Current state of CFTR modulators for treatment of Cystic Fibrosis

BEAT-CF (Bayesian Evidence Adaptive Treatment for people with Cystic Fibrosis): description of a prospective cohort for nested studies in cystic fibrosis

BACKGROUND

Despite recent improvements in treatment modalities for cystic fibrosis (CF), there is currently limited evidence and a lack of consensus regarding optimal treatment strategies for the different aspects of CF, including pulmonary exacerbations (PEx). We aimed to establish a prospective cohort of people with CF (pwCF) to evaluate alternative approaches to managing CF in the era of modulator therapies.

METHODS

We prospectively enrolled children and adults with CF receiving care at specialist CF centres across Australia. Participant data were systematically collected on demography, clinical signs and symptoms, comorbidities, spirometry, participant reported outcomes, microbiology and treatments received. Here we describe the demographic, microbiological and clinical characteristics of the participants at enrolment, to understand the representativeness of the cohort for planning future nested studies.

RESULTS

Between October 14, 2020 and December 31, 2023, 927 pwCF were enrolled across eleven Australian CF centres. Of these, 51% (n=472) were male, 77% (n=709) were <18 years old, 90% (n=831) had a highest ppFEV1 (percent predicted forced expiratory volume exhaled in the first second) of ≥70% in the preceding year, and 35% (n=322) reported detection of Pseudomonas aeruginosa in their airway specimens.

CONCLUSIONS

We have established a contemporary cohort of pwCF with granular clinical and treatment data for PEx. This cohort will enable future nested studies focused on PEx management and other aspects of CF care. Understanding the baseline characteristics of these participants, as presented here, is critical for interpreting subsequent outcomes and for identifying factors that may influence disease progression and response to therapies.

Deubiquitinase-Targeting Chimeras (DUBTACs) as a Potential Paradigm-Shifting Drug Discovery Approach

Developing proteolysis-targeting chimeras (PROTACs) is well recognized through target protein degradation (TPD) toward promising therapeutics. While a variety of diseases are driven by aberrant ubiquitination and degradation of critical proteins with protective functions, target protein stabilization (TPS) rather than TPD is emerging as a unique therapeutic modality. Deubiquitinase-targeting chimeras (DUBTACs), a class of heterobifunctional protein stabilizers consisting of deubiquitinase (DUB) and protein-of-interest (POI) targeting ligands conjugated with a linker, can rescue such proteins from aberrant elimination. DUBTACs stabilize the levels of POIs in a DUB-dependent manner, removing ubiquitin from polyubiquitylated and degraded proteins. DUBTACs can induce a new interaction between POI and DUB by forming a POI-DUBTAC-DUB ternary complex. Herein, therapeutic benefits of TPS approaches for human diseases are introduced, and recent advances in developing DUBTACs are summarized. Relevant challenges, opportunities, and future perspectives are also discussed.

Cutting-Edge Advances in Cystic Fibrosis: From Gene Therapy to Personalized Medicine and Holistic Management

Cystic fibrosis (CF), a genetic disorder characterized by mutations in the CFTR gene, has seen significant advances in treatment through cutting-edge approaches such as gene therapy and personalized medicine. This review examines the current and emerging strategies shaping CF care, focusing on novel therapies that target the root cause of CF and optimize patient outcomes. CFTR modulators have transformed cystic fibrosis management by enhancing protein function for specific mutations, leading to improved lung function and quality of life. Concurrently, gene therapy offers transformative potential by aiming to correct CFTR mutations using tools like CRISPR/Cas9 or prime editing, though challenges remain in delivery and long-term efficacy. The integration of precision medicine, facilitated by genomic and computational technologies, allows for personalized treatment plans that account for genetic variability and disease severity. Complementing these approaches, holistic management emphasizes the importance of psychological support and nutritional optimization, acknowledging CF's multi-system impact. Future directions include exploring anti-inflammatory agents and microbiome modulation to further mitigate disease morbidity. However, global disparities in treatment access continue to challenge equitable healthcare delivery, underscoring the need for policy reform and international cooperation. By synthesizing these developments, this review highlights the transformative potential of modern CF treatments, advocating for continued innovation and global healthcare equity, with the ultimate goal of dramatically improving life expectancy and quality of life for individuals with CF.

