Epidemiology, methods of diagnosis, and clinical management of patients with arginase 1 deficiency (ARG1-D): A systematic review.

BACKGROUND: Arginase 1 Deficiency (ARG1-D) is a rare, progressive, metabolic disorder that is characterized by devastating manifestations driven by elevated plasma arginine levels. It typically presents in early childhood with spasticity (predominately affecting the lower limbs), mobility impairment, seizures, developmental delay, and intellectual disability. This systematic review aims to identify and describe the published evidence outlining the epidemiology, diagnosis methods, measures of disease progression, clinical management, and outcomes for ARG1-D patients. METHODS: A comprehensive literature search across multiple databases such as MEDLINE, Embase, and a review of clinical studies in ClinicalTrials.gov (with results reported) was carried out per PRISMA guidelines on 20 April 2020 with no date restriction. Pre-defined eligibility criteria were used to identify studies with data specific to patients with ARG1-D. Two independent reviewers screened records and extracted data from included studies. Quality was assessed using the modified Newcastle-Ottawa Scale for non-comparative studies. RESULTS: Overall, 55 records reporting 40 completed studies and 3 ongoing studies were included. Ten studies reported the prevalence of ARG1-D in the general population, with a median of 1 in 1,000,000. Frequently reported diagnostic methods included genetic testing, plasma arginine levels, and red blood cell arginase activity. However, routine newborn screening is not universally available, and lack of disease awareness may prevent early diagnosis or lead to misdiagnosis, as the disease has overlapping symptomology with other diseases, such as cerebral palsy. Common manifestations reported at time of diagnosis and assessed for disease progression included spasticity (predominately affecting the lower limbs), mobility impairment, developmental delay, intellectual disability, and seizures. Severe dietary protein restriction, essential amino acid supplementation, and nitrogen scavenger administration were the most commonly reported treatments among patients with ARG1-D. Only a few studies reported meaningful clinical outcomes of these interventions on intellectual disability, motor function and adaptive behavior assessment, hospitalization, or death. The overall quality of included studies was assessed as good according to the Newcastle-Ottawa Scale. CONCLUSIONS: Although ARG1-D is a rare disease, published evidence demonstrates a high burden of disease for patients. The current standard of care is ineffective at preventing disease progression. There remains a clear need for new treatment options as well as improved access to diagnostics and disease awareness to detect and initiate treatment before the onset of clinical manifestations to potentially enable more normal development, improve symptomatology, or prevent disease progression.

Health care resource utilization in the management of patients with Arginase 1 Deficiency in the US: a retrospective, observational, claims database study.

BACKGROUND: Arginase 1 Deficiency (ARG1-D) is an inherited metabolic disease that leads to significant morbidity. AIMS: Despite the recognized burden of disease, information on health care resource utilization (HCRU) among patients with ARG1-D is lacking. We, therefore, sought to evaluate HCRU in ARG1-D relative to non-ARG1-D cohort. MATERIALS AND METHODS: Patients with ≥2 ICD-10-CM diagnosis codes for ARG1-D were identified (first diagnosis code = index date) using professional fee claims linked with prescription claims. Patients with ARG1-D were matched 1:1 to a comparator cohort of patients with other medical conditions. Matching variables included age, sex, index year, payer type (Medicare, Medicaid, third party) and geographic region. RESULTS: A total of 77 patients met the inclusion criteria for the ARG1-D cohort, with a median age of 15 years, 52% <18 years, and 52% male. Several concurrent diagnoses were recorded at a higher frequency in the ARG1-D cohort versus the matched comparator (spasticity 7 times higher; developmental delay ∼2 times higher; intellectual disability 5 times higher; and seizures 8 times higher). Emergency room visits occurred twice as often, laboratory tests were performed 1.5 times more often, hospitalization was required 3 times more often, and mean length of stay was longer for patients with ARG1-D than the comparator cohort (2.4 days vs. 0.3 days). LIMITATIONS: A relatively short study period while the burden of ARG1-D increases over a lifetime due to disease progression. CONCLUSIONS: Patients with ARG1-D had significantly greater HCRU compared with those without the disease; they presented with a more extensive comorbidity profile, accessed the health care system more frequently, required more intense monitoring and management, and had more frequent and longer hospitalizations relative to the comparator group. These findings demonstrate a high health burden in ARG1-D that is not mitigated by standard-of-care measures and emphasize the need for improved treatment options.

Price analysis of multiple sclerosis disease-modifying therapies marketed in the United States.

OBJECTIVES: This study assessed trends in the average wholesale price (AWP) at the market entry of disease-modifying therapies (DMTs) approved by Food and Drug Administration (FDA) in the period 1987-2014. METHODS: DMT regulatory information was derived from the FDA website. The AWPs per unit at market entry data were derived from the Red Book (Truven Health Analytics Inc.). The AWP history for each DMT was collected from its date of approval to 31 December 2014. The FDA approved label defined daily dose (DDD) for adult patients was obtained from FDA approved labels. The AWP per DDD and the AWP/DDD per year of therapy were computed. Descriptive statistics, Wilcoxon tests, t-test, and multiple linear regression were performed. The statistical significance level was set at 0.05. RESULTS: The FDA approved 12 multiple sclerosis (MS) DMTs, including five new drug applications (NDAs) and seven biologic license applications (BLAs) as of 31 December 2014. The FDA granted orphan designation to five DMTs. There was one DMT approved by the FDA in the 1980s, three in the 1990s, three in 2000s, and five in the period 2010-2014. The market entry inflation-adjusted AWP per DDD was $10.23 for the first DMT (mitoxantrone hydrochloride) that was approved in the 1980s. The median market entry inflation-adjusted AWP per DDD was $12.41 (interquartile range [IQR] = 4.51) for DMTs approved in the 1990s, $71.26 (IQR = 58.35) in the 2000s, and $172.56 (IQR = 84.97) in the period 2010-2014. The median AWP per DDD was statistically significantly different (p = 0.011) for orphan (median = $41.82, IQR = 56.077) compared to non-orphan drugs (median = $171.32, IQR = 199.29). Year of market entry was positively associated with DMT prices at US market entry (p = 0.01). CONCLUSIONS: The AWP per DDD for DMTs at market entry increased substantially over time. The increase in DMTs prices exceeded the general consumer price index.