A Phase 2a Study of TPN-101 in Patients With C9ORF72 ALS/FTD

Inclusion Criteria: * Documentation of a clinical genetic test demonstrating a hexanucleotide repeat expansion (HRE) in the C9orf72 gene * Has a reliable caregiver/informant to accompany the patient to all study visits For patients with ALS (with or without FTD): * Diagnosis of ALS (probable, possible, laboratory-supported probable or definite) according to the World Federation of Neurology revised E1 Escorial criteria * Onset of weakness within 3 years prior to Screening * Slow vital capacity (SVC) ≥ 60% of predicted normal adjusted for sex, age, and height (from the sitting position) * Able to perform reproducible pulmonary function tests. * ALS Functional Rating Scale-Revised (ALSFRS-R) ≥ 30 and score of 3 or 4 on Item #3 (swallowing) at Screening For patients with FTD: * A gradual, progressive decline in behavior, language, or motor function consistent with mild cognitive impairment, mild behavioral impairment, mild cognitive/behavioral impairment, behavioral variant FTD, primary progressive aphasia, or amnestic syndrome * CDR Dementia Staging Instrument plus National Alzheimer's Coordinating Center Behavior and Language Domains (CDR plus NACC FTLD) global score of 0.5-2.0 at Screening Exclusion Criteria: * Presence of other significant neurological or psychiatric disorders * History of clinically significant brain abnormality * Clinically significant medical illness * Tracheostomy or diaphragmatic pacing * Autoimmune disease requiring treatment or management (quiescent rheumatoid arthritis, psoriasis, or controlled Type 1 diabetes are acceptable) * History of human immunodeficiency virus (HIV) or hepatitis B infection, or any active infection during Screening, unless the patient will have been symptom-free for at least 30 days prior to randomization