Achieving efficacy in subjects with sustained pegvaliase-neutralizing antibody responses

Pegvaliase for the treatment of phenylketonuria: Final results of a long-term phase 3 clinical trial program

Phenylketonuria (PKU) is a genetic disorder caused by deficiency of the enzyme phenylalanine hydroxylase (PAH), which results in phenylalanine (Phe) accumulation in the blood and brain, and requires lifelong treatment to keep blood Phe in a safe range. Pegvaliase is an enzyme-substitution therapy approved for individuals with PKU and uncontrolled blood Phe concentrations (>600 μmol/L) despite prior management. Aggregated results from the PRISM clinical trials demonstrated substantial and sustained reductions in blood Phe with a manageable safety profile, but also noted individual variation in time to and dose needed for a first response. This analysis reports longer-term aggregate findings and characterizes individual participant responses to pegvaliase using final data from the randomized trials PRISM-1 (NCT01819727) and PRISM-2 (NCT01889862), and the open-label extension study 165-304 (NCT03694353). In 261 adult participants with a mean of 36.6 months of pegvaliase treatment, 71.3%, 65.1%, and 59.4% achieved clinically significant blood Phe levels of ≤600, ≤360, and ≤ 120 μmol/L, respectively. Some participants achieved blood Phe reductions with <20 mg/day pegvaliase, although most required higher doses. Based on Kaplan-Meier analysis, median (minimum, maximum) time to first achievement of a blood Phe threshold of ≤600, ≤360, or ≤ 120 μmol/L was 4.4 (0.0, 54.0), 8.0 (0.0, 57.0), and 11.6 (0.0, 66.0) months, respectively. Once achieved, blood Phe levels remained below clinical threshold in most participants. Sustained Phe response (SPR), a new method described within for measuring durability of blood Phe response, was achieved by 85.5%, 84.7%, and 78.1% of blood Phe responders at blood Phe thresholds of ≤600, ≤360, or ≤ 120 μmol/L, respectively. Longer-term safety data were consistent with previous reports, with the most common adverse events (AEs) being arthralgia, injection site reactions, headache, and injection site erythema. The incidence of most AEs, including hypersensitivity AEs, was higher during the early treatment phase (≤6 months) than later during treatment. In conclusion, using data from three key pegvaliase clinical trials, participants treated with pegvaliase were able to reach clinically significant blood Phe reductions to clinical thresholds of ≤600, ≤360, or ≤ 120 μmol/L during early treatment, with safety profiles improving from early to sustained treatment. This study also supports the use of participant-level data and new ways of looking at durable blood Phe responses to better characterize patients' individual PKU treatment journeys.

Best practice recommendations for the management of anxiety during the pegvaliase journey

BACKGROUND

Pegvaliase, an enzyme substitution therapy, is a treatment option for phenylketonuria (PKU). Due to the neuropathophysiology and disease burden of PKU, individuals can experience baseline anxiety unrelated to pegvaliase therapy. In addition, there are aspects of pegvaliase therapy that may be anxiety-inducing for those considering or receiving treatment. The aim of this manuscript is to present best practice recommendations for the identification and management of anxiety symptoms that can occur along the pegvaliase journey.

METHODS

A modified Delphi approach was used to seek consensus among a multidisciplinary panel of experts. To this end, an in-person meeting was held that was preceded by a medical specialist- and patient-specific survey to develop preliminary recommendations on ways to address anxiety along the pegvaliase journey. After the meeting, an additional survey was conducted to rank the proposed solutions and mitigation strategies from which a set of recommendations was developed. All recommendations were voted on with the aim of consensus generation, defined as achieving ≥75% agreement among experts.

RESULTS

The panel reached consensus on a total of 28 best practice recommendations for the management of anxiety during the pre-treatment, induction and titration, early maintenance (pre-efficacy), and late maintenance (post-efficacy) stages. The recommendations offer strategies to identify and address the most common causes of pegvaliase-related anxiety, including self-injection, side effects, the titration schedule, prescribed dietary changes, and variable time to efficacy. Overall, managing anxiety in those considering or receiving pegvaliase involves patient-centered communication, shared decision-making, and personalized treatment plans.

CONCLUSIONS

The best practice recommendations described herein can guide healthcare providers in proactively addressing anxiety during the different stages of pegvaliase treatment, and support providers with initiating and managing pegvaliase in individuals who may experience baseline and treatment-related anxiety.

Advancements in therapeutics for inborn errors of metabolism

PURPOSE OF REVIEW

To present new therapeutic modalities for inborn errors of metabolism that are in clinical trials or recently approved by the US Food and Drug Administration (FDA) and to improve pediatricians' understanding of therapies their patients with inborn errors of metabolism receive.

RECENT FINDINGS

New therapies that move beyond the old standard modalities of recombinant human enzyme therapies, diet and medications have been recently approved by the US FDA to include nonhuman enzyme therapies, gene therapy and chaperone therapies.

SUMMARY

These new therapies offer more therapeutic options for individuals with inborn errors of metabolism. These new therapies have the potential to improve patient compliance and outcomes. Many other novel modalities are in the development pipeline, and are likely to transform the management of inborn errors of metabolism over the coming decade.

Pegvaliase dosing in adults with PKU: Requisite dose for efficacy decreases over time

Novel pharmaceutical therapies such as pegvaliase, phenylalanine ammonia lyase (PAL), have enhanced disease control for many individuals with phenylketonuria (PKU). We present a retrospective chart review to assess pegvaliase doses over time in individuals followed at the Boston Children's Hospital PAL Clinic, including those who started pegvaliase in a clinical trial ("trial patients") and those who started after drug came to market ("post-market patients"). Trial patients were on pegvaliase an average of 4.8 years longer, and their mean current pegvaliase dose was 126 ± 92 compared to 223 ± 147 mg/week for post-market patients (p = 0.0155), suggesting that the pegvaliase dose for target efficacy may decrease over time in adults with PKU. In post-market patients, we demonstrated a significant, inverse correlation with dose change and number of weeks from response (r = -0.46, p = 0.046). The entire cohort showed significant variability in terms of time to achieve a therapeutic response, response dose, and current dose. Our data suggest that patients tolerate a reduction in pegvaliase dose over time while maintaining efficacy. This is a clinically meaningful finding as it indicates that patients may reduce number of weekly injections over time on pegvaliase.