\documentclass{article}

\usepackage{fontspec}

\newfontface{\cuneiform}[Scale=MatchUppercase]{Santakku}
\DeclareTextFontCommand{\textcuneiform}{\cuneiform}

\newcommand{\AN}{\symbol{"1202D}}
\newcommand{\KA}{\symbol{"12157}}

\begin{document}

This is cuneiform \textcuneiform{\AN\KA}.

%This is cuneiform \textcuneiform{𒀭𒅗}.

\end{document}