(W0930-02-08) Lumbar Intrathecal Infusion of an siRNA Formulation via Cannulation in Rats Demonstrated Comparable Tissue Distributions and Improved Animal Response as Comparing to Non-Cannulated Free Hand Method

Purpose: To compare the drug exposure, tissue distribution and animal reaction after two intrathecal (IT) siRNA delivery techniques, via a pre-implanted cannula or via free-hand administration.

Methods: Two rats with IT-catheter implanted between T13 and L1 and extended to L3-L5 were used in the present study. An siRNA formulated in sterile artificial CSF (aCSF) was infused via a pump at approximately 1 µL/sec for 20-30 seconds to the conscious rats with a total volume of 30 µL. Pressure was held for an additional 1-2 minute before the catheter was locked by sterile aCSF. A modified Mini-Irwin test was performed 24 hrs post dose and terminal collections including brain (hippocampus, prefrontal cortex, striatum, and cerebellum), spinal cord (cervical, thoracic, and lumbar regions), kidney, and liver were performed. Levels of the siRNA, as expressed as its antisense strand, in all tissue samples were quantified via a LC-MS/MS method based on a calibration curve prepared in rat brain homogenate (LLOQ = 25 ng/mL). Historical data collected from five non-cannulated rats, intrathecally dosed with the same siRNA and sacrificed 14 days post-dose were used in the comparisons.

Results: Both animals treated with the siRNA via cannulated IT administration showed detectable siRNA levels in all tissue types (central and peripheral) examined in this study (Figure 1).  There is no observable difference noted between cannulated and non-cannulated rats in terms of tissue distribution and exposure of the siRNA (Figure 2). Rats that underwent cannulated IT administration exhibited normal, undisturbed behaviors 24 hrs post dose with normal auditory reflexes and tail suspension ability.  No noticeable stress signals were observed during and after the IT infusion (Table 1).

Conclusion: The IT-cannulation delivery resulted in comparable siRNA exposures in rat brain and spinal cord. No noticeable stress was observed in the cannulated animals at the time of IT infusion. The administration did not need the use of anesthesia. This technique may improve the overall animal welfare of lumbar intrathecal administration and study quality/consistency.

Acknowledgements: The work conducted was reviewed and approved by WuXi AppTec’s Institutional Animal Care and Use Committee (IACUC) according to the Guide for the Care and Use of Laboratory Animals.


Figure 1 Tissue Exposure of the siRNA in Rat Brain, Spinal Cord, and Peripheral Tissues from the IT-Cannulated Administration


Figure 2 Tissue Exposure Comparison of the siRNA in Rat Brain and Spinal Cord from Cannulated vs. Non-cannulated IT-Administrations


Table 1 Post Administration Mini-Irwin Functional Observation Battery Test in Cannulated IT-dosed Rats