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Infantile-onset Pompe disease (IOPD) is caused by a deficiency in the enzyme acid alpha-glucosidase (GAA). It is characterized by severe and progressive hypertrophic cardiomyopathy and muscle weakness with death in the first 2 years of life if left untreated. Enzyme replacement therapy (ERT) with alglucosidase-alfa is lifesaving, but its effectiveness is influenced by the patient's cross-reactive immunologic material (CRIM) status, dose of ERT, and the development of high antibody titers, which can reduce the therapy's efficacy. The inability of CRIM-negative IOPD patients to produce native GAA exposes them to a high risk of development of anti-rhGAA IgG antibody titers, leading to treatment failure. We present the case of CRIM-negative dizygotic twins treated with high-dose alglucosidase-alfa (40 mg/kg/week), initiated at 28 days (Twin A) and 44 days (Twin B). Both twins received immune tolerance induction (ITI) with rituximab, methotrexate, and IVIG to mitigate antibody response. Initial evaluations revealed elevated left ventricular mass index (LVMI) and elevated biomarkers (urine glucose tetrasaccharide (Glc4), creatine kinase (CK), and aspartate aminotransferase (AST)) in both twins. Following treatment, cardiac function and biomarkers normalized within several months, with a slight delay in Twin B compared to Twin A, likely attributed to the later initiation of ERT. Both twins safely tolerated ITI, achieving immune tolerance with low antibody titers. At 28 months, the twins transitioned to avalglucosidase-alfa (40 mg/kg every other week (EOW)), which was well tolerated without an increase in antibody titers. At 39 months, both twins exhibited normal cardiac function, LVMI, and biomarkers. Motor skills continued to improve, though some kinematic concerns persisted. These cases underscore the importance of early, high-dose ERT combined with ITI in managing CRIM-negative IOPD. While transitioning to avalglucosidase-alfa at 40 mg/kg/EOW was beneficial and well-tolerated in our patients, further studies are needed to confirm its long-term efficacy compared to the high-dose weekly 40 mg/kg alglucosidase-alfa.

Infantile onset Pompe disease (IOPD) is a rare devastating disease that presents in early infancy with rapidly progressive hypertrophic cardiomyopathy, severe generalized myopathy and death within the first year of life. The emergence of enzyme replacement therapy (ERT) with recombinant human acid alpha glucosidase (rhGAA) has improved the natural course of IOPD with a significant impact on cardiomyopathy but has a more limited effect on the progression of myopathy and consequently the later deterioration of the disease. Possible reasons for reduced ERT efficacy include insufficient enzyme, partial targeting of skeletal muscle and the development of IgG rhGAA antibodies especially in patients who are cross-reactive immunological material (CRIM) negative. We report a CRIM-negative IOPD female patient who started treatment upon diagnosis at 4.5 months with ERT at 20 mg/kg every other week and a course of combined immunomodulation with rituximab, methotrexate and IVIG according to the published Duke protocol and increased ERT within a month to 40 mg/kg/week. Despite initial good clinical response to ERT and immunomodulation, monthly monitoring identified a gradual increase of serum antibody titers to rhGAA necessitating a second course of immunomodulation with bortezomib and maintenance rituximab and methotrexate. A gradual reduction in frequency of immunotherapy was instituted and over a period of 14 months was discontinued. Serum anti-rhGAA antibody titers remained negative for 5 months since cessation of immunomodulation and the patient is now immune tolerant with recovery of CD19. At the age of 30 months the patient is walking independently and has normal cardiac function and anatomy. We recommend initiating ERT at 40 mg/kg/week in CRIM-negative IOPD patients, concomitant with immunomodulation and monthly monitoring of serum anti-rhGAA IgG titers upon confirmation of the diagnosis.

