Protein precipitation was employed to remove protein interference for plasma and CSF matrix. The LC‒MS/MS assay was validated to be satisfactory in terms of linearity, precision, and accuracy. This method was successfully applied to measure plasma (n = 44) and CSF (n = 6) concentrations of EGFR-TKIs in NSCLC patients. The chromatographic separation was achieved by a Hypersil Gold aQ column within 3 min. The median plasma concentrations were 325.76, 1981.50, 42.62, 40.27, and 340.92 ng/ml for gefitinib erlotinib, afatinib 30 mg/day, afatinib 40 mg/day, and osimertinib, respectively. The CSF penetration rates were 2.15% for the patients receiving erlotinib therapy, 0.59% for afatinib, 0.08–1.12% for osimertinib 80 mg/day, and 2.18% for those receiving osimertinib 160 mg/day. This assay helps to predict the effectiveness and toxicities of EGFR-TKIs in the pursuit of precision medicine for lung cancer patients.

Antiretroviral Levels in the Cerebrospinal Fluid: The Effect of Inflammation and Genetic Variants.

Neurocognitive impairments are common in people living with HIV. Some conditions, such as chronic inflammation, astrocyte infection and an impaired blood-brain barrier (BBBi), along with host genetic variants in transporter genes, may affect antiretroviral (ARV) exposure in the cerebrospinal fluid (CSF). The aim of this study was to evaluate ARV CSF penetration according to compartmental inflammation, BBB permeability and single-nucleotide polymorphisms (SNPs) in drug transporter encoding genes. CSF neopterin (ELISA), plasma and CSF ARV concentrations (HPLC) and host genetic variants in ABCC2, HNF4α, SLCO1A2 and SLC22A6 (real-time PCR) were measured. Bi- and multivariate analyses were performed for single ARV and classes. We included 259 participants providing 405 paired plasma and CSF samples. CSF/plasma ratios (CPR) showed an increase for NRTIs and nevirapine with low penetrations for the majority of ARVs. At bi-variate analysis, several associations, including the effect of BBBi (emtricitabine, raltegravir), age (zidovudine and darunavir), and high CSF neopterin (NRTIs and border-line for PIs) were suggested. An association was found between genetic variants and integrase strand transfer (ABCC2 and HNF4α), non-nucleoside reverse transcriptase inhibitors (SLCO1A2), and protease inhibitors (SLC22A6). At multivariate analysis age, gender, BMI, and altered BBB were independent predictors of nucleoside reverse transcriptase CSF concentrations; age (for protease inhibitors) and body mass index and altered BBB (integrase strand transfer inhibitors) were also associated with ARV CSF exposure. We describe factors associated with CSF concentrations, showing that demographic, BBB integrity and, partially, genetic factors may be predictors of drug passage in the central nervous system.

Dynamic 18F-Pretomanid PET imaging in animal models of TB meningitis and human studies

Pretomanid is a nitroimidazole antimicrobial active against drug-resistant Mycobacterium tuberculosis and approved in combination with bedaquiline and linezolid (BPaL) to treat multidrug-resistant (MDR) pulmonary tuberculosis (TB). However, the penetration of these antibiotics into the central nervous system (CNS), and the efficacy of the BPaL regimen for TB meningitis, are not well established. Importantly, there is a lack of efficacious treatments for TB meningitis due to MDR strains, resulting in high mortality. We have developed new methods to synthesize 18F-pretomanid (chemically identical to the antibiotic) and performed cross-species positron emission tomography (PET) imaging to noninvasively measure pretomanid concentration-time profiles. Dynamic PET in mouse and rabbit models of TB meningitis demonstrates excellent CNS penetration of pretomanid but cerebrospinal fluid (CSF) levels does not correlate with those in the brain parenchyma. The bactericidal activity of the BPaL regimen in the mouse model of TB meningitis is substantially inferior to the standard TB regimen, likely due to restricted penetration of bedaquiline and linezolid into the brain parenchyma. Finally, first-in-human dynamic 18F-pretomanid PET in six healthy volunteers demonstrates excellent CNS penetration of pretomanid, with significantly higher levels in the brain parenchyma than in CSF. These data have important implications for developing new antibiotic treatments for TB meningitis.

