Pegzilarginase 2mg/0.4ml solution for injection vials

Background: Arginase 1 Deficiency (ARG1-D) is a rare debilitating, progressive, inherited, metabolic disease characterized by marked increases in plasma arginine (pArg) and its metabolites, with increased morbidity, substantial reductions in quality of life, and premature mortality. Effective treatments that can lower arginine and improve clinical outcomes is currently lacking. Pegzilarginase is a novel human arginase 1 enzyme therapy. The present trial aimed to demonstrate efficacy of pegzilarginase on pArg and key mobility outcomes. Methods: This Phase 3 randomized, double-blind, placebo-controlled, parallel-group clinical trial (clinicaltrials.govNCT03921541, EudraCT 2018-004837-34), randomized patients with ARG1-D 2:1 to intravenously/subcutaneously once-weekly pegzilarginase or placebo in conjunction with their individualized disease management. It was conducted in 7 countries; United States, United Kingdom, Canada, Austria, France, Germany, Italy. Primary endpoint was change from baseline in pArg after 24 weeks; key secondary endpoints were change from baseline at Week 24 in Gross Motor Function Measure part E (GMFM-E) and 2-min walk test (2MWT). Full Analysis Set was used for the analyses. Findings: < 0.0001) and normalized levels in 90.5% of patients (vs 0% with placebo). In addition, clinically relevant functional mobility improvements were demonstrated with pegzilarginase treatment. These effects were sustained long-term through additional 24 weeks of subsequent exposure. Pegzilarginase was well-tolerated, with adverse events being mostly transient and mild/moderate in severity. Interpretation: These results support pegzilarginase as the first potential treatment to normalize pArg in ARG1-D and achieve clinically meaningful improvements in functional mobility. Funding: Aeglea BioTherapeutics.

Abstract licence: CC BY

BACKGROUND: Arginase 1 deficiency (ARG1-D) is a rare hereditary urea cycle disorder characterized by elevated arginine levels, resulting in progressive neurological impairment and severe physical and cognitive disability. Due to its low prevalence, overlapping symptoms with other neurological disorders, and current limitations in newborn screening tools, ARG1-D is often misdiagnosed or diagnosed late, limiting access to early interventions. AIM: This review and expert opinion aim to provide an overview of the clinical manifestations, diagnostic challenges, and treatment options for ARG1-D, offering a practical resource for specialists to recognize this rare, progressive, yet treatable disease. RESULTS: ARG1-D typically presents with progressive spastic paraplegia, developmental delays, cognitive impairment, and seizures, with symptom onset and severity varying by age. Differential diagnoses mainly include hereditary spastic paraplegia, cerebral palsy, and hyperornithinemia-hyperammonemia-homocitrullinuria syndrome, each with distinct clinical features and biochemical markers. Potential red flags for ARG1-D include elevated plasma arginine levels, spasticity, seizures, and cognitive impairment. These should prompt further examinations to confirm the diagnosis, which is based on biochemical assays for hyperargininemia and on genetic testing. Once confirmed, early treatment is advised, including dietary protein restriction, ammonia scavengers, antiepileptic drugs, and novel therapies, such as pegzilarginase, which targets the disease's metabolic root. CONCLUSION: Experts stress the importance of increased awareness of ARG1-D characteristics, noting that early recognition and treatment are crucial to patient outcomes. Greater recognition of ARG1-D's distinctive features, differential diagnosis, and diagnostic tools, even among non-specialist clinicians, could help prevent misdiagnoses and facilitate the identification of this rare yet treatable condition.

