Pegzilarginase

Stockholm, August 29, 2025 – Immedica is pleased to announce the publication of favorable long-term data on Loargys (pegzilarginase), demonstrating sustained clinical benefits including clinically significant improvements in mobility and spasticity in patients 2 years and older with Arginase 1 deficiency (ARG1-D). ARG1-D is an autosomal recessive urea cycle disorder (UCD) characterized by chronic hyperargininemia, leading to progressive spasticity, developmental delay, and seizures. Current standard of care involves a strict protein-restricted diet, essential amino acid supplementation, and symptom management. Despite these interventions, maintaining normal plasma arginine levels and slowing disease progression remains challenging. The data, derived from two long-term follow-up studies involving 45 patients over up to five years of treatment and follow-up, highlights the significant benefits of Loargys. With longer-term treatment, Loargys has shown to sustainably improve mobility and reduce spasticity in patients with ARG1-D, alongside durable biochemical control and a favorable long-term safety profile. Key findings include: Pegzilarginase demonstrated sustained plasma arginine control to normalization. Improvements in functional mobility, meeting pre-defined minimum clinically important difference thresholds, as assessed by timed walk tests and dimensions of the Gross Motor Function Measure (GMFM) tool related to patient’s ability to stand, walk, run, and jump. 95% of patients (N=39) met composite response or achieved maximum score in at least one motor function domain. Most adverse events were mild to moderate, with no treatment-related discontinuations or persistent antibodies. These gains frequently exceeded stabilization, with several patients showing partial reversal of impairment. "The long-term data on Loargys underscore our commitment to addressing unmet needs in rare metabolic diseases," said Dr. Mattias Rudebeck, Head of Global Integrated Evidence Generation and Global Medical Head for RARE Metabolic diseases at Immedica. "These results demonstrate not only sustained biochemical control, but also clinically meaningful and durable improvements in mobility and spasticity for patients living with ARG1-D whom previously had few effective treatment options." "This is the largest and longest dataset we have on pegzilarginase to date, and the clinical benefits demonstrated are both encouraging and significant," said Dr. Markey McNutt, Assistant Professor at UT Southwestern Medical Center and lead author of the study. "For patients with ARG1-D, the sustained improvements in motor function and spasticity—and even signs of functional recovery—are a remarkable step forward in the management of this progressive condition." The publication can be accessed here: Long-term efficacy and tolerability of pegzilarginase in arginase 1 deficiency: results of two international multicenter open-label extension studies. Loargys is approved in the EU and the UK for treatment of ARG1-D in patients 2 years and older. In regions such as the U.S. where pegzilarginase is not approved, pegzilarginase is an investigational product and health authorities have not established the safety and efficacy of pegzilarginase. About the Trials Trial 1 (PEACE, NCT03921541) was a multicenter, double-blind, placebo-controlled trial evaluating the safety and efficacy of once weekly pegzilarginase in 32 pediatric and adult subjects aged 2 to 29 years at enrollment. The median duration of pegzilarginase exposure in the long-term extension, excluding the 24 weeks double-blind period, was 94 weeks (range: 62 to 152 weeks). Trial 2 (NCT03378531), was an open-label extension study evaluating long-term safety and efficacy of pegzilarginase. A total of 14 subjects aged 6 to 32 years were enrolled and treated with pegzilarginase once weekly. The median duration of pegzilarginase exposure was 208 weeks (range: 186 to 260 weeks). About Loargys® Loargys (pegzilarginase) is a novel recombinant human enzyme and has been shown to rapidly and sustainably lower levels of the amino acid arginine and its toxic metabolites in plasma accompanied by improvements in clinical outcomes. It is the first and only disease-modifying treatment. About ARG1-D ARG1-D is one of the eight urea cycle disorder (UCD) subtypes. It shares overlapping features with other UCDs and the most prominent is the impairment in excreting nitrogen. However, in ARG1-D, hyperammonemia is generally less severe and instead these patients show spasticity, which other subtypes do not. The principal defect in ARG1-D leads to accumulation of plasma arginine and its toxic metabolites, which occurs in almost all patients with this disorder. Patients are often diagnosed in late infancy or early childhood and the symptoms include spasticity, seizures, developmental delay, intellectual disability, and early mortality. About Immedica Immedica is a pharmaceutical company, headquartered in Stockholm, Sweden, focused on the commercialization of medicines for rare diseases and specialty care products. Immedica’s capabilities cover marketing and sales, compliance, pharmacovigilance, quality assurance, regulatory, medical affairs and market access, as well as a global distribution network serving patients in more than 50 countries. Immedica is fully dedicated to helping those living with diseases which have a large unmet medical need. Immedica’s therapeutic areas are within RARE metabolic, RARE hematology & oncology, RARE neurology and specialty care. Immedica was founded in 2018 and employs today around 140 people across Europe, the Middle East and the United States. Immedica is backed by the investment firms KKR and Impilo. For more information visit www.immedica.com. Immedica contact: Linda Holmström VP, Head of HR & Communication linda.holmstrom@immedica.com Immedica Pharma AB Solnavägen 3H SE-113 63 Stockholm Follow us to stay up to date with what is happening at Immedica. We believe we have an important role to fill in society – bringing new, innovative treatments to patients with rare diseases. Focus areas are within RARE metabolic, RARE neurology, RARE hematology & oncology and specialty care. We operate products from phase 2 and all the way to mature products. ESG is an integrated part of our business model. Stay up to date with our latest news. Telephone: +46 (0) 8 533 39 500 E-mail: info@immedica.com