Study to Determine the Safety, Tolerability, and Pharmacokinetic Profile of HPN-07 and HPN-07 Plus NAC

This study is a single-center, randomized, placebo-controlled, double-blind, single
ascending dose escalation study to determine the safety, tolerability, and PK profile of
oral administration of HPN-07 in single doses to healthy male and female subjects between 18
and 55 years of age.

Approximately 32 subjects will be enrolled in a panel of 4 cohorts with approximately 8
subjects per cohort. There will be approximately 3 sequential ascending dosing levels of
HPN-07, with each cohort administered 1 dose of HPN-07 ranging from 500 mg to 1,500 mg and
the fourth cohort administered the highest tolerated dose of HPN-07 plus 1,200 mg NAC.

The primary endpoint of this trial is to establish the safety and tolerability of HPN-07 and
HPN-07 plus N-acetylcysteine (NAC). Pharmacokinetics (PK) analysis of HPN-07 will enable a
preliminary determination of the relationship between dose and the time course of the drug
concentration in the body. Blood samples will be collected at regular intervals over the
predicted time of HPN-07 systemic exposure.

Inclusion Criteria:

- Male or female subjects, 18-55 years of age (inclusive), at the time of enrollment.

- Healthy as judged by a responsible physician with no clinically significant
abnormality identified on the medical or laboratory evaluation, including 12-lead
electrocardiogram (ECG). A subject with a clinical abnormality or laboratory
parameters outside the reference range for this age group may be included only if the
Investigator considers that the finding will not introduce additional risk factors
and will not interfere with the study procedures (as defined as the research site's
standard operating procedures).

- Male subjects who are surgically sterile OR agree to abstain from sexual intercourse
with a female partner OR agree to use a condom and spermicide during sexual
intercourse with a female partner who meets the following criteria: 1) uses another
form of contraception, such as an intrauterine device (IUD), occlusive cap (diaphragm
or cervical/vault cap) with spermicide, oral contraceptives, injectable progesterone,
subdermal implants, female condom, contraceptive patch, or contraceptive vaginal
ring; and/or 2) has had a tubal ligation or hysterectomy. These criteria must be
followed from the time of the first dose of study medication until 14 days after the
last dose of study medication. Men must also abstain from sperm donation from the
time of the first dose of study medication until 14 days after the last dose of study
medication.

- Female subjects of childbearing potential must be practicing abstinence or are using,
and willing to continue using, a medically acceptable form of birth control for at
least 1 month prior to Screening (at least 3 months for hormonal contraceptives) and
for at least 2 months after the last study drug administration. Medically acceptable
forms of contraception include abstinence, hormonal contraceptives (oral, patch or
vaginal ring), intrauterine device, progestin implant or injection, bilateral tubal
ligation, or double-barrier methods (i.e., male condom in addition to a diaphragm or
a contraceptive sponge).

- Female subjects of non-childbearing potential, defined as: having undergone
successful surgical sterilization (hysterectomy and/or bilateral
oophorectomy/salpingo-oophorectomy, as determined by subject medical history) or
post-menopausal. Postmenopausal is defined as being amenorrheic for at least 1 year
without another cause and a follicle-stimulating hormone (FSH) level ~50 mlU/ml.

- Female subjects must have a negative pregnancy test at screening and Day -1
(admission).

- Minimum body weight of 50.0 kg and body mass index (BMI) between 18.0 kg/m2 and 33.0
kg/m2 (inclusive).

- Non-smoker (refrained from any tobacco usage, including smokeless tobacco, nicotine
patches, etc:, for 6 months prior to the administration of the study medication) and
has negative findings on a breath carbon monoxide (CO) test.

- Willing and able to comply with study instructions and commit to all follow-up
visits, and willing and able to abide by all study requirements and restrictions.

- Ability to understand, agree to, and sign the study informed consent form (ICF) prior
to initiation of any protocol related procedures.

Exclusion Criteria:

- Self-reported substance or alcohol dependence or abuse (excluding nicotine and
caffeine) within the past 2 years, as defined by the Diagnostic and Statistical
Manual of Mental Disorders (DSM-IV) and/or subjects who have ever been in a substance
or alcohol rehabilitation program to treat their substance or alcohol dependence.

- History of serious adverse reactions or hypersensitivity to any drug; or known
allergy to any of the test product(s), or any components in the test product(s); or
history of hypersensitivity; or allergic reactions to any of the study preparations
as described in the Investigator's Brochure; or severe allergic reaction (including
anaphylaxis) to any food, or bee stings or previous status asthmaticus.

- History of renal stones or taking cardiac nitrates.

- Any clinically significant central nervous system (e.g., seizures), cardiac,
pulmonary, metabolic, renal, hepatic, or gastrointestinal conditions or history of
such conditions that, in the opinion of the investigator, may place the subject at an
unacceptable risk as a participant in this trial or may interfere with the
distribution, metabolism, or excretion of drugs.

- Abnormal physical findings of clinical significance, at screening or on Day -1, which
would interfere with the objectives of the study.

- History or presence of orthostatic hypotension (~20 mmHg drop in systolic blood
pressure, or ~10 mmHg drop in diastolic blood pressure, or subject experiences
lightheadedness or dizziness) at screening or on Day-1.

- Clinically significant abnormal laboratory values (as determined by the Investigator)
at the screening evaluation.

- Presence or history of allergies requiring acute or chronic treatment (except
seasonal allergic rhinitis).

- 12-lead ECG obtained at screening with PR >240 msec, QRS >110 msec, and QTc >440 msec
for males and >450 msec for females, bradycardia (<50 bpm), or clinically significant
minor ST wave changes on the screening ECG or any other changes on the screening ECG
that would interfere with measurement of the QT interval.

- Major surgical interventions within 6 months before the study.

- Has a positive pre-study hepatitis B surface antigen; positive hepatitis C virus
(HCV) antibody or detectable HCV ribonucleic acid (RNA); or positive human
immunodeficiency virus (HIV) antibody result.

- Use of a prohibited medication or supplement, as specified in Section 9.6.

- Has a history of regular alcohol consumption averaging >14 drinks/week for men and >9
drinks/week for women (1 drink (10 g alcohol] = 100 ml of wine or 280 ml of standard
strength beer or 30 ml of 80 proof distilled spirits) within 6 months of the
screening visit.

- Loss of 500 ml, or more, of blood during the 3-month period before the drug
administration, e.g., blood donor.

- Symptoms of a significant somatic or mental illness in the 4-week period preceding
drug administration, as per investigator discretion.

- Exclude subjects with a positive breath alcohol test or urine drug screen at
screening. Suspected false positive results may be repeated at the discretion of the
Investigator.

- Concurrent participation in another drug or device research study or within 30 days
of participation in another drug or device research study.

- Considered by the Investigator to be an unsuitable candidate for this study.

- Women who are breastfeeding, pregnant, or intend to become pregnant during the course
of the study.

- An employee of the sponsor or research site personnel directly affiliated with this
study or their immediate family members defined as a spouse, parent, child, or
sibling, whether biological or legally adopted.