Persistent hematopoietic polyclonality after lentivirus-mediated gene therapy for Fabry disease

Progress and Challenges in the Treatment of Fabry Disease

Fabry disease is a rare but life-threatening, X-linked, inherited lysosomal storage disorder in which globotriaosylceramide is insufficiently metabolized because of reduced α-galactosidase A activity. Cellular globotriaosylceramide accumulation causes a multisystemic disease, which, if left untreated, reduces life expectancy in female and male individuals by around 10 and 20 years, respectively, leading to progressive renal failure, hypertrophic cardiomyopathy, cardiac arrhythmia, and premature cerebral infarction. The method of choice for confirming the diagnosis is the determination of reduced α-galactosidase A activity in leukocytes in male individuals and the molecular genetic detection of a disease-causing mutation in female individuals. Current approved treatment includes enzyme replacement therapy (agalsidase alfa [0.2 mg/kg body weight], agalsidase beta or pegunigalsidase alfa [both 1.0 mg/kg body weight]) every other week intravenously or, if a responding ('amenable') α-galactosidase A mutation is present, oral pharmacological chaperone therapy (migalastat 123 mg, every other day). Future therapeutic options may include substrate reduction therapy, gene therapy, messenger RNA therapy, and/or vesicle-packaged enzyme replacement therapy. This review presents current and future treatment options with advantages and disadvantages of the different treatment options.

Clinical insights in enzyme replacement therapy for metabolic storage disorders: lessons from Pompe disease

Metabolic storage disorders, including lysosomal storage disorders, pose complex challenges in management due to their progressive and life-threatening nature. Although enzyme replacement therapy has substantially improved outcomes for patients with lysosomal storage disorders, limitations of this therapy have become apparent throughout two decades of use. New clinical features of these diseases have emerged as patients live longer, leading to unresolved questions regarding ongoing treatment and long-term care. Innovative therapies are emerging that aim to improve targeting of tissues, particularly for previously inaccessible areas such as the CNS. These next-generation treatments hold promise for enhancing patient outcomes beyond what enzyme replacement therapy can do. Continued exploration of novel therapeutic strategies will be crucial for providing more effective and personalised care for these complex diseases.

Lentivirus-mediated gene therapy for Fabry disease: 5-year End-of-Study results from the Canadian FACTs trial

BACKGROUND

Fabry disease is an X-linked lysosomal storage disorder due to a deficiency of α-galactosidase A (α-gal A) activity. Our goal was to correct the enzyme deficiency in Fabry patients by transferring the cDNA for α-gal A into their CD34+ hematopoietic stem/progenitor cells (HSPCs). Overexpression of α-gal A leads to secretion of the hydrolase; which can be taken up and used by uncorrected bystander cells. Gene-augmented HSPCs can circulate and thus provide sustained systemic correction. Interim results from this 'first-in-the-world' Canadian FACTs (Fabry Disease Clinical Research and Therapeutics) trial were published in 2021. Herein we report 5-year 'End-of-Study' results.

METHODS

Five males with classical Fabry disease were treated. Their HSPCs were mobilized, enriched, and transduced with a recombinant lentivirus engineering expression of α-gal A. Autologous transduced cells were infused after conditioning with a nonmyeloablative, reduced dose, melphalan regimen. Safety monitoring was performed. α-Gal A activity was measured in plasma and peripheral blood (PB) leucocytes. Globotriaosylceramide (Gb3) and lyso-Gb3 levels in urine and plasma were assessed by mass spectrometry. qPCR assays measured vector copy number in PB leucocytes. Antibody titers were measured by ELISA. Body weight, blood pressure, urinary protein levels, eGFR, troponin levels, and LVMI were tracked.

RESULTS

Four out of 5 patients went home the same day as their infusions; one was kept overnight for observation. Circulating α-gal A activity was observed at Day 6-8 in each patient following infusion and has remained durable for 5+ years. LV marking of peripheral blood cells has remained durable and polyclonal. All 5 patients were eligible to come off biweekly enzyme therapy; 3 patients did so. Plasma lyso-Gb3 was significantly lower in 4 of 5 patients. There was no sustained elevation of anti-α-gal A antibodies. Patient weight was stable in 4 of the 5 patients. All blood pressures were in the normal range. Kidney symptoms were stabilized in all patients.

