This clinical study is designed to study the effect of a single dose of varegacestat on cardiac repolarization in healthy adult participants.

This is a double-blind (with respect to varegacestat and placebo only), single-dose, randomized, placebo- and positive- controlled, 3-way crossover study.

On Day 1 of each period, participants will receive one of 3 treatments: a single dose of varegacestat (Treatment A), a single dose of varegacestat matching placebo (Treatment B), or a single dose of moxifloxacin (Treatment C). In each period, cardiodynamic ECGs will be collected predose and for 24 hours postdose. PK samples will be collected predose and up to 168 hours post-dose for assessments of varegacestat and AL102 MTB, and up to 24 hours post-dose for assessment of moxifloxacin.

There will be a washout of at least 14 days between doses. Safety will be monitored throughout the study by repeated clinical and laboratory evaluations.

Inclusion Criteria:

• Healthy, adult, male or female (of non childbearing potential), 18 to 55 years of age, inclusive, at the screening visit.
• Medically healthy with no clinically significant medical history, physical examination, clinical laboratory profiles, and vital signs, as deemed by the PI or designee

Exclusion Criteria:

• History of any illness that, in the opinion of the PI or designee, might confound the results of the study or pose an additional risk to the participant by their participation in the study.
• Have taken an investigational drug or participated in a clinical trial evaluating an investigational drug or device within 30 days (or 5 half-lives) prior to the study drug dose, whichever is longer.

Double (Participant, Investigator) This is a double-blind study (with respect to varegacestat and placebo only; moxifloxacin will be open label).