• Number of subjects experiencing unacceptable safety or tolerability events after oral administration of KNS-760704 compared to placebo for 12 weeks in subjects with ALS (Part 1) [ Time Frame: 12 weeks ] [ Designated as safety issue: Yes ]
  

• Number of subjects experiencing unacceptable safety or tolerability events after oral administration of KNS-760704 compared to placebo for up to 76 weeks in subjects with ALS (Part 2) [ Time Frame: 76 weeks ] [ Designated as safety issue: Yes ]
  
• Change from Baseline in ALSFRS-R [ Time Frame: 12 weeks (part 1) and 28 weeks (part 2) ] [ Designated as safety issue: Yes ]
  
• Change from baseline to Week 12 in upright and supine vital capacity [ Time Frame: 12 weeks ] [ Designated as safety issue: No ]
  
• Changes in cystatin C and neurofilament H [ Time Frame: 12 weeks ] [ Designated as safety issue: No ]
  

This is a double-blind, randomized, placebo-controlled study evaluating the safety and efficacy of KNS-760704 compared to placebo. The study will be conducted in 2 parts.

In Part 1, approximately 80 eligible patients will be randomized to 1 of 4 treatment groups for 12 weeks of treatment: placebo; low-dose; mid-dose; or high-dose KNS-760704. Participants meeting eligibility requirements will be enrolled at approximately 20 centers in the U.S. In addition to the visit to determine eligibility and the first visit to take study drug, participants will be required to make 5 additional research clinic visits in Part 1.

Participants who complete all 12 weeks of Part 1 will be eligible for randomization to Part 2. The duration of Part 2 of the study is 76 weeks. Subjects will receive 1 of 2 active treatment groups for 72 weeks (low-dose or high-dose KNS-760704) and placebo for the remaining 4-week period in Part 2. Participants will not be told when the 4 weeks of placebo treatment will be given. During Part 2, participants will be required to make 12 research clinic visits, including the baseline visit.