A post hoc analysis of Projected Retained Ability Scores (PRAS) for the longitudinal assessment of cognitive functioning in patients with neuronopathic mucopolysaccharidosis II receiving intrathecal idursulfase-IT.

BACKGROUND: Norm-based scores used to assess cognitive ability have clinical value when describing functioning of patients with neuronopathic disorders compared with unaffected, same-age peers. However, they have limitations when used to assess change in cognitive ability between two timepoints, especially in children with severe cognitive decline. Calculation of Projected Retained Ability Scores (PRAS) is a novel method developed to characterize absolute change in norm-based ability test scores. In this analysis, PRAS were calculated post hoc for children with mucopolysaccharidosis II (MPS II; Hunter syndrome) and early cognitive impairment in a 52-week phase 2/3 randomized controlled trial (RCT) and its extension study of intrathecal idursulfase (idursulfase-IT). Patients completing the first year of the extension after receiving idursulfase-IT in the RCT and extension (n = 32 of 34 enrolled) or the extension only (n = 15 of 15 enrolled) were categorized according to changes in Differential Ability Scales, Second Edition, General Conceptual Ability (DAS-II GCA) scores and PRAS at 1 and 2 years. Analyses were conducted in the overall population and a subpopulation aged < 6 years at baseline (idursulfase-IT in the RCT and extension [n = 27] and extension only [n = 12]). RESULTS: PRAS methodology differentiated patients with decreases in DAS-II GCA scores into three separate categories reflecting below-average cognitive growth rates, plateauing cognitive development, and deteriorating cognitive functioning. After 1 year in the RCT, 72.4% of patients who initiated idursulfase-IT had above-average or average cognitive growth rates in DAS-II GCA scores compared with 53.3% of those who did not receive idursulfase-IT; 6.9% versus 20.0% experienced deteriorating cognitive functioning. Similar results were seen in children aged < 6 years: 76% (idursulfase-IT group) versus 50% (no idursulfase-IT) had above-average or average cognitive growth rates in DAS-II GCA scores; 4% versus 17% had deteriorating cognitive functioning. The difference in the distributions of cognitive categories at 1 year in children aged < 6 years was significant (p = 0.048). At 2 years, the proportions of patients in different cognitive categories were more similar between treatment groups. CONCLUSIONS: PRAS methodology may help to differentiate changes in cognitive development in MPS II, and therefore may represent a valuable addition to existing approaches for interpreting changes in cognitive scores over time. TRIAL REGISTRATION: ClinicalTrials.gov NCT02055118 (registration date: 4 February 2014) and NCT02412787 (registration date: 9 April 2015).

Eficacia y seguridad de idursulfasa en el tratamiento del síndrome de hunter / Efficacy and safety of idursulfase in the treatment of hunter syndrome