Jaw and neck muscle activity during chewing and craniocervical dysfunction index in children, adolescents, and adults with and without cystic fibrosis: a comparative analysis

OBJECTIVE

To compare masticatory muscle activity between people with cystic fibrosis (pwCF) and healthy controls and to verify whether craniocervical dysfunction is associated with the presence of CF.

METHODS

Fifty-six participants were assessed and divided into pwCF and healthy control (HC) groups, each one composed of 13 children and adolescents at 9 (SD 3) years old and 15 adults at 25 (SD 6) years old. Craniocervical Dysfunction Index assessed symptoms of dysfunction and cervical spine mobility. Electromyography was used to evaluate the jaw and neck muscle activity during chewing.

RESULTS

Muscle activity during chewing was not statistically different between groups. Prevalence of craniocervical dysfunction was 75% for pwCF vs 64% for healthy controls. Individuals with CF are 1.53 [1.260, 1.870] times more likely to have reduced cervical mobility compared to healthy controls (p = 0.000).

CONCLUSION

These results reinforce the need for musculoskeletal disorders treatment in the management of pwCF.

Optimisation of a novel series of ENaC inhibitors, leading to the selection of the long-acting inhaled clinical candidate ETD001, a potential new treatment for cystic fibrosis

Cystic Fibrosis (CF) results from the loss of function of the cystic fibrosis transmembrane conductance regulator (CFTR), an ion channel of key importance in the airway epithelia. CFTR helps control optimal hydration of the airways, a crucial requirement for healthy lungs. CFTR modulators have recently been approved as an effective treatment option for many genetic variants of CF. The epithelial sodium channel (ENaC), unlike CFTR which is secretory, is an absorptive pathway, and therefore its inhibition is an alternative and potentially complementary approach to aid hydration of the airways. Due to the adverse effect of ENaC inhibition in the kidney we, as have several others, focused on the design and synthesis of novel ENaC inhibitors for direct delivery to the airways via inhalation. A new series of ENaC inhibitors is described, wherein the well-established pyrazine core of first-generation inhibitors was replaced with a pyrrolopyrazine. Aiming for high retention at the surface of the lung following inhalation, optimisation of this template focused on significantly increasing polarity to minimize passive cellular permeability. The resulting optimized clinical candidate ETD001 demonstrates potent inhibition of ENaC (59 nM) prolonged retention in the airways of rats (13 % of the delivered dose retained after 6h) following intratracheal administration and a potent and long-acting effect in a sheep model of mucociliary clearance following inhalation (ED100 (4-6h) = 9 μg/kg). ETD001 entered a phase II study in CF patients in July 2024.

Outcomes of Modulator Therapy Discontinued After Short-Term Use in Adult Cystic Fibrosis

INTRODUCTION

Cystic fibrosis transmembrane conductance regulator modulator therapies (CFTR-MT) have altered management, reducing exacerbations and slowing pulmonary function decline. Nevertheless, it is still uncertain if the benefits of CFTR-MTs last when they are stopped. This study aimed to assess pulmonary function changes, and exacerbation rates during and after CFTR-MT use in adult cystic fibrosis patients.

METHODS

Between 2018 and 2022, we conducted a study involving adult CF patients who initially used CFTR-MTs but later discontinued them due to reimbursement issues. The study was divided into three phases: predrug (T1), in-drug (T2), and postdrug (T3). We recorded pulmonary function tests, laboratory and culture results, and the number of exacerbations.

