A Study to Evaluate the Effects of Multiple Doses of CK-2017357 in Patients With Amyotrophic Lateral Sclerosis (ALS)

Key Inclusion Criteria: 1. Able to comprehend and willing to sign an Informed Consent Form (ICF) 2. Males or females 18 years of age or older 3. A diagnosis of familial or sporadic ALS (defined as meeting the possible, laboratory-supported probable, probable, or definite criteria for a diagnosis of ALS according to the World Federation of Neurology El Escorial criteria) 4. Maximum voluntary grip strength in at least one hand between 10 \& 40 pounds (females) and 10 \& 60 pounds (males) 5. Upright Slow Vital Capacity (SVC) \>50% of predicted for age, height, and sex 6. Able to swallow tablets with water 7. Willing and able to remain off riluzole for 4 weeks (Part A only) 8. Currently taking and tolerating a stable dose of 50 mg BID riluzole (Part B only) 9. Willing and able to reduce daily dose of riluzole to 50 mg for 4 weeks (Part B only) 10. Willing and able to refrain from caffeine-containing products during study participation 11. Willing and able to remain off warfarin and theophylline-containing medications during study participation 12. Has a caregiver who is capable of observing and reporting patient status, and also assisting in the proper use of nocturnal oximetry equipment 13. Able to perform pulmonary function tests Key Exclusion Criteria: 1. Life expectancy \<3 months 2. Participation in any trial in which receipt of investigational study drug occurred within 30 days or 5 half-lives of the prior agent, whichever is greater, prior to dosing 3. Any prior treatment with CK-2017357 4. Use of non-invasive positive pressure ventilation (NIPPV) for any part of the day or night Other protocol-defined inclusion/exclusion criteria may apply.