For a special class of bipartite states we calculate explicitly the asymptotic relative entropy of entanglement E∞R with respect to states having a positive partial transpose. This quantity is an upper bound to distillable entanglement. The states considered are invariant under rotations of the form O⊗O, where O is any orthogonal matrix. We show that in this case E∞R is equal to another upper bound on distillable entanglement, constructed by Rains. To perform these calculations, we have introduced a number of results that are interesting in their own right: (i) the Rains bound is convex and continuous; (ii) under some weak assumption, the Rains bound is an upper bound to E∞R (iii) for states for which the relative entropy of entanglement ER is additive, the Rains bound is equal to ER.