Arcturus' Investigational Inhaled Therapy Lacks Meaningful Lung Function Improvement, Analyst Notes Mixed Picture

Arcturus Therapeutics Holdings Inc. (NASDAQ:ARCT) stock was trading lower on Wednesday after the company shared interim results from its ongoing Phase 2 trial of ARCT-032, an investigational inhaled mRNA therapy for cystic fibrosis.

In the second cohort of the study, six Class I CF adults received inhaled 10 mg doses of ARCT-032 daily over 28 days. The treatment was generally safe and well-tolerated.

Treatment-related AEs identified in the single-dose Phase 1 study were also observed in some participants for the first few doses but ceased with continued dosing. One SAE occurred in a participant well after the end of the dosing period.

The Data Monitoring Committee found no convincing evidence that the SAE is related to ARCT-032 and approved the study to proceed.

The expanded third cohort is ongoing and aims to enroll up to six subjects to determine if there is a dose escalation response at 15 mg and to assess whether ARCT-032 is generally safe and well-tolerated.

Initial analysis comparing FEV₁ values from Day 1 to Day 28 did not demonstrate meaningful improvement.

However, a post hoc exploratory analysis comparing the average of two pre-treatment FEV₁ measurements (screening and Day 1) for the baseline with the Day 42 post-treatment value, assuming an extended activity of functional CFTR protein triggered by daily ARCT-032 administration, suggests improvements in lung function, in four of six Class I CF participants with an average absolute increase of 3.8% and a relative increase of 5.1% in percent predicted FEV₁ (ppFEV₁).

High-resolution computed tomography (HRCT) scans revealed reductions in mucus burden in four Class I CF participants.

Decrease in mucus plugs and volume in four of six Class I CF participants is a meaningful trend indicative of ARCT-032 therapeutic activity.

A larger, longer-duration study is planned.

The HRCT mucus reduction and supporting lung function data from the second cohort (10 mg), combined with additional data collected from the ongoing third cohort (15 mg) will guide dose selection, treatment duration, and endpoint strategy for future studies, including the conduct of a 12-week safety and preliminary efficacy clinical trial that is planned to begin in the first half of 2026.

William Blair wrote that the interim Phase 2 data paint a mixed picture of the efficacy of ARCT-03.

Analyst Myles Minter said that with Arcturus moving into a 12-week efficacy study, the question now becomes whether longer treatment duration or a higher dose of ARCT-032 can boost efficacy signals beyond mucus clearance and reduce data variability to give a clearer picture.

Price Action: ARCT stock is down 56.30% to $10.12 as of the last check on Wednesday.

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