RESULTS

The study involved 33 patients, with 28 (84.8%) receiving Elexacaftor/Tezacaftor/Ivacaftor and 5 (15.2%) receiving Ivacaftor. The median treatment and interruption durations were 3.1 (IQR = 2.9-5.7), and 2.5 (IQR = 1.5-4.0) months, respectively. The mean FEV1% was 54.3% (± 26.6), 70.4% (± 27.4), and 60.2% (± 26.5) during T1, T2, and T3, respectively (p < 0.001). The mean FVC% was 65.5% (± 23.9) in T1, increased to 81.5% (± 24.5) in T2, and decreased to 71.6% (± 25.9) in T3 (p < 0.001). The number of Psedomonas aeruginosa, and Aspergillus positive sputum cultures decreased significantly with drug use (T1: 72.7%, 39.4%; T2: 48.5%, 9.1%; T3: 45.5%, 18.2%; p = 0.014, p = 0.004, respectively). The median number of hospitalizations was 1.0 (0-5.0) in T1, 0 (0-0) in T2, and 0 (0-1.0) in T3.

CONCLUSION

This study revealed that CFTR-MTs are effective even in the short term for adult CF patients, but their beneficial effects quickly diminish after discontinuation. Real-life data obtained as a result of discontinuation of drugs due to reimbursement problems has highlighted the significance of regular and uninterrupted use of modulators.

My path to citrin deficiency

Citrin belongs to the SLC25 transport protein family found mostly in inner mitochondrial membranes. The family prototype, the ADP-ATP carrier, delivers ATP made inside mitochondria to the cellular cytoplasm and returns ADP to the mitochondrion for resynthesis of ATP. In pre-genomic 1981, I noticed that the protein sequence of the bovine ADP-ATP carrier consists of three related sequences, each containing two transmembrane α-helices traveling in opposite senses. Colleagues and I demonstrated that two other mitochondrial carriers had similar features. From emergent genomic sequences, it became apparent that they represented a large family of transport proteins with the same characteristic threefold repeats. The human genome encodes 53 members, but the functions of many were unknown. So, colleagues and I determined how to make these proteins in Escherichia coli and introduce them into liposomes to allow exploration of their transport functions. The 27 human family members to have been thus identified include citrin and the closely related protein aralar. Both exchange aspartate from the mitochondrial matrix for cytosolic glutamate plus a proton. Citrin is expressed predominantly in liver and non-excitable tissues, whereas aralar is the dominant form in the brain. Each has a membrane extrinsic N-terminal Ca2+-binding domain, a transport domain, and a C-terminal amphipathic α-helix. Human mutations in citrin impair the urea cycle, malate-aspartate shuttle, gluconeogenesis, amino acid breakdown, and energy metabolism leading to citrin deficiency. Currently, the complex etiology of this condition is poorly understood and new knowledge would help to improve diagnosis, therapies, and finding a cure. My aims are to seek a basic understanding of the etiology of citrin deficiency and to use that knowledge in improving diagnostic procedures and in developing new treatments and a cure.

Diagnosis and treatment of ADHD in pediatric patients during the first year of elexacaftor/tezacaftor/ivacaftor

BACKGROUND

With elexacaftor/tezacaftor/ivacaftor (ETI), children with cystic fibrosis (CwCF) are living healthier lives with a focus on typical developmental issues such as attention deficit/hyperactivity disorder (ADHD). This paper characterizes CwCF with ADHD within the first year of ETI treatment.

METHODS

This retrospective, observational analysis examines a subgroup of CwCF participating in a longitudinal study obtaining prospective data regarding the impact of ETI on mental health. All participants started on ETI were offered enrollment, with rolling enrollment as younger children became eligible. Clinical data regarding CF symptoms, mental health diagnoses, medications, changes in mental health symptoms and BMI were collected via chart review.

RESULTS

Before ETI, ADHD diagnoses were identified in 21 children; an additional 3 were diagnosed within the first year. Eleven children were treated with ADHD medication at ETI initiation; nine children did not use ADHD medication during the study period. In the 1-year follow-up, four children started ADHD medication. Of the 11 who started ETI on ADHD medication, five increased doses, three changed medications and/or decreased dose, and one discontinued medication. Two children experienced no changes to their treatment.

CONCLUSION

Most CwCF on ADHD medication underwent changes in dosing and/or medication after ETI initiation. Several children were diagnosed with ADHD after starting ETI. The role of ETI in these recent diagnoses and treatment plans is unclear. Given the prevalence of pediatric ADHD diagnoses and the medication changes that were needed by this population, additional research is warranted to clarify the relationship between ETI and ADHD in CwCF.

