A Study to Evaluate the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of DNL593 in Healthy Participants and Participants With Frontotemporal Dementia (FTD-GRN)

Key Inclusion Criteria: Part A: * Women of non-childbearing potential (surgically sterilized or post menopausal) or men, aged ≥18 to ≤ 55 years * BMI of ≥ 18 to ≤ 32 kg/m² * When engaging in sex with a woman of child bearing potential, two forms of birth control are required Part B: * Women of non-childbearing potential (surgically sterilized or post menopausal) or men, aged ≥18 to ≤ 80 years. Women who are of childbearing potential but on highly effective, low user dependent contraceptive methods will be allowed. * BMI of ≥ 18 to ≤ 32 kg/m² * Have a Clinical Dementia Rating® plus National Alzheimer's Coordinating Center frontotemporal lobar degeneration global score ≥ 0.5 * Have confirmed granulin (GRN) mutation via genetic testing or historical records available for review by investigator * When engaging in sex with a woman of child bearing potential, both the male participant and his female partner must use highly effective contraception Part C: * All participants who completed Part B of this trial are eligible for an 18-month OLE if the participant has no unresolved clinically significant TEAEs, where continued dosing may represent a risk to participant safety. Key Exclusion Criteria: * Have any history of clinically significant neurologic, psychiatric, endocrine, pulmonary, cardiovascular, gastrointestinal, hepatic, pancreatic, renal, metabolic, hematologic, immunologic, or allergic disease, or other major disorders * Have a history of malignancy, except fully resected basal cell carcinoma or other malignancies at low risk of recurrence * Have a clinically significant history of stroke, cognitive impairment due to causes other than FTD, seizure within 5 years of screening, or head trauma with loss of consciousness within 2 years of screening * Have a positive serum pregnancy test or are currently lactating or breastfeeding