INTRODUCCIÓN: El presente informe expone la evaluación del uso de idursulfasa para el tratamiento de pacientes con diagnóstico de mucopolisacaridosis tipo II (síndrome de Hunter) en comparación a mejor tratamiento de soporte o placebo. La mucopolisacaridosis tipo II (MPS II) o síndrome de Hunter es una enfermedad de depósito lisosomal. Esta se debe a la deficiencia de iduronato-2-sulfatasa, responsable de la acumulación en los lisosomas de los diferentes tejidos de glicosaminoglicanos (GAG). Dicha deficiencia es causada por mutaciones en el gen iduronato-2-sulfatasa (IDS) localizado en el cromosoma X (gen Xq28), que codifica la enzima (IDS). La enfermedad tiene dos formas de presentación: tempranas y tardías. Las formas tempranas (diagnóstico alrededor de 2 a 4 años) son las más graves; los pacientes tienen daño cerebral que conduce a retraso mental y muerte prematura (10 años). Las formas tardías son las más moderadas; la supervivencia es más prolongada. Las complicaciones son principalmente osteoarticulares y cardiorrespiratorias. TECNOLOGÍAS SANITARIA DE INTERÉS: IDURSULFASA: El idursulfasa (Elaprase®, ShireHuman Genetic Therapies, Inc, Cambridge, MA) es la forma recombinante de la enzima humana lisozima, iduronato-2-sulfatasa (IDS). METODOLOGÍA: Se realizó una búsqueda de la literatura con respecto a la eficacia y seguridad de uso de idursulfasa para el tratamiento de pacientes con diagnóstico de MPS II (síndrome de Hunter) en comparación a mejor tratamiento de soporte o placebo. Esta búsqueda se realizó utilizando los meta-buscadores: Translating Research into Practice (TRIPDATABASE), National Library of Medicine (Pubmed-Medline) y Health Systems Evidence. Adicionalmente, se amplió la búsqueda revisando la evidencia generada por grupos internacionales que realizan revisiones sistemáticas (RS), evaluación de tecnologías sanitarias (ETS) y guías de práctica clínica (GPC), tales como la Cochrane Group, The National Institute for Health and Care Excellence (NICE), The Agency for Health care Research and Quality (AHRQ), The Canadian Agency for Drugs and Technologies in Health (CADTH), El Haute Autorité de Santé (HAS) y The Scottish Medicines Consortium (SMC). Esta búsqueda se completó ingresando a la página web www.clinicaltrials.gov, para así poder identificar ensayos clínicos en elaboración o que no hayan sido publicados aún, y así disminuir el riesgo de sesgo de publicación. RESULTADOS: La mejor evidencia disponible del uso de idursulfasa intravenoso proviene de un único ensayo clínico aleatorizado (ECA) publicado por Muenzer et al., 2006. Este fue un ECA controlado con placebo, doble ciego, realizado en 96 pacientes entre 5 y 31 años tratados por 52 semanas. El tratamiento con idursulfasa mejoró la prueba de caminata de 6 minutos o 6MWT (por sus siglas en inglés 6 minutes walking test) en comparación con el placebo, pero la relevancia clínica de la ganancia es cuestionable. El efecto de idursulfasa en la función pulmonar no pudo establecerse claramente: no se observó diferencia en el porcentaje de capacidad vital forzada (CVF) predicha. Aunque hubo una disminución significativa en los volúmenes del hígado, bazo y excreción urinaria de GAG, estos efectos biológicos no se tradujeron en mejoras de los múltiples desenlaces clínicos de esta enfermedad (i.e apnea del sueño, masa ventricular, movilidad de las articulaciones, calidad de vida, dolor, tasa de hospitalizaciones y función auditiva). Tampoco hay datos clínicos que demuestren un beneficio en las manifestaciones neurológicas de la enfermedad. CONCLUSIONES: La mucopolisacaridosis tipo II o síndrome de Hunter es una enfermedad de depósito lisosomal del grupo de mucopolisacaridosis. Las formas tempranas de la enfermedad (diagnóstico alrededor de 2 a 4 años) son las más graves; los pacientes tienen daño cerebral que conduce a retraso mental y muerte prematura (10 años). Las formas tardías son las más moderadas; la sobrevida es prolongada y la capacidad intelectual está preservada. Las complicaciones son principalmente osteoarticulares y cardiorrespiratorias. El tratamiento general se enfoca a los síntomas de la enfermedad y requiere el uso de un equipo multidisciplinario. Se puede proponer el trasplante alogénico de médula ósea, aunque el beneficio clínico es limitado, ya que no previene el deterioro intelectual. Idursulfasa es la primera y única terapia de reemplazo de enzimas disponible para el tratamiento de estos pacientes. Idursulfasa se evaluó en un único ECA que mostró que tras de un año de tratamiento, los pacientes tratados con idursulfasa 0.5 mg/semana tuvieron una mejora estadísticamente significativa en el 6WMT (aumento del 9 % respecto al valor basal), una reducción estadísticamente significativa de los volúmenes del hígado y bazo, y excreción urinaria de GAG. Sin embargo, no hubo cambios significativos en el %CVF predicha, la calidad de vida, dolor y movimiento articular. Los efectos de idursulfasa observados al año de tratamiento en el único ECA, no se confirmaron en pacientes tratados en la práctica clínica a mayor plazo. Así, el estudio de extensión (3 años) solo mostró una diferencia estadística del 6WMT, respecto al basal, solo en un punto temporal y no hubo cambios en el %CVF predicha. No hubo diferencias en el resto de desenlaces evaluados. El registro HOS concebido con el fin de evaluar a mayor plazo (10 años) los efectos de idursulfasa y solicitado por las agencias evaluadoras del medicamento, no cumplió con su objetivo debido a la gran cantidad de cuestionarios de seguimientos faltantes a partir del primer año. Se han detectado anticuerpos contra idursulfasa en casi la tercera parte de los pacientes y su efecto en la eficacia y seguridad de idursulfasa aún no está completamente evaluado. Puede que idursulfasa mejore la condición física, disminuya la organomegalia y la excreción urinaria de GAG, pero no ha mostrado mejorar desenlaces clínicamente relevantes como la calidad de vida, el dolor, las tasas de hospitalización o los recursos requeridos para los cuidados en casa. A la fecha, idursulfasa es una tecnología sanitaria que tiene un perfil de costo-oportunidad poco ventajoso para sistemas públicos de servicios de salud, debido a que los beneficios biológicos observados no se han traducido en desenlaces clínicamente relevantes para los pacientes con MPS II. el Instituto de Evaluación de Tecnologías en Salud e Investigación IETSI no aprueba el uso de idursulfasa para el tratamiento de pacientes con MPS II.

