Successful reduction of high-sustained anti-idursulfase antibody titers by immune modulation therapy in a patient with severe mucopolysaccharidosis type II

An updated management approach of Pompe disease patients with high-sustained anti-rhGAA IgG antibody titers: experience with bortezomib-based immunomodulation

Introduction

High sustained anti-rhGAA antibody titers (HSAT; ≥12,800) are directly linked to reduced efficacy of enzyme replacement therapy (ERT) and subsequent clinical deterioration in infantile-onset Pompe disease (IOPD). We have previously demonstrated the safety and effectiveness of a bortezomib-based immune-tolerance induction (ITI) regimen (bortezomib, rituximab, methotrexate, and IVIG) in eliminating HSAT.

Methods

Here, we describe two IOPD cases (patients 6 and 8) who developed HSAT at 8 and 10 weeks on ERT despite transient low-dose methotrexate ITI administration in the ERT-naïve setting and were treated with a bortezomib-based ITI regimen, and we compare their courses to a series of six historical patients (patients 1-5, and 7) with a similar presentation who exemplify our evolving approach to treatment.

Results

In total, patients 6 and 8 received 16 and 8 doses of bortezomib (4 doses=1 cycle) respectively reducing titers from 25,600 to seronegative, but differences in the course of their therapy were instructive regarding the optimal approach to initial treatment of HSAT; specifically, patient 6 was treated initially with only a single course of bortezomib rescue therapy, while patient 8 received two back-to-back courses. Patient 8 received IVIG therapy throughout the immunosuppression whereas patient 6 received IVIG therapy and was switched to subcutaneous IgG replacement. Patient 6 had a transient reduction in anti-rhGAA antibodies, after receiving a single initial cycle of bortezomib, but had a recurrence of high anti-rhGAA antibody titer after 160 weeks that required 3 additional cycles of bortezomib to ultimately achieve tolerance. In contrast, patient 8 achieved tolerance after being given two consecutive cycles of bortezomib during their initial treatment and had B cell recovery by week 54. Since the reduction in anti-rhGAA antibodies, both patients are doing well clinically, and have decreasing ALT, AST, and CK. No major infections leading to interruption of treatment were observed in either patient. The bortezomib-based ITI was safe and well-tolerated, and patients continue to receive ERT at 40 mg/kg/week.

Discussion

These case studies and our previous experience suggest that to achieve an effective reduction of anti-rhGAA antibodies in the setting of HSAT, bortezomib should be initiated at the earliest sign of high anti-rhGAA antibodies with a minimum of two consecutive cycles as shown in the case of patient 8. It is important to note that, despite initiation of ERT at age 2.3 weeks, patient 8 quickly developed HSAT. We recommend close monitoring of anti-rhGAA antibodies and early intervention with ITI as soon as significantly elevated anti-rhGAA antibody titers are noted.

Development of high sustained anti-drug antibody titers and corresponding clinical decline in a late-onset Pompe disease patient after 11+ years on enzyme replacement therapy

A late-onset Pompe disease patient developed high sustained antibody titers (HSAT) of ≥51,200 after 11+ years on alglucosidase alfa and previous tolerance. There was a corresponding worsening of motor function and rise in urinary glucose tetrasaccharide (Glc₄). Following immunomodulation therapy, HSAT were eliminated with improved clinical outcomes and biomarker trends. This report highlights the importance of continued surveillance of antibody titers and biomarkers, the negative impact of HSAT, and improved outcomes with immunomodulation therapy.

Effect of Anti-Iduronate 2-Sulfatase Antibodies in Patients with Mucopolysaccharidosis Type II Treated with Enzyme Replacement Therapy

OBJECTIVE

To assess the relationship between anti-Iduronate 2-sulfatase (IDS) antibodies, IDS genotypes, phenotypes and their impact in patients with enzyme replacement therapy (ERT)-treated Mucopolysaccharidosis type II.

STUDY DESIGN

Dutch patients treated with ERT were analyzed in this observational cohort study. Antibody titers were determined by enzyme-linked immunosorbent assay. Neutralizing effects were measured in fibroblasts. Pharmacokinetic analysis of ERT was combined with immunoprecipitation. Urinary glycosaminoglycans were measured using mass spectrometry and dimethylmethylene blue.

RESULTS

Eight of 17 patients (47%) developed anti-IDS antibodies. Three patients with the severe, neuronopathic phenotype, two of whom did not express IDS protein, showed sustained antibodies for up to 10 years of ERT. Titers of 1:5120 or greater inhibited cellular IDS uptake and/or intracellular activity in vitro. In 1 patient who was neuronopathic with a titer of 1:20 480, pharmacokinetic analysis showed that all plasma recombinant IDS was antibody bound. This finding was not the case in 2 patients who were not neuronopathic with a titer of 1:1280 or less. Patients with sustained antibody titers showed increased urinary glycosaminoglycan levels compared with patients with nonsustained or no-low titers.

