A clinical trial for people living with phenylketonuria (PKU) 


A clinical trial for people living with PKU

The purpose of the Synpheny-3 clinical trial is to evaluate an investigational drug, SYNB1934. Its goal: to see how well and how safely SYNB1934 reduces blood phenylalanine (Phe) levels in people with PKU.

If you qualify, you may receive:
– Investigational medication at no cost
– Payment for study visits
– Payment for travel costs
– Study-related monitoring


Find out if you qualify for Synpheny-3

Synpheny-3 is for adults with PKU ages 18 years and older who have Phe levels ≥ 360 μmol/L (6mg/dL) despite current management.

There is no specific diet required; participants may follow their normal diet.

A Synlogic Case Manager can discuss this with you and provide additional information.

About the Synpheny-3 clinical trial

SYNB1934 has been studied in Phase 1 and 2 clinical trials in healthy volunteers and people who have PKU.
The Synpheny-3 study includes three parts, described below.

Part 1:


9-15 Weeks

Participants will receive increasing doses of the investigational drug to find the best dose.

Part 2:

Randomized Withdrawal

4 Weeks

Half of study participants will stay on the investigational drug. Half will receive a placebo.

Part 3:

Open Label Extension (OLE)

Up to 36 months

Participants will stay on the investigational drug for up to 3 years.


Getting Started

Before taking part in the clinical trial, you need to:

  1. Answer a few short questions online. 
  2. Speak to a Case Manager. The Synlogic Case Manager will contact you within 1 to 2 business days with more information and to answer your questions. 
  3. Speak to a clinical trial site. The Case Manager will introduce you to a clinical trial team. Members of this team will stay in close contact with you during the clinical trial. 

Meet Leyla:
Synlogic’s Case Manager

Leyla will contact you to discuss the Synpheny-3 clinical trial and answer your questions.

There are different ways people can participate in this study: in-person, virtually, or a combination of the two. Leyla can help you decide which format is best for you and connect you with the clinical team at that site.

Planned Clinical Trial Locations

The Synpheny-3 clinical trial will soon have a virtual site and study locations in medical centers near you.

A Synlogic Case Manager will help you decide which works best for you.

About Investigational Medication SYNB1934

SYNB1934 is a specially engineered probiotic, or healthy bacterium, that has been designed to consume Phe in the GI tract.

SYNB1934 is based on the helpful probiotic E. coli Nissle (EcN). Many people around the world use EcN as a treatment for common intestinal problems like diarrhea and constipation. 

Frequently Asked Questions (FAQs)

What is an investigational drug?

A medication that has not yet been approved as effective and safe by a regulatory agency.

What is a clinical trial?

Researchers use clinical trials to understand and test investigational drugs so they can: 
– Find out if the investigational drug is safe for people to take.
– Understand any side effects and how to manage them.
– See if it works to treat a disease.
– Collect data to increase understanding about a condition to aid future scientists and medical researchers.

What are the different phases of a clinical trial?

There are often four phases of clinical trials, with each asking a different question.

Phase 1  – Researchers test an investigational drug in a small group of people who may or may not have the disease being investigated. The goal: see if the drug is safe, appropriate doses, and any potential side effects. 

Phase 2 – The investigational drug is given to a larger group of people. The goal: see if it is effective and if there are side effects. 

Phase 3 – This trial has an even larger group of participants. The goal: collect a lot of data about effectiveness, side effects, and how the medication compares to other common treatments or a placebo. This information is important because it can determine if the medication is safe, effective, and may be prescribed to participants.

Phase 4 – This phase of the trial is usually completed after a medication has been approved by a regulatory agency like the FDA in the U.S. The goal: gather more data about risks and benefits. 

Why should I participate in a clinical trial?

People may participate in clinical trials for different reasons, such as to:
– Access potential new treatments. 
– Learn more about their disease.
– Support science and research.

Learn more about your rights as a participant.