  We calculate radiative corrections to the light-cone sum rule for the
semileptonic form factor in $B\to\pi e\nu$ decays and thus remove the major
uncertainty in determining the CKM mixing angle $|V_{ub}|$ by this method. We
discuss the remaining uncertainties and perspectives for further studies. The
structure of the radiative corrections suggests factorization of soft
(end-point) and hard rescattering contributions in heavy-to-light decays in the
heavy quark limit.
