Synlogic has announced plans to suspend the clinical development of SYNB1020 following negative results from the candidate’s Phase Ib/IIa clinical trial in hyperammonemia patients.

The randomised, double-blind, placebo-controlled trial assessed the safety and tolerability of SYNB1020 in a total of 23 participants with cirrhosis and high blood ammonia.

It monitored changes in blood ammonia levels and early-stage hepatic encephalopathy (HE)-related exploratory endpoints.

According to top-line results from interim analysis, the Synthetic Biotic medicine failed to lower blood ammonia. In addition, no changes were observed in other exploratory endpoints when compared to placebo.

However, the drug was found to be well-tolerated in cirrhosis patients. Increased plasma and urinary nitrate were also observed in SYNB1020-treated patients, suggesting that the therapeutic strain was active.

Synlogic president and CEO Aoife Brennan said: “We are disappointed that results from our Phase Ib/IIa study of SYNB1020 did not demonstrate an activity profile in ammonia lowering that warranted continued development of the programme.

“Moving forward, we will focus our resources on advancement of SYNB1618 for the treatment of phenylketonuria, SYNB1891 for the treatment of solid tumours and several new programmes in early development.”

The company started dosing patients in the Phase Ib/IIa study in April last year.

In the trial’s first part, an open-label cohort of six participants with cirrhosis and a Model for End-Stage Liver Disease (MELD) score of less than 12 were treated with SYNB1020 for six days.

The second randomised, double-blinded, placebo-controlled part, involving 17 subjects with cirrhosis and hyperammonemia, commenced after a review of the data by a safety data monitoring committee.

During this part, patients received either SYNB1020 or placebo over six days.