Reviewing nucleic acid therapy strategies for cystic fibrosis variants unresponsive to CFTR modulators
Background: CFTR variants that are difficult to address with current modulators
A review has outlined DNA- and RNA-based therapeutic strategies for cystic fibrosis variants that do not respond to existing CFTR modulators. Its central contribution is a framework linking molecular defects that disrupt CFTR expression with therapeutic approaches to help prioritize further development. This is distinct from an experimental study demonstrating the efficacy of a new therapy.
Cystic fibrosis is an autosomal recessive disorder caused by pathogenic variants in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Impaired chloride ion transport in epithelial cells leads to systemic symptoms, including progressive loss of lung function. Small-molecule CFTR modulators have improved treatment outcomes by helping defective proteins reach the cell surface and increasing their activity.
However, not all genotypes respond to modulators. The review focuses on nonsense and splicing variants that disrupt CFTR expression at the transcriptional or translational level. It reflects the view that these expression defects must also be considered to understand the limitations of existing approaches that regulate protein trafficking and activity.
Key findings: Linking molecular defects to DNA- and RNA-based therapeutic approaches
The main mechanisms examined in the review are premature termination codons, nonsense-mediated messenger RNA (mRNA) decay (NMD), and abnormal precursor mRNA splicing. The authors consider how these mechanisms limit modulator efficacy and examine them as potential points of intervention for other therapeutic strategies.
DNA-targeted strategies include gene replacement and gene editing. RNA-targeted approaches include mRNA replacement, antisense oligonucleotides (ASOs), CFTR amplifiers, translation termination codon readthrough inducers, and NMD inhibition. The review centers on prioritizing therapeutic approaches according to the molecular defect.
The assessment covers variant-specific sensitivity, previously reported clinical and preclinical evidence, and practical considerations. However, the available abstract does not provide effect sizes for individual strategies, study populations or sample sizes, dosing conditions, or clinical trial phases. This material alone makes it difficult to judge the relative merits of the therapies or the likelihood of success for a specific variant.
Significance and outlook: An evidence framework for prioritizing therapeutic development
The review’s contribution is to connect molecular defects that block CFTR expression with candidate therapeutic approaches. It offers an evidence framework for considering development options for patients who may derive little benefit from current modulators. It may also help determine which clinical or preclinical data on particular approaches to examine first.
However, this framework does not validate patient-specific treatment choices or establish the clinical efficacy of new nucleic acid therapies. Assessing the applicability of individual approaches requires further examination of variant-specific results, safety, and conditions of use in the full review and its cited original studies. The conclusion supported by the abstract is limited to rationally prioritizing intervention strategies according to molecular defects.
Source: Bibliographic information and abstract of the review published in Human Molecular Genetics.
Cystic fibrosis (CF) is a life-limiting autosomal recessive disorder caused by pathogenic variants in the CF transmembrane conductance regulator (CFTR) gene that impair epithelial chloride ion transport, leading to progressive lung dysfunction among other systemic manifestations. Small molecule CFTR modulators have dramatically improved outcomes for people with CF (pwCF) by promoting the trafficking of defective CFTR protein to the cell surface and enhancing its activity. However, a substantial proportion of pwCF harbor genotypes which remain refractory to CFTR modulators and thus lack approved disease-modifying treatments, most commonly nonsense and splicing variants that disrupt CFTR expression at the transcript or translation level. This review delineates the molecular mechanisms underlying modulator-refractory CFTR genotypes, focusing on premature termination codons, nonsense-mediated mRNA decay (NMD), and aberrant pre-mRNA splicing. We examine how these biological phenomena determine and constrain modulator efficacy while simultaneously defining therapeutic entry points. We evaluate emerging DNA-targeted strategies, such as gene replacement and gene editing, alongside RNA-directed approaches, including mRNA replacement, antisense oligonucleotides, CFTR amplifiers, translational readthrough agents and NMD inhibition. Variant-specific sensitivity, reported clinical and preclinical evidence, and practical considerations for implementation are critically assessed. By aligning molecular defect with therapeutic modality, this framework enables rational prioritization of intervention strategies for modulator-refractory CFTR genotypes.
Development teams evaluating candidate treatments for CFTR variants that do not respond to modulators can use this review to organize the problems each variant causes during gene expression and compare the evidence for relevant DNA- and RNA-based approaches. For example, they could examine candidate strategies related to nonsense variants and abnormal splicing, as well as variant-specific response data. This is a potential use for prioritizing further evidence review. The abstract alone makes it difficult to select a suitable treatment for an individual patient or predict a candidate technology’s likelihood of clinical success. Actual development decisions require further examination of the results and conditions of use reported in individual clinical and preclinical studies.