The goal of this clinical trial is to evaluate whether both Form H and Form II, 100mg brincidofovir tablets are bioequivalent, when given under fasting conditions in healthy adults.

Participants will be randomized to each receive one tablet of Form H and one tablet of Form II,14 days apart and undergo pharmacokinetic testing pre-dose and post-dose to evaluate safety. This is an open-label, single-dose, randomized, two-period, crossover study.

Primary Objectives:

• To evaluate the bioequivalence (BE) of brincidofovir (BCV) hydrate (Form H) tablet and the Form II tablet when administered under fasting conditions in healthy adult participants.
• To characterize plasma BCV pharmacokinetics (PK) following single doses of BCV when administered in healthy adult participants.

Safety Objective:

- To evaluate the safety of BCV following administration of single dose of 100 mg BCV Form H and BCV Form II tablet in healthy adult participants.

Inclusion Criteria:

• Able and willing to provide informed consent voluntarily signed by participant.

• Male or female between 18 to 70 years of age, inclusive at screening.

• Body mass index (BMI) from 18 to 32 kg/m² with a minimum body weight of ≥ 50 kg, inclusive at screening.

• Women must be of nonchildbearing potential, i.e., postmenopausal woman (defined as spontaneous amenorrhea for 1-year prior to Period 1 Day 1) with a confirmed follicle stimulating hormone (FSH) level in laboratory's "postmenopausal" reference range; or a premenopausal woman documented as surgically sterile following either a hysterectomy and/or bilateral oophorectomy, bilateral salpingectomy, tubal ligation.

• Males must be surgically sterilized (confirmed by documented azoospermia at least 90 days after procedure).

• Overtly healthy as determined by medical evaluation and judgment of the investigator including medical history, physical examination (PE), laboratory tests, vital signs (VS), and eletrocardiogram (ECG) at screening and Day -1. [Note: hematology, serum chemistry, and urinalysis parameters must fall within the laboratory's normal reference ranges or have been determined by the investigator to have no clinical significance in the context of this study.] Except:

  1. Alanine transaminase (ALT), aspartate aminotransferase (AST) and gammaglutamyl transferase (GGT) x ≤1.5 upper limit of normal reference range (ULN)
  2. Total Bilirubin x ≤1.5 ULN
  3. Hemoglobin (Hb) ≥10.5 g/dL for females or ≥12 g/dL for males

• Able to comply with the dosing instructions and available to complete the study schedule of assessments.

Exclusion Criteria:

• History or current symptoms of any serious psychiatric illness, including addiction, which could interfere with participant treatment, assessment, or compliance with the protocol.
• History of chronic liver disease or hepatic impairment, including but not limited to alcoholic liver disease, chronic viral hepatitis, autoimmune hepatitis, steatosis, or hemochromatosis. Note: A remote (≥12 months prior to screening) history of hepatitis A infection will not be cause for exclusion.
• History of Gilbert's syndrome or current evidence of the disease based on laboratory information at screening visit or Day -1.
• History of hematological disorders, including disorders such as a bleeding disorder or a risk of gastrointestinal bleeding.
• Clinically significant history of difficulty with blood donation, including vasovagal syncope (fainting), and/or poor venous access for the purposes of phlebotomy.
• Positive (reactive) serological test result at the screening evaluation consistent with possible infection with Hepatitis B virus (HBV), Hepatitis C virus (HCV), or Human immunodeficiency virus type 1 or 2 (HIV).
• Positive test for drugs of abuse and/or alcohol at either screening or check-in days.
• Clinically significant infection (e.g., COVID-19, cold, flu, or febrile illness) within 14 days prior to Period 1 Day 1.
• Donated a unit of blood or had clinically significant blood loss within 30 days prior to Period 1 Day 1 or donated plasma within 14 days prior to Period 1 Day 1.
• Received any investigational drug, agent, or device within 30 days prior to Period 1 Day 1, or current participation in another interventional study.
• Consumed any fruit juice including grapefruit juice, pomegranate juice, cranberry juice, orange juice, and Seville orange juice (also known as sour, bitter or bigarade orange) within 3 days prior to Period 1 Day 1 and throughout the study, unless prior approval is granted by both the investigator and the medical monitor.
• Received any medication or herbal product (e.g., St. John's wort) known to induce or inhibit hepatic metabolizing enzymes and/or transporters within 30 days or 5 half-lives of the compound, whichever is longer, prior to Period 1 Day 1 and throughout the study, unless approval is granted by both the investigator and the medical monitor.
• Received any vaccines (including COVID-19 vaccine) within 14 days prior to Period 1 Day 1 and throughout the study, unless approval is granted by both the investigator and the medical monitor.
• Any condition or set of circumstances that, in the judgment of the investigator, could interfere with the participant's ability to comply with the dosing schedule and completion of the study evaluations (e.g., participants who are unable to communicate or cooperate with the investigator).