Synlogic, Inc. announced the initiation of Synpheny-3, a global, pivotal Phase 3 study evaluating the efficacy and safety of SYNB1934 as a potential treatment for phenylketonuria (PKU). Synpheny-3 is a randomized, placebo-controlled, global, multi-center, pivotal Phase 3 clinical trial designed to evaluate the efficacy and safety of SYNB1934 as a treatment for PKU. The final trial design incorporates feedback from global regulatory agencies including the U.S. Food and Drug Administration (FDA).

The global study will enroll approximately 150 patients with plasma phenylalanine (Phe) levels at baseline of >360 µM. Synpheny-3 will include patients ages 18 years and older; an initial subset of data from patients in Part 1 will be used to assess the opportunity to lower the age of enrollment to 12 years of age. Study participants may follow their usual diet while participating in the trial. Synpheny-3 is expected to be conducted at approximately 30 clinical sites across the United States, Canada, Germany, Denmark, Israel, Turkey and Georgia.

The study has been designed for patient convenience, and offers opportunities to participate in person, or in a virtual or hybrid format. The study consists of three parts: Part 1 is a run-in period, enabling individualized titration across three potential dose levels (3x1011, 6x1011 and 1x1012), with patients spending a minimum of three weeks at each dose. Part 2 of the trial is a four-week, placebo-controlled, randomized withdrawal that will be used to assess the primary endpoint: change in levels of plasma Phe, with a primary analysis conducted among responders from Part 1. The definition for responders is a reduction in plasma Phe from baseline of >20%.

Part 3 is an open-label extension that may extend for up to three years.