Abstract licence: CC BY

Arginine deprivation has gained increasing traction as a novel and safe antimetabolite strategy for the treatment of several hard-to-treat cancers characterised by a critical dependency on arginine. Small cell lung cancer (SCLC) displays marked arginine auxotrophy due to inactivation of the rate-limiting enzyme argininosuccinate synthetase 1 (ASS1), and as a consequence may be targeted with pegylated arginine deiminase or ADI-PEG20 (pegargiminase) and human recombinant pegylated arginases (rhArgPEG, BCT-100 and pegzilarginase). Although preclinical studies reveal that ASS1-deficient SCLC cell lines are highly sensitive to arginine-degrading enzymes, there is a clear disconnect with the clinic with minimal activity seen to date that may be due in part to patient selection. Recent studies have explored resistance mechanisms to arginine depletion focusing on tumor adaptation, such as ASS1 re-expression and autophagy, stromal cell inputs including macrophage infiltration, and tumor heterogeneity. Here, we explore how arginine deprivation may be combined strategically with novel agents to improve SCLC management by modulating resistance and increasing the efficacy of existing agents. Moreover, recent work has identified an intriguing role for targeting arginine in combination with PD-1/PD-L1 immune checkpoint inhibitors and clinical trials are in progress. Thus, future studies of arginine-depleting agents with chemoimmunotherapy, the current standard of care for SCLC, may lead to enhanced disease control and much needed improvements in long-term survival for patients.

Abstract licence: CC BY-NC

Arginase 1 deficiency (ARG1-D) is an autosomal recessive urea cycle disorder characterised by chronic hyperargininaemia, progressive spasticity, loss of mobility, and cognitive dysfunction. Standard of care (SOC), based on dietary protein restriction, rarely prevents progression. Pegzilarginase, a recombinant human enzyme, is the first approved disease-modifying therapy. We report outcomes from Study 102A (n = 14; up to 5 years) and the PEACE long-term extension (LTE) (n = 31; up to 3 years). Weekly pegzilarginase was administered with SOC. Outcomes included functional mobility (2-/6-minute walk tests [2MWT/6MWT], Gross Motor Function Measure [GMFM] D/E), spasticity (Modified Ashworth Scale [MAS]), plasma arginine, guanidino compounds, and safety. In PEACE, LTE arms were named according to initial 24-week double-blind treatment: placebo-pegzilarginase or pegzilarginase-pegzilarginase. Of 39 evaluable participants, 37 (95%) met composite response or achieved maximum score in ≥ 1 motor function domain. In 102A, mean 6MWT improved to 68.2 m (+19%; n = 12); GMFM-D/E increased by 2.7/3.7. In PEACE (pegzilarginase-pegzilarginase; placebo-pegzilarginase), 2MWT improved to 16.5 m (+25%; n = 6) and 13.5 m (+16%; n = 2); GMFM-D/E improved by 4.3/6.0 (n = 6) and 5.3/11.3 (n = 3). Spasticity improved in 21/25 (84%), with 12 reaching MAS 0 (no spasticity). Pegzilarginase sustained plasma arginine control: in 102A, means were 118 μmol/L at Week 192 (n = 9); in PEACE, < 115 μmol/L through Week 96 (n = 11). Guanidinoacetic acid normalised; N-acetylarginine approached normal; argininic acid and α-keto-δ-guanidinovaleric acid declined by > 50%. Most adverse events were mild/moderate; no treatment-related discontinuations or persistent antibodies occurred. Pegzilarginase produced sustained improvements in mobility, spasticity and biochemical control, supporting early intervention, long-term use and disease modification in ARG1-D.

