US-based biotechnology firm Synlogic has begun a Phase III trial of SYNB1934 for the treatment of phenylketonuria (PKU), a rare metabolic disease.

The Synpheny-3 trial will be carried out as a global, pivotal, multi-centre, randomised, placebo-controlled study.

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It will consist of three parts to assess the safety and efficacy of SYNB1934 in patients with PKU.

The trial will be carried out at up to 30 clinical sites across Germany, Turkey, the US, Georgia, Israel, Canada and Denmark.

Part I of the study is a run-in period that will enable individual titration across three potential dose levels, namely 3×10¹¹, 6×10¹¹ and 1×10¹¹, for at least three weeks at each dose.

The second part of the trial will be conducted as a four-week, placebo-controlled, randomised withdrawal to evaluate the primary endpoint of change in levels of plasma phenylalanine (Phe) from a baseline of >20% among responders from Part I.

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Part III will be an open-label extension that is expected to extend for up to three years.

Synpheny-3 will enrol up to 150 patients aged 18 years and older with plasma Phe levels at a baseline of >360μM.

An initial subset of data from patients in Part I will be used to evaluate the opportunity to reduce the enrolment age to 12 years.

Synlogic president and CEO Aoife Brennan said: “We have worked tirelessly to advance this programme and today is an important milestone for Synlogic and for the patient community living with the extreme burden of PKU.

“We have partnered on this pivotal trial design with key stakeholders, including clinician experts, global regulatory agencies and people living with PKU, and are very grateful for their many insights.

“In particular, feedback from patients has heightened our sense of urgency to bring forward a new oral therapeutic that can be used either as a monotherapy or adjunctive medical treatment.”

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