Purpose: Mini-COMET (NCT03019406; Sanofi) is a phase 2, open-label, ascending-dose, 3-cohort study, evaluating avalglucosidase alfa safety, pharmacokinetics, and efficacy in individuals with infantile-onset Pompe disease aged <18 years who previously received alglucosidase alfa and showed clinical decline (cohorts 1 and 2) or suboptimal response (cohort 3)., Methods: During a 25-week primary analysis period, cohorts 1 and 2 received avalglucosidase alfa 20 and 40 mg/kg every other week, respectively, for 6 months, whereas cohort 3 individuals were randomized (1:1) to receive avalglucosidase alfa 40 mg/kg every other week or alglucosidase alfa (current stable dose) for 6 months., Results: In total, 22 individuals were enrolled (cohort 1 [n = 6], cohort 2 [n = 5], cohort 3-avalglucosidase alfa [n = 5], and cohort 3-alglucosidase alfa [n = 6]). Median treatment compliance was 100%. None of the individuals discontinued treatment or died. Percentages of individuals with treatment-emergent adverse events were similar across dose and treatment groups. No serious or severe treatment-related treatment-emergent adverse events occurred. Trends for better motor function from baseline to week 25 were observed for 40 mg/kg every other week avalglucosidase alfa compared with either 20 mg/kg every other week avalglucosidase alfa or alglucosidase alfa up to 40 mg/kg weekly., Conclusion: These data support the positive clinical effect of avalglucosidase alfa in patients with infantile-onset Pompe disease previously declining on alglucosidase alfa., Competing Interests: Conflict of Interest P.S.K. reports advisory board participation for Amicus Therapeutics, Baebies, and Sanofi; receiving consulting fees from Amicus Therapeutics, Asklepios Biopharmaceutical Inc (AskBio), JCR Pharma Co Ltd, Maze Therapeutics, and Sanofi; performing contracted research for Amicus Therapeutics and Sanofi; receiving honoraria from Amicus Therapeutics, AskBio, Maze Therapeutics, and Sanofi; having ownership interest of <5% (stocks, stock options, or other ownership interest excluding diversified mutual funds) in AskBio and Maze Therapeutics; and receiving travel expenses from Amicus Therapeutics and Sanofi. D.K. reports advisory board participation for AskBio and Sanofi; performing contracted research for Sanofi; serving on the Speaker’s bureau for Sanofi; and receiving travel expenses from AskBio and Sanofi. A.Bra. reports advisory board participation for Alexion, Sanofi, and Shire; receiving consulting fees from Alexion; and receiving travel expenses from Alexion, BioMarin, Orphan Europe, Sanofi, and Shire. A.Bro. reports advisory board participation for Sanofi and receiving honoraria from Orchard Therapeutics and Sanofi. J.D. reports advisory board participation for Sanofi, Recordati RRD, and Orchard Therapeutics; receiving consulting fees from bluebird bio Inc; and serving on the Speaker’s bureau for Sanofi, Recordati RRD, and FYMCA Medical Ltd. S.H.H. reports advisory board participation for Alexion Pharmaceutical Inc; performing contracted research for Sanofi; receiving honoraria from Alexion Pharmaceutical Inc; membership of the Seattle Children’s Hospital workforce; serving as temporary CEO of KEY PROTEO, Inc; being an inventor of intellectual property that has been licensed to KEY PROTEO, Inc; being a founder of KEY PROTEO, Inc and having ownership equity interests in the company; and receiving royalties from UpToDate. S.K., F.L., and H.O. declare no conflicts of interest. S.P. reports receiving travel expenses from Sanofi. S.G.P. reports performing contracted research for Sanofi and receiving consulting fees from Sanofi. K.A.H. and her spouse are employees of Sanofi and both have ownership interest of <5% (stocks, stock options, or other ownership interest excluding diversified mutual funds) in Sanofi. B.K. is an employee of Sanofi and has ownership interest of <5% (stocks, stock options, or other ownership interest excluding diversified mutual funds) in Sanofi. X.M. is an employee of TechData Service LLC (contracted to Sanofi). S.S. is an employee of Sanofi and has ownership interest of <5% (stocks, stock options, or other ownership interest excluding diversified mutual funds) in Sanofi. C.W. reports receiving consulting fees from Sanofi and Regenxbio. A.Z. is an employee of Sanofi and has ownership interest of <5% (stocks, stock options, or other ownership interest excluding diversified mutual funds) in Sanofi Canada. Y.-H.C. reports advisory board participation for Amicus Therapeutics and Sanofi; receiving consulting fees from Amicus Therapeutics and Sanofi; performing contracted research for Sanofi; and receiving honoraria from Biogen, Novartis, Sanofi, and Takeda., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Purpose: The study aimed to describe central nervous system (CNS) progression in patients with infantile-onset Pompe disease (IOPD) and explore the potential clinical impact and predictors., Methods: Patients with IOPD treated with enzyme replacement therapy were longitudinally followed with brain magnetic resonance imaging (MRI) and evaluation for IQ scores from 2004 to 2021. Investigation of CNS involvement focused on white matter (WM) abnormalities and was quantified using a scoring system for metachromatic leukodystrophy. MRI scores were correlated with plasma neurofilament light chain (NfL) concentration and IQ scores., Results: A total of 19 patients who started enzyme replacement therapy at a mean age of 26 days were analyzed; the median age at last examination was 12.1 (range = 1.7-19) years. MRI abnormalities were found in all patients, from supratentorial central WM to U-fibers, then to infratentorial WM, and eventually to gray matter. MRI scores progressed (n = 16) at variable rates (range = 0.8-2.7/y) and were positively correlated with age (n = 16) and negatively correlated with IQ scores (n = 8). Plasma NfL concentration was positively correlated with MRI scores (r 2  = 0.8569; P < .001; n = 13)., Conclusion: Our results suggest that the progression of CNS involvement in IOPD may be associated with neuroaxonal injury and decreased IQ scores. NfL could serve as a biomarker for CNS involvement in IOPD., Competing Interests: Conflict of Interest Y.-H.C. has served on the advisory boards of Amicus Therapeutics, Inc and Sanofi Genzyme, undertaken contracted research for Sanofi Genzyme, and received honoraria and consulting fees from Sanofi Genzyme. W.-L.H. has served on the advisory boards of Audentes Therapeutics and Sanofi Genzyme, undertaken contracted research for Sanofi Genzyme, and received honoraria and consulting fees from Sanofi Genzyme. N.-C.L. has served on the registry advisory boards of Sanofi Genzyme and received honoraria from Sanofi Genzyme. All other authors declare no conflicts of interest., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)