The work at hand introduces a regularized microplane damage formulation into the Material Point Method (MPM) using an implicit time integration scheme. A material characterization at finite deformations to describe rock-like materials is applied, which is characterized by strain-softening behavior. The nonlinear response of the material is captured by a damage formulation within the microplane framework. Regularization of the model is achieved by an implicit gradient enhancement. The model is implemented into an in-house Material Point Method code, and its capabilities are shown by a numerical example.