MAPT and metastatic melanoma: Similarly to AV-1451, MK-6240 exhibits strong off-target binding to neuromelanin- and melanin-containing cells including pigmented neurons in the substantia nigra (regardless of the presence or absence of nigral tau pathology), leptomeningeal melanocytes, metastatic melanoma and retinal pigment epithelium, with some weaker off-target binding to brain hemorrhages as well.