Low Pulsed Electrical Fields for Inducing Subtle/transient BBB Disruption, Depicted by the Trams, Enabling Efficient Delivery of Therapeutic Drug Doses into the Brain: Study in Mice

Introduction: Brain diseases are extremely hard to treat, mainly due to poor drug penetration across the BBB. We have discovered that low pulsed electric fields (L-PEFs) can induce transient BBB disruption (BBBd) non-invasively.

Methods: Electrodes were pressed against the skulls of anesthetized mice and 25-400 pulses were applied (50µs pulses, 100-300V, 4Hz, treatment duration 25-100sec). BBBd extent was studied by BBB maps, calculated from delayed-contrast MRI using pixel-by-pixel 3-exponential fit analysis, by Evans-Blue studies, and by brain concentrations assays of different sizes therapeutics (Doxorubicin 580Da, ATX-Potential biologics for AD 54KDa and Herceptin 150KDa). Antineoplastic efficacy was studied by applying combined L-PEFs (25 pulses, 300V) with Doxorubicin (IV) to nude mice bearing U87 glioma tumors. Tumor/treatment-effects volumes were calculated using our previously introduced MRI-based TRAMs.

Results: Significant BBBd was depicted in the BBB maps for all treatment parameters. Significant correlation was found between BBBd volumes and L-PEFs parameters (amplitude and number of pulses: r2=0.91 and 0.96, respectively) in agreement with the Evans-Blue results. Full BBB recovery was achieved at 1h for 100V and 4hrs for 300V.
Drug accumulation studies showed increased brain concentrations of all tested drugs. Doxorubicin brain concentration 4hrs post L-PEFs was 885±85 µM, which is X431 its IC50 in GL261 glioma cells while undetected in the sham group. ATX showed an increase of X13 (p < 0.0001) and Herceptin X13.7 (p < 0.004) compared to sham.
Preliminary efficacy results revealed that mice treated with L-PEFs+Doxorubicin showed significantly lower tumor growth rates (1.13±0.23 vs 2.26±0.44, p< 0.02) and larger volumes of treatment-effects (44.0±8.8% vs 13.4±7.8% of the enhancing lesion volumes, p< 0.04) compared with Doxorubicin only.

Conclusion : These results demonstrate the feasibility of delivering therapeutic drug doses into the brain by transient/safe BBBd, induced in a mouse model by L-PEFs, leading the way to new means for efficient, non-invasive drug delivery into the CNS.