This study is a double blind, randomized, placebo-controlled, Phase 1 study in three parts: single ascending doses and food effect (Part 1), multiple ascending doses (Part 2) and Relative Bioavailability of Two Formulations (Part 3).

THB335 is a highly potent and selective inhibitor of the receptor tyrosine kinase KIT that is expressed on mast cells.

The study will evaluate the safety, pharmacokinetics, pharmacodynamics, and food effect profile of THB335 administered orally in healthy participants.

Inclusion Criteria:

• In good health, determined by no clinically significant findings from medical history, 12 lead electrocardiogram (ECG), vital sign measurements, and clinical laboratory evaluations
• Males or females, of any race, between 18 and 65 years of age, inclusive.
• Participants must understand the nature of the study and must provide signed and dated written informed consent in accordance with local regulations before the conduct of any study related procedures
• Body weight of ≥ 50.0 kg for men and ≥ 45.0 kg for women and Body Mass Index (BMI) of 17.5-32.0 kg/m2 (inclusive) at Screening

Exclusion Criteria:

• Significant history or clinical manifestation of cancer or any metabolic, allergic, dermatological, hepatic, biliary, renal, hematological, pulmonary, cardiovascular, gastrointestinal, neurological, respiratory, endocrine, or psychiatric disorder
• Vaccinated within 14 days prior to Day -1 or intention to receive vaccination during the study
• A positive urine drug screen/alcohol breath test
• The participant currently smokes, vapes, or uses nicotine-containing products.