available for disease treatment. It is effective in most infantile patients,

whereas the improvement is quite variable in adults. We analyzed

muscle biopsies from 14 late-onset patients at molecular, biochemical,

and histopathological level before and after ERT. We evaluated the

following morphological parameters: CSA, number of vacuolated fibers,

degree of glycogen accumulation, percentage of vacuolization in type I

and II fibers. Pre-treatment muscle biopsies showed marked

histopathological variability ranging from almost normal morphology to

severe vacuolar myopathy. Post-treatment muscle biopsies

morphologically improved in seven patients, worsened in two patients

and were unchanged in all the other subjects. Immunohistochemical

analysis of the autophagic/lysosomal markers EEA1 (early endosome

antigen 1), LC3 (microtubule-associated protein 1 light chain 3), and

LAMP2 (lysosome associated membrane protein 2) showed a variable

binding in both the first and the second biopsies. GAA enzymatic

activity, tested by a fluorimetric assay in both lymphocytes and muscle

tissue from 5 patients after ERT, was mildly increased in skeletal muscle

compared with pre-treatment levels. Also, GAA expression assessed by

immunoblotting slightly increased in a few patients. All patients

clinically improved or remained stable after ERT.

http://dx.doi:10.1016/j.nmd.2014.06.254

T.P.19

Effects of antibody formation during enzyme replacement therapy in 73 adult

patients with Pompe disease

J.M. de Vries, E. Kuperus, M. Hoogeveen-Westerveld, S.C.A. Wens,

M.A. Kroos, M.E. Kruijshaar, P.A. van Doorn, A.T. van der Ploeg,

W.W.M. Pijnappel

Center for Lysosomal and Metabolic Diseases, Erasmus MC University

Medical Center, Rotterdam, The Netherlands

High sustained antibody titers against enzyme replacement therapy

(ERT) with alglucosidase alfa adversely affect clinical outcome in

classic-infantile Pompe disease. The long-term effects of antibody

formation on therapeutic efficacy in non-classic Pompe disease are yet

unknown. We studied whether the presence of anti-alglucosidase alfa

antibodies has an impact on treatment outcome and occurrence of

infusion-associated reactions (IARs) in a large cohort of adult patients.

This prospective single-centre cohort study included 73 adult patients

who were treated with 20 mg/kg alglucosidase alfa every other week and

started to receive ERT at least 3 years ago. Antibody titers were

measured at approximately 6, 12 and 36 months of ERT using ELISA

and their effects on enzyme activity were measured in the medium and

in cultured fibroblasts in vitro. Clinical parameters included muscle

strength (MRC sumscore), pulmonary function (FVC in upright and

supine positions), and IARs. 71 of the 73 (97%) patients developed

antibodies against alglucosidase alfa. The mean titer peaked at 6 months

to 1:1259 and thereafter declined to 1:270 at 36 months of treatment.

Individual titers and titer courses varied, but in the majority (93%) of

patients titers decreased or stabilized with continued ERT. Patients with

high peak titers showed moderate to high levels of in vitro enzyme

inhibition. An increased risk for IARs was found in patients with higher

antibody peak titers as 7 (44%) of 16 patients with high titers

(P1:31,250) experienced IARs, 5 (19%) of 27 patients with intermediate

titers (1:1250 to <1:31,250), and only 1 (3%) of 30 patients with a low

or no titer (0 to <1250) (p = 0.001). No relation was found with

antibody titer and poorer clinical outcome for MRC sumscore and FVC

in upright and supine positions after a 36 months treatment period.

Antibody formation to alglucosidase alfa in non-classic Pompe patients

increases the risk for infusion-associated reactions, but is not associated

with unfavorable clinical outcome during 3 years of treatment.

http://dx.doi:10.1016/j.nmd.2014.06.255

T.P.20

Effect of enzyme replacement therapy in late onset Pompe disease: Open

pilot study of 60 weeks follow up

J.S. Park 1, Y.E. Park 2, Y.C. Choi 3, J.H. Shin 4, J.M. Lee 4, D.S. Kim 4

1 Kyungpook National University School of Medicine, Daegu, Republic

of Korea; 2 Pusan National Univerisity Hospital, Pusan, Republic of

Korea; 3 College of Medicine, Yonsei University, Seoul, Republic of

Korea; 4 Pusan National Univerisity Yangsan Hospital, Yangsan,

Republic of Korea

Late-onset Pompe disease (LOPD) is an autosomal recessive disorder

caused by deficiency of the enzyme acid glucosidase alfa (GAA),

Recently, enzyme replacement therapy (ERT) using recombinant human

GAA (rhGAA) became clinically available, and is expected to modify

clinical course of LOPD. In this study, we have evaluated the efficacy

and adverse events of ERT for 60 weeks in Korean LOPD patients.

Five Korean LOPD patients were included in the study. At baseline,

clinical and laboratory features including motor and pulmonary

function was assessed, and rhGAA was infused every two weeks. Then,

patients were examined at every 12 weeks interval to evaluate their

changes in motor and pulmonary function for 48 weeks along with

adverse reactions of ERT. The motor and pulmonary function of the

patients demonstrated mild improvement or stabilization after 60 weeks

of ERT. And none of them showed deterioration in their ambulatory or

respiratory status. One of our patients developed a serious anaphylactic

reaction which necessitated the cessation of further ERT. This is the

first report of clinical study on the ERT of Korean LOPD patients. Our

study showed ERT for 48 weeks produced only mild improvement or

stabilization of motor and pulmonary function in LOPD patients,

suggesting that advanced pathological change is responsible for the

limited efficacy of ERT.

http://dx.doi:10.1016/j.nmd.2014.06.256

T.P.21

Assessing immunogenicity of rhGAA in adult Pompe disease subjects

E. Masat 1, P. Laforet 2, D. Amelin 1, P. Veron 3, K. Laloui 4,

O. Benveniste 5, F. Mingozzi 6

1 University Pierre and Marie Curie, Paris, France; 2 AP-HP,

Pitie-Salpetriere University Hospital, Paris-Est Neuromuscular Center,

Paris, France; 3 Genethon, Evry, France; 4 AP-HP, Pitie-Salpetriere

University Hospital, Institute of Myology, Paris, France; 5 AP-HP,

Pitie-Salpetriere University Hospital, Department of Internal Medicine 1,

Paris, France; 6 University Pierre and Marie Curie, Genethon, Paris, France

Pompe disease (PD) is an inherited metabolic myopathy caused by a

deficiency of the lysosomal enzyme acid a-glucosidase (GAA). Enzyme

replacement therapy (ERT) has improved the outcome of PD,

unfortunately the immune responses against GAA are not uncommon

and in some cases prevent therapeutic efficacy. The aim of this study

was to investigate the mechanisms of the immune responses against

recombinant human GAA (rhGAA) in adult patients undergoing ERT.

About one-third of all subjects screened (n = 35) showed significant

levels of anti-rhGAA binding antibodies, mainly IgG4. After dendritic

cell maturation in the presence of rhGAA a positive IFN-gamma

ELISpot signal was detectable in some of the subject’s peripheral blood

870 Abstracts / Neuromuscular Disorders 24 (2014) 791–924