Fatty acid abnormalities in cystic fibrosis-the missing link for a cure?

The care for cystic fibrosis (CF) has dramatically changed with the development of modulators, correctors, and potentiators of the CFTR molecule, which lead to improved clinical status of most people with CF (pwCF). The modulators influence phospholipids and ceramides, but not linoleic acid (LA) deficiency, associated with more severe phenotypes of CF. The LA deficiency is associated with upregulation of its transfer to arachidonic acid (AA). The AA release from membranes is increased and associated with increase of pro-inflammatory prostanoids and the characteristic inflammation is present before birth and bacterial infections. Docosahexaenoic acid is often decreased, especially in associated liver disease Some endogenously synthesized fatty acids are increased. Cholesterol and ceramide metabolisms are disturbed. The lipid abnormalities are present at birth, and before feeding in transgenic pigs and ferrets. This review focus on the lipid abnormalities and their associations to clinical symptoms in CF, based on clinical studies and experimental research.

Elexacaftor/Tezacaftor/Ivacaftor use in Pediatric Cystic Fibrosis Patients with Advanced Liver Disease

BACKGROUND

Cystic fibrosis transmembrane conductance regulator (CFTR) modulator therapy extends the life expectancy of people with cystic fibrosis (PwCF). However, CFTR modulators have not been well studied in patients with cystic fibrosis liver disease (CFLD), specifically those with advanced liver disease with portal hypertension. The purpose of this report is to describe the use of elexacaftor/tezacaftor/ivacaftor (ETI) in pediatric CF patients with advanced CFLD.

METHODS

This retrospective case series included PwCF < 18 years old with baseline advanced CFLD initiated on ETI.

RESULTS

Eleven PwCF and advanced CFLD were treated with ETI; six started a reduced dose regimen. No patient required treatment interruption and four patients received dose changes related to increase in transaminase and/or bilirubin elevations. Mean (SD) change in ppFEV1 from prior to ETI to highest value during therapy was 14.27 % (4.25) (p = 0.007). When evaluating the group as whole, AST decreased from baseline to last reported -15.18 (23.23) units/L (p = 0.054) and ALT slightly increased 0.73 (39.13) units/L (p = 0.96). Bilirubin increased minimally overall for patients with mean change from baseline of 0.83 (1.33) mg/dL [range -0.5-3] (p = 0.17). A model for time on ETI showed a significant decrease in AST over time of 0.955 per month of ETI but no other liver biochemistries were significant. No patient experienced decompensation of CFLD.

CONCLUSION

ETI therapy in pediatric CF patients with advanced CFLD can be beneficial in improving pulmonary and nutritional outcomes without negative impact on liver biochemistries or hepatic outcomes. Close monitoring is recommended to ensure safety and tolerability.

Diversity of CFTR variants across ancestries characterized using 454,727 UK biobank whole exome sequences

BACKGROUND

Limited understanding of the diversity of variants in the cystic fibrosis transmembrane conductance regulator (CFTR) gene across ancestries hampers efforts to advance molecular diagnosis of cystic fibrosis (CF). The consequences pose a risk of delayed diagnoses and subsequently worsened health outcomes for patients. Therefore, characterizing the spectrum of CFTR variants across ancestries is critical for revolutionizing molecular diagnoses of CF.

METHODS

We analyzed 454,727 UK Biobank (UKBB) whole-exome sequences to characterize the diversity of CFTR variants across ancestries. Using the PanUKBB classification, the participants were assigned into six major groups: African (AFR), American/American Admixed (AMR), Central South Asia (CSA), East Asian (EAS), European (EUR), and Middle East (MID). We segregated ancestry-specific CFTR variants, including those that are CF-causing or clinically relevant. The ages of certain CF-causing variants were determined and analyzed for selective pressure effects, and curated phenotype analysis was performed for participants with clinically relevant CFTR genotypes.