Cerebrospinal fluid concentrations of fluoroquinolones and carbapenems in tuberculosis meningitis.

Background: Tuberculosis meningitis (TBM) is the most lethal form of TB. It is difficult to treat in part due to poor or uncertain drug penetration into the central nervous system (CNS). To help fill this knowledge gap, we evaluated the cerebrospinal fluid (CSF) concentrations of fluoroquinolones and carbapenems in patients being treated for TBM. Methods: Serial serum and CSF samples were collected from hospitalized patients being treated for TBM. CSF was collected from routine lumbar punctures between alternating timepoints of 2 and 6h after drug administration to capture early and late CSF penetration. Rich serum sampling was collected after drug administration on day 28 for non-compartmental analysis. Results: Among 22 patients treated for TBM (8 with confirmed disease), there was high use of fluoroquinolones (levofloxacin, 21; moxifloxacin, 10; ofloxacin, 6) and carbapenems (imipenem, 11; meropenem, 6). Median CSF total concentrations of levofloxacin at 2 and 6h were 1.34mg/L and 3.36mg/L with adjusted CSF/serum ratios of 0.41 and 0.63, respectively. For moxifloxacin, the median CSF total concentrations at 2 and 6h were 0.78mg/L and 1.02mg/L with adjusted CSF/serum ratios of 0.44 and 0.62. Serum and CSF concentrations of moxifloxacin were not affected by rifampin use. Among the 76 CSF samples measured for carbapenem concentrations, 79% were undetectable or below the limit of detection. Conclusion: Fluoroquinolones demonstrated high CSF penetration indicating their potential usefulness for the treatment of TBM. Carbapenems had lower than expected CSF concentrations.

Safety, Tolerability, and Pharmacokinetic Profile of Single and Multiple Ascending Doses of GB5121, a CNS-Penetrant BTK Inhibitor, in Healthy Subjects

Background: GB5121 is an oral, brain-penetrant, potent, highly selective, irreversible, small molecule Bruton's tyrosine kinase inhibitor (BTKi) in development for hematologic malignancies with CNS involvement. Preclinical studies demonstrated that GB5121 exhibited several characteristics differentiating it from other BTKis, including rapid equilibrium into the brain, increased brain target occupancy, and fast inactivation rate. These characteristics combined with GB5121's kinase selectivity and activity in in vitro and in vivo DLBCL models support its clinical investigation in BTK-driven CNS lymphomas. This first-in-human study was designed to evaluate the single- and multiple-dose safety, tolerability, pharmacokinetics (PK; including CNS penetrance) and pharmacodynamics (PD), the effect of food, drug interactions, and cardiac safety of GB5121 to inform dosing and concomitant medications in clinical studies. Methods: This is an ongoing Phase 1, double-blind, randomized, placebo-controlled, single ascending and multiple ascending dose (SAD, MAD) study in healthy subjects, with staggered dose escalations and adaptive dose selection. Safety is assessed throughout the study and PK and PD are characterized using serial blood samples collected up to 48 hours post-dose for GB5121 plasma concentrations, BTK target occupancy (TO), and target engagement (TE). Cerebrospinal fluid (CSF) samples are collected at 2 hours post-dose to characterize the relationship between GB5121 plasma concentrations and CNS penetrance. GB5121 PK parameters (e.g., AUClast, AUCinf, Cmax, Tmax, t1/2) are estimated by standard noncompartmental methods. Results: Preliminary PK results from 3 completed SAD cohorts are presented, including 23 subjects (7 receiving 5 mg, 8 receiving 15 mg, and 8 receiving 45 mg: randomized in a 3:1 ratio to receive GB5121 or placebo) in a fed state (moderate-fat meal). A review of blinded safety data thus far indicated that the study drug was generally well tolerated with no serious adverse events or early study discontinuations reported. PK parameters are presented in Table 1. GB5121 was rapidly absorbed following oral administration with mean plasma Tmax ranging from 1-2 hours and exhibited a terminal half-life of approximately 3 hours. Single-dose GB5121 exposure (AUCinf) increased in a greater than dose-proportional manner from 5 to 15 mg and near dose-proportional from 15 to 45 mg. Mean GB5121 CSF:unbound plasma concentration ratios approximated 1, indicating unimpeded access of unbound drug in plasma into the CNS. The observed GB5121 plasma exposure, CNS penetrance, and preliminary TO and TE PD data were consistent with that of a translational PK/PD model. Conclusions: Data from the first 3 SAD cohorts in healthy subjects indicated that low doses of GB5121 provided plasma exposure and CSF penetrance adequate to drive desired BTK inhibition in the CNS. Blinded safety data indicated that single-dose study drug administration was well tolerated across the dose range. PD analysis and additional evaluations are ongoing and final results will be presented. The safety and PK profiles of GB5121 support its continued evaluation in the ongoing Phase 1b/2 open-label, international study in adult subjects with relapsed/refractory primary/secondary CNS lymphoma, or primary vitreoretinal lymphoma (STAR CNS; NCT05242146). Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Preclinical and clinical evaluation of the LRRK2 inhibitor DNL201 for Parkinson's disease.

Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most common genetic risk factors for Parkinson's disease (PD). Increased LRRK2 kinase activity is thought to impair lysosomal function and may contribute to the pathogenesis of PD. Thus, inhibition of LRRK2 is a potential disease-modifying therapeutic strategy for PD. DNL201 is an investigational, first-in-class, CNS-penetrant, selective, ATP-competitive, small-molecule LRRK2 kinase inhibitor. In preclinical models, DNL201 inhibited LRRK2 kinase activity as evidenced by reduced phosphorylation of both LRRK2 at serine-935 (pS935) and Rab10 at threonine-73 (pT73), a direct substrate of LRRK2. Inhibition of LRRK2 by DNL201 demonstrated improved lysosomal function in cellular models of disease, including primary mouse astrocytes and fibroblasts from patients with Gaucher disease. Chronic administration of DNL201 to cynomolgus macaques at pharmacologically relevant doses was not associated with adverse findings. In phase 1 and phase 1b clinical trials in 122 healthy volunteers and in 28 patients with PD, respectively, DNL201 at single and multiple doses inhibited LRRK2 and was well tolerated at doses demonstrating LRRK2 pathway engagement and alteration of downstream lysosomal biomarkers. Robust cerebrospinal fluid penetration of DNL201 was observed in both healthy volunteers and patients with PD. These data support the hypothesis that LRRK2 inhibition has the potential to correct lysosomal dysfunction in patients with PD at doses that are generally safe and well tolerated, warranting further clinical development of LRRK2 inhibitors as a therapeutic modality for PD.

Pharmacokinetics of metronomic temozolomide in cerebrospinal fluid of children with malignant central nervous system tumors

PurposeAlthough temozolomide is widely used in the treatment of childhood central nervous system (CNS) tumors, information on its pharmacokinetic profile in the brain or cerebrospinal fluid (CSF) is sparse. This study aimed at investigating whether measurable and clinically relevant concentrations of temozolomide are reached and maintained in CSF for continuous oral administration in pediatric patients. A population pharmacokinetic model was developed to quantify CSF penetration of temozolomide.MethodsEleven pediatric CNS tumor patients (aged 4–14 years) treated with oral temozolomide using a metronomic schedule (24–77 mg/m2/day) were included. Temozolomide concentrations in 28 plasma samples and 64 CSF samples were analyzed by high-performance liquid chromatography. Population pharmacokinetic modeling and simulations were performed using non-linear mixed effects modeling (NONMEM 7.4.2).ResultsMedian temozolomide concentrations in plasma and CSF were 0.96 (range 0.24–5.99) µg/ml and 0.37 (0.06–1.76) µg/ml, respectively. A two-compartment model (central/plasma [1], CSF [2]) with first-order absorption, first-order elimination, and a transit compartment between CSF and plasma adequately described the data. Population mean estimates for clearance (CL) and the volume of distribution in the central compartment (Vc) were 3.29 L/h (95% confidence interval (CI) 2.58–3.95) and 10.5 L (8.17–14.32), respectively. Based on simulations, we found a median area under the concentration vs. time curve ratio (AUCCSF / AUCplasma ratio) of 37%.ConclusionMetronomic oral temozolomide penetrates into the CSF in pediatric patients, with even higher concentration levels compared to adults.