Inclusion Criteria:
- Confirmation of C9orf72 mutation - Diagnosis of ALS by revised El Escorial criteria - Time since onset of muscle weakness due to ALS ≤36 months at the time of the Screening Visit - Slow Vital Capacity (VC) ≥50% of predicted capacity at the time of the Screening Visit - If taking riluzole, must be on a stable dose of riluzole for at least 30 days prior to the Screening Visit. Riluzole naive participants are allowed.
- If taking edaravone, must have completed at least one cycle of edaravone prior to the Screening Visit and plan to continue edaravone during the study. Edaravone naive participants are allowed.
- Females must not be pregnant, breastfeeding or planning to conceive within the study period. Males must agree to use acceptable contraception - Capable of providing informed consent at the Screening visit and complying with study procedures throughout the study Exclusion Criteria:
- Clinically significant, unstable, medical condition (other than ALS) - Clinically significant heart disease, liver disease or kidney disease - Cognitive impairment or dementia - Current uncontrolled hypertension - History of unresolved cancer - Any experimental gene therapy - Any experimental vaccine (any vaccine against COVID-19 either approved or administered under an Emergency Use Authorization is allowed)

This is a phase 2 double-blind, placebo-controlled trial to test the safety, tolerability, pharmacokinetics, and pharmacodynamics of AL001 in participants with C9orf72-associated Amyotrophic Lateral Sclerosis.

• Alector Inc.

NCT05053035 (First Published: 9/1/2021)