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For most of the history of cystic fibrosis, treatment worked around the problem — clearing mucus, treating infections, replacing enzymes, supporting nutrition. Since 2012 a family of tablets called CFTR modulators has treated the problem itself, by making the faulty protein work better. They do not cure CF, they are not suitable for everyone, and they do not remove the need for the rest of your care. This page explains how the treatments developed, what is being tested now, and where physiotherapy fits.
From working around the problem to fixing the protein
Cystic fibrosis is caused by faults in a single gene, CFTR, which makes a channel that moves chloride and water onto the surface of the airways, gut and other organs. When the channel is missing or does not work, secretions become thick and sticky. Lungs get repeatedly infected and scarred; the pancreas is blocked; sweat becomes salty.
The condition was first described in 1938. For the next fifty years, every advance was a way of managing the consequences — the sweat test to diagnose it, pancreatic enzymes, nutrition, physiotherapy for airway clearance, and increasingly effective antibiotics. Together these turned CF from a disease of early childhood death into one where most people reached adulthood.
The gene was identified in 1989. It then took more than twenty years for that discovery to become a medicine.
What CFTR modulators do
Modulators are tablets that act on the faulty protein. Different faults need different help, which is why there is more than one drug:
- Potentiators hold the channel open for longer once it has reached the cell surface.
- Correctors help a misfolded protein fold properly and get to the surface in the first place.
- Modern treatment combines two correctors with a potentiator in one tablet, which works far better than any single agent.
The effect for many people has been substantial: better lung function, far fewer chest infections, weight gain, and a marked drop in the need for hospital admission and intravenous antibiotics.
Who can take them
Modulators only work if there is some protein there to act on. Eligibility depends on which CFTR variants you carry, and it has widened steadily — both to younger children and to more variant combinations. In Australia these medicines are prescribed through specialist CF centres and subsidised under the Pharmaceutical Benefits Scheme, with criteria that change as new evidence and approvals come through.
Around one in ten people with CF carry variants that produce no protein at all, and current modulators cannot help them. Closing that gap is the single biggest priority in CF research, and it is where gene and RNA therapies come in.
What changes when you start — and what does not
People often describe coughing less and bringing up much less sputum. That is a real improvement, and it raises a genuinely difficult question: if there is far less mucus, do you still need to do airway clearance every day?
The honest answer is that we do not fully know yet, and it should be an individual decision made with your CF team rather than something you stop on your own. Damage that has already happened to the airways does not reverse, and stopping everything at once has not been shown to be safe over the long term.
What is being tested now
- Newer, simpler modulator combinations — including once-daily regimens that lower sweat chloride further than current treatment.
- Inhaled messenger RNA — delivering the instructions to make working CFTR directly to the airway, which would work regardless of which variant a person carries.
- Gene therapy — delivering a working copy of the gene itself, with the aim of a durable or one-off treatment.
- Better anti-infectives and anti-inflammatories — for the airway damage and inflammation that persist even on effective modulators.
Why physiotherapy still matters
The modulator era has changed what physiotherapy is for, not whether it is needed. As chest symptoms settle, other problems become the limiting factors — fitness, musculoskeletal pain, pelvic floor problems, weight and metabolic health, and simply having the confidence to be active. Exercise remains one of the few factors that independently predicts how people do.
We work alongside your CF centre, not instead of it: reviewing and simplifying airway clearance so it is the shortest routine that still works, prescribing and progressing exercise, and dealing with the musculoskeletal and continence problems that often go unmentioned.
A clinician-level synthesis of how cystic fibrosis therapeutics arrived at variant-specific treatment, the pivotal randomised trials for each modulator generation, what is currently in phase 2 and 3, Australian access, and what the modulator era does to physiotherapy practice. Prepared July 2026. A reference summary, not a prescribing protocol — verify current TGA approvals and PBS criteria before clinical use.
1 · The arc: 1938 to variant-specific therapy
Andersen's 1938 description of cystic fibrosis of the pancreas defined the syndrome; Di Sant'Agnese's observation of salt loss in the 1953 heatwave produced the sweat test and, with it, reliable diagnosis.1 The following four decades delivered incremental but transformative supportive care: pancreatic enzyme replacement, aggressive nutrition, airway clearance physiotherapy, and inhaled and intravenous antibiotics directed at Pseudomonas aeruginosa. None addressed the underlying defect, yet together they moved median survival from infancy into adulthood.
