Ataluren‐driven restoration of Shwachman‐Bodian‐Diamond syndrome protein function in Shwachman‐Diamond syndrome bone marrow cells

Abstract

Shwachman-Diamond syndrome (SDS) is a rare inherited recessive disease mainly caused by mutations in the Shwachman-Bodian-Diamond syndrome (SBDS) gene, which encodes for the homonymous protein SBDS, whose function still remains to be fully established. SDS affects several organs causing bone marrow failure, exocrine pancreatic insufficiency, skeletal malformations, and cognitive disorders. About 15% of SDS patients develop myelodysplastic syndrome (MDS) and are at higher risk of developing acute myeloid leukemia (AML). Deficiency in SBDS expression has been associated with increased apoptosis and lack of myeloid differentiation in bone marrow hematopoietic progenitors. Importantly, most SDS patients carry nonsense mutations in SBDS. Since ataluren is a well-characterized small molecule inhibitor that can suppress nonsense mutations, here, we have assessed the efficacy of this drug in restoring SBDS expression in hematopoietic cells obtained from a cohort of SDS patients. Remarkably, we show that ataluren treatment readily restores SBDS protein expression in different cell types, particularly bone marrow stem cells. Furthermore, ataluren promotes myeloid differentiation in hematopoietic progenitors, reduces apoptotic rate in primary PBMCs, and brings mammalian target of rapamycin phosphorylation levels back to normal in both lymphoblasts and bone marrow mesenchymal stromal cells (BM-MSCs). Since a specific therapy against SDS is currently lacking, these results provide the rationale for ataluren repurposing clinical trials.

In vitro metabolism, reaction phenotyping, enzyme kinetics, CYP inhibition and induction potential of ataluren

“…Ataluren has shown to produce full length, functional dystrophin ( 2 , 4 , 13 ) in the nonsense mutation mdx mouse and sapje zebrafish models of DMD. Ataluren activity has also been demonstrated in multiple cell‐based and animal disease models of other nonsense mutation genetic disorders, corroborating its ability to promote readthrough of premature stop codons and its potential for treating genetic disease caused by nonsense mutations 14–19 . Comprehensive nonclinical studies have been conducted in safety pharmacology and secondary pharmacodynamics, pharmacokinetics and metabolism, and toxicology programs.…”

Nonsense Suppression Therapy: New Hypothesis for the Treatment of Inherited Bone Marrow Failure Syndromes

“…Furthermore, ataluren has shown less toxicity and better safety tolerability than aminoglycosides [212,214]. This last feature arises from the fact that ataluren displays its therapeutic activity at concentration much lower (i.e., 3 µM) than gentamicin (i.e., 1 mM) and other aminoglycosides [5,178,197]. It has been demonstrated that the readthrough efficacy of ataluren depends on the sequence of the premature termination codon (PTC) (UAA<UAG<UGA) as well as the sequences of the flanking regions of PTC [195,196,215].…”

“…Finally, nonsense suppression efficiency may depend on the NMD. The readthrough activity sustained by ataluren was reported in several studies both in vivo and in vitro [189,192,196,197,200,214], but the mechanism of action of ataluren in cells harboring nonsense mutation remains poorly understood [195,216,217], beyond its proposed interaction with mRNA [218]. The use of ataluren as a potential therapeutic agent for genetic disorders has been early proposed for the treatment of DMD and CF [192,193,214].…”

“…In addition, we recently studied the effect of ataluren on the nonsense mutated SBDS gene in different hematological and non-hematological cells obtained from 13 patients with SDS [197]. In those experiments, ataluren restored full-length SBDS protein expression in bone marrow hematopoietic progenitors, mesenchymal stromal cells, and lymphoblasts.…”

Targeting Nonsense: Optimization of 1,2,4-Oxadiazole TRIDs to Rescue CFTR Expression and Functionality in Cystic Fibrosis Cell Model Systems

“…Nonsense mutations are found in about 11% of genetic disorders such as cystic fibrosis (CF) [ 17 ], Duchenne muscular dystrophy (DMD) [ 18 ], spinal muscular atrophy [ 19 , 20 ], neurofibromatosis [ 21 ], retinitis pigmentosa [ 22 , 23 , 24 ], lysosomal storage disease [ 13 , 25 , 26 ], Rett syndrome [ 27 ], Shwachman–Diamond syndrome [ 28 , 29 ], and Usher’s syndrome (USH) [ 30 ]. In this context and despite its limits, the translational readthrough of PTCs can represent a valuable pharmaceutical approach to target the specific genetic defect caused by nonsense mutations.…”