CONCLUSIONS

This treatment was well tolerated as only two SAEs occurred (during the treatment phase) and only two AEs were reported since 2021. We demonstrate that this therapeutic approach has merit, is durable, and should be explored in a larger clinical trial.

HIGHLIGHTS

This was the first gene therapy clinical trial to be completed for Fabry disease. There were no adverse events of any grade attributable to the cellular gene therapy intervention or host conditioning throughout the follow-up interval of 5 years. After reduced-intensity melphalan treatment, all patients engrafted their autologous modified α-gal A expressing cells. All patients synthesized and secreted α-gal A throughout the course of the study. Expression of α-gal A resulted in a decrease in plasma lyso-Gb3 in four of five patients and stabilization of kidney symptoms in all patients.

Preclinical lentiviral hematopoietic stem cell gene therapy corrects Pompe disease-related muscle and neurological manifestations

Pompe disease, a rare genetic neuromuscular disorder, is caused by a deficiency of acid alpha-glucosidase (GAA), leading to an accumulation of glycogen in lysosomes, and resulting in the progressive development of muscle weakness. The current standard treatment, enzyme replacement therapy (ERT), is not curative and has limitations such as poor penetration into skeletal muscle and both the central and peripheral nervous systems, a risk of immune responses against the recombinant enzyme, and the requirement for high doses and frequent infusions. To overcome these limitations, lentiviral vector-mediated hematopoietic stem and progenitor cell (HSPC) gene therapy has been proposed as a next-generation approach for treating Pompe disease. This study demonstrates the potential of lentiviral HSPC gene therapy to reverse the pathological effects of Pompe disease in a preclinical mouse model. It includes a comprehensive safety assessment via integration site analysis, along with single-cell RNA sequencing analysis of central nervous tissue samples to gain insights into the underlying mechanisms of phenotype correction.

Anderson-Fabry disease management: role of the cardiologist

Anderson-Fabry disease (AFD) is a lysosomal storage disorder characterized by glycolipid accumulation in cardiac cells, associated with a peculiar form of hypertrophic cardiomyopathy (HCM). Up to 1% of patients with a diagnosis of HCM indeed have AFD. With the availability of targeted therapies for sarcomeric HCM and its genocopies, a timely differential diagnosis is essential. Specifically, the therapeutic landscape for AFD is rapidly evolving and offers increasingly effective, disease-modifying treatment options. However, diagnosing AFD may be difficult, particularly in the non-classic phenotype with prominent or isolated cardiac involvement and no systemic red flags. For many AFD patients, the clinical journey from initial clinical manifestations to diagnosis and appropriate treatment remains challenging, due to late recognition or utter neglect. Consequently, late initiation of treatment results in an exacerbation of cardiac involvement, representing the main cause of morbidity and mortality, irrespective of gender. Optimal management of AFD patients requires a dedicated multidisciplinary team, in which the cardiologist plays a decisive role, ranging from the differential diagnosis to the prevention of complications and the evaluation of timing for disease-specific therapies. The present review aims to redefine the role of cardiologists across the main decision nodes in contemporary AFD clinical care and drug discovery.

A mass spectrometry assay for detection of endogenous and lentiviral engineered hemoglobin in cultured cells and sickle cell disease mice

Sickle cell disease (SCD) results from a sequence defect in the β-globin chain of adult hemoglobin (HbA) leading to expression of sickle hemoglobin (HbS). It is traditionally diagnosed by cellulose-acetate hemoglobin electrophoresis or high-performance liquid chromatography. While clinically useful, these methods have both sensitivity and specificity limitations. We developed a novel mass spectrometry (MS) method for the rapid, sensitive and highly quantitative detection of endogenous human β-globin and sickle hβ-globin, as well as lentiviral-encoded therapeutic hβAS3-globin in cultured cells and small quantities of mouse peripheral blood. The MS methods were used to phenotype homozygous HbA (AA), heterozygous HbA-HbS (AS) and homozygous HbS (SS) Townes SCD mice and detect lentiviral vector-encoded hβAS3-globin in transduced mouse erythroid cell cultures and transduced human CD34+ cells after erythroid differentiation. hβAS3-globin was also detected in peripheral blood 6 weeks post-transplant of transduced Townes SS bone marrow cells into syngeneic Townes SS mice and persisted for over 20 weeks post-transplant. As several genome-editing and gene therapy approaches for severe hemoglobin disorders are currently in clinical trials, this MS method will be useful for patient assessment before treatment and during follow-up.