  We have studied the prospects of using the Drell-Yan dilepton process in
pion-nucleus collisions as a novel input in the global analysis of nuclear
parton distribution functions (nPDFs). In a NLO QCD framework, we find the
measured nuclear cross-section ratios from the NA3, NA10 and E615 experiments
to be largely insensitive to the pion parton distributions and also compatible
with the EPS09 and nCTEQ15 nPDFs. These data sets can thus be, and in EPPS16
have been, included in global nPDF analyses without introducing significant new
theoretical uncertainties or tension with the other data. In particular, we
explore the constraining power of these data sets on the possible flavour
asymmetry in the valence-quark nuclear modifications. Moreover, using the
COMPASS kinematics we present predictions for pion charge-difference ratio, a
new measurable which could help to further constrain this asymmetry.
