Safety, Tolerability and Pharmacodynamics of SYNB1020

In Part 1, a sentinel open-label cohort of subjects with cirrhosis and Model for End-Stage Liver Disease (MELD) score <12 was admitted to an inpatient facility for a run-in diet, baseline assessments, IMP administration, safety monitoring, and collection of blood, urine, and stool samples for evaluation of safety, tolerability, and pharmacokinetic (PK) and pharmacodynamic (PD) evaluations. Subjects in Part 1 were enrolled sequentially to receive SYNB1020. Once the safety and tolerability were established in Part 1, enrollment was opened to subjects in Part 2.

Part 2 comprised a randomized, double-blind, placebo-controlled study in subjects with cirrhosis and hyperammonemia. Subjects were permitted to be pre-screened for eligibility based on medical history and a single fasting spot venous ammonia measurement. Eligible subjects with elevated fasting spot venous ammonia then underwent full screening within 7 days of pre-screening. Eligible subjects were admitted to an inpatient facility for a run-in diet and 24-hour ammonia profile, and those with an elevated 24-hour ammonia area under the curve (AUC) (>1.2 × the upper limit of normal \[ULN\]) proceeded with computer-generated randomization in a 1:1 ratio to receive either SYNB1020 or matching placebo. Randomization was followed by IMP administration, safety monitoring, and collection of blood, urine, and stool samples for PK and PD evaluations.

• SYNB1020 (Drug): SYNB1020 was supplied at a concentration of approximately 1 × 10\^11 CFU/mL in a buffered solution in 5 mL cryovials with a nominal 5 mL fill volume, administered with 100 mL of masking buffer solution.
• Placebo (Other): Subjects received placebo orally in a chilled buffered solution (100 mL).

Primary outcomes

• Number of Participants With Treatment-Emergent Adverse Events [Up to 70 days]: Toxicity was graded in accordance with the National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events (CTCAE), version 4.03, as follows: Grade 1 (mild/asymptomatic; no intervention); Grade 2 (moderate; minimal intervention); Grade 3 (severe/medically significant; hospitalization indicated; disabling); Grade 4 (life-threatening; urgent intervention required). Adverse events (AEs) were reported based on clinical laboratory tests, vital sign and weight measurements, physical examinations, and any other medically indicated assessments, including subject interviews, from the time informed consent was signed through the end of the safety follow-up period. AEs were considered to be treatment emergent adverse events (TEAEs) if they occurred or worsened in severity after the first dose of study treatment. TEAEs were considered treatment-related if relationship to study drug was possibly related, probably related, definitely related, or a missing relationship.

Secondary outcomes

• Number of Participants With Clearance of SYNB1020 From Feces [Up to 65 days]: SYNB1020 transit through the gastrointestinal tract was measured with qualitative and quantitative polymerase chain reaction (PCR) fecal assays from fecal samples collected at baseline, daily during the dosing period (Days 1 through 6), at the time of discharge from the inpatient unit (Day 7), and at follow-up visits beginning 7±1 days after the last dose and continuing biweekly until a subject had a negative SYNB1020 fecal test. SYNB1020 clearance reflects a test value of below the limit of quantitation (BLQ) occurring after the indicated number of days following the last dose of study treatment.
• Daily Fasting Spot Venous Ammonia [Up to 9 days]: Fasting spot venous ammonia was collected at baseline (Day -2) and at the time of discharge from the inpatient unit (Day 7).

Sex: All, ages: 18 Years to 74 Years

Key Inclusion Criteria:

* Age ≥ 18 to < 75 years
* Females must have been of non-childbearing potential
* Able and willing to complete informed consent process
* Available for and agreed to all study procedures
* Screening laboratory evaluations within defined acceptable limits or judged to be not clinically significant by the Investigator
* Diagnosis of chronic, stable, hepatic insufficiency with features of cirrhosis due to any etiology
* Evidence of elevated portal hypertension by either liver stiffness measurement, the presence of abdominal or esophageal varices, splenomegaly or ascites (Part 2 only)
* Elevated venous ammonia (Part 2 only)

Key Exclusion Criteria:

* Body mass index < 18.5 or ≥ 40 kg/m\^2
* Administration or ingestion of an investigational drug within 8 weeks or 5 half-lives, whichever was longer, prior to screening or current enrollment in an investigational study
* Allergy to ranitidine or intolerance to any of the excipients (glycerol, CS Health Easy Fiber)
* Any condition, prescription medication or over-the-counter product that may possibly have affected absorption of medications or nutrients
* Dependence on drugs of abuse
* Apart from chronic liver disease, any acute or chronic medical, surgical, psychiatric, or social condition including history of cerebrovascular disease (stroke, transient ischemic attack) or dementia, or laboratory abnormality that may have increased the subject risk associated with study participation, compromised adherence to study procedures and requirements, confounded interpretation of the safety, kinetics, or PD results, and, in the judgment of the Investigator, made the subject inappropriate for enrollment
* Current or past hepatic encephalopathy of Grade 2 or higher requiring hospitalization
* Child-Turcotte-Pugh score > 9
* History of liver transplant

Participant flow

Outcome results

• Number of Participants With Treatment-Emergent Adverse Events (Primary), Number, participants: Part 1: SYNB1020 4; Part 2: SYNB1020 8; Part 2: Placebo 4
• Number of Participants With Clearance of SYNB1020 From Feces (Secondary), Count of participants, Participants: Part 1: SYNB1020 6; Part 2: SYNB1020 9; Part 2: Placebo 0
• Daily Fasting Spot Venous Ammonia (Secondary), Mean, μmol/L: Part 1: SYNB1020 64.7 +/- 25.00; Part 2: SYNB1020 82.0 +/- 36.41; Part 2: Placebo 55.6 +/- 18.18

Adverse events

Time frame: All AEs occurring from the time a subject signs informed consent through the safety follow-up period (i.e.,up to 70 days) were documented, regardless of the causal relationship to study drug. AEs that occurred or worsened in severity after the first dose of study treatment were considered treatment emergent (i.e., TEAEs).

Serious adverse events by term

Other adverse events by term

Limitations and caveats: Interim futility analyses identified a lack of SYNB1020 efficacy (plasma ammonia AUC) compared with placebo, resulting in study termination.

• Study Protocol (PDF, 2018-11-27)
• Statistical Analysis Plan (PDF, 2019-04-01)