Hematopoietic Stem Cell Gene Therapy for Cystinosis: From Bench-to-Bedside

Abstract

Cystinosis is an autosomal recessive metabolic disease that belongs to the family of lysosomal storage disorders. The gene involved is the CTNS gene that encodes cystinosin, a seven-transmembrane domain lysosomal protein, which is a proton-driven cystine transporter. Cystinosis is characterized by the lysosomal accumulation of cystine, a dimer of cysteine, in all the cells of the body leading to multi-organ failure, including the failure of the kidney, eye, thyroid, muscle, and pancreas, and eventually causing premature death in early adulthood. The current treatment is the drug cysteamine, which is onerous and expensive, and only delays the progression of the disease. Employing the mouse model of cystinosis, using Ctns−/− mice, we first showed that the transplantation of syngeneic wild-type murine hematopoietic stem and progenitor cells (HSPCs) led to abundant tissue integration of bone marrow-derived cells, a significant decrease in tissue cystine accumulation, and long-term kidney, eye and thyroid preservation. To translate this result to a potential human therapeutic treatment, given the risks of mortality and morbidity associated with allogeneic HSPC transplantation, we developed an autologous transplantation approach of HSPCs modified ex vivo using a self-inactivated lentiviral vector to introduce a functional version of the CTNS cDNA, pCCL-CTNS, and showed its efficacy in Ctns−/− mice. Based on these promising results, we held a pre-IND meeting with the Food and Drug Administration (FDA) to carry out the FDA agreed-upon pharmacological and toxicological studies for our therapeutic candidate, manufacturing development, production of the GMP lentiviral vector, design Phase 1/2 of the clinical trial, and filing of an IND application. Our IND was cleared by the FDA on 19 December 2018, to proceed to the clinical trial using CD34+ HSPCs from the G-CSF/plerixafor-mobilized peripheral blood stem cells of patients with cystinosis, modified by ex vivo transduction using the pCCL-CTNS vector (investigational product name: CTNS-RD-04). The clinical trial evaluated the safety and efficacy of CTNS-RD-04 and takes place at the University of California, San Diego (UCSD) and will include up to six patients affected with cystinosis. Following leukapheresis and cell manufacturing, the subjects undergo myeloablation before HSPC infusion. Patients also undergo comprehensive assessments before and after treatment to evaluate the impact of CTNS-RD-04 on the clinical outcomes and cystine and cystine crystal levels in the blood and tissues for 2 years. If successful, this treatment could be a one-time therapy that may eliminate or reduce renal deterioration as well as the long-term complications associated with cystinosis. In this review, we will describe the long path from bench-to-bedside for autologous HSPC gene therapy used to treat cystinosis.

Hematopoietic Stem Cell Gene Therapy Alleviates Disease Phenotypes in a Murine Model of Danon Disease

“…More recently, our group has evaluated this approach in a phase 1/2 human clinical trial for cystinosis (NCT03897361). 31 We also showed the bene cial impact of wildtype HSPCs transplantation on the cardiac function in Friedreich's ataxia 23 . One of the mechanisms by which modi ed HSPC leads to tissue preservation in cystinosis involves the transfer of lysosomes across TNTs 12 .…”

CTNSmRNA as a potential treatment for nephropathic cystinosis

“…8 However, this therapy requires leukapheresis, myeloablation and harbours other potential risks, which are not expected for mRNA-based approaches. 7,8,12 We studied the potential of CTNS mRNA therapy to ameliorate cystinosis, a monogenic disease having a well-defined phenotype (cystine accumulation, and both podocyte and proximal tubular dysfunction.…”

“…6 Preliminary results of gene therapy by transplanting CTNS lentiviral vector-transduced autologous hematopoietic stem cells (HSC) showed a successful reduction of tissue cystine accumulation and preserved eye, thyroid and kidney function. 7 Nevertheless, HSC transplantation has several disadvantages, such as the risk of insertional mutagenesis and the need for leukapheresis and myeloablation. 7,8 Messenger RNA (mRNA-)based approaches have recently gained a lot of attention during SARS-CoV2 pandemic following the extended use of mRNA vaccines.…”

“…7 Nevertheless, HSC transplantation has several disadvantages, such as the risk of insertional mutagenesis and the need for leukapheresis and myeloablation. 7,8 Messenger RNA (mRNA-)based approaches have recently gained a lot of attention during SARS-CoV2 pandemic following the extended use of mRNA vaccines. [9][10][11] Additionally, mRNA therapies are currently in pre-clinical or clinical trial phase for several genetic diseases, such as cystic fibrosis and propionic acidaemia.…”

Advantages and Limitations of Gene Therapy and Gene Editing for Friedreich’s Ataxia

“…Clinical trials using gene-modified autologous CD34 + HSPCs are being undertaken for genetic diseases such as X-SCID, ADA-SCID, Wiskott-Aldrich syndrome, metachromatic leukodystrophy, X-linked cerebral adrenoleukodystrophy, and mucopolysaccharidosis type I ( Gentner et al, 2021 ; Mamcarz et al, 2019 ; De Ravin et al, 2016 ; Kohn et al, 2021 ; Magnani et al, 2022 ; Ma et al, 2021 ; Ferrua and Aiuti, 2017 ; Morris et al, 2017 ; Biffi et al, 2013 ; Eichler et al, 2017b ; Fumagalli et al, 2022 ). Currently, our lab is conducting a phase 1/2 clinical trial for cystinosis ( ClinicalTrials.gov Identifier: NCT03897361), a multisystemic lysosomal storage disorder, characterized by accumulation of cystine in all tissues and due to mutations or deletions in CTNS gene, encoding a lysosomal cystine transporter ( Cherqui, 2021 ). Single infusion of ex vivo gene-corrected HSPCs using a self-inactivated lentiviral vector carrying CTNS cDNA in the mouse model of cystinosis led to long-term preservation of the kidney ( Yeagy et al, 2011 ), eye ( Rocca et al, 2015 ) and thyroid ( Gaide Chevronnay et al, 2016 ) functions.…”