RESULTS

We detected over 4000 CFTR variants, including novel ancestry-specific variants, across six ancestries. Europeans had the most unique CFTR variants [n = 2212], while the American group had the least unique variants [n = 23]. F508del was the most prevalent CF-causing variant found in all ancestries, except in EAS, where V520F was the most prevalent. Common EAS variants such as 3600G > A, V456A, and V520, which appeared approximately 270, 215, and 338 generations ago, respectively, did not show evidence of selective pressure. Sixteen participants had two CF-causing variants, with two being diagnosed with CF. We found 154 participants harboring a CF-causing and varying clinical consequences (VCC) variant. Phenotype analysis performed for participants with multiple clinically relevant variants returned significant associations with CF and its pulmonary phenotypes [Bonferroni-adjusted p < 0.05].

CONCLUSIONS

We leveraged the UKBB database to comprehensively characterize the broad spectrum of CFTR variants across ancestries. The detection of over 4000 CFTR variants, including several ancestry-specific and uncharacterized CFTR variants, warrants the need for further characterization of their functional and clinical relevance. Overall, the presentation of classical CF phenotypes seen in non-CF diagnosed participants with more than one CF-causing variant indicates that they may benefit from current CFTR modulator therapies.

Cyclic diacyl thioureas enhance activity of corrector Lumacaftor on F508del-CFTR

Cystic fibrosis is a genetic disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) protein. In the search of novel series of CFTR modulators, a library of mono and diacyl thioureas were prepared by sequential synthesis. When tested alone, the obtained compounds 5 and 6 poorly affected F508del-CFTR conductance but, in combination with Lumacaftor, selected derivatives showed the ability to increase the activity of the approved modulator. Analogue 6 i displayed the most marked enhancing effect and acylthioureas 6 d and 6 f were also able to improve efficacy of Lumacaftor. All compounds proved to be non-cytotoxic against different cancer cell lines. Good pharmacokinetic properties were predicted for derivatives 5 and 6, thus supporting the value of these compounds for the development of novel modulators potentially useful for cystic fibrosis.

Paediatric Thoracic Imaging in Cystic Fibrosis in the Era of Cystic Fibrosis Transmembrane Conductance Regulator Modulation

Cystic fibrosis (CF) is one of the most common progressive life-shortening genetic conditions worldwide. Ground-breaking translational research has generated therapies that target the primary cystic fibrosis transmembrane conductance regulator (CFTR) defect, known as CFTR modulators. A crucial aspect of paediatric CF disease is the development and progression of irreversible respiratory disease in the absence of clinical symptoms. Accurate thoracic diagnostics have an important role to play in this regard. Chest radiographs are non-specific and insensitive in the context of subtle changes in early CF disease, with computed tomography (CT) providing increased sensitivity. Recent advancements in imaging hardware and software have allowed thoracic CTs to be acquired in paediatric patients at radiation doses approaching that of a chest radiograph. CFTR modulators slow the progression of CF, reduce the frequency of exacerbations and extend life expectancy. In conjunction with advances in CT imaging techniques, low-dose thorax CT will establish a central position in the routine care of children with CF. International guidelines regarding the choice of modality and timing of thoracic imaging in children with CF are lagging behind these rapid technological advances. The continued progress of personalised medicine in the form of CFTR modulators will promote the emergence of personalised radiological diagnostics.

Exhaled Breath Analysis Detects the Clearance of Staphylococcus aureus from the Airways of Children with Cystic Fibrosis

BACKGROUND

Electronic nose (eNose) technology can be used to characterize volatile organic compound (VOC) mixes in breath. While previous reports have shown that eNose can detect lung infections with pathogens such as Staphylococcus aureus (SA) in people with cystic fibrosis (CF), the clinical utility of eNose for longitudinally monitoring SA infection status is unknown.

METHODS

In this longitudinal study, a cloud-connected eNose, the SpiroNose, was used for the breath profile analysis of children with CF at two stable visits and compared based on changes in SA infection status between visits. Data analysis involved advanced sensor signal processing, ambient correction, and statistics based on the comparison of breath profiles between baseline and follow-up visits.

