## 4 Discussion  
The concept of the present study has been successfully applied to support first-in-human clinical trials and has found acceptance by regulatory bodies (BfArM in Germany). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Sex**} & \multicolumn{4}{c}{**NVP13**} \\ \cline{2-5}  & \multicolumn{2}{c}{**Males**} & \multicolumn{2}{c}{**Females**} \\ \hline Dose Level (mg/animal) & 0.4 & 4.0 & 0.4 & 4.0 \\ \hline Number Examined & 4 & 4 & 4 & 4 \\
**Brain** & & & & \\ Vacuoles, neuron & & & & \\  & Minimal & 0 & 1 & 0 & 1 \\ Infiltrate, mononuclear cells & & & & \\  & Minimal & 3 & 2 & 2 & 4 \\ Slight & & 1 & 2 & 2 & 0 \\ Perivascular cuff & & & & & \\  & Minimal & 0 & 2 & 1 & 0 \\  & Slight & 0 & 0 & 1 & 0 \\ Edema, meninges & & & & & \\  & Minimal & 3 & 3 & 2 & 2 \\  & Slight & 1 & 1 & 2 & 1 \\ Gliosis & & & & & \\  & Minimal & 0 & 0 & 1 & 1 \\
**Spinal cord, cervical** & & & & & \\  & Infiltrate, mononuclear cells & & & & \\  & Minimal & 2 & 3 & 3 & 1 \\  & Slight & 1 & 0 & 0 & 0 \\
**Spinal cord, thoracic** & & & & & \\  & Infiltrate, mononuclear cells & & & & \\  & Minimal & 2 & 3 & 2 & 2 \\  & Slight & 0 & 0 & 0 & 1 \\
**Spinal cord, lumbar** & & & & & \\  & Infiltrate, mononuclear cells & & & & \\  & Minimal & 3 & 1 & 2 & 2 \\  & Slight & 1 & 2 & 1 & 2 \\ Inflammation, subacute; dura & & & & & \\  & Slight & 1 & 1 & 1 & 0 \\
**Intratheal Injection Site** & & & & & \\  & Infiltrate, mononuclear cells & & & & \\  & Minimal & 2 & 2 & 2 & 4 \\  & Slight & 2 & 2 & 2 & 0 \\ Inflammation, subacute; dura & & & & & \\  & Slight & 0 & 2 & 2 & 1 \\ \hline \hline \end{tabular}
\end{table} 
Table 11: Incidence and severity of NVP-13-related microscopic findings in Phase C. Repeated intrathecal NVP-13 administration for 13 consecutive weeks (Phase C) resulted in minimal to slight microscopic dose-independent alterations withing central nervous tissue. The entire non-GLP program was completed within less than 6 months and represents a valuable blueprint for fast-track development of oligonucleotides. Furthermore, applying the described concept will result in using fewer animals in comparison to the conduct of three independent studies (maximum tolerated dose study, pharmacokinetic and biodistribution study, and repeated dose-range-finding study). As we move forward with ASO-based therapies [5], the design and conduct of non-human primate studies will require constant review and improvement, as, in comparison to classical small molecules and biologics, comparison data are utmost limited. By measuring ASO concentrations within CNS tissue, CSF, peripheral tissue, and plasma, physiological and physical, neurobehavioral and neurological, but also hematological and clinical chemistry parameters, this study paradigm gives a good characterization profile of the respective test compound. Due to the inability of ASO crossing the blood brain barrier on the one hand and the need for central ASO concentrations to treat neurodegenerative disorders, an intrathecal administration was performed as described in other studies [4]. In vivo NVP-13 i.th. administrations led to dose-dependent ASO concentrations within CNS tissue. Hereby, dose levels indirectly correlated with distance to the respective area of injection, the lumbar spinal cord, which is in line with previous studies in mice, juvenile cynomolgus monkeys, human infants, and own in vivo data ([PERSON] et al., Pharmaceuticals, under review). Within the CNS, ASOs are well distributed by intrinsic CSF dynamics. For details, see [PERSON] et al., 2019 [4]. NVP-13 levels were also detectable in peripheral organs, namely the kidney and the liver, at treatment active drug levels, but also indicating the regular physiological way of substance distribution and decay. Calculation for gender ratios (male/female) indicated sex differences in the toxicokinetics of NVP-13 following i.th administration. Further, concentration-time profiles show a general enhancement of NVP-13 levels with increasing dose levels for all three phases.