Pegvaliase for the treatment of phenylketonuria: Results of a long-term phase 3 clinical trial program (PRISM).

Abstract

BACKGROUND:

Phenylketonuria (PKU) is caused by phenylalanine hydroxylase (PAH) deficiency that results in phenylalanine (Phe) accumulation. Pegvaliase, PEGylated recombinant Anabaena variabilis phenylalanine ammonia lyase (PAL), converts Phe to trans-cinnamic acid and ammonia, and is a potential enzyme substitution therapy to lower blood Phe in adults with PKU.

METHODS:

Two Phase 3 studies, PRISM-1 and PRISM-2, evaluated the efficacy and safety of pegvaliase treatment using an induction, titration, and maintenance dosing regimen in adults with PKU. In PRISM-1, pegvaliase-naïve participants with blood Phe >600 μmol/L were randomized 1:1 to a maintenance dose of 20 mg/day or 40 mg/day of pegvaliase. Participants in PRISM-1 continued pegvaliase treatment in PRISM-2, a 4-part clinical trial that includes an ongoing, open-label, long-term extension study of pegvaliase doses of 5 mg/day to 60 mg/day.

RESULTS:

Of 261 participants who received pegvaliase treatment, 72.0% and 32.6% reached ≥12 months and ≥ 24 months of study treatment, respectively, and 65% are still actively receiving treatment. Mean (SD) blood Phe was 1232.7 (386.4) μmol/L at baseline, 564.5 (531.2) μmol/L at 12 months, and 311.4 (427) μmol/L at 24 months, a decrease from baseline of 51.1% and 68.7%, respectively. Within 24 months, 68.4% of participants achieved blood Phe ≤600 μmol/L, 60.7% of participants achieved blood Phe ≤360 μmol/L, below the upper limit recommended in the American College of Medical Genetics and Genomics PKU management guidelines, and 51.2% achieved blood Phe ≤120 μmol/L, below the upper limit of normal in the unaffected population. Improvements in neuropsychiatric outcomes were associated with reductions in blood Phe and were sustained with long-term pegvaliase treatment. Adverse events (AEs) were more frequent in the first 6 months of exposure (early treatment phase) than after 6 months of exposure (late treatment phase); 99% of AEs were mild or moderate in severity and 96% resolved without dose interruption or reduction. The most common AEs were arthralgia (70.5%), injection-site reaction (62.1%), injection-site erythema (47.9%), and headache (47.1%). Acute systemic hypersensitivity events consistent with clinical National Institute of Allergy and Infectious Diseases and the Food Allergy and Anaphylaxis Network anaphylaxis criteria were observed in 12 participants (17 events); of these, 6 participants remained on treatment. Acute systemic hypersensitivity events including potential events of anaphylaxis were not associated with immunoglobulin E, and all events resolved without sequelae.

CONCLUSION:

Results from the PRISM Phase 3 program support the efficacy of pegvaliase for the treatment of adults with PKU, with a manageable safety profile in most participants. The PRISM-2 extension study will continue to assess the long-term effects of pegvaliase treatment.

• Authors: Janet Thomas, Harvey Levy, Stephen Amato, Jerry Vockley, Roberto Zori, David Dimmock, Cary O Harding, Deborah A Bilder, Haoling H Weng, Joy Olbertz, Markus Merilainen, Joy Jiang, Kevin Larimore, Soumi Gupta, Zhonghua Gu, Hope Northrup, PRISM investigators
• Journal: Molecular genetics and metabolism (Mol Genet Metab) Vol. 124 Issue 1 Pg. 27-38 (05 2018) ISSN: 1096-7206 [Electronic] United States
• PMID: 29653686 (Publication Type: Clinical Trial, Phase III, Journal Article, Randomized Controlled Trial, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Chemical References

• Recombinant Proteins
• Phenylalanine
• Phenylalanine Ammonia-Lyase
• pegvaliase

Topics

• Adult
• Female
• Humans
• Male
• Phenylalanine (blood)
• Phenylalanine Ammonia-Lyase (administration & dosage, adverse effects, therapeutic use)
• Phenylketonurias (drug therapy)
• Recombinant Proteins (administration & dosage, adverse effects, therapeutic use)
• Time Factors
• Young Adult