Enzyme replacement therapy (ERT) with recombinant AGAL (i.e. agalsidase alpha/beta) has been shown to be effective in reducing intracellular Gb3 load and lyso-Gb3 plasma levels, which is associated with an improvement in clinical disease course. However, intravenous infusion of recombinant AGAL can lead to the formation of anti-drug antibodies (ADA) that can neutralize ERT, which can cause a clinically relevant problem, especially in male FD patients (40-70% of treated males). A positive antibody status is associated with an impaired therapeutic effect on Gb3 reduction and consequently with a poorer clinical disease course in affected patients (Linthorst et al. 2004; Rombach et al. 2012; Lenders et al. 2016).

For almost 10 years, we have been studying the effects of neutralizing ADAs on the clinical efficacy of ERT. To this end, we have developed and adapted various methods to measure ADA titers in patient sera, expressed either as concentrations or as inhibitory capacities. Furthermore, we could show that depending on the epitopes of the antibodies, the cellular uptake of recombinant AGAL can be impaired and that internalized ADA/AGAL complexes do not dissociate in lysosomes. These mechanisms may lead to reduced therapeutic efficacy of ERT in affected patients and thus to disease progression. Nevertheless, we were able to show that not all affected patients suffer from disease progression, which could be explained by a higher infused AGAL dose in the presence of individual antibody titers or their varying degree of inhibitory capacities.

As one of the leading laboratories, we believe we have a responsibility to further elucidate the mechanisms of antibody formation and their respective impact on the various current and future therapeutic options, including but not limited to next-generation ERTs and gene therapy. Finally, we are evaluating the possibility of developing therapeutic protocols and algorithms that could prevent the formation of antibodies against ERT in the future.

Current ongoing studies

A) Detailed characterization of anti-PEG antibodies in Fabry disease patients (DaPaF)

Description

This study analyses the presence (frequency) and impact of antibodies against polyethylene glycol (PEG) and pegunigalsidase-alfa in pegunigalsidase-alfa-naïve and pegunigalsidase-alfa-treated patients.

Background and rationale

Pegunigalsidase-alfa was developed to overcome the pitfalls of agalsidase-alfa and agalsidase-beta: prolonged plasma half-life and lower immunogenicity were achieved by PEGylation. Our recent studies have shown that pre-existing ADAs against agalsidase-alfa/-beta have a lower affinity for pegunigalsidase-alfa, probably due to PEGylation-dependent masked epitopes (Lenders et al. 2022; Lenders et al. 2023). However, due to the presence of polyethylene glycol (stabilizer) in cosmetics, food, drugs and COVID-19 mRNA-based vaccines, up to 40% of the population appears to have anti-PEG antibodies. Therefore, the effects of these antibodies on pegunigalsidase-alfa need to be investigated.

Our hypothesis is that a significant proportion of ERT-naïve FD patients may have pre-formed anti-PEG antibodies. The potential importance for the safety and efficacy of treatment with PEGylated drugs is controversially discussed. This could represent an uncertainty for treating physicians when initiating therapy with pegunigalsidase-alfa in Fabry patients. The aim of this study is to analyze the biochemical effects of these antibodies on the function of pegunigalsidase-alfa in order to gain a better understanding of patients treated with pegunigalsidase-alfa and their clinical outcomes.

Study objectives

The project objectives are1) the determination of pre-existing anti-PEG antibodies in ERT-naïve (n=75) and pegunigalsidase-alfa-treated (n=15) FD patients, 2) the determination of affinities and inhibitory capacities of anti-PEG antibodies against pegunigalsidase-alfa, 3) the isotyping (IgA, IgG, IgM, IgE) of anti-PEG antibodies, 4) the determination of the potential impact of anti-PEG antibodies on cellular pegunigalsidase-alfa uptake and intracellular activity, 5) the determination of the impact of anti-PEG antibodies on serum/plasma half-life and clearance of pegunigalsidase-alfa, and 6) the determination of the impact of anti-PEG antibodies on antibody/ pegunigalsidase-alfa complex formation.

Funding

A funding of this study is provided by Chiesi GmbH, Germany.

B) Antibody-mediated inhibition of enzyme replacement therapies in Fabry disease (AMORE)

Description

The evaluation of neutralizing antibodies in FD patients on enzyme replacement therapy (ERT) is critical as ADAs significantly limit ERT efficacy. By comparing the inhibitory capacities of ADAs against agalsidase-alfa/agalsidase-beta with pegunigalsidase-alfa, it can be assessed whether existing ADAs inhibit pegunigalsidase-alfa less (lower affinity), which could improve patient outcomes over time.

Background and rationale

Our recent study has shown that pre-existing ADAs against agalsidase-alfa/-beta have a lower affinity for pegunigalsidase-alfa, which is likely due to PEGylation-dependent masked epitopes [Lenders et al. 2022]. Furthermore, it is not yet known whether de novo formed ADAs against pegunigalsidase-alfa have similar biochemical properties as existing ADAs against agalsidase-alfa and agalsidase-beta. Therefore, the effect of these antibodies on pegunigalsidase-alfa needs to be investigated and the measurement needs to be offered to interested FD centers and physicians in D-A-CH (Germany, Austria and Switzerland) to improve patient care.

Our rationale is that FD-treating physicians should know the ADA status of their patients in order to be able to make a safe therapy decision (possibly switching to pegunigalsidase-alfa).

Study objectives

The aim of the project is to determine the neutralizing ADA status in ERT-treated male and female Fabry patients from Fabry centers in Germany, Austria and Switzerland (D-A-CH) in order to 1) identify affected risk patients, 2) analyze whether the individually infused ERT dose is sufficient to supersaturate ADA titers, by determining individual inhibitory capacities, 3) to determine the half-life of agalsidase-beta and pegunigalsidase-alfa in individual serum samples, and 4) to analyze whether the neutralizing properties of antibodies against agalsidase-beta are similar to those against pegunigalsidase-alfa (and vice versa), to analyze whether theoretically an approved switch (from agalsidase-alfa [0. 2 mg/kg] or agalsidase-beta [1.0 mg/kg] to pegunigalsidase-alfa [1 mg/kg] will theoretically lead to a higher activity of pegunigalsidase-alfa compared to other ERTs.

Funding

A comprehensive funding of this study is provided by Chiesi GmbH, Germany.