Arcturus Therapeutics (NASDAQ:ARCT) executives highlighted progress across the company’s cystic fibrosis and ornithine transcarbamylase (OTC) deficiency mRNA therapeutic programs, provided updates on its partnered COVID-19 vaccine and BARDA-funded pandemic flu effort, and discussed year-over-year financial changes during the company’s fourth quarter and fiscal year 2025 earnings call.
ARCT-032 cystic fibrosis program moves toward 12-week Phase 2 study
Management said ARCT-032, an inhaled mRNA therapeutic candidate for cystic fibrosis (CF) pulmonary disease delivered via the company’s LUNAR lipid-mediated aerosol platform, has progressed through higher-dose testing. CEO Joe Payne said higher dose testing at 15 milligrams in four Class 1 CF adults showed no safety concerns. Chief Medical Officer Dr. Alan Cohen added that the company completed once-daily dosing of 15 milligrams over 28 days in the third dosing cohort and observed no safety or tolerability concerns at that dose level.
Executives emphasized that the upcoming study design differs from the earlier dose-ranging cohorts. Cohen said the company is tightening enrollment criteria to ensure patients have stable and reproducible baseline lung function before being enrolled, with the aim of improving the “noise to signal ratio” when assessing clinical changes. He noted that while spirometry can be subject to variability and requires active patient performance, LCI is a more passive, reproducible measure that can capture early and subtle changes in small airways.
Payne clarified during Q&A that while safety and tolerability were established at 15 milligrams, the company plans to initiate the fourth cohort—the 12-week study—at 10 milligrams. He said Arcturus saw early clinical signals at 10 milligrams in a prior cohort and intends to extend treatment duration and evaluate a larger group. The company also said the open-label design provides flexibility to increase dosing to 15 milligrams if needed, and Payne noted that manufacturing cost considerations also favor keeping the dose lower if possible.
On enrollment strategy, Cohen said Arcturus expanded its U.S. sites and added European and Middle Eastern sites, citing the intent to recruit in regions with a higher prevalence of null (Type 1) CF mutations to facilitate timely identification and enrollment of eligible participants. Management also said it continues to work with the Cystic Fibrosis Foundation and the Therapeutics Development Network, which reviewed early cohort data and permitted progression into the longer study.
Payne also discussed the rationale for a longer study duration, noting an “onboarding” period observed in the 28-day experience, where early dosing may be limited by congested airways. He suggested a 12-week study could provide substantially more time to observe potential healing and efficacy signals.
ARCT-810 OTC deficiency program heads toward Type C regulatory meetings
Arcturus said ARCT-810, its mRNA therapeutic candidate for OTC deficiency, is advancing toward pivotal development, with a strategy intended to address both adults with late-onset disease and young children with the most severe forms of OTC deficiency. Payne and Cohen said Type C regulatory meetings with health authorities are planned for the first half of 2026 and are expected to provide clarity on clinical development next steps, including trial design considerations across the adult and pediatric populations.
In response to analyst questions, management indicated it expects different approaches for pediatric and adult populations given disease severity differences. Cohen said the company is encouraged by ongoing interactions and referenced recent FDA guidance suggesting flexibility for ultra-rare populations with severe outcomes, while emphasizing that endpoints and study requirements remain a key focus for upcoming discussions. Payne said questions around outcomes such as reduction in standard-of-care measures (including dietary restrictions and scavengers) are on the Type C meeting agenda, and the company expects to provide more detail after receiving feedback.
Vaccines: UK approval for KOSTAIVE and BARDA-funded H5N1 data
Payne said that in January 2026 the UK Medicines and Healthcare Products Regulatory Agency (MHRA) granted approval for KOSTAIVE, a self-amplifying mRNA COVID-19 vaccine, for use in individuals aged 18 and older. In Q&A, Payne said that the current U.S. administration has made it “challenging” to progress KOSTAIVE toward licensure or approval in the near term in the U.S., and he added that CSL and Arcturus are in active discussions regarding their collaboration, with more detail expected in the coming months.
Separately, Payne provided an update on ARCT-2304, the company’s next-generation STARR vaccine candidate for pandemic A/H5N1 influenza, which is contracted with and funded by BARDA. He said Arcturus completed a Phase 1 study enrolling 212 young adults and 80 older adults, and that 8-month follow-up data showed all three dose levels generated a durable immune response. Management said the vaccine was well-tolerated across tested doses with no safety concerns reported, and the data reinforced the sa-mRNA platform’s ability to drive meaningful cell-mediated immunity.
Financial update: lower revenue and expenses, runway extended into 2028
On financial performance, Payne directed listeners to the company’s press release and Form 10-K for details, while summarizing key year-over-year changes. He said annual and quarterly revenue decreased by $70.3 million and $15.6 million, respectively, driven by reductions in revenue from the CSL collaboration as supply agreement activity declined and development-based milestone achievements were reduced as KOSTAIVE moved into commercialization.
Payne said annual and quarterly R&D expenses declined by $83.0 million and $19.3 million year over year, primarily due to lower manufacturing and clinical costs tied to the LUNAR-COV19 program’s transition from development to commercial phase. He also cited lower manufacturing for LUNAR-CF and LUNAR-FLU programs and lower clinical costs for LUNAR-OTC as the company wraps up certain clinical activities, partially offset by Phase 2 clinical costs for the CF program.
General and administrative expenses decreased $6.7 million year over year on an annual basis due to reduced payroll and benefits and lower share-based compensation, though quarterly G&A rose $1.6 million year over year due to an acceleration of employee stock options. Payne said the company expects G&A to continue decreasing over the next 12 months, driven by lower share-based compensation expense.
Arcturus reported cash equivalents and restricted cash of $232.8 million as of Dec. 31, 2025, compared with $293.9 million as of Dec. 31, 2024. Payne said the company has extended its cash runway into the second quarter of 2028 following a strategic refocus on its rare disease clinical programs in fiscal 2025.
Other notes
Payne briefly noted that Arcturus’ lawsuit against AbbVie and Capstan Therapeutics, filed Sept. 23, 2025, remains ongoing.
About Arcturus Therapeutics (NASDAQ:ARCT)
Arcturus Therapeutics Holdings Inc is a clinical-stage biotechnology company dedicated to developing messenger RNA (mRNA) medicines that address a range of diseases. The company leverages its proprietary STARR® mRNA platform to enable precise control over mRNA expression, supported by its lipid nanoparticle delivery technology, LUNAR®. Arcturus’s approach is designed to address both therapeutic and prophylactic applications, with an emphasis on vaccines and treatments for rare genetic and infectious diseases.
The company’s pipeline includes ARCT-810, an mRNA therapeutic candidate for phenylketonuria (PKU), and ARCT-021 (also known as LUNAR-COV19), a COVID-19 vaccine candidate developed in collaboration with Duke-NUS Medical School in Singapore.