A comparison study of bioanalytical methods for characterization of anti-idursulfase antibodies.

AIM: Legacy methods with complex testing scheme for characterization of anti-idursulfase antibodies (ADA) were simplified and optimized in order to meet current regulatory guidance and provide more timely and cost-effective support for routine patient care. RESULTS: To compare the performance of the original and updated methods, patient samples receiving commercially prescribed Elaprase treatment were analyzed by both test methods. The ADA and neutralizing antibody results obtained by both methods were highly correlated and the updated method had an overall higher ADA and neutralizing antibody positive rates and higher ADA titers. CONCLUSION: The updated methods and test schemes are much simpler, more sensitive, but are also highly comparable with the original methods for the measurement of total and neutralizing ADA.

Cost-Effectiveness of the Quantification of Enzymatic Activity in Leukocytes in Comparison to Its Nonrealization for a Rare Disease in Latin America: The Case of Mucopolysaccharidosis Type II in Colombia.

BACKGROUND: Mucopolysaccharidosis (MPS) type II is produced by a deficiency of iduronate-2-sulfatase (I2S). The quantification of the enzyme activity in leukocytes is used as diagnostic confirmation of MPS. OBJECTIVE: To determinate the cost-effectiveness of the measurement of I2S enzyme activity in leukocytes compared with not carrying out the enzyme activity measurement for diagnostic confirmation of MPS II from the perspective of the Colombian health system. METHODS: A cost-effectiveness analysis was conducted on the basis of a decision tree model. The measure of effectiveness was the correct diagnosis of cases of MPS II. The costs of I2S enzymatic quantification in leukocytes, consultation with a geneticist and with other specialists, and costs of diagnostic procedures were included. The time horizon was less than 1 year. A probabilistic sensitivity analysis was performed using Monte-Carlo simulation with 10,000 iterations. RESULTS: The incremental cost was -US $43,145 with an incremental effectiveness of 42 cases. The probabilistic sensitivity analysis confirms the results of basal data, in which the quantification of I2S enzyme activity was less costly and more effective than the alternative. CONCLUSIONS: The quantification of I2S enzymatic activity is a dominant technology for the diagnostic confirmation of MPS II, compared with not making the quantification, from the perspective of the Colombian health system.

Informe de adopción de ETS: idursulfasa para síndrome de Hunter / ETS adoption report: idursulfase for Hunter syndrome

El uso de Idursulfasa como tratamiento del síndrome de Hunter o Mucopolisacaridosis tipo II, genera beneficios a los pacientes, relacionados a la capacidad de desempeñar algunas funciones como caminar y mejoría en el tamaño del bazo y el hígado que podrían producir molestias al paciente. Se recomienda la cobertura del medicamento Idursulfasa como tratamiento del síndrome de Hunter o Mucopolisacaridosis tipo II, bajo la modalidad de cobertura con generación de evidencia.(AU)

Protocolo de evaluación rápida de seguridad y efectividad del uso de Idursulfasa en el tratamiento de pacientes con síndrome de Hunter / Protocol of rapid evaluation of safety and effectiveness of the use of Idursulfase in the treatment of patients with Hunter syndrome

El Síndrome de Hunter o Mucopolisacaridosis tipo II (MPSII) es una enfermedad de almacenamiento lisosomal ocasionada por la deficiencia de la enzima iduronato 2 sulfatasa, su incidencia se calcula en aproximadamente 1 por cada 132 000 recién nacidos vivos varones de acuerdo al reporte de algunos estudios europeos, esta enfermedad es una entidad progresiva, incapacitante y con daños irreversibles. Las personas que padecen la forma de aparición temprana (severa) generalmente viven durante 10 a 20 años, mientras que las personas con la forma de aparición tardía (leve) viven de 20 a 60 años. El Fondo Intangible Solidario de Salud solicita la evaluación de la tecnología sanitaria idursulfasa como tratamiento síndrome de Hunter, la cual a su vez fue solicitada Instituto Nacional de Salud del Niño, a raíz de la aparición de un caso. Luego de una primera revisión, se determina que la tecnología idursulfasa, comercializada en el Perú como Elaprase 2 mg/mL, supera la tolerancia al riesgo para evaluación de tecnologías sanitarias en el Seguro Integral de Salud, por lo se consideró sea evaluada por el área de Evaluación de Tecnologías Sanitarias en el SIS Central.(AU)