RESULTS

Seventy-two children with CF, with a mean (IQR) age of 13.8 (9.8-16.4) years, were studied. In those with SA-positive airway cultures at baseline but SA-negative cultures at follow-up (n = 19), significant signal differences were detected between Baseline and Follow-up at three distinct eNose sensors, i.e., S4 (p = 0.047), S6 (p = 0.014), and S7 (p = 0.014). Sensor signal changes with the clearance of SA from airways were unrelated to antibiotic treatment. No changes in sensor signals were seen in patients with unchanged infection status between visits.

CONCLUSIONS

Our results demonstrate the potential applicability of the eNose as a non-invasive clinical tool to longitudinally monitor pulmonary SA infection status in children with CF.

Prognostic imagination: Genetic counseling amidst therapeutic innovation and evolving futures

Despite the moniker "precision medicine," genetic diagnoses are often imprecise with respect to prognosis. In a period when prognoses are evolving in lockstep with advances in genetic diagnostics and therapeutics, it is critical that clinicians and researchers consider how prognosis is communicated beyond the moment of diagnosis. Research has shown that genetic diagnoses are described differently in pre- and postnatal contexts, but we know relatively little about how patients and families make sense of prognostic information as affected children grow up. Here, I draw on research and personal narratives to describe how prognostic information impacts individuals' conceptions of the future. A deeper understanding of how patients and families view prognosis is important because parents may need support as prognostic conversations arise and because perceptions of prognosis may influence ideas about the future, psychological health, decisions, and planning. By exploring how specific ideas about an individuals' future take hold, clinicians and researchers may begin to identify the benefits, harms, and accuracy of varied sources of prognostic information, opening new areas of bioethical investigation. In closing, I propose prognostic imagination as a useful concept for considering how patients and families experience prognostic information amidst therapeutic innovations and evolving futures.

It Takes Two to Tango! Protein-Protein Interactions behind cAMP-Mediated CFTR Regulation

Over the last fifteen years, with the approval of the first molecular treatments, a breakthrough era has begun for patients with cystic fibrosis (CF), the rare genetic disease caused by mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR). These molecules, known as CFTR modulators, have led to unprecedented improvements in the lung function and quality of life of most CF patients. However, the efficacy of these drugs is still suboptimal, and the clinical response is highly variable even among individuals bearing the same mutation. Furthermore, not all patients carrying rare CFTR mutations are eligible for CFTR modulator therapies, indicating the need for alternative and/or add-on therapeutic approaches. Because the second messenger 3',5'-cyclic adenosine monophosphate (cAMP) represents the primary trigger for CFTR activation and a major regulator of different steps of the life cycle of the channel, there is growing interest in devising ways to fine-tune the cAMP signaling pathway for therapeutic purposes. This review article summarizes current knowledge regarding the role of cAMP signalosomes, i.e., multiprotein complexes bringing together key enzymes of the cAMP pathway, in the regulation of CFTR function, and discusses how modulating this signaling cascade could be leveraged for therapeutic intervention in CF.

Factors associated with frequent high-cost individuals with cystic fibrosis and their healthcare utilization and cost patterns

Cystic fibrosis (CF) is a progressive multi-organ disease with significant morbidity placing extensive demands on the healthcare system. Little is known about those individuals with CF who continually incur high costs over multiple years. Understanding their characteristics may help inform opportunities to improve management and care, and potentially reduce costs. The purpose of this study was to identify and understand the clinical and demographic attributes of frequent high-costing CF individuals and characterize their healthcare utilization and costs over time. A longitudinal study of retrospective data was completed in British Columbia, Canada by linking the Canadian CF Registry with provincial healthcare administrative databases for the period between 2009 and 2017. Multivariable Cox regression models were employed to identify baseline factors associated with becoming a frequent high-cost CF user (vs. not a frequent high-cost CF user) in the follow-up period. We found that severe lung impairment (Hazard Ratio [HR]: 3.71, 95% confidence interval [CI], 1.49-9.21), lung transplantation (HR: 4.23, 95% CI, 1.68-10.69), liver cirrhosis with portal hypertension (HR: 10.96, 95% CI: 3.85-31.20) and female sex (HR: 1.97, 95% CI: 1.13-3.44) were associated with becoming a frequent high-cost CF user. Fifty-nine (17% of cohort) frequent high-cost CF users accounted for more than one-third of the overall total healthcare costs, largely due to inpatient hospitalization and outpatient medication costs.

