Abstracts

Rationale: For treatment of refractory epilepsy, Cerebral Therapeutics, Inc. is developing a combination drug-device product to deliver a proprietary formulation of sodium valproate injection (CT-010) direct to the central nervous system (CNS) via continuous intracerebroventricular (ICV) infusion.

Quantitative Mass spectrometry imaging (QMSI) allows the visualization and quantification of the spatial distribution of proteins, peptides, small-molecule drugs (and their metabolites), biomarkers or other chemicals within thin slices of animal tissues.

The objective of this work was to evaluate the distribution and quantification of valproic acid (VPA), its metabolites, and gamma-aminobutyric acid (GABA) in rats by Matrix-Assisted Laser Desorption/Ionization (MALDI) imaging following 3-days of continuous ICV infusion of CT-010.

Methods: Ten male rats were surgically implanted with an ICV cannula attached to an ALZET® osmotic pump and administered 0.9% sodium chloride (preservative free) or CT-010 at 50 mg/mL sodium valproate by continuous ICV infusion for 3 days. The nominal flow rate was 2.5 µL/hr.

MALDI MSI analysis was performed for the detection of Valproic acid, its metabolites and GABA using a Solarix 7T MALDI-FTICR (Bruker Daltonics, Billerica, MA) equipped with a Smartbeam II laser at a repetition rate at 2000 Hz. For the detection of VPA and its metabolites, mass spectra were acquired in positive mode with a Continuous Accumulation of Selected Ions (CASI) mode of acquisition within m/z 338 to 358 Da range and a spatial resolution of 100 µm. For the detection of GABA, mass spectra were acquired in positive with a Continuous Accumulation of Selected Ions (CASI) mode of acquisition within m/z 255 to 295 Da range and a spatial resolution of 100 µm. The mass spectrum obtained for each position of the images corresponded to the averaged mass spectra of 300 consecutive laser shots on the same location. Bruker software packages including suite FTMS control 2.2.0 and FlexImaging 5.0 were used for recording the data and the previsualization of the data.

Multimaging™ 1.2.5.9 (ImaBiotech, Boston, MA) was used to create the molecular distributions, determine absolute quantification of valproate and relative quantitation of its metabolite as well as GABA.

Results: The plasma levels of VPA just prior to necropsy are presented.

Mass Spectrometry Imaging (MSI) allowed the evaluation of the distribution and the quantification of VPA, its metabolites as well as GABA in the rat male brain treated by an ICV continuous infusion of CT-010. The comparison of the distribution as well as the quantification data of GABA shows one effect of valproate treatment is an increase in GABA levels in the mail rat brain.

Conclusions: MSI helped better understand the distribution of VPA, its metabolites, and the impact of these on GABA concentrations in different regions of the brain. One effect of ICV infusion of sodium valproate in male rat brains is an increase in GABA.

Funding: Please list any funding that was received in support of this abstract.: None.