CONCLUSIONS

Patients with the neuronopathic form and lack of IDS protein expression were most at risk to develop sustained anti-IDS antibody titers, which inhibited IDS uptake and/or activity in vitro, and the efficacy of ERT in patients by lowering urinary glycosaminoglycan levels.

Long-term open-label phase I/II extension study of intrathecal idursulfase-IT in the treatment of neuronopathic mucopolysaccharidosis II

PURPOSE

Intrathecal (IT) idursulfase-IT for the treatment of cognitive impairment is being investigated in pediatric patients with neuronopathic mucopolysaccharidosis II (MPS II) in addition to intravenous idursulfase. In this article, we report the findings for 54 months of idursulfase-IT treatment in an ongoing phase I/II extension trial (NCT01506141).

METHODS

A total of 15 male participants with neuronopathic MPS II (aged 3-11 years at enrollment) who were previously treated with intravenous idursulfase entered the extension study. Idursulfase-IT 10 mg or 30 mg was administered monthly via an IT drug delivery device or lumbar puncture, if indicated. The primary endpoint was safety and tolerability; secondary endpoints included pharmacokinetics, cerebrospinal fluid glycosaminoglycan levels, and cognitive function.

RESULTS

In total, 15 participants received a median (range) of 50 (18-55) idursulfase-IT doses. Idursulfase-IT was generally well tolerated; there were no life-threatening adverse events (AEs) or deaths. Most serious AEs were related to the IT drug delivery device; only 2 serious AEs were related solely to idursulfase-IT. After treatment with idursulfase-IT, cerebrospinal fluid glycosaminoglycans were decreased in all participants; these decreases were maintained. Cognitive function was stabilized in 3 of 4 testable participants at month 55.

CONCLUSION

These long-term results support the clinical development of idursulfase-IT for patients with MPS II with cognitive impairment.

Mechanisms of Neutralizing Anti-drug Antibody Formation and Clinical Relevance on Therapeutic Efficacy of Enzyme Replacement Therapies in Fabry Disease

Fabry disease (FD) is a rare X-linked lysosomal storage disorder caused by mutations in the α-galactosidase A (AGAL/GLA) gene. The lysosomal accumulation of the substrates globotriaosylceramide (Gb₃) and globotriaosylsphingosine (lyso-Gb₃) results in progressive renal failure, cardiomyopathy associated with cardiac arrhythmia, and recurrent strokes, significantly limiting life expectancy in affected patients. Current treatment options for FD include recombinant enzyme-replacement therapies (ERTs) with intravenous agalsidase-α (0.2 mg/kg body weight) or agalsidase-β (1 mg/kg body weight) every 2 weeks, facilitating cellular Gb₃ clearance and an overall improvement of disease burden. However, ERT can lead to infusion-associated reactions, as well as the formation of neutralizing anti-drug antibodies (ADAs) in ERT-treated males, leading to an attenuation of therapy efficacy and thus disease progression. In this narrative review, we provide a brief overview of the clinical picture of FD and diagnostic confirmation. The focus is on the biochemical and clinical significance of neutralizing ADAs as a humoral response to ERT. In addition, we provide an overview of different methods for ADA measurement and characterization, as well as potential therapeutic approaches to prevent or eliminate ADAs in affected patients, which is representative for other ERT-treated lysosomal storage diseases.

Therapeutic Options for Mucopolysaccharidosis II (Hunter Disease)

BACKGROUND

Mucopolysaccharidosis type II (Hunter syndrome, or MPS II) is an X-linked lysosomal disorder caused by the deficiency of iduronate-2-sulfatase, which leads to the accumulation of glycosaminoglycans (GAGs) in a variety of tissues, resulting in a multisystemic disease that can also impair the central nervous system (CNS).

OBJECTIVE

This review focuses on providing the latest information and expert opinion about the therapies available and under development for MPS II.

METHODS

We have comprehensively revised the latest studies about hematopoietic stem cell transplantation (HSCT), enzyme replacement therapy (ERT - intravenous, intrathecal, intracerebroventricular, and intravenous with fusion proteins), small molecules, gene therapy/genome editing, and supportive management.

