To evaluate the PK, safety and tolerability of orally administered NPT520-34 in healthy subjects at single and multiple doses that may be therapeutically relevant.

Inclusion Criteria:

1. informed of, and willing and able to comply with, all of the protocol requirements and the investigational nature of the study, and have signed an informed consent form in accordance with institutional and regulatory guidelines;
2. male or female adults between 18 and 55 years of age, inclusive;
3. female subjects must be of non-childbearing potential (i.e. post-menopausal for at least 2 years) or surgically sterile (hysterectomy, bilateral oophorectomy, tubal ligation) or nonsurgically sterile (hysteroscopic sterilization, i.e. Essure);
4. male subjects must be willing to use an adequate barrier method of contraception for the duration of the study and for 90 days after dosing and no sperm donations for the duration of the study and for 90 days after dosing. Male subjects who are surgically sterile (16 weeks post-surgery, or documented proof of Post-Vasectomy Semen Analysis (PVSA) with negative sperm results) need not employ a method of contraception;
5. non-smokers for at least six months;
6. BMI = 18.0 - 32.0 kg/m2 inclusive;
7. in good health, in the judgment of the Investigator, as determined by: 7a. medical history indicative of no serious or severe chronic conditions requiring frequent medical intervention or continual pharmacologic management, and no medical or social conditions that would potentially interfere with the subject's ability to comply with the study visit schedule or the study assessments; 7b. no clinically significant abnormalities in body temperature, heart rate, respiratory rate, blood pressure; 7c. no clinically significant abnormalities in the 12-lead electrocardiogram (ECG); 7d. no clinically significant abnormalities in clinical chemistry (ALT, AST, total bilirubin must be at or below the upper limit of normal and eGFR must be ≥ 90 mL/min), hematology (hemoglobin ≥ 11.5 g/dL for females and ≥ 13 g/dL for males), coagulation and urinalysis; lab tests may be repeated, if necessary (details are provided in the attached flow chart of study assessments).
8. negative results on the following screening laboratory tests: urine drug screen, urine alcohol screen, serum pregnancy test, hepatitis B surface antigen, hepatitis C antibody, and human immunodeficiency virus antibody.

Exclusion Criteria:

1. females of child bearing potential
2. history of a significant medical condition, including cholecystectomy or clinically significant GI tract resection, that may interfere with absorption, distribution or elimination of NPT520-34, or with the clinical and laboratory safety assessments in this study;
3. history of pre-existing thyroid abnormalities, such as hyper or hypothyroidism;
4. history of lactose intolerance;
5. history of drug hypersensitivity and disorders affecting respiratory function (e.g., COPD, asthma) and cardiac disorders predisposing to cardiac adverse events
6. history of or current alcohol abuse and/or other drug addiction < 2 years prior to screening, or a positive urine drug or alcohol screen (e.g., amphetamines, barbiturates, benzodiazepines, opiates, cannabinoids, alcohol and cocaine);
7. positive for HBVsAg, HCV Ab, HIV Ab;
8. 12 lead ECG showing the following: having a corrected QTc interval > 450 msec or <340 msec (Fridericia's correction);
9. sustained supine systolic blood pressure > 140 or < 90 mm Hg or supine diastolic blood pressure > 90 or < 50 mm Hg at Screening or Day -1. The average of the 2 assessments of BP taken at each visit will be used to exclude a subject;
10. resting pulse rate at screening of > 100 or < 45.
11. donated or lost > 500 mL of blood < 56 days prior to enrollment into this study;
12. plasma donation within 7 days prior to enrollment into this study;
13. active infection or febrile illness < 14 days prior to the first dose of study medication;
14. use of prescription (including hormone replacement therapy) or over-the-counter medications or herbal supplements ≤ 14 days prior to dosing and until completion of follow-up visit on Day 7 for the SAD subjects and Day 21 for the MAD subjects;
15. excessive regular caffeine intake (>250 mg of caffeine per day);
16. have participated in other clinical studies of a new chemical entity within 30 days prior to admission to the CRU.