The sensitive clays exhibit a decrease in shear strength at high strains and have low remolded shear strength. As a result, when a landslide occurs in sensitive clays, the failed soil mass behaves like a fluid, potentially causing flow-like disasters with extreme mobility. After the initial failure, the exposed slope may experience additional retrogressive failures due to the lack of support from the landslide deposits. To assess the landslide risk on sensitive clays, the NGI-ADP-Soft constitutive model was implemented in the ANURA3D software to simulate retrogressive slope failures and large displacements via the material point method (MPM) while considering shear-softening behavior and different shear modes (active, direct simple, passive) along the slip surface. The NGI-ADP-Soft model in ANURA3D was verified by comparing the results of the biaxial compression simulation with the NGI-ADP-Soft implemented in PLAXIS2D via finite element methods (FEM). The landslide at Gjerdrum, Norway, in 2020 was simulated to provide insights into the mechanisms of retrogressive failures in sensitive clays and contribute to understanding landslide propagation. The simulation results were compared with the observations. The effects of anisotropic hardening and mesh sizes on the Gjerdrum landslide were investigated through a parametric study.