  Generalized parton distributions (GPDs) encoding multidimensional information
of hadron partonic structure appear as the building blocks in a factorized
description of hard exclusive reactions. The nucleon GPDs have been accessed by
deeply virtual Compton scattering and deeply virtual meson production with
lepton beam. A complementary probe with hadron beam is the exclusive
pion-induced Drell-Yan process. We discuss recent theoretical advances on
describing this process in terms of the partonic subprocess convoluted with the
nucleon GPDs and the pion distribution amplitudes. Furthermore, we mention the
feasibility study for measuring the exclusive pion-induced Drell-Yan process,
$\pi^- p \to \mu^+ \mu^- n$, via a spectrometer at the High Momentum Beamline
being constructed at J-PARC in Japan. We also point out the possible soft
partonic mechanisms beyond the QCD factorization framework, which could give
important contributions at J-PARC kinematics, and present an estimate of the
soft mechanisms making use of dispersion relations and quark-hadron duality.
Realization of the measurement of the exclusive pion-induced Drell-Yan process
at J-PARC will provide a new test of QCD descriptions of a novel class of hard
exclusive reactions. It will also offer the possibility of experimentally
accessing nucleon GPDs at large timelike virtuality.
