LRRK2 and Parkinson disease: However, when considering that both amplifications (gain of function) and whole gene deletions (loss of function) of LRRK2 are associated with a worse prognosis in cancer, it must be acknowledged that the modulation of the kinase activity by LRRK2 small molecule inhibitors in G2019S-mutated PD patients might lead to a normal kinase function rather than a loss of kinase activity.