ARCT-032 Shows Early Signals of Mucus Reduction in Cystic Fibrosis Phase 2 Study
Promising Interim Results: ARCT-032 May Reduce Mucus Burden in Class I CF Patients
Arcturus Therapeutics released interim Phase 2 data for its inhaled mRNA therapy, ARCT-032, targeting cystic fibrosis (CF) — a disease marked by chronic lung problems and limited treatment options for patients with specific genetic mutations. Early findings suggest ARCT-032 is not only generally safe but may reduce mucus accumulation in some patients who typically don’t respond to currently available therapies.
Safety Profile Remains Positive Across Second Cohort
In the second cohort, six adults with Class I CF received 10 mg daily doses of ARCT-032 for 28 days. Treatment was mostly well tolerated, with side effects similar to those seen in earlier single-dose studies resolving over time. One serious adverse event occurred after dosing ended, but investigators found no convincing link to ARCT-032. The study is proceeding with a planned dose escalation in a third cohort.
Mucus Reduction Trends in Four Out of Six Patients Stand Out
Notably, high-resolution CT scans analyzed with AI tools showed reductions in both the number of mucus plugs and mucus volume in four out of six participants at day 28. The table below highlights these changes among all participants:
| Subject | Dose (mg) | % Change in Mucus Plugs @ Day 28 |
% Change in Mucus Volume @ Day 28 |
|---|---|---|---|
| 2 | 10 | -38.5% | -67.4% |
| 4 | 10 | -34.9% | -27.5% |
| 6 | 10 | -28.5% | -29.5% |
| 5 | 10 | -9.1% | -6.1% |
| 3 | 10 | 23.8% | 9.1% |
| 1 | 10 | 25.6% | 60.9% |
For most of these patients, the number of mucus plugs and total mucus volume dropped, with Subject 2 showing the most dramatic changes: a 38.5% decrease in plugs and a 67.4% reduction in volume. Two participants did see increases, underlining the natural variability of response at this early stage.
Exploratory Lung Function Results Provide Directional Support
The trial also explored changes in lung function via FEV1 measurements. While standard Day 1 to Day 28 analysis didn’t show meaningful improvement, a post hoc comparison of baseline versus Day 42 hinted at a potential positive trend: four of six participants had an average absolute increase of 3.8% and a relative rise of 5.1% in percent predicted FEV1. While modest and within normal fluctuation ranges, this direction supports the idea that ARCT-032 could benefit lung health with longer use or higher doses.
Larger, Longer Study Planned to Clarify Clinical Impact
To build on these interim results, Arcturus plans a 12-week safety and preliminary efficacy study for up to 20 participants beginning in the first half of 2026. This expanded study aims to better quantify mucus reduction, dose-response relationships, and lasting changes in lung function.
What to Watch Next: Safety and Efficacy in the Pipeline
These interim findings are a step forward for people with CF mutations unresponsive to current therapies. The results also underline the complexity of the disease — not every participant benefited, but early biological activity and tolerability support continued development. If future data continue to trend positive, ARCT-032 could address a substantial unmet need in cystic fibrosis care.
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