Pulsed electric fields for non-invasive/efficient delivery of therapeutics into the CSF and assessment of resulting CSF dynamics using delayed-contrast MRI

Introduction: Leptomeningeal diseases are extremely hard to treat, mainly due to poor drug penetration across the blood-CSF-barrier (BCSFB). We have previously shown that pulsed electrical fields (PEFs) can be applied non-invasively for inducing BBB disruption for efficient drug delivery into mice brains. Here we demonstrate PEFs application for transient BCSFB disruption (BCSFBd).

Methods: Electrodes were pressed against the scalps of anesthetized rats and 100 50µs pulses were applied (300-700V, 4Hz, 25sec). BCSFBd dynamics were studied by treatment-response-assessment-maps (TRAMs) calculated from delayed-contrast MRI, by Evans-Blue studies, and by CSF concentrations assays of different therapeutics (Doxorubicin 580Da, ATX-potential biologics for AD 54KDa and Herceptin 150KDa). Pixel-by-pixel MR image dynamics analysis of the segmented CSF regions included fitting to bi-exponential function. Pixels showing r2 < 0.6 were excluded. The volume of contrast accumulation was calculated from pixels with signal increase of >5% and the volume of contrast clearance was calculated from pixels with negative slops.

Results: CSF drug concentration analysis showed significant BCSFBd for all molecules and all treatment parameters. Following PEFs, small molecules penetration over the BCSFB was increased by up to x11±1 vs sham. Proteins by x22.5±5 and antibodies by x20±8. BCSFB function reached full recovery up to 4 hrs post-PEFs.
Volumes of contrast accumulation, depicted red in the TRAMs, increased exponentially with the applied voltage (r²=0.99), while time to peak decreased linearly (r²=0.98). Volumes of contrast clearance, depicted blue, were unaffected by PEFs, suggesting no effect on CSF clearance rates. The clearance slope was x2.4 faster for the sham versus treated rats (p < 0.03), with no correlation between the slope and the applied voltage.

Conclusion : These results demonstrate the feasibility of delivering therapeutic drug doses into the CSF by transient/safe BCSFBd, induced in rats by PEFs, leading the way to new efficient, non-invasive treatments for leptomeningeal diseases.