RESULTS AND DISCUSSION

Intravenous ERT is a well-established specific therapy, which ameliorates the somatic features but not the CNS manifestations. Intrathecal or intracerebroventricular ERT and intravenous ERT with fusion proteins, presently under development, seem to be able to reduce the levels of GAGs in the CNS and have the potential of reducing the impact of the neurological burden of the disease. Gene therapy and/or genome editing have shown promising results in preclinical studies, bringing hope for a "one-time therapy" soon. Results with HSCT in MPS II are controversial, and small molecules could potentially address some disease manifestations. In addition to the specific therapeutic options, supportive care plays a major role in the management of these patients.

CONCLUSION

At this time, the treatment of individuals with MPS II is mainly based on intravenous ERT, whereas HSCT can be a potential alternative in specific cases. In the coming years, several new therapy options that target the neurological phenotype of MPS II should be available.

Immune Modulation for Enzyme Replacement Therapy in A Female Patient With Hunter Syndrome

A 3.5 year old Hispanic female presented with signs and symptoms concerning for MPS II (Hunter Syndrome). The diagnosis of MPS II was confirmed by enzyme and molecular testing. Genetic evaluation revealed undetectable plasma iduronate-2-sulfatase enzyme activity and an inversion between intron 7 of the IDS gene and a region near exon 3 of IDS-2. This inversion is the molecular cause for ~8% of cases of MPS II and often results in a severe phenotype. X-inactivation studies revealed an inactivation ratio of 100:0. Given the patient's undetectable enzyme level, in combination with a severe IDS gene mutation, classic features at time of presentation, and the significantly skewed X inactivation, there was concern that she was at high risk of developing high and sustained antibody titers to idursulfase which would limit her benefit from enzyme replacement therapy (ERT). Anti-drug neutralizing antibodies to idursulfase have been associated with reduced systemic exposure to idursulfase and poorer clinical outcomes. Therefore, the decision was made to concurrently treat the patient with immune tolerance induction therapy during the first month of treatment with idursulfase in order to decrease the risk of developing high sustained antibody titers. The immune tolerance induction protocol consisted of rituximab weekly for 4 weeks, methotrexate three times a week for 3 weeks and monthly IVIG through B-cell and immunoglobulin recovery. Immune tolerance induction was initiated concurrently with the start of ERT. The patient had no significant adverse effects related to undergoing immune tolerance induction therapy and two and half years later is doing well with significantly reduced urine glycosaminoglycans and very low anti-drug antibody titers. This immune tolerance induction protocol could be considered for other patients with MPS II as well as patients with other lysosomal storage disorders who are starting on enzyme replacement therapy and are at high risk of developing neutralizing anti-drug antibodies.

Intravenous Enzyme Replacement Therapy in Mucopolysaccharidoses: Clinical Effectiveness and Limitations

The aim of this review is to summarize the evidence on efficacy, effectiveness and safety of intravenous enzyme replacement therapy (ERT) available for mucopolysaccharidoses (MPSs) I, II, IVA, VI and VII, gained in phase III clinical trials and in observational post-approval studies. Post-marketing data are sometimes conflicting or controversial, possibly depending on disease severity, differently involved organs, age at starting treatment, and development of anti-drug antibodies (ADAs). There is general agreement that ERT is effective in reducing urinary glycosaminoglycans and liver and spleen volume, while heart and joints outcomes are variable in different studies. Effectiveness on cardiac valves, trachea and bronchi, hearing and eyes is definitely poor, probably due to limited penetration in the specific tissues. ERT does not cross the blood-brain barrier, with the consequence that the central nervous system is not cured by intravenously injected ERT. All patients develop ADAs but their role in ERT tolerance and effectiveness has not been well defined yet. Lack of reliable biomarkers contributes to the uncertainties about effectiveness. The data obtained from affected siblings strongly indicates the need of neonatal screening for treatable MPSs. Currently, other treatments are under evaluation and will surely help improve the prognosis of MPS patients.

Enzyme replacement therapy: efficacy and limitations

Enzyme replacement therapy (ERT) is available for mucopolysaccharidosis (MPS) I, MPS II, MPS VI, and MPS IVA. The efficacy of ERT has been evaluated in clinical trials and in many post-marketing studies with a long-term follow-up for MPS I, MPS II, and MPS VI. While ERT is effective in reducing urinary glycosaminoglycans (GAGs) and liver and spleen volume, cartilaginous organs such as the trachea and bronchi, bones and eyes are poorly impacted by ERT probably due to limited penetration in the specific tissue. ERT in the present formulations also does not cross the blood–brain barrier, with the consequence that the central nervous system is not cured by ERT. This is particularly important for severe forms of MPS I and MPS II characterized by cognitive decline. For severe MPS I patients (Hurler), early haematopoietic stem cell transplantation is the gold standard, while still controversial is the role of stem cell transplantation in MPS II. The use of ERT in patients with severe cognitive decline is the subject of debate; the current position of the scientific community is that ERT must be started in all patients who do not have a more effective treatment. Neonatal screening is widely suggested for treatable MPS, and many pilot studies are ongoing. The rationale is that early, possibly pre-symptomatic treatment can improve prognosis. All patients develop anti-ERT antibodies but only a few have drug-related adverse reactions. It has not yet been definitely clarified if high-titre antibodies may, at least in some cases, reduce the efficacy of ERT.

