TTP02-28 Subleading Shape Functions and the Determination of $V_{ub}$

The endpoint region of the inclusive lepton energy spectrum in $B \to X_u \ell \bar\nu$ can be used for a determination of $V_{ub}$ by comparing it to the endpoint region of the inclusive photon spectrum of $B \to X_s \gamma$. We consider the subleading twist contributions to this $V_{ub}$ determination.