Poor prognosis for many brain tumors is partly attributed to the limited penetration of hydrophilic anticancer agents across the blood-brain barrier (BBB). Historical intracranial dye studies suggested that direct delivery into the central nervous system can bypass the BBB. This study evaluated whether a protracted intraventricular infusion of the hydrophilic antimetabolite gemcitabine achieves therapeutically relevant central nervous system concentrations and whether such delivery is tolerated in a large-animal model.
The investigators used complementary approaches in small and large animals and in vitro assays. Distribution of a hydrophilic vital dye (Bleu Patente) was compared after intracranial versus intravenous injection in guinea pigs, and after a 24-hour protracted intraventricular infusion in sheep to assess tissue penetration from ventricular CSF into cortex. Gemcitabine concentrations in biological samples were measured by high-performance liquid chromatography. Human glioblastoma cell lines (A172, U87-MG, U118-MG) were exposed to gemcitabine in vitro and then maintained in drug-free medium for 72 hours prior to viability assessment with Crystal Violet. Tolerance of a single 24-hour intraventricular infusion of gemcitabine (20 mg) was evaluated in sheep.
Gemcitabine, a hydrophilic antimetabolite, was quantified in cerebrospinal fluid (CSF) and brain tissue using validated high-performance liquid chromatography. In vitro potency was assessed by determining concentrations required to produce 90% inhibition (IC90) for the three tested human glioblastoma cell lines; the abstract reports that measured in vivo concentrations were compared against these IC90 values.
In guinea pigs, intracranial injection of the hydrophilic dye produced visible staining of brain tissue, whereas intravenous administration did not stain the brain, demonstrating limited systemic-to-parenchymal diffusion for the dye when given intravenously. After a 24-hour intraventricular infusion in sheep, the dye penetrated deeply into the cerebral cortex, indicating that prolonged ventricular delivery enables distribution from the CSF into brain parenchyma.
In guinea pigs, brain concentrations of gemcitabine were higher after intracranial injection than after intravenous administration. In the sheep model, following a 24-hour intraventricular infusion of 20 mg gemcitabine, mean concentrations at the end of infusion were reported as 1,415 micrograms per liter (µg/l) in CSF and 850 micrograms per kilogram (µg/kg) in brain tissue. These measured concentrations exceeded the IC90 values for the A172, U87-MG, and U118-MG human glioblastoma cell lines tested in vitro, indicating that the delivered doses achieved levels expected to be cytotoxic to these cell lines.
A single 24-hour intraventricular infusion of 20 mg gemcitabine was described as being well tolerated in the sheep evaluated. The abstract reports good tolerance but does not provide detailed safety endpoints, neurological assessments, or histopathologic findings in the source text.
Based on the observed penetration of dye and gemcitabine from ventricular CSF into cortex, the authors hypothesize that intraventricular administration allows hydrophilic drugs to circumvent the blood-brain barrier by leveraging the glymphatic system — a CSF-mediated pathway facilitating fluid and solute movement into brain interstitium.
Given the high CSF and brain concentrations achieved after a 24-hour intraventricular infusion and the reported tolerability in sheep, the authors propose clinical investigation of protracted intraventricular gemcitabine for patients with refractory primary and secondary brain tumors and for meningeal metastasis. The proposal is framed as a next-step recommendation rather than as clinical evidence of efficacy in humans.
The abstract does not report patient data, human safety or efficacy outcomes, long-term tolerability, or specific infusion protocols for clinical use. Detailed adverse-event profiling, dose-escalation data, repeated-dose safety, and clinical efficacy endpoints were not provided in the source abstract and therefore are not available in this summary.
Protracted intraventricular infusion of gemcitabine produced deep cortical penetration of a hydrophilic dye and achieved CSF and brain concentrations in sheep that exceeded in vitro IC90s for several glioblastoma cell lines, with a single 24-hour 20 mg infusion described as well tolerated. The authors suggest the approach merits clinical evaluation to overcome the blood-brain barrier for treatment of refractory brain tumors and meningeal metastasis.