Browsing by Author "Burton, Barbara K."

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    Pegvaliase for the treatment of phenylketonuria: A pivotal, double-blind randomized discontinuation Phase 3 clinical trial
    (Elsevier, 2018) Harding, Cary O.; Amato, R. Stephen; Stuy, Mary; Longo, Nicola; Burton, Barbara K.; Posner, John; Weng, Haoling H.; Merilainen, Markus; Gu, Zhonghua; Jiang, Joy; Vockley, Jerry; Medical and Molecular Genetics, School of Medicine
    Introduction Pegvaliase is a recombinant Anabaena variabilis phenylalanine ammonia lyase (PAL) enzyme under investigation for treatment of adult phenylketonuria (PKU). This manuscript describes results of a randomized discontinuation trial (RDT) designed to evaluate the effects of pegvaliase treatment on blood phenylalanine (Phe) and neuropsychiatric outcomes in adults with PKU. Methods PRISM-2 is a 4-part, Phase 3 study that enrolled adults with PKU receiving pegvaliase treatment (initiated in a prior Phase 2 or Phase 3 study). The RDT, Part 2 of PRISM-2, was an 8-week trial that evaluated change in blood Phe concentrations, neuropsychiatric and neurocognitive measures, and safety outcomes in PRISM-2 participants who had achieved at least a 20% blood Phe reduction from pre-treatment baseline with pegvaliase treatment. Participants were randomized 2:1 to either continue pegvaliase (20 mg/day or 40 mg/day) or switch to matching placebo. Results The pooled pegvaliase group enrolled 66 participants and each placebo group enrolled 14 participants. The primary endpoint of change in blood Phe concentration from RDT entry to RDT Week 8 was met with clinically meaningful and statistically significant differences between the pegvaliase and placebo groups. Mean (SD) blood Phe at the beginning of the RDT when all participants were receiving pegvaliase was 563.9 μM (504.6) in the group assigned to the 20 mg/day placebo group (n = 14), 508.2 μM (363.7) in those assigned to the 40 mg/day placebo group (n = 14), and 503.9 μM (520.3) in those assigned to continue pegvaliase treatment (n = 58). At Week 8 of the RDT, the least squares mean change (95% confidence interval) in blood Phe was 949.8 μM (760.4 to 1139.1) for the 20 mg/day placebo group and 664.8 μM (465.5 to 864.1) for the 40 mg/day placebo group in comparison to 26.5 μM (−68.3 to 121.3) for the pooled (20 mg/day and 40 mg/day) pegvaliase group (P < 0.0001 for pooled pegvaliase group vs each placebo group). Adverse events (AEs) were usually lower in the pooled placebo group when compared to the pooled pegvaliase group. The most common AEs for the pooled pegvaliase and pooled placebo groups were arthralgia (13.6% and 10.3%, respectively), headache (12.1% and 24.1%), anxiety (10.6% and 6.9%), fatigue (10.6% and 10.3%), and upper respiratory tract infection (1.5% and 17.2%). Conclusion Mean blood Phe reduction was sustained in the pegvaliase group, while placebo groups had mean blood Phe concentration increase toward pre-treatment baseline levels. Results from this study confirmed the efficacy of pegvaliase in maintaining reduced blood Phe concentrations with a manageable safety profile for most participants.
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    Real-world treatment, dosing, and discontinuation patterns among patients treated with pegvaliase for phenylketonuria: Evidence from dispensing data
    (Elsevier, 2022-09-25) Lah, Melissa; Cook, Keziah; Gomes, Dumingu Aparna; Liu, Stephanie; Tabatabaeepour, Nadia; Kirson, Noam; Chen, Er; Lindstrom, Kristin; Bulloch Whitehall, Kaleigh; Van Backle, Joost; Burton, Barbara K.; Medical and Molecular Genetics, School of Medicine
    Background: Phenylketonuria (PKU) is an inborn metabolic error characterized by a deficiency of the enzyme required for the metabolism of phenylalanine, an essential amino acid found in most protein-containing foods. Pegvaliase (Palynziq®) is an enzyme substitution therapy approved for adults with PKU who have inadequate blood phenylalanine control (≥600 μmol/L) on existing management. Objective: To characterize the treatment, discontinuation, and dosing patterns in patients treated with pegvaliase in real-world practice settings in the United States following commercial availability in 2018. Study design: Retrospective cohort study using BioMarin's proprietary drug dispense database associated with the pegvaliase REMS program. Methods: Sample construction identified all patients who properly initiated pegvaliase in real world settings ('full cohort') and a subset of patients ('extended follow-up cohort') with ≥12 months between first dispense of maximum dose and last pegvaliase dispense. Key outcomes were quantified across patients in both cohorts: maximum daily dose; time to maximum daily dose; maximum daily syringes; and dose escalation over time. The overall dose at discontinuation and time to discontinuation were calculated. Patients who subsequently reinitiated therapy were identified. For the extended follow-up cohort, 12-month changes in dose and syringes and dispensing gaps during the 12 months after maximum dose were quantified across all patients and were further stratified by maximum dose. Results: Overall, 1596 patients associated with 33,814 dispenses were reflected in the pegvaliase dispense dataset during the study period from July 9, 2018, through December 31, 2021; 1280 patients associated with 25,973 dispenses met inclusion criteria for the full cohort, with 19.9 dispenses each on average. Of these patients, 483 patients associated with 15,149 dispenses also met the extended follow-up criteria, with an average of 31.4 dispenses.Average treatment duration in the full cohort was 82.2 weeks, including 50.8 weeks after maximum daily dose was achieved. The average maximum daily dose was 30 mg with an average time to maximum dose of 31.8 weeks: 43.0% of patients had a maximum dose of 20 mg, 31.3% a maximum dose of 40 mg, and 12.0% a maximum dose of 60 mg. At data cut-off, 289 patients (22.6%) had discontinued; within this group, 126 patients (43.6%) discontinued within the first 6 months after reaching maximum dose.The overall average treatment duration for patients in the extended follow up cohort at data cut off was 131.2 weeks, including 98.6 weeks after maximum dose was achieved. The average maximum daily dose across the cohort was 32.9 mg: 42.4% of patients had a maximum dose of 20 mg, 41.0% a maximum dose of 40 mg, and 11.2% a maximum dose of 60 mg. At 12 months after achieving maximum dose, 35% of patients had down-dosed, with a 46.8% decrease (on average) from their maximum dose. Conclusions: Real-world use of pegvaliase reflects longer titration periods than in the dosing schedule based on trial experience. Over time, a substantial number of patients are able to reduce their daily dose by titrating down from their maximum dose, a finding of great interest to clinicians and patients alike.