Abstract licence: CC BY

Arginase 1 deficiency (ARG1-D) is an ultra-rare inherited metabolic disorder of the urea cycle, caused by partial or complete loss of arginase 1 function, characterised by hyperargininaemia and a distinct, progressive neurological phenotype. The clinical development programme of pegzilarginase, a recombinant human ARG1 enzyme therapy, provides an opportunity to study the largest ARG1-D cohort to date. The analysis included 48 paediatric and adult subjects (≥ 2 years) enrolled in the pegzilarginase trials. Baseline data collected before treatment included demographics, genotypes, red blood cell arginase activity, biochemical measures, age of symptom onset, neuromotor and neurological characteristics, growth indicators, quality of life, and use of treatments and assistive devices. The mean (SD) age of onset was 2.2 (3.6) years, which preceded diagnosis at 3.7 (5.0) years. Clinical features included motor impairment (48/48, 100%), spasticity (33/48, 69%), cognitive deficits (31/48, 65%), intellectual disability (23/36, 64%), speech and language deficits (26/48, 54%), and seizures (18/48, 38%), with symptom-onset data consistent with a progressive phenotype. Median GMFCS Level II indicated moderate mobility limitation; two-thirds scored < 69 on FSIQ, and mean PedsQL total proxy scores were around 20% lower than typically developing peers. All subjects followed a protein-restricted diet, and 90% used ammonia scavengers. ARG1-D presents with a heterogeneous array of progressive and debilitating neurologic symptoms. These findings reflect the progressive impact of the disease and offer insights into its burden and natural history based on a large cohort, assessed using standardised neuromotor, cognitive, and quality-of-life instruments across international sites.

Abstract licence: CC BY

ABSTRACT Pegzilarginase is the first disease‐modifying drug for arginase 1 deficiency. In clinical trials, pegzilarginase effectively normalised plasma arginine (pArg), which was associated with clinically relevant improvements in neuromotor outcomes. We report from a French early access scheme the first report on experience from pegzilarginase therapy outside a clinical trial. Sixteen patients were started in the programme between September 2022 and September 2024. Six had previously participated in a clinical trial (PCT) and 10 were treatment naïve (TN). Clinical data was collected at baseline, after 3 months, and then 6‐monthly. Mean pegzilarginase exposure was 78.9 weeks. Fourteen patients had been treated for ≥ 12 months. At the 3‐month follow‐up, mean pArg had dropped from 430 to 128 μmol/L (70%) for the TN group and from 168 to 107 μmol/L (36%) for the PCT group. Interestingly, one patient discontinued after 69 weeks of therapy due to absence of decrease of pArg despite stepwise increase of dose. After discontinuation of pegzilarginase, the presence of anti‐drug antibodies (ADAs) was confirmed. For the whole cohort, average daily intake of dietary protein increased from 0.61 to 0.91 g/kg/day during the first 12 months ( p = 0.02). No firm conclusions could be drawn from quality‐of‐life data, but trends were positive. In conclusion, our results are in line with what has been previously reported from clinical trials.

Abstract licence: CC BY

BACKGROUND: Arginase 1 deficiency (ARG1-D) is an ultra-rare urea cycle disorder characterized by hyperargininemia and progressive neurological impairment, including spasticity, loss of motor function, and reduced quality of life. Conventional management based on dietary protein restriction and ammonia scavengers rarely achieves adequate metabolic control or prevents neurological deterioration. Pegzilarginase, a recombinant human arginase 1 enzyme, is the first disease-modifying therapy for ARG1-D. METHODS: We report the first Italian real-world experience with pegzilarginase in three pediatric patients with genetically confirmed ARG1-D enrolled in the phase 3 PEACE trial. Clinical, biochemical, functional, nutritional and quality-of-life data were retrospectively collected over a long-term follow-up (2003-2025). Outcomes were evaluated across three phases: treatment initiation (Start), a 13-month treatment interruption due to trial closure (Stop), and therapy re-initiation through an early access program (Restart). RESULTS: Pegzilarginase rapidly normalized plasma arginine levels and was associated with improvements in motor function, spasticity, walking endurance, dietary protein tolerance, bone mineral density, and quality of life. During treatment interruption, all patients experienced biochemical worsening and clinical deterioration, including increased spasticity, reduced mobility, and emotional distress. Re-initiation of pegzilarginase restored metabolic control and led to progressive neurological and functional recovery, including partial reversal of long-standing motor deficits. CONCLUSIONS: This real-world experience supports pegzilarginase as a disease-modifying therapy for ARG1-D. Sustained normalization of plasma arginine, rather than subthreshold biochemical control, correlates with functional and neurological improvement and may partially reverse non-lesional metabolic brain injury. Early initiation of pegzilarginase, including in newborn-screened patients, may further modify the natural history of ARG1-D.

Abstract licence: CC BY