Identification of CFTR in 1989 was expected to deliver gene therapy within a decade.2 It did not. Repeated attempts at viral and non-viral gene transfer through the 1990s and 2000s produced measurable but clinically marginal and non-durable effects. The route that succeeded was pharmacological rather than genetic: small molecules that rescue the function of the defective protein.
2 · CFTR biology and why variant class dictates drug choice
CFTR is a cAMP-regulated anion channel at the apical membrane of secretory epithelia. Loss of function reduces chloride and bicarbonate secretion and dysregulates ENaC-mediated sodium absorption, dehydrating the periciliary layer, impairing mucociliary transport and lowering airway surface pH — impairing innate defence as well as clearance.
Variants are conventionally grouped by the mechanism of failure, and the grouping is clinically useful because it predicts which drug class can help:
Figure 1. CFTR variant classes by mechanism of failure, with the drug class that rescues each. Reading left to right and top to bottom, the defect moves progressively closer to a working channel — and the therapeutic options widen with it. The argument the classification exists to make is that class dictates drug: class I has nothing at the membrane for a modulator to act on, which is why it remains the field’s central equity problem.
- 1. The six-class scheme is a working simplification. Many variants show features of more than one class, some behave differently in different tissues, and class assignment for rarer variants is not always settled.
- 2. The function indicator is qualitative and pre-treatment — a visual ordering of residual CFTR activity at the membrane, not a measured percentage.
- 3. Approximately 85 per cent of people with cystic fibrosis carry at least one F508del allele. Roughly one in ten carry two class I variants and are ineligible for any currently approved modulator.
F508del is carried by roughly 85 per cent of people with CF on at least one allele, which is why corrector development dominated the field.
3 · The drug classes
- Potentiators (ivacaftor) increase channel open probability once CFTR is at the membrane.
- Correctors (lumacaftor, tezacaftor, elexacaftor, vanzacaftor) act as pharmacological chaperones improving folding and trafficking. Elexacaftor binds a distinct site from tezacaftor, which is why dual correction outperforms either alone.
- Amplifiers (nesolicaftor and related) aim to increase CFTR message and protein quantity — still investigational.
- Read-through agents and nonsense suppressors aim to bypass premature stop codons for class I variants. ELX-02 did not deliver clinically meaningful benefit, and the approach remains unproven.
- Nucleic-acid therapies (inhaled mRNA, gene transfer, gene editing) are mutation-agnostic and are the only credible route for class I variants.
4 · The approved modulator era — pivotal trials by generation
Ivacaftor monotherapy (gating variants, 2012). STRIVE randomised adults and adolescents with at least one G551D allele and produced a 10.6 percentage-point absolute improvement in ppFEV1 at 24 weeks, a 55 per cent reduction in pulmonary exacerbations, weight gain and a large fall in sweat chloride.3 The effect size was unlike anything previously seen in CF, and it validated the target.
Lumacaftor/ivacaftor (F508del homozygous, 2015). TRAFFIC and TRANSPORT showed only a 2.6 to 4.0 percentage-point ppFEV1 benefit with a meaningful exacerbation reduction, limited by respiratory adverse events, chest tightness on initiation and substantial CYP3A induction affecting co-prescribed drugs.4 It established proof of principle for correction while making clear that first-generation correction was inadequate.
Tezacaftor/ivacaftor (2018). EVOLVE (F508del homozygous) and EXPAND (F508del with a residual-function variant) delivered comparable modest efficacy with markedly better tolerability and fewer interactions than lumacaftor.5,6
Elexacaftor/tezacaftor/ivacaftor (2019) — the step change. In F508del/minimal-function heterozygotes, previously untreatable, ETI produced a 13.8 percentage-point ppFEV1 improvement over placebo at 24 weeks, a 63 per cent reduction in exacerbations, and a 41.8 mmol/L fall in sweat chloride.7 In F508del homozygotes already on tezacaftor/ivacaftor, ETI added a further 10 points.8 Registry data since have shown large falls in transplant listing and mortality at population level.9
5 · Extending eligibility — age and genotype
Label extensions have moved ETI progressively down the age range to early childhood, on the rationale that preventing structural damage matters more than reversing it. Open-label paediatric studies show sweat chloride and lung-clearance-index improvements with an acceptable safety profile, and the argument for the youngest cohorts rests on structural prevention rather than on spirometric change, which is often already normal.10 Ophthalmological surveillance for lens opacities and monitoring of transaminases are part of paediatric follow-up.