Eficácia e segurança da terapia com idursulfase em pacientes com mucopolissacaridose tipo II, com e sem comparação com placebo: revisão sistemática e metanálise / Efficacy and safety of idursulfase therapy in patients with mucopolysaccharidosis type II with and without comparison to placebo: systematic review and meta-analysis / Eficacia y seguridad del tratamiento con idursulfasa en pacientes con mucopolisacaridosis tipo II con y sin comparación con el placebo: revisión sistemática y metaanálisis

A mucopolissacaridose tipo II (MPS II) é uma doença genética de amplo espectro clínico, caracterizada por deficiência da enzima iduronato-2sulfatase. Revisão sistemática avaliou a eficácia e segurança da terapia de reposição enzimática (TRE) com idursulfase (IDS) na MPS II. As bases de dados PubMed/MEDLINE, Embase, LILACS e Biblioteca Cochrane foram pesquisados até 30 de novembro de 2012. Apenas cinco estudos preencheram os critérios de inclusão (ensaios clínicos randomizados - ECRs, ECRs abertos ou séries de caso prospectivas, incluindo cinco ou mais pacientes e avaliando desfechos relevantes). Metanálise foi realizada para capacidade vital forçada (CVF; valores absolutos e em %) e para a distância percorrida no teste da caminhada dos seis minutos, com mudanças significativas em ambas as variáveis; também foi encontrado risco aumentado de reações leves relacionadas à infusão e de desenvolvimento de anticorpos IgG à IDS. Em face dos dados apresentados neste estudo, conclui-se que a TRE com IDS é segura e tem benefício potencial em MPS II, mas estudos adicionais são necessários.

Mucopolysaccharidosis type II (MPS II) is a genetic disease of broad clinical spectrum, characterized by a deficiency of the enzyme iduronate2-sulfatase. The aim of this study was to assess whether enzyme replacement therapy (ERT) with idursulfase (IDS) for MPS II is effective and safe. PubMed/MEDLINE, Embase, LILACS, and Cochrane Library were searched until November 30, 2012. Only five articles met the inclusion criteria (randomized controlled trials - RCTs, or open-label trials/prospective case series including > 5 patients and evaluating relevant outcomes). A meta-analysis was performed for forced vital capacity (FVC; absolute and %) and for distance walked on the 6-minute walking test (6MWT). There was a statistically significant increase, but not clinically relevant, in both variables; an increased risk for development of mild infusion-related reactions and IgG antibodies to IDS were also found. The data suggest that ERT with IDS is safe and has a potential benefit for MPS II patients, but further studies are required.

La mucopolisacaridosis tipo II (MPS II) es una enfermedad genética de amplio espectro clínico, caracterizada por una deficiencia de la enzima iduronato-2-sulfatasa. El objetivo fue evaluar la seguridad y eficacia de la Terapia de Reemplazo Enzimático (TRE) con idursulfasa (IDS) en la MPS II. En las bases PubMed/MEDLINE, EMBASE, LILACS y Cochrane Library se inició la búsqueda hasta el 30 de noviembre de 2012. Sólo cinco estudios cumplieron los criterios de inclusión (ensayos controlados aleatorios -ECA, o ECA abiertos o series de casos prospectivo incluyendo > 5 pacientes y evaluación de los resultados pertinentes). El metaanálisis se realizó para la capacidad vital forzada (FVC; absoluta y %) y la distancia caminada en 6 minutos, con cambios significativos en ambas variables; el riesgo también se encuentra aumentado por reacciones leves y anticuerpos IgG, relacionados con la infusión con IDS. El TRE con IDS es seguro y tiene un beneficio potencial en la MPS II, pero se necesitan estudios adicionales.

Home treatment in paediatric patients with Hunter syndrome: the first Italian experience.

