The goal of this Phase 1 interventional study is to assess the safety, tolerability and pharmacokinetics of ATH-1105 in healthy male and female participants.

The study is a Phase 1, First-In-Human study consisting of two parts (A and B). Part A will comprise a single-dose, double-blind, placebo-controlled, sequential-group design. Part B will comprise a multiple-dose, placebo-controlled, sequential-group design.

Inclusion Criteria:

• Body mass index between 18.0 and 32.0 kg/m2 inclusive.
• In good health, determined by no clinically significant findings from medical history, 12-lead ECG, vital signs measurements, and clinical laboratory evaluations at screening and check-in or predose on Day 1
• Females will not be pregnant or lactating, and females of childbearing potential and males will agree to use contraception
• Able to comprehend and willing to sign an ICF and to abide by the study restrictions.

Exclusion Criteria:

Medical Conditions:

• Significant history or clinical manifestation of any metabolic, allergic, dermatological, hepatic, renal, hematological, pulmonary, cardiovascular, gastrointestinal, neurological, respiratory, endocrine, or psychiatric disorder

• History of significant hypersensitivity, intolerance, or allergy to any drug compound, food, or other substance

• History of stomach or intestinal surgery or resection that would potentially alter absorption and/or excretion of orally administered drugs

• Any of the following:

  1. QTcF >450 ms in males or >470 ms in females
  2. QRS duration >110 ms
  3. PR interval >220 ms
  4. Findings which would make QTc measurements difficult or QTc data uninterpretable.
  5. History of additional risk factors for torsades de pointes

• Confirmed systolic blood pressure >140 or <90 mmHg, diastolic blood pressure >90 or <50 mmHg, and pulse rate >100 or <40 beats per minute.

• Positive hepatitis panel and/or positive human immunodeficiency virus test

• Part B only: Current psychiatric disorder, suicidal ideation in the previous 2 years (as assessed by the Columbia-Suicide Severity Rating Scale [C-SSRS]), or a lifetime suicide attempt.

Prior/concomitant therapy:

• Administration of any vaccine in the 30 days prior to dosing.
• Use or intend to use any medications/products known to alter drug absorption, metabolism, or elimination processes
• Use or intend to use any prescription medications/products other than hormone replacement therapy, oral, implantable, transdermal, injectable, or intrauterine contraceptives within 14 days prior to dosing
• Use or intend to use slow-release medications/products considered to still be active within 14 days prior to check-in
• Use or intend to use any nonprescription medications/products including vitamins, minerals, and phytotherapeutic/herbal/plant-derived preparations within 7 days prior to check-in