FDA-approved drug screening in patient-derived organoids demonstrates potential of drug repurposing for rare cystic fibrosis genotypes

BACKGROUND

Preclinical cell-based assays that recapitulate human disease play an important role in drug repurposing. We previously developed a functional forskolin induced swelling (FIS) assay using patient-derived intestinal organoids (PDIOs), allowing functional characterization of CFTR, the gene mutated in people with cystic fibrosis (pwCF). CFTR function-increasing pharmacotherapies have revolutionized treatment for approximately 85% of people with CF who carry the most prevalent F508del-CFTR mutation, but a large unmet need remains to identify new treatments for all pwCF.

METHODS

We used 76 PDIOs not homozygous for F508del-CFTR to test the efficacy of 1400 FDA-approved drugs on improving CFTR function, as measured in FIS assays. The most promising hits were verified in a secondary FIS screen. Based on the results of this secondary screen, we further investigated CFTR elevating function of PDE4 inhibitors and currently existing CFTR modulators.

RESULTS

In the primary screen, 30 hits were characterized that elevated CFTR function. In the secondary validation screen, 19 hits were confirmed and categorized in three main drug families: CFTR modulators, PDE4 inhibitors and tyrosine kinase inhibitors. We show that PDE4 inhibitors are potent CFTR function inducers in PDIOs where residual CFTR function is either present, or created by additional compound exposure. Additionally, upon CFTR modulator treatment we show rescue of CF genotypes that are currently not eligible for this therapy.

CONCLUSION

This study exemplifies the feasibility of high-throughput compound screening using PDIOs. We show the potential of repurposing drugs for pwCF carrying non-F508del genotypes that are currently not eligible for therapies.

ONE-SENTENCE SUMMARY

We screened 1400 FDA-approved drugs in CF patient-derived intestinal organoids using the previously established functional FIS assay, and show the potential of repurposing PDE4 inhibitors and CFTR modulators for rare CF genotypes.

CFTR Modulators: Current Status and Evolving Knowledge

In the past decade, the medical management of people with cystic fibrosis (pwCF) has changed with the development of small molecules that partially restore the function of the defective CF transmembrane conductance regulator (CFTR) protein and are called CFTR modulators. Ivacaftor (IVA), a CFTR potentiator with a large effect on epithelial ion transport, was the first modulator approved in pwCF carrying gating mutations. Because IVA was unable to restore sufficient CFTR function in pwCF with other mutations, two CFTR correctors (lumacaftor and tezacaftor) were developed and used in combination with IVA in pwCF homozygous for F508del, the most common CFTR variant. However, LUM/IVA and TEZ/IVA were only moderately effective in F508del homozygous pwCF and had no efficacy in those with F508del and minimal function mutations. Elexacaftor, a second-generation corrector, was thus developed and combined to tezacaftor and ivacaftor (ELX/TEZ/IVA) to target pwCF with at least one F508del variant, corresponding to approximately 85% of pwCF. Both IVA and ELX/TEZ/IVA are considered highly effective modulator therapies (HEMTs) in eligible pwCF and are now approved for nearly 90% of the CF population over 6 years of age. HEMTs are responsible for rapid improvement in respiratory manifestations, including improvement in symptoms and lung function, and reduction in the rate of pulmonary exacerbations. The impact of HEMT on extrapulmonary manifestations of CF is less well established, although significant weight gain and improvement in quality of life have been demonstrated. Recent clinical trials and real-world studies suggest that benefits of HEMT could even prove greater when used earlier in life (i.e., in younger children and infants). This article shortly reviews the past 10 years of development and use of CFTR modulators. Effects of HEMT on extrapulmonary manifestations and on CF demographics are also discussed.