Hunter syndrome (mucopolysaccharidosis type II [MPS II], OMIM309900) is a rare X-linked lysosomal storage disorder caused by the deficiency of the enzyme iduronate-2-sulphatase, resulting in accumulation of glycosaminoglycans, progressive multisystem organ failure, and early death. Enzyme replacement therapy (ERT) with weekly intravenous infusions of idursulfase, a treatment for MPS II and commercially available since 2007, has been shown to improve certain symptoms and signs of the disease. The efficacy and safety data of this enzyme preparation have been widely reported and, after a change to the idursulfase Summary of Product Characteristics in March 2010, home ERT by infusion is now an option for selected patients. Previously reported experiences of home therapy in MPS II have shown increased treatment compliance and an improvement in quality of life for both patients and families. We report the results of the home therapy experience of 3 paediatric patients with MPS II in southern Italy. This pilot experience with home infusion is the first reported from Italy.

An evaluation framework for funding drugs for rare diseases.

OBJECTIVES: For rare diseases it may be difficult to generate data from randomized trials to support funding of a drug. Enzyme replacement therapies for diseases of inherited metabolic enzyme deficiency provide an example of this dilemma. The Ontario Public Drug Programs convened the Drugs for Rare Diseases Working Group to develop a policy for assessing these drugs. METHODS: The Drugs for Rare Diseases Working Group developed terms of reference expecting that the ideal policy product would be transparent and consistent and address unique aspects of the treatment of a specific rare condition while being adaptable to other dissimilar conditions. The perspective was that of a public payer addressing requests for funding generated for a specific drug, and included respect for the principles of "accountability for reasonableness" of Daniels and Sabin. RESULTS: A seven-step framework was developed and tested by using the case study of idursulfase for mucopolysaccharidosis II (Hunter disease). Estimation of clinical effectiveness was done by using decision modeling. The model developed informed funding recommendations and ultimately led to an agreement with the manufacturer allowing funding of idursulfase in Ontario. CONCLUSIONS: This policy framework attempts to address the policy challenges of funding drugs for rare diseases. The framework will be used to assess other drugs in future and will inevitably require modification with experience. It is hoped that it may be of value to other policymakers.

Development of the multi-attribute Adolescent Health Utility Measure (AHUM).

OBJECTIVE: Obtain utilities (preferences) for a generalizable set of health states experienced by older children and adolescents who receive therapy for chronic health conditions. METHODS: A health state classification system, the Adolescent Health Utility Measure (AHUM), was developed based on generic health status measures and input from children with Hunter syndrome and their caregivers. The AHUM contains six dimensions with 4-7 severity levels: self-care, pain, mobility, strenuous activities, self-image, and health perceptions. Using the time trade off (TTO) approach, a UK population sample provided utilities for 62 of 16,800 AHUM states. A mixed effects model was used to estimate utilities for the AHUM states. The AHUM was applied to trial NCT00069641 of idursulfase for Hunter syndrome and its extension (NCT00630747). RESULTS: Observations (i.e., utilities) totaled 3,744 (12*312 participants), with between 43 to 60 for each health state except for the best and worst states which had 312 observations. The mean utilities for the best and worst AHUM states were 0.99 and 0.41, respectively. The random effects model was statistically significant (p < 0.0001; adjusted R2 = 0.361; RMSE = 0.194). When AHUM utilities were applied to the idursulfase trial, mean utilities in the idursulfase weekly and placebo groups improved +0.087 and +0.006, respectively, from baseline to week 53. In the extension, when all patients received idursulfase, the utilities in the treatment group remained stable and the placebo group improved +0.039. DISCUSSION: The AHUM health state classification system may be used in future research to enable calculation of quality-adjust life expectancy for applicable health conditions.

[Consequences of the judicialization of health policies: the cost of medicines for mucopolysaccharidosis]. / Consequências da judicialização das políticas de saúde: custos de medicamentos para as mucopolissacaridoses.

This study analyzes expenditures backed by court rulings to ensure the public provision of medicines for treatment of mucopolysaccharidosis (MPS), a rare disease that requires high-cost drugs not covered by the Brazilian government's policy for pharmaceutical care and which have disputed clinical efficacy. The methodology included a review of files from 196 court rulings ordering the Brazilian Ministry of Health to provide the medicines, in addition to Ministry of Health administrative records. According to the analysis, the "judicialization" of the health system subjected the Brazilian government to a monopoly in the distribution of medicines and consequently the loss of its capacity to manage drug purchases. The study also indicates that the imposition of immediate, individualized purchases prevents obtaining economies of scale with planned procurement of larger amounts of the medication, besides causing logistic difficulties in controlling the amounts consumed and stored. In conclusion, litigation results from the lack of a clear policy in the health system for rare diseases in general, thereby leading to excessive expenditures for MPS treatment.