6 · The pipeline now
Next-generation modulators. The vanzacaftor/tezacaftor/deutivacaftor triple has completed phase 3 (SKYLINE and RIDGELINE programmes) with once-daily dosing, non-inferior ppFEV1 versus ETI and a greater reduction in sweat chloride — a signal of more complete CFTR restoration — and has entered regulatory approval in some jurisdictions.11 Whether deeper biochemical correction converts into additional clinical benefit in an already well-treated population is the open question.
Inhaled mRNA. Delivering CFTR message to airway epithelium would treat any genotype. Early programmes were limited by delivery and durability; MRT5005 did not produce consistent lung-function change. Later inhaled candidates including VX-522 and ARCT-032 are in early-phase evaluation, with repeat dosing and distribution to distal airways as the central problems.12
Gene therapy and editing. Lentiviral and AAV-based approaches, and ex vivo and in vivo editing strategies, remain in phase 1 and 2. The barriers are unchanged from the 1990s: crossing mucus and the apical membrane, transducing the correct progenitor population, and achieving durability without re-dosing immunogenicity.12
Beyond CFTR. ENaC inhibition, which would rehydrate the airway surface independent of genotype, has repeatedly disappointed. Anti-inflammatory candidates including acebilustat and LAU-7b have produced mixed results, and the anti-infective pipeline — including bacteriophage therapy for multidrug-resistant infection — is early but of real interest in the residual bronchiectasis phenotype.
7 · Australian access and the equity problem
Modulators are specialist-initiated and PBS-subsidised through CF centres, with genotype and age criteria that have widened repeatedly since Kalydeco was first listed. Two equity issues persist and are worth naming in clinical conversation: people carrying two class I variants remain ineligible for any modulator, and access for people who have already progressed to advanced disease or transplantation is a different clinical calculus. The non-modulatable minority is now the group with the greatest unmet need and the least therapeutic momentum.
8 · What the modulator era does to physiotherapy practice
- Sputum volume falls substantially, and with it the face validity of daily clearance. Symptom-led reasoning that worked in the pre-modulator era now under-detects retained secretions and structural disease.
- Established bronchiectasis does not reverse. Regional clearance failure, haemoptysis risk and infective exacerbation remain possible in a patient who feels well.
- The limiting factor shifts. Deconditioning, musculoskeletal chest and back pain, pelvic floor dysfunction and urinary incontinence, weight gain and metabolic health, and preserved-but-not-normal exercise capacity increasingly dominate the clinical picture.
- Exercise remains independently prognostic and is the intervention least affected by the change in pharmacotherapy; the Cochrane review supports improvements in exercise capacity and quality of life, while noting modest certainty.13 Prescribed, progressed and reviewed exercise is arguably now the core physiotherapy contribution.
- Adherence reasoning changes. The shortest effective regimen a patient will genuinely perform beats a theoretically optimal one they abandon — more true, not less, when they feel well. European standards of care continue to specify individualised airway clearance, annual physiotherapy review and exercise prescription for all patients, including those on modulators.14
9 · The treatment-simplification question
This is the live clinical controversy and physiotherapists are asked about it constantly. SIMPLIFY randomised people with CF on ETI and preserved lung function to continue or discontinue hypertonic saline, or dornase alfa, and found discontinuation non-inferior for ppFEV1 over six weeks.15 That is a genuine evidence base for simplifying mucoactive drugs in a selected, well-preserved population over a short horizon.
SIMPLIFY tested inhaled mucoactive therapies, not airway clearance techniques; it enrolled people with relatively preserved lung function; and six weeks says nothing about structural progression over decades. There is no equivalent randomised evidence for discontinuing airway clearance. De-escalation should be individualised, staged, and monitored objectively — not inferred, and not patient-initiated in isolation.
Where de-escalation is being considered, objective monitoring matters more than symptoms: spirometry alone is insensitive in this population, and multiple-breath washout and the lung clearance index or interval imaging give a better view of small-airway disease.
10 · Principal evidence gaps
- Whether, when and by how much airway clearance can be safely reduced on highly effective modulator therapy — the field's most pressing physiotherapy question, and unanswered by randomised trial.15
- Optimal exercise modality, dose and monitoring in a modulator-treated population whose exercise capacity is near-normal.