Managing Prognosis in Precision Medicine: Utility, Imagination, and Communication

Research on how physicians predict and communicate prognosis focuses primarily on end-of-life care. Unsurprisingly, as genomic technology gains traction as a prognostic tool, the focus has also been on terminality, with research focused on how genetic results may be used to terminate pregnancies or redirect care towards palliation for neonates. However, genomic results also have powerful impacts on how patients who live prepare for their futures. Genomic testing provides broad-reaching and early—albeit complex, uncertain, and shifting—prognostic information. In this essay, we argue that as genomic testing occurs earlier and increasingly in a screening context, researchers and clinicians must strive to understand and manage the prognostic implications of results. While our understanding of the psychosocial and communicational aspects of prognosis in symptomatic populations is incomplete, it has progressed further than our understanding in a screening context and therefore provides useful lessons and feasible opportunities for further research. By providing an interdisciplinary and inter-specialty perspective on the psychosocial and communicational aspects of prognosis in genetics, we discuss prognostication with respect to genetics from the neonatal period through adulthood, highlighting medical specialties and patient populations that are especially informative for considering the longitudinal management of prognostic information in genomic medicine.

Between early and established chronic pancreatitis: A proposal of "acinar-ductal hybrid mechanism"

BACKGROUND/OBJECTIVES

The recently proposed "new mechanistic definition of chronic pancreatitis (CP)" categorized early CP as a reversible condition. However, there is no clear explanation regarding the pathological condition of early CP, the reason for the development of the disease in only a small portion of the patients with risk factors, and the mechanism for transition from a reversible pathological condition to an irreversible one.

METHODS

Based on the available information, a mechanism that could provide answers to the queries associated with CP was proposed.

RESULTS

Acinar-ductal coordination is very important for the physiological secretion of pancreatic juice. Inflammation originating from acinar cells undermines the function of proximal ducts and leads to a vicious cycle of sustained inflammation by increasing the viscosity and decreasing the alkalinity of pancreatic juice. Persistent elevation of ductal pressure due to stagnation of pancreatic juice caused by protein plugs, stones, or fibrous scar of ducts converts the reversible pathological condition of early CP to an irreversible one. Diagnostic criteria for early CP proposed by Japanese researchers have enabled to the recognition of patients showing a progression from early to established CP. However, most patients diagnosed with early CP do not experience progression of the disease, suggesting the inadequate specificity of the criteria.

CONCLUSION

The "acinar-ductal hybrid mechanism" may explain the pathological condition and progression of early CP. To diagnose early CP more accurately, it is essential to discover specific biomarkers that can discriminate "early CP" from "acute pancreatitis (AP)/recurrent acute pancreatitis (RAP)" and "established CP." Therapeutic intervention in clinical practices through various new approaches is expected to improve the prognosis of patients with CP.

KDM2A and KDM3B as Potential Targets for the Rescue of F508del-CFTR

Cystic fibrosis (CF) is caused by mutations in the gene encoding of the cystic fibrosis transmembrane conductance regulator (CFTR), an anion-selective plasma membrane channel that mainly regulates chloride transport in a variety of epithelia. More than 2000 mutations, most of which presumed to be disease-relevant, have been identified in the CFTR gene. The single CFTR mutation F508del (deletion of phenylalanine in position 508) is present in about 90% of global CF patients in at least one allele. F508del is responsible for the defective folding and processing of CFTR, failing to traffic to the plasma membrane and undergoing premature degradation via the ubiquitin–proteasome system. CFTR is subjected to different post-translational modifications (PTMs), and the possibility to modulate these PTMs has been suggested as a potential therapeutic strategy for the functional recovery of the disease-associated mutants. Recently, the PTM mapping of CFTR has identified some lysine residues that may undergo methylation or ubiquitination, suggesting a competition between these two PTMs. Our work hypothesis moves from the idea that favors methylation over ubiquitination, e.g., inhibiting demethylation could be a successful strategy for preventing the premature degradation of unstable CFTR mutants. Here, by using a siRNA library against all the human demethylases, we identified the enzymes whose downregulation increases F508del-CFTR stability and channel function. Our results show that KDM2A and KDM3B downregulation increases the stability of F508del-CFTR and boosts the functional rescue of the channel induced by CFTR correctors.