Consequências da judicialização das políticas de saúde: custos de medicamentos para as mucopolissacaridoses / Consequences of the judicialization of health policies: the cost of medicines for mucopolysaccharidosis

O estudo analisa os gastos da judicialização de medicamentos para a mucopolissacaridose (MPS), uma doença rara, de alto custo, fora da política de assistência farmacêutica e com benefício clínico. O levantamento de dados foi realizado nos arquivos de 196 dossiês que determinou que o Ministério da Saúde fornecesse medicamentos no período entre 2006 e 2010, e nos registros administrativos e contábeis do Ministério da Saúde. A análise identifica sujeição do governo brasileiro a monopólios de distribuição de medicamentos e, consequentemente, perda de sua capacidade de administrar compras. Também identifica que a imposição da aquisição imediata e individualizada impede a obtenção de economias de escala com a compra planejada de maiores quantidades de medicamento, e impõe dificuldades logísticas para o controle das quantidades consumidas e estocadas. Conclui-se que a judicialização decorre da ausência de uma política clara do sistema de saúde para doenças raras em geral, e tem como consequência gastos acima do necessário para o tratamento.

This study analyzes expenditures backed by court rulings to ensure the public provision of medicines for treatment of mucopolysaccharidosis (MPS), a rare disease that requires high-cost drugs not covered by the Brazilian government's policy for pharmaceutical care and which have disputed clinical efficacy. The methodology included a review of files from 196 court rulings ordering the Brazilian Ministry of Health to provide the medicines, in addition to Ministry of Health administrative records. According to the analysis, the "judicialization" of the health system subjected the Brazilian government to a monopoly in the distribution of medicines and consequently the loss of its capacity to manage drug purchases. The study also indicates that the imposition of immediate, individualized purchases prevents obtaining economies of scale with planned procurement of larger amounts of the medication, besides causing logistic difficulties in controlling the amounts consumed and stored. In conclusion, litigation results from the lack of a clear policy in the health system for rare diseases in general, thereby leading to excessive expenditures for MPS treatment.

Enzyme reconstitution/replacement therapy for lysosomal storage diseases.

PURPOSE OF REVIEW: Over the past 15 years, the lysosomal storage diseases have become paradigms for the specific treatment of monogenic disorders, particularly those affecting children. This review summarizes the phenotypes and recent literature regarding enzyme reconstitution (replacement) therapy and outcomes for such treatable lysosomal storage diseases: Gaucher disease, Fabry disease, Pompe disease and the mucopolysaccharidoses. RECENT FINDINGS: Recent clinical trials have shown that enzyme reconstitution therapy effectively treats many of the manifestations of the lysosomal storage diseases. When initiated early in the disease course, enzyme reconstitution therapy can reverse some disease manifestations, but may not completely alleviate the disease progression. Enzyme reconstitution therapy is generally well tolerated. Many adverse events are antibody-related, but can be managed without requiring cessation of enzyme reconstitution therapy. Documented IgE reactions, i.e. anaphylactoid, are quite rare (fewer than 1%). SUMMARY: Enzyme reconstitution therapy is a safe and effective treatment modality available for several of the lysosomal storage diseases. Owing to the short history of enzyme reconstitution therapy, the long-term outcomes of enzyme reconstitution therapy-treated individuals are unknown and require further investigation. Medical professionals must learn to identify patients likely to benefit from these life-changing therapies so as to prevent many of the devastating, irreversible complications of the lysosomal storage diseases.

Assessment of iduronate-2-sulfatase mRNA expression in Hunter syndrome (mucopolysaccharidosis type II).

Eight unrelated patients with Hunter syndrome were investigated for expression of iduronate-2-sulfatase (IDS) mRNA by reverse transcription (RT) linked to polymerase chain reaction (PCR), or RT-PCR. The entire coding region was studied by amplification of two overlapping segments of 0.7 and 1.1 kb. Seven children with Hunter syndrome had PCR products indistinguishable in size from normal. One patient, with clinically severe disease, did not produce either IDS product although mRNA for a control gene was readily amplified. This method rapidly identifies patients having absent or qualitatively abnormal IDS mRNA and may be useful in investigating genotype-phenotype relationships.