- Long-term modulator safety — hepatic, ophthalmological, neuropsychiatric — and safety in pregnancy and lactation, where practice currently runs ahead of data.
- Any disease-modifying option for people with two class I variants.
- Management of the ageing CF population, now the majority, including cardiovascular and metabolic risk that the field has never had to consider before.
- Whether deeper biochemical correction with next-generation modulators yields clinical benefit beyond ETI.11
References & evidence base
- Andersen DH. Cystic fibrosis of the pancreas and its relation to celiac disease. Am J Dis Child 1938;56(2):344–399.
- Riordan JR, Rommens JM, Kerem B, et al. Identification of the cystic fibrosis gene: cloning and characterization of complementary DNA. Science 1989;245(4922):1066–1073.
- Ramsey BW, Davies J, McElvaney NG, et al. A CFTR potentiator in patients with cystic fibrosis and the G551D mutation. N Engl J Med 2011;365(18):1663–1672.
- Wainwright CE, Elborn JS, Ramsey BW, et al. Lumacaftor–ivacaftor in patients with cystic fibrosis homozygous for Phe508del CFTR. N Engl J Med 2015;373(3):220–231.
- Taylor-Cousar JL, Munck A, McKone EF, et al. Tezacaftor–ivacaftor in patients with cystic fibrosis homozygous for Phe508del. N Engl J Med 2017;377(21):2013–2023.
- Rowe SM, Daines C, Ringshausen FC, et al. Tezacaftor–ivacaftor in residual-function heterozygotes with cystic fibrosis. N Engl J Med 2017;377(21):2024–2035.
- Middleton PG, Mall MA, Ďevı́nek P, et al. Elexacaftor–tezacaftor–ivacaftor for cystic fibrosis with a single Phe508del allele. N Engl J Med 2019;381(19):1809–1819.
- Heijerman HGM, McKone EF, Downey DG, et al. Efficacy and safety of the elexacaftor plus tezacaftor plus ivacaftor combination regimen in people with cystic fibrosis homozygous for the F508del mutation: a double-blind, randomised, phase 3 trial. Lancet 2019;394(10212):1940–1948.
- Burgel PR, Durieu I, Chiron R, et al. Rapid improvement after starting elexacaftor–tezacaftor–ivacaftor in patients with cystic fibrosis and advanced pulmonary disease. Am J Respir Crit Care Med 2021;204(1):64–73.
- Goralski JL, Hoppe JE, Mall MA, et al. Phase 3 open-label clinical trial of elexacaftor/tezacaftor/ivacaftor in children aged 2 through 5 years with cystic fibrosis and at least one F508del allele. Am J Respir Crit Care Med 2023;208(1):59–67.
- Keating C, Yonker LM, Vermeulen F, et al. Vanzacaftor–tezacaftor–deutivacaftor for cystic fibrosis: phase 3 randomised trials. Lancet Respir Med 2025. [Verify current TGA and PBS status before clinical use.]
- Sui H, Xu X, Su Y, et al. Gene therapy for cystic fibrosis: challenges and prospects. Front Pharmacol 2022;13:1015926.
- Radtke T, Smith S, Nevitt SJ, Hebestreit H, Kriemler S. Physical activity and exercise training in cystic fibrosis. Cochrane Database Syst Rev 2022;(8):CD002768.
- Castellani C, Duff AJA, Bell SC, et al. ECFS best practice guidelines: the 2018 revision. J Cyst Fibros 2018;17(2):153–178.
- Mayer-Hamblett N, Ratjen F, Russell R, et al. Discontinuation versus continuation of hypertonic saline or dornase alfa in modulator-treated people with cystic fibrosis (SIMPLIFY): results from two parallel, multicentre, open-label, randomised, controlled, non-inferiority trials. Lancet Respir Med 2023;11(4):329–340.
References are numbered in citation order (Vancouver/BMJ style) and were current at the time of writing. Guidelines are living documents — verify against the latest version before clinical use. Drug approvals in cystic fibrosis are moving quickly — verify current Australian PBS and TGA status before clinical use.
Corrections: If something on this page is wrong, out of date or unclear, we want to know. Email reception@inspireclinic.au with the page name and what you believe is incorrect. Substantive corrections are made promptly, and the guide’s version and last-updated date are changed to reflect it.