The present invention provides a novel crystalline form of verubecestat (Crystalline Form II of Verubecestat) and pharmaceutically acceptable compositions thereof, each of which may be useful in treating, preventing, ameliorating, and/or delaying the onset of an Aβ pathology and/or a symptom or symptoms thereof. Non-limiting examples of such Aβ pathologies, including Alzheimer's disease and mild cognitive impairment, are disclosed herein.