NCT07477691 · BioMarin Pharmaceutical
Immune Modulation During Palynziq® Treatment in Adults (IMPALA)
What this study is about
Study 165-401 is a Phase 4, where both patients and doctors know the treatment given study designed to examine the concomitant use of methotrexate (MTX) to suppress immune responses to Palynziq and improve tolerability and effectiveness in adults with PKU.
View original scientific description
Study 165-401 is a Phase 4, open-label study designed to examine the concomitant use of methotrexate (MTX) to suppress immune responses to Palynziq and improve tolerability and efficacy in adults with PKU.
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
Inclusion criteria
- Adults between 18 and 65 years old
- Have a confirmed diagnosis of phenylketonuria (PKU)
- Are in generally good health based on medical evaluation
- Are willing and medically eligible to receive Palynziq and methotrexate (MTX) Cohort A: Have never taken Palynziq before and are willing to start it during the study Cohort B: Have blood \> 600 μmol/L after taking Palynziq for at least 24 weeks, are on a daily dose of at least 20mg and unable to increase the dose further
- Agree to use required contraception if they or their partner could become pregnant
- Are willing to carry two epinephrine devices at all times during Palynziq treatment
Exclusion criteria
- Pregnant, breastfeeding, planning to become pregnant, planning to father a child, or not using effective birth control if applicable
- Have a known severe allergy or hypersensitivity reaction to methotrexate (MTX), Palynziq, or other PEG-containing medications
- Have a serious active infection or a history of severe or recurrent infections
- Have significant medical conditions that may affect safety or participation (such as serious heart, lung, liver, kidney, immune, neurological, psychiatric, or cancer-related conditions)
- Have a history of substance or alcohol abuse within the past 12 months
- Have had an organ transplant or are taking chronic immunosuppressive medications
- Are currently taking medications that are not allowed in the study, including other PKU treatments besides Palynziq
- Are using, or plan to use, injectable PEG-containing medications other than Palynziq during the study
- Have major surgery planned during the study participation period
- Are currently participating in another clinical study involving Palynziq
- In the opinion of the study doctor, are not a suitable candidate for the study or may have difficulty complying with study requirements
Where
- Los Angeles, California
- Aurora, Colorado
- Tampa, Florida
- Chicago, Illinois
- Indianapolis, Indiana
- Minneapolis, Minnesota
- Rochester, New York
- Portland, Oregon
- Philadelphia, Pennsylvania
- Dallas, Texas
- Salt Lake City, Utah
- Milwaukee, Wisconsin
Frequently asked questions
What is a clinical trial?
A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.
Is it safe to participate?
Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.
Will I be compensated?
Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.
Will I receive a placebo instead of treatment?
When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.
Can I leave a trial if I change my mind?
Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.
How long does a clinical trial last?
Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.
Data: ClinicalTrials.gov · synced Jun 17, 2026 · Source of record for eligibility and locations