Table 2.

Comparison of different oligonucleotide delivery routes

Route	Delivery site	Convenience to patients	Probability of adverse events	Applicability to CNS delivery of naked ODNs
Oral (PO)	By mouth	++++++	+	−
Intranasal	Inhalation or application of gel/liquid formulation inside the nose	++++++	+	++
Subcutaneous injection (SC)	Intra-skin injection	++++	++	−
Intraperitoneal injection (IP)	Injection into body cavity	++	+++	−
Intramuscular injection (IM)	Injection deep into the muscle	+++	+++	N.A.
Intravenous injection (IV)	Injection directly into vein	+++	++++	−
Intrathecal injection (IT)	Injection through brain/spinal cord sheath, usually between lumbar vertebrae	++	+++++	++++++
Intracerebroventricular injection (ICV)	Injection deep inside the brain, into a ventricle, requires brain surgery to install a catheter	+	++++++++	++++++

+, high; N.A., not applicable; −, low