Diagnosis & Management

DIAGNOSIS & MANAGEMENT

ARG1-D can be verified in routine testing

For newborns with a positive screen or people with a medical history, symptoms, and physical findings suggestive of ARG1-D, plasma arginine levels should be measured in a routine plasma quantitative amino acid analysis.^1-3

If hyperargininemia is present, the ARG1-D diagnosis may be confirmed by a genetic test¹*

*Due to the genetic heterogeneity of ARG1 genotypes, not all variants causing ARG1-D have been identified.¹

Management of ARG1-D requires an integrated approach

ARG1-D is a lifelong, chronic disease requiring a multidisciplinary care team. This care team could include a metabolic geneticist, a neurologist, a dietician, a physical therapist, and other healthcare professionals recommended by the team.^5,6

The current standard of care for ARG1-D primarily focuses on symptom management, including dietary protein restriction, arginine-free food supplements containing essential amino acids, and nitrogen scavengers.^1,4,7

LOARGYS is the first and only therapy proven to lower arginine⁸

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References: 1. Sun A, et al. Arginase deficiency. In: Adams MP, et al, eds. GeneReviews^®. Seattle, WA: University of Washington, Seattle; 2020. 2. Ah Mew N, et al. Urea Cycle Disorders Overview. 2003. Available at: https://www.ncbi.nlm.nih.gov/books/NBK1217/. Accessed May 31, 2025. 3. Therrell BL, et al. Newborn screening for hyperargininemia due to arginase 1 deficiency. Mol Gen Metab. 2017;121:308-313. 4. Häberle J, et al. Suggested guidelines for the diagnosis and management of urea cycle disorders: First revision. J Inherit Metab Dis. 2019;1-39. 5. NORD Guides for Physicians. The Physician’s Guide to Urea Cycle Disorders. 2012. Available at https://nucdforg.presencehost.net/file_download/79b6b024-9942-4e78-bcb7-24d6a77eeeeb. Accessed May 31, 2025. 6. Amayreh W, et al. Treatment of arginase deficiency revisited: guanidinoacetate as a therapeutic target and biomarker for therapeutic monitoring. Dev Med Child Neurol. 2014;56:1021-1024. 7. Diaz GA, et al. The role and control of arginine levels in arginase 1 deficiency. J Inherit Metab Dis. 2023;46(1):3-14. 8. Russo RS, et al. Efficacy and safety of pegzilarginase in arginase 1 deficiency (PEACE): a phase 3, randomized, double-blind, placebo-controlled, multi-centre trial. EClinicalMedicine. 2024;68:102405.

IMPORTANT SAFETY INFORMATION

WARNING: HYPERSENSITIVITY REACTIONS INCLUDING ANAPHYLAXIS
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Initiate LOARGYS in a healthcare setting with appropriate medical monitoring and support measures, including access to cardiopulmonary resuscitation equipment. If a severe hypersensitivity reaction (e.g., anaphylaxis) occurs, discontinue LOARGYS, and immediately initiate appropriate medical treatment, including use of epinephrine.

WARNINGS AND PRECAUTIONS

Hypersensitivity Reactions Including Anaphylaxis: Life-threatening hypersensitivity reactions, including anaphylaxis, have occurred in patients treated with enzyme replacement therapies, including LOARGYS. Hypersensitivity reactions that were mild to moderate in severity occurred in 13% (6/48) of LOARGYS-treated subjects in clinical trials. Hypersensitivity reactions have included facial swelling, rash, flushing and dyspnea. The reactions generally occurred with the first few doses but may occur later in treatment.

Administration of LOARGYS should be supervised by a healthcare provider knowledgeable in the management of hypersensitivity reactions including anaphylaxis in a healthcare setting with appropriate medical monitoring and support measures. Premedication with an antihistamine and/or corticosteroid should be considered in patients who previously have developed a hypersensitivity reaction. If a severe hypersensitivity reaction (e.g., anaphylaxis) occurs, discontinue LOARGYS and immediately initiate appropriate medical treatment, including use of epinephrine. Consider the risks and benefits of re-administering LOARGYS in patients who have experienced a severe hypersensitivity reaction. Caution should be exercised upon rechallenge. Inform patients of the symptoms of life-threatening hypersensitivity reactions and to seek immediate medical attention should symptoms occur. If a mild or moderate reaction occurs, consider treatment with antihistamines and/or corticosteroids.

ADVERSE REACTIONS

The most common adverse reactions are vomiting, pyrexia, infusion associated reactions and constipation.

USE IN SPECIFIC POPULATIONS

Pregnancy: There are no available data on LOARGYS use in pregnant females to evaluate for a drug-associated risk of major birth defects, miscarriage or other adverse maternal or fetal outcomes.

Lactation: There is no data on the presence of LOARGYS in either human or animal milk, the effects on the breastfed infant, or the effects on milk production. The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for LOARGYS and any potential adverse effects on the breast-fed infant from LOARGYS or from the underlying maternal condition.

Pediatric: The safety and effectiveness of LOARGYS have been established for the reduction of plasma arginine in pediatric patients 2 years and older with ARG-1 D, in conjunction with dietary protein restriction. The safety and effectiveness of LOARGYS have not been established for the reduction of plasma arginine in pediatric patients aged less than 2 years with ARG-1 D.

Geriatric: Clinical studies of LOARGYS did not include subjects 65 years of age and older to determine whether they respond differently from younger adult subjects.

Indication

LOARGYS is an arginine specific enzyme indicated for the treatment of hyperargininemia in adult and pediatric patients 2 years of age and older with Arginase 1 Deficiency (ARG1-D), in conjunction with dietary protein restriction.

This indication is approved under accelerated approval based on reduction of plasma arginine. Continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial.