Correlation between Ivacaftor-induced CFTR Activation in Airway Epithelial Cells and Improved Lung Function: A Proof-of-Concept Study

Laboratory Tools to Predict CFTR Modulator Therapy Effectiveness and to Monitor Disease Severity in Cystic Fibrosis

The implementation of cystic fibrosis (CF) transmembrane conductance regulator (CFTR) modulator drugs into clinical practice has been attaining remarkable therapeutic outcomes for CF, a life-threatening autosomal recessive genetic disease. However, there is elevated CFTR allelic heterogeneity, and various individuals carrying (ultra)rare CF genotypes remain without any approved modulator therapy. Novel translational model systems based on individuals' own cells/tissue are now available and can be used to interrogate in vitro CFTR modulator responses and establish correlations of these assessments with clinical features, aiming to provide prediction of therapeutic effectiveness. Furthermore, because CF is a progressive disease, assessment of biomarkers in routine care is fundamental in monitoring treatment effectiveness and disease severity. In the first part of this review, we aimed to focus on the utility of individual-derived in vitro models (such as bronchial/nasal epithelial cells and airway/intestinal organoids) to identify potential responders and expand personalized CF care. Thereafter, we discussed the usage of CF inflammatory biomarkers derived from blood, bronchoalveolar lavage fluid, and sputum to routinely monitor treatment effectiveness and disease progression. Finally, we summarized the progress in investigating extracellular vesicles as a robust and reliable source of biomarkers and the identification of microRNAs related to CFTR regulation and CF inflammation as novel biomarkers, which may provide valuable information for disease prognosis.

Advances in Preclinical In Vitro Models for the Translation of Precision Medicine for Cystic Fibrosis

The development of preclinical in vitro models has provided significant progress to the studies of cystic fibrosis (CF), a frequently fatal monogenic disease caused by mutations in the gene encoding the CF transmembrane conductance regulator (CFTR) protein. Numerous cell lines were generated over the last 30 years and they have been instrumental not only in enhancing the understanding of CF pathological mechanisms but also in developing therapies targeting the underlying defects in CFTR mutations with further validation in patient-derived samples. Furthermore, recent advances toward precision medicine in CF have been made possible by optimizing protocols and establishing novel assays using human bronchial, nasal and rectal tissues, and by progressing from two-dimensional monocultures to more complex three-dimensional culture platforms. These models also enable to potentially predict clinical efficacy and responsiveness to CFTR modulator therapies at an individual level. In parallel, advanced systems, such as induced pluripotent stem cells and organ-on-a-chip, continue to be developed in order to more closely recapitulate human physiology for disease modeling and drug testing. In this review, we have highlighted novel and optimized cell models that are being used in CF research to develop novel CFTR-directed therapies (or alternative therapeutic interventions) and to expand the usage of existing modulator drugs to common and rare CF-causing mutations.

Left behind: The potential impact of CFTR modulators on racial and ethnic disparities in cystic fibrosis

The advent of CFTR modulators, a genomic specific medication, revolutionized the treatment of CF for many patients. However, given that these therapeutics were only developed for specific CFTR mutations, not all people with CF have access to such disease-modifying drugs. Racial and ethnic minority groups are less likely to have CFTR mutations that are approved for CFTR modulators. This exclusion has the potential to widen existing health disparities.

Perspectives on the translation of in-vitro studies to precision medicine in Cystic Fibrosis

Recent strides towards precision medicine in Cystic Fibrosis (CF) have been made possible by patient-derived in-vitro assays with the potential to predict clinical response to small molecule-based therapies. Here, we discuss the status of primary and stem-cell derived tissues used to evaluate the preclinical efficacy of CFTR modulators highlighting both their potential and limitations. Validation of these assays requires correlation of in-vitro responses to in-vivo measures of clinical biomarkers of disease outcomes. While initial efforts have shown some success, this translation requires methodologies that are sensitive enough to capture treatment responses in a CF population that now predominantly has mild lung disease. Future development of in-vitro and in-vivo biomarkers will facilitate the generation of new therapeutics particularly for those patients with rare mutations where clinical trials are not feasible so that in the future every CF patient will have access to effective targeted therapies.

Elexacaftor is a CFTR potentiator and acts synergistically with ivacaftor during acute and chronic treatment

Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR), which lead to early death due to progressive lung disease. The development of small-molecule modulators that directly interact with CFTR to aid in protein folding (“correctors”) and/or increase channel function (“potentiators”) have proven to be highly effective in the therapeutic treatment of CF. Notably, incorporation of the next-generation CFTR corrector, elexacaftor, into a triple combination therapeutic (marketed as Trikafta) has shown tremendous clinical promise in treating CF caused by F508del-CFTR. Here, we report on a newly-described role of elexacaftor as a CFTR potentiator. We explore the acute and chronic actions, pharmacology, and efficacy of elexacaftor as a CFTR potentiator in restoring function to multiple classes of CFTR mutations. We demonstrate that the potentiating action of elexacaftor exhibits multiplicative synergy with the established CFTR potentiator ivacaftor in rescuing multiple CFTR class defects, indicating that a new combination therapeutic of ivacaftor and elexacaftor could have broad impact on CF therapies.

CFTR function and clinical response to modulators parallel nasal epithelial organoid swelling

In vitro biomarkers to assess cystic fibrosis transmembrane conductance regulator activity are desirable for precision modulator selection and as a tool for clinical trials. Here, we describe an organoid swelling assay derived from human nasal epithelia using commercially available reagents and equipment and an automated imaging process. Cells were collected in nasal brush biopsies, expanded in vitro, and cultured as spherical organoids or as monolayers. Organoids were used in a functional swelling assay with automated measurements and analysis, whereas monolayers were used for short-circuit current measurements to assess ion channel activity. Clinical data were collected from patients on modulators. Relationships between swelling data and short-circuit current, as well as between swelling data and clinical outcome measures, were assessed. The organoid assay measurements correlated with short-circuit current measurements for ion channel activity. The functional organoid assay distinguished individual responses as well as differences between groups. The organoid assay distinguished incremental drug responses to modulator monotherapy with ivacaftor and combination therapy with ivacaftor, tezacaftor, and elexacaftor. The swelling activity paralleled the clinical response. In conclusion, an in vitro biomarker derived from patients' cells can be used to predict responses to drugs and is likely to be useful as a preclinical tool to aid in the development of novel treatments and as a clinical trial outcome measure for a variety of applications, including gene therapy or editing.

Nasal Epithelial Cell-Based Models for Individualized Study in Cystic Fibrosis

The emergence of highly effective CFTR modulator therapy has led to significant improvements in health care for most patients with cystic fibrosis (CF). For some, however, these therapies remain inaccessible due to the rarity of their individual CFTR variants, or due to a lack of biologic activity of the available therapies for certain variants. One proposed method of addressing this gap is the use of primary human cell-based models, which allow preclinical therapeutic testing and physiologic assessment of relevant tissue at the individual level. Nasal cells represent one such tissue source and have emerged as a powerful model for individual disease study. The ex vivo culture of nasal cells has evolved over time, and modern nasal cell models are beginning to be utilized to predict patient outcomes. This review will discuss both historical and current state-of-the art use of nasal cells for study in CF, with a particular focus on the use of such models to inform personalized patient care.

PROMISE: Working with the CF community to understand emerging clinical and research needs for those treated with highly effective CFTR modulator therapy

Highly effective CFTR modulator drug therapy is increasingly available to those with cystic fibrosis. Multiple observational research studies are now being conducted to better understand the impacts of this important therapeutic milestone on long-term outcomes, patient care needs, and future research priorities. PROMISE is a large, multi-disciplinary academic study focused on the broad impacts of starting elexacaftor/tezacaftor/ivacaftor in the US population age 6 years and older. The many areas of investigation and rationale for each are discussed by organ systems, along with recognition of remaining important questions that will not be addressed by this study alone. Knowledge gained through this and multiple complementary studies around the world will help to understand important health outcomes, clinical care priorities, and research needs for a large majority of people treated with these or similarly effective medications targeting the primary cellular impairment in cystic fibrosis.

Avatar acceptability: views from the Australian Cystic Fibrosis community on the use of personalised organoid technology to guide treatment decisions

Background

Patient-oriented research approaches that reflect the needs and priorities of those most affected by health research outcomes improves translation of research findings into practice. Targeted therapies for cystic fibrosis (CF) are now a viable treatment option for some eligible individuals despite the heterogeneous patient-specific therapeutic response. This has necessitated development of a clinical tool that predicts treatment response for individual patients. Patient-derived mini-organs (organoids) have been at the forefront of this development. However, little is known about their acceptability in CF patients and members of the public.

Methods

We used a cross-sectional observational design to conduct an online survey in people with CF, their carers and community comparisons. Acceptability was examined in five domains: 1) willingness to use organoids, 2) perceived advantages and disadvantages of organoids, 3) acceptable out-of-pocket costs, 4) turnaround time and 5) source of tissue.

Results

In total, 188 participants completed the questionnaire, including adults with CF and parents of children with CF (90 (48%)), and adults without CF and parents of children without CF (98 (52%)). Use of organoids to guide treatment decisions in CF was acceptable to 86 (95%) CF participants and 98 (100%) community participants. The most important advantage was that organoids may improve treatment selection, improving the patient's quality of life and life expectancy. The most important disadvantage was that the organoid recommended treatment might be unavailable or too expensive.

Conclusions

These findings indicate acceptance of patient-derived organoids as a tool to predict treatment response by the majority of people surveyed. This may indicate successful future implementation into healthcare systems.

The perspective regarding clinical use of patient-derived organoid models to enable cystic fibrosis personalised therapeutic decision-making of 188 participating adults surveyedhttps://bit.ly/30nWDJ7