Respiratory · Clinical trials
Cystic Fibrosis Clinical Trials
Approved therapies, the pivotal-trial endpoints they were judged on, the magnitude of benefit — and the drugs that failed their endpoints, and why.
Indication overview
About cystic fibrosis — and why its trials are hard
Cystic fibrosis (CF) is an autosomal recessive disease caused by mutations in the CFTR gene encoding a chloride channel. Defective CFTR impairs epithelial ion and fluid transport, producing thick secretions that cause chronic airway infection, progressive lung damage, pancreatic insufficiency, malnutrition and reduced survival. Care historically centered on airway clearance, inhaled antibiotics, mucolytics such as dornase alfa and hypertonic saline, pancreatic enzyme replacement and nutritional support. The transformative advance was small-molecule CFTR modulators that correct the underlying protein defect. Ivacaftor, a potentiator, dramatically helped patients with gating mutations. Corrector-potentiator combinations (lumacaftor/ivacaftor, tezacaftor/ivacaftor) extended benefit to F508del homozygotes. The landmark triple therapy elexacaftor/tezacaftor/ivacaftor (Trikafta) reaches roughly 90% of patients carrying at least one F508del allele, delivering large, durable gains in lung function and reductions in exacerbations, and reshaping the disease trajectory. Percent-predicted FEV1 (ppFEV1) is the pivotal efficacy endpoint, with sweat chloride as a mechanistic biomarker and pulmonary exacerbations as a key clinical measure.
Approved therapies & pivotal evidence
What's been approved — and by how much it moved the endpoint
| Drug (brand) | Approved | Setting | Pivotal trial | Primary endpoint | Magnitude of benefit |
|---|---|---|---|---|---|
| ivacaftor (Kalydeco) | 2012 | CF patients with a CFTR gating mutation (initially G551D) | STRIVE (Phase 3) | Absolute change in ppFEV1 through week 24 | ~10.6 percentage-point improvement in ppFEV1 vs placebo; large sweat chloride reduction |
| lumacaftor/ivacaftor (Orkambi) | 2015 | F508del homozygous CF patients | TRAFFIC / TRANSPORT (Phase 3) | Absolute change in ppFEV1 at week 24 | ~2.6-4.0 percentage-point improvement in ppFEV1 vs placebo; modest exacerbation reduction |
| elexacaftor/tezacaftor/ivacaftor (Trikafta) | 2019 | CF patients aged 12+ (later expanded younger) with at least one F508del mutation | Phase 3 VX17-445-102 (F508del/minimal function) | Absolute change in ppFEV1 at week 4 and through week 24 | 13.8 percentage-point ppFEV1 improvement at week 4 and ~14.3 points through week 24 vs placebo; 63% fewer pulmonary exacerbations and large sweat chloride drop |
Where trials have failed
Drugs that missed their endpoint — and what contributed
The most instructive lessons in cystic fibrosis development come from programmes that failed the endpoint that mattered.
| Drug / trial | Endpoint outcome | What contributed |
|---|---|---|
| ataluren (PTC124) — ACT CF (Phase 3, nonsense-mutation CF) | Did not achieve a statistically significant improvement in ppFEV1 or pulmonary exacerbation rate | Readthrough of premature stop codons proved insufficient in vivo; possible confounding interaction with concomitant inhaled aminoglycosides |
| lancovutide / older gene therapy and channel approaches — Various early inhaled gene-transfer and alternative-channel programs | Failed to deliver durable, clinically meaningful lung-function benefit | Inefficient airway gene delivery, immune responses and transient expression limited efficacy before small-molecule modulators dominated (unverified specifics) |
Choosing the right endpoint
Primary endpoints that matter in cystic fibrosis trials
- Percent-predicted FEV1 (ppFEV1) — Primary efficacy endpoint across CFTR modulator registration trials
- Sweat chloride concentration — Direct biomarker of CFTR function and target engagement
- Pulmonary exacerbation rate — Key clinical endpoint reflecting disease events and hospitalizations
- CFQ-R respiratory domain — Validated patient-reported respiratory quality-of-life measure
- BMI / weight — Nutritional endpoint important given pancreatic insufficiency and growth
How iNGENū runs cystic fibrosis trials
Physician-led design, built for FDA submission
Endpoint & biomarker strategy
Board-certified specialists design endpoints and patient selection aligned to current FDA guidance for this indication.
FDA-ready data
Built to ICH-GCP and 21 CFR 312.120, with direct FDA submission — data accepted by the FDA, EMA and MHRA.
Faster, lower-cost delivery
~4-week ethics via the TGA CTN scheme, up to 43.5% R&D rebate, and 80–90% below US CRO cost.
Request a fixed-milestone proposal and a tailored endpoint & feasibility summary for this indication.
Frequently asked questions
Cystic Fibrosis clinical trials — FAQs
Do CFTR modulators work for everyone with CF?
Is Trikafta a cure for cystic fibrosis?
Are airway clearance and antibiotics still needed on modulators?
Ready to discuss your cystic fibrosis trial?
Talk to our physician-led team about an FDA-ready, cost-efficient trial design.
Request a proposal