Cystic Fibrosis

Overview

Cystic fibrosis (CF) is an inherited disease caused by changes in the CFTR gene, which normally helps control salt and water movement across cell surfaces. When CFTR protein is absent or faulty, thick, sticky mucus builds up in the lungs, pancreas, and other organs, contributing to chronic lung infections, progressive lung damage, digestive problems, and other complications. CFTR Modulator Types The outlook has improved substantially: among people with CF born in 2020–2024 in the United States, half are predicted to live to at least age 65, although prognosis varies considerably, particularly for people who cannot use CFTR modulators. 2024 Patient Registry Highlights

Current care combines treatment of the underlying CFTR defect, when a person’s mutations are responsive, with lifelong management of consequences: airway-clearance techniques, inhaled medicines and antibiotics as needed, nutritional support, pancreatic enzyme replacement for many people, exercise, and specialist follow-up. Managing Your Treatment Plan CFTR modulators such as elexacaftor/tezacaftor/ivacaftor improve the function of existing abnormal CFTR protein but do not repair the gene and do not work for people who make little or no CFTR protein. CFTR Modulator Therapies

Scope of Recent Research (2020–present)

Since 2020, CF research has shifted from improving defective protein toward delivering, replacing, or permanently correcting CFTR genetic instructions, especially for people with rare or “nonsense” mutations who are not helped by modulators. The central questions are whether genetic medicines can reach enough of the right airway cells through mucus and immune barriers, persist long enough to matter clinically, and do so safely enough for repeat dosing or permanent editing. Research Into Genetic Therapies The field is highly active and has reached early human trials for gene-addition and messenger-RNA approaches, but no genetic therapy has yet been approved and no therapy can yet be described as a proven cure. CF Foundation Response to RFI on Improving Access to Gene Therapies

Major Breakthroughs and Emerging Therapies

Small-molecule CFTR modulators remain the most clinically mature disease-modifying strategy, although they are not curative. Real-world registry evidence found that elexacaftor/tezacaftor/ivacaftor was associated with fewer pulmonary exacerbations and hospitalizations, improved lung function and body-mass index, and lower observed death and transplant rates over the first two years of follow-up. Real-world ETI registry study In December 2024, the FDA approved once-daily vanzacaftor/tezacaftor/deutivacaftor, marketed as Alyftrek, for eligible people aged six years and older; it is another combination that improves residual CFTR function rather than correcting the underlying DNA. FDA Alyftrek Drug Trials Snapshot

Gene addition aims to give airway cells a functional CFTR gene regardless of the person’s mutation. The leading clinical example is 4D-710, an inhaled, engineered adeno-associated virus (AAV) vector designed to deliver a healthy CFTR gene to lung cells. 4D-710 pipeline profile Its Phase 1 AEROW study reported interim results in December 2025 after enrolling 16 adults who were ineligible for or unable to tolerate CFTR modulators; the sponsor reported safety, lung delivery and transgene-expression findings, but the small, uncontrolled early-stage study cannot establish clinical efficacy or cure. 4D-710 Phase 1 interim update

Inhaled RNA replacement is a potentially repeatable alternative to viral gene delivery. These therapies package a full-length CFTR messenger RNA (mRNA)—the temporary genetic instruction used to make protein—inside lipid nanoparticles, allowing treated cells to make functional CFTR without altering DNA. ARCT-032, developed by Arcturus Therapeutics, is in Phase 2 for adults with CF who are not taking modulators and is intended to be mutation-agnostic, including for nonsense mutations. ARCT-032 pipeline profile The experience has also shown the difficulty of lung delivery: Vertex ended development of its inhaled mRNA candidate VX-522 after persistent tolerability issues in its Phase 1/2 study prevented a full efficacy and safety assessment. Vertex first-quarter 2026 results

Gene editing has produced striking laboratory proof-of-concept results but remains preclinical for CF. Prime editing, a CRISPR-derived method that can write precise DNA changes without making a conventional double-strand DNA break, restored CFTR protein processing and channel function after correction of L227R or N1303K mutations in patient-derived rectal organoids and nasal airway cells. Prime editing in CF organoids and airway cells Separately, lipid nanoparticles carrying base-editor mRNA and guide RNA corrected the R553X CFTR mutation in mouse lung stem cells and restored CFTR function in patient-derived bronchial cells and organoids, demonstrating the appeal of editing long-lived airway progenitor cells. In vivo lung stem-cell editing A 2026 study also reported inhaled lipid nanoparticles that delivered a base editor to the lung and restored CFTR expression and chloride-channel function for the G542X mutation in cell, organoid, mouse, and ferret experiments. Inhaled base editing for lung correction

Clinical Trials and Experimental Approaches

The most notable mutation-agnostic genetic-therapy trials as of October 13, 2026 are 4D Molecular Therapeutics’ Phase 1/2 program for 4D-710 and Arcturus’ Phase 2 program for ARCT-032. 4D-710 pipeline profile ARCT-032 pipeline profile These studies primarily test safety, tolerability, airway delivery, and biological activity; neither has yet reported the controlled, long-term evidence needed to show durable clinical benefit, much less cure. 4D-710 Phase 1 interim update

Modulator development continues in parallel because earlier and more complete restoration of CFTR activity may prevent damage before it becomes irreversible. In two Phase 3 trials underpinning FDA approval, Alyftrek was compared with elexacaftor/tezacaftor/ivacaftor in 971 participants, using lung-function change as the primary outcome. FDA Alyftrek Drug Trials Snapshot However, the VX-522 termination illustrates why promising preclinical RNA delivery does not guarantee a usable inhaled medicine. Vertex first-quarter 2026 results

