In Utero Mapping and Development Role of CFTR in Lung and Gastrointestinal Tract of Cystic Fibrosis Patients

The role of CFTR in the eye, and the effect of early highly effective modulator treatment for cystic fibrosis on eye health

Cystic fibrosis transmembrane conductance regulator (CFTR) is a protein that plays a crucial role in various human organs, including the respiratory and digestive systems. Dysfunctional CFTR is the key variant of the lethal genetic disorder, cystic fibrosis (CF). In the past decade, highly effective CFTR modulator therapies, including elexacaftor-tezacaftor-ivacaftor, have revolutionised CF management by correcting the underlying molecular defect to improve patient outcomes and life expectancy. Despite demonstrating multiorgan efficacy, clinical studies have largely overlooked the potential for ocular disturbances with CFTR modulator therapy, with the exception of a few case studies reporting the presence of crystalline lens pathologies in young children on CFTR modulators, and in breastfed infants born to individuals who were on CFTR modulator treatment during pregnancy. CFTR is present in multiple tissues during embryonic development, including the eye, and its expression can be influenced by genetic and environmental factors. This review summarises the role of CFTR in the eye, and the potential impact of CFTR on eye function and vision later in life. This information provides a framework for understanding the use and possible effects of CFTR-modulating therapeutics in the context of eye health, including the potential to leverage the eye for non-invasive and accessible diagnostic and monitoring capabilities in patients with CF.

Extent of foetal exposure to maternal elexacaftor/tezacaftor/ivacaftor during pregnancy

BACKGROUND AND PURPOSE

Cystic fibrosis (CF) patients are living longer and healthier due to improved treatments, e.g. cystic fibrosis transmembrane conductance regulator (CFTR) modulator therapy elexacaftor/tezacaftor/ivacaftor (ETI), with treatment possibly occurring in pregnancy. The risk of ETI to foetuses remain unknown. Thus the effect of maternally administered ETI on foetal genetic and structural development was investigated.

EXPERIMENTAL APPROACH

Pregnant Sprague Dawley rats were orally treated with ETI (6.7 mg·kg-1·day-1 elexacaftor + 3.5 mg·kg-1·day-1 tezacaftor + 25 mg·kg-1·day-1 ivacaftor) for 7 days from E12 to E19. Tissue samples collected at E19 were analysed using histology and RNA sequencing. Histological changes and differentially expressed genes (DEG) were assessed.

KEY RESULTS

No overt structural abnormalities were found in foetal pancreas, liver, lung and small intestine after 7-day ETI exposure. Very few non-functionally associated DEG in foetal liver, lung and small intestine were identified using RNA-seq. 29 DEG were identified in thymus (27 up-regulated and two down-regulated) and most were functionally linked to each other. Gene ontology enrichment analysis revealed that multiple muscle-related terms were significantly enriched. Many more DEG were identified in cortex (44 up-regulated and four down-regulated) and a group of these were involved in central nervous system and brain development.

CONCLUSION AND IMPLICATION

Sub-chronic ETI treatment in late pregnancy does not appear to pose a significant risk to the genetic and structural development of many foetal tissues. However, significant gene changes in foetal thymic myoid cells and cortical neuronal development requires future follow-up studies to assess the risk to these organs.

Recommended Tool Compounds for Modifying the Cystic Fibrosis Transmembrane Conductance Regulator Channel Variants

Cystic fibrosis (CF) is a genetic disorder arising from variations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, leading to multiple organ system defects. CFTR tool compounds are molecules that can modify the activity of the CFTR channel. Especially, patients that are currently not able to benefit from approved CFTR modulators, such as patients with rare CFTR variants, benefit from further research in discovering novel tools to modulate CFTR. This Review explores the development and classification of CFTR tool compounds, including CFTR blockers (CFTRinh-172, GlyH-101), potentiators (VRT-532, Genistein), correctors (VRT-325, Corr-4a), and other approved and unapproved modulators, with detailed descriptions and discussions for each compound. The challenges and future directions in targeting rare variants and optimizing drug delivery, and the potential synergistic effects in combination therapies are outlined. CFTR modulation holds promise not only for CF treatment but also for generating CF models that contribute to CF research and potentially treating other diseases such as secretory diarrhea. Therefore, continued research on CFTR tool compounds is critical.

Ocular development after highly effective modulator treatment early in life

Highly effective cystic fibrosis (CF) transmembrane conductance regulator (CFTR) modulator therapies (HEMT), including elexacaftor-tezacaftor-ivacaftor, correct the underlying molecular defect causing CF. HEMT decreases general symptom burden by improving clinical metrics and quality of life for most people with CF (PwCF) with eligible CFTR variants. This has resulted in more pregnancies in women living with CF. All HEMT are known to be able pass through the placenta and into breast milk in mothers who continue on this therapy while pregnant and breast feeding. Toxicity studies of HEMT in young rats demonstrated infant cataracts, and case reports have reported the presence of congenital cataracts in early life exposure to HEMT. This article reviews the evidence for how HEMT influences the dynamic and interdependent processes of healthy and abnormal lens development in the context of HEMT exposure during pregnancy and breastfeeding, and raises questions that remain unanswered.