A Study of Safety and Efficacy of HPN-100 in Subjects With Cirrhosis and Episodic Hepatic Encephalopathy

Part A: Open-label, dose-escalation lead-in to assess HPN-100 safety and PK Approximately 10
subjects with HE and cirrhosis classified as Child Pugh B or C will undergo a one-step dose
escalation over 4 weeks. Subjects will initially receive 6 mL HPN-100 BID for 1 week. On Day
7 and following satisfactory safety assessment of the subject, the dose will be escalated to
9 mL BID for an additional 3 weeks.

In addition to a safety assessment, subjects will undergo 12-hour PK assessments on Days 7
and 28, with sampling at the following time points (relative to the first dose): 0
(pre-first daily dose of HPN-100), 2, 4, 8 (approximately 2 hours before the second daily
dose of HPN 100), and 12 hours post-first dose (approximately 2 hours after the second daily
dose of HPN-100). Additional PK samples will be collected on Days 8, 15, and 21 (at
pre-first dose and 4 hours post-first dose).

The DSMB will review all safety information, including laboratory values, to determine if
Part B may be initiated.

Subjects enrolled in Part A may be eligible for Part B as long as they meet the eligibility
criteria.

Part B: Randomized, double-blind assessment of HPN-100 in HE subjects Subjects who meet all
entry criteria and are judged to be compliant with their prescribed SOC will be eligible for
randomization to receive either HPN-100 or matching placebo for 16 weeks. Efficacy will be
assessed by the proportion of subjects experiencing episodes of HE, as well as by other
outcome measures, including daily home assessments.

Inclusion Criteria:

- Subjects aged 18 and over

- Clinical diagnosis of cirrhosis of any cause

- Potential to benefit from HE treatment

- History of greater than or equal to 2 documented episodes of WH Grade 2 or more HE
within the past 6 months, at least one of which occurred within the preceding 3
months

- No change in other HE-specific medications within 1 week before randomization

- Able to give informed consent and comply with study activities

- Availability of at least one designated family member or caregiver who is capable of
and willing to assume responsibility for facilitating subject compliance with study
procedures

- All females of childbearing age and all sexually active males must agree to use an
acceptable method of contraception throughout the study.

Exclusion Criteria:

- Use of any investigational drug within 30 days

- Use of prohibited medications

- Uncontrolled infection

- Active GI bleeding or a history of GI bleeding requiring blood transfusion (> 2
units) within 3 months

- Transjugular intrahepatic portosystemic shunt (TIPS) placement or revision within the
past 90 days

- Recreational drug use or alcohol consumption for subjects with a history of alcohol
or drug abuse within 6 months

- Lactating and/or pregnant females

- Active malignancy

- Clinically significant bowel disease, including obstruction, inflammatory bowel
disease, or malabsorption

- Expected to undergo transplantation within 6 months

- Model for end-stage liver disease (MELD) score of > 25