Methodologies and Scientific Approaches

Researchers increasingly test candidate therapies in patient-derived intestinal organoids, nasal cells, and bronchial epithelial cells grown at an air–liquid interface, where scientists can measure whether corrected cells regain CFTR-mediated ion transport. Prime editing in CF organoids and airway cells Common functional readouts include organoid swelling in response to stimulation, electrical measurements of chloride transport, sweat chloride, lung function, respiratory exacerbations, and detection of CFTR RNA or protein in airway samples. In vivo lung stem-cell editing

Delivery technology is now as important as the genetic payload. Programs compare inhaled AAV vectors, lipid nanoparticles, biodegradable ionizable lipids, and formulations designed to penetrate CF mucus and enter epithelial or stem cells while limiting immune reactions. Inhaled base editing for lung correction For durable editing, researchers are particularly interested in airway basal stem cells because corrected progenitor cells could generate corrected airway lining cells over time. In vivo lung stem-cell editing

Leading Institutions and Funding

The Cystic Fibrosis Foundation (CFF) is the leading U.S. philanthropic driver of this work, reporting annual investments of more than $200 million in CF research and drug development, including its Therapeutics Development Network and therapeutics laboratory. CFF Media Center It has partially funded the clinical development of both 4D-710 and ARCT-032 through that network. 4D-710 pipeline profile ARCT-032 pipeline profile

CFF is also investing in earlier-stage genome editing: in July 2025 it committed up to an additional $24 million to Prime Medicine, on top of a prior commitment of up to $15 million, to develop a prime-editing treatment initially focused on the G542X nonsense mutation. CFF–Prime Medicine funding announcement Academic groups contributing important preclinical work include teams using patient organoids and airway cultures in Europe and North America, as well as lipid-nanoparticle and stem-cell-editing platforms supported in part by U.S. National Institutes of Health grants. In vivo lung stem-cell editing

Strengths, Limitations, and Challenges

The major strength of genetic approaches is that a single platform could potentially serve people across many CFTR mutations, including those left behind by protein modulators. Research Into Genetic Therapies Gene editing is especially compelling because successful correction of DNA in the right long-lived cells could, in principle, provide lasting production of normal CFTR protein. Prime editing in CF organoids and airway cells Modulators already demonstrate that restoring even partial CFTR function can produce major health benefits, providing a clear biological benchmark for newer therapies. Real-world ETI registry study

The principal barriers are reaching enough cells throughout diseased lungs, traversing thick mucus, avoiding inflammatory or immune responses, achieving durable expression or editing in renewing airway tissue, and proving that laboratory correction translates into meaningful long-term health outcomes. CFF–Prime Medicine funding announcement Permanent editors also require exceptionally careful assessment of unintended genetic changes, while RNA therapies may require repeated dosing and viral vectors may be difficult to re-dose. Research Into Genetic Therapies Affordability, global access, and the question of whether lung-directed treatment can address CF disease in the pancreas, intestine, reproductive tract, and other organs remain unresolved. CF Foundation Response to RFI on Improving Access to Gene Therapies

Outlook and Future Directions

As of October 13, 2026, CF is closer to broadly applicable genetic treatment than it was in 2020, but not yet close enough to claim that a cure is imminent. The most important milestones to watch are durable clinical results from 4D-710 and ARCT-032, evidence that new nonviral delivery systems can safely reach airway stem cells in humans, and progression of prime- or base-editing programs from corrected patient cells and animal models into first-in-human trials. 4D-710 pipeline profile ARCT-032 pipeline profile A true cure will likely require not only restoring CFTR function in the lungs, but also demonstrating safe, lasting benefit across the organs affected by CF. CF Foundation Response to RFI on Improving Access to Gene Therapies

References

• ARCT-032 pipeline profile — Cystic Fibrosis Foundation, 2026.
• CFF Media Center — Cystic Fibrosis Foundation, 2026.
• CFF–Prime Medicine funding announcement — Cystic Fibrosis Foundation, 2025.
• CF Foundation Response to RFI on Improving Access to Gene Therapies — Cystic Fibrosis Foundation, 2024.
• CFTR Modulator Therapies — Cystic Fibrosis Foundation, 2026.
• CFTR Modulator Types — Cystic Fibrosis Foundation, 2026.
• FDA Alyftrek Drug Trials Snapshot — U.S. Food and Drug Administration, 2024.
• Inhaled base editing for lung correction — Wang et al., Nature Materials, 2026.
• In vivo lung stem-cell editing — Yin et al., Science, 2024.
• Managing Your Treatment Plan — Cystic Fibrosis Foundation, 2026.
• Prime editing in CF organoids and airway cells — Bulcaen et al., Cell Reports Medicine, 2024.
• Real-world ETI registry study — Bower et al., Journal of Cystic Fibrosis, 2023.
• Research Into Genetic Therapies — Cystic Fibrosis Foundation, 2026.
• 2024 Patient Registry Highlights — Cystic Fibrosis Foundation, 2025.
• 4D-710 Phase 1 interim update — 4D Molecular Therapeutics, 2025.
• 4D-710 pipeline profile — Cystic Fibrosis Foundation, 2026.
• Vertex first-quarter 2026 results — Vertex Pharmaceuticals, 2026.