Correlation between urinary GAG and anti-idursulfase ERT neutralizing antibodies during treatment with NICIT immune tolerance regimen: A case report

INTRODUCTION

Antibodies to intravenous idursulfase enzyme replacement therapy (ERT) for patients with Hunter syndrome (mucopolysaccharidosis type II, MPS II) can have a harmful clinical impact, including both increasing risk of infusion reactions and inhibiting therapeutic activity. Thus, failure to monitor anti-idursulfase antibodies and neutralizing antibodies, and delays in reporting results, may postpone critical clinical decisions.

HYPOTHESIS

Urinary glycosaminoglycan (GAG) levels may be used as a biomarker for anti-idursulfase antibodies and neutralizing antibodies to improve timeliness in monitoring and managing ERT.

METHODS

This is a case report describing a patient with MPS II with high levels of neutralizing antibodies and worsened clinical status who was treated for five years with a non-immunosuppressive and non-cytotoxic immune tolerance (NICIT) regimen, consisting of intravenous immune globulin and frequent infusions of idursulfase. Neutralizing antibodies and total anti-idursulfase antibodies were measured by two different methods, the direct 1,9-dimethylmethylene blue (DMB) assay and cetylpyridinium chloride carbazole-borate (CPC) assay.

RESULTS

Neutralizing antibodies, measured as percent inhibition of enzyme activity and also by total neutralizing antibody titer, were correlated with quantitative urinary GAG measured by DMB assay (p=0.026, p=0.0067), and quantitative urinary GAG by CPC assay with percent inhibition of enzyme activity by neutralizing antibodies (p=0.0475). The NICIT regimen showed a sustained immune tolerance after five years and was well-tolerated.

CONCLUSIONS

Urinary GAG, measured by DMB assay, may be a biomarker for anti-idursulfase neutralizing antibodies and is useful for managing immune tolerance regimens for patients with MPS II who have high levels of anti-idursulfase neutralizing antibodies. This study highlights the importance of regular and frequent monitoring of urinary GAG in patients with MPS II who are receiving ERT. The NICIT regimen, with less drug toxicities, may be preferred in patients with MPS who have a high risk of infections and whose disease progresses less rapidly than some other lysosomal storage diseases, such as infantile Pompe disease.

Durable and sustained immune tolerance to ERT in Pompe disease with entrenched immune responses

BACKGROUND

Enzyme replacement therapy (ERT) has prolonged survival and improved clinical outcomes in patients with infantile Pompe disease (IPD), a rapidly progressive neuromuscular disorder. Yet marked interindividual variability in response to ERT, primarily attributable to the development of antibodies to ERT, remains an ongoing challenge. Immune tolerance to ongoing ERT has yet to be described in the setting of an entrenched immune response.

METHODS

Three infantile Pompe patients who developed high and sustained rhGAA IgG antibody titers (HSAT) and received a bortezomib-based immune tolerance induction (ITI) regimen were included in the study and were followed longitudinally to monitor the long-term safety and efficacy. A trial to taper the ITI protocol was attempted to monitor if true immune tolerance was achieved.

RESULTS

Bortezomib-based ITI protocol was safely tolerated and led to a significant decline in rhGAA antibody titers with concomitant sustained clinical improvement. Two of the 3 IPD patients were successfully weaned off all ITI protocol medications and continue to maintain low/no antibody titers. ITI protocol was significantly tapered in the third IPD patient. B cell recovery was observed in all 3 IPD patients.

CONCLUSION

This is the first report to our knowledge on successful induction of long-term immune tolerance in patients with IPD and HSAT refractory to agents such as cyclophosphamide, rituximab, and methotrexate, based on an approach using the proteasome inhibitor bortezomib. As immune responses limit the efficacy and cost-effectiveness of therapy for many conditions, proteasome inhibitors may have new therapeutic applications.

FUNDING

This research was supported by a grant from the Genzyme Corporation, a Sanofi Company (Cambridge, Massachusetts, USA), and in part by the Lysosomal Disease Network, a part of NIH Rare Diseases Clinical Research Network (RDCRN).