As described in the introduction, we have previously evaluated the disease-mechanism and identified a possible drug treatment candidate for HSP-SPAST using patient-derived stem cell models: olfactory neurosphere-derived stem cells and iPS cell derived-neurons (Abrahamsen et al., 2013; Fan et al., 2014; Wali et al., 2016, 2018, 2020). The gene discussed is SPAST; the disease is hereditary spastic paraplegia.