Arcturus Therapeutics NASDAQ: ARCT reported progress across its rare-disease pipeline during the second quarter of 2026, completed enrollment and dosing in its Phase II ornithine transcarbamylase deficiency study, and regained global rights to its KOSTAIVE COVID-19 vaccine and self-amplifying mRNA platform following the end of its collaboration with CSL Seqirus.
President and CEO Joe Payne said the company’s Phase II study of ARCT-032, an inhaled mRNA treatment candidate for cystic fibrosis, remains on schedule. Screening and enrollment are active in the U.S., Israel and Turkey, with the international sites intended to support recruitment among people with Class I or null mutations.
Cohort Four is evaluating 10 milligrams of ARCT-032 administered daily by inhalation for 12 weeks. The study is assessing safety and potential clinical benefit using pulmonary-function measures, including percent predicted FEV1 and lung clearance index, along with quality-of-life assessments and high-resolution CT imaging.
Arcturus expects to decide whether to advance ARCT-032 into Phase III during the fourth quarter of 2026. Payne said a decision to proceed would trigger additional support from Thermo Fisher, including manufacturing, clinical research and related services.
CF Trial Focuses on Class I Mutation Population
Chief Medical Officer Alan Cohen said Israel and Turkey have a comparatively high prevalence of people with CF who have Class I or null mutations. While up to 10% of U.S. patients with CF may be ineligible for modulators due to null mutations, Cohen said the proportion can reach approximately 30% to 40% in Turkey and Israel, respectively.
Management said it will use the totality of the Phase II dataset to guide its Phase III decision, rather than relying on a single metric. In addition to FEV1 and lung clearance index, the company is gathering CT imaging and patient quality-of-life data.
During the question-and-answer session, Cohen said lung clearance index could provide a more sensitive measure of changes in smaller airways than traditional spirometry. He noted that the Cystic Fibrosis Foundation’s REACH study is expected to provide additional normative data relevant to the measure.
Payne said ARCT-032 has been administered to more than 50 participants to date, including doses up to 15 milligrams for 28 days of daily treatment. He said the program has proceeded without steroid treatment before, during or after dosing, and participants have been permitted to self-administer treatment at home. The company did not provide detailed safety results from the ongoing 12-week cohort.
OTC Deficiency Study Enrollment and Dosing Completed
Arcturus completed enrollment in its Phase II trial of ARCT-810 for ornithine transcarbamylase, or OTC, deficiency, and all enrolled participants have completed study-drug dosing. The company expects to disclose Phase II data and provide details on its regulatory plan during the third quarter of 2026.
Payne said the update will include data from U.S. and European participants as well as supplementary information requested by the Food and Drug Administration during a Type C meeting earlier this year. Arcturus is preparing for regulatory discussions, including an end-of-Phase-II meeting addressing potential adult and pediatric development paths.
Cohen said the study is evaluating participants receiving five doses over approximately 12 weeks. The trial is not designed to enroll patients who are unstable enough to be expected to experience hyperammonemic crises during that period. Instead, the company is examining the impact of treatment on measures including ammonia and glutamine, as well as quality-of-life and functional outcomes.
“It really will be the totality of all the data” that the FDA is interested in, Cohen said, including safety, tolerability, biomarkers and patient function.
CSL Seqirus Agreement Returns Vaccine Rights
Arcturus announced the conclusion of its self-amplifying RNA, or saRNA, collaboration with CSL Seqirus. Under the agreement, the company regained global rights to KOSTAIVE and its broader infectious-disease vaccine portfolio, which includes programs targeting seasonal influenza, pandemic influenza, RSV and EBV.
The agreement also settled arbitration related to a European regulatory-approval milestone payment. CSL Seqirus made a one-time $12 million cash payment to Arcturus, while Arcturus was released from liabilities including those connected to an R&D credit with an aggregate value of approximately $16 million, according to Payne.
KOSTAIVE has been approved for licensure in Europe, Japan and the United Kingdom, Payne said. He added that Arcturus has received guidance from the FDA on what would be needed for a potential U.S. approval, though he did not provide details of the required steps.
Arcturus plans to explore commercialization and partnering opportunities for the returned assets. In Japan, KOSTAIVE is distributed through Meiji, and Payne said Arcturus is supporting manufacturing and dose shipments for the upcoming fall season. The prior three-way profit-sharing arrangement will become a two-way arrangement, though terms remain under discussion with Meiji.
Payne also said the company has completed a Phase I study of ARCT-2304, its pandemic influenza vaccine program. A manuscript describing results from the study, conducted with BARDA and the U.S. government, has been accepted by Nature Communications, he said. Arcturus plans to seek scientific advice from the European Medicines Agency regarding a potential licensure path later in 2026.
Revenue Declines as CSL Collaboration Ends
Chief Financial Officer Dennis Mulroy reported cash and cash equivalents of $191.5 million as of June 30, compared with $230.8 million at Dec. 31, 2025. The company said the $39.3 million decline during the first half reflected its operating activities.
- Second-quarter revenue was $3 million, compared with $28.3 million a year earlier.
- First-half revenue was $5 million, compared with $57.7 million in the prior-year period.
- Second-quarter research and development expense was $17.5 million, down from $29.6 million a year earlier.
- First-half research and development expense was $39 million, compared with $64.5 million in the comparable 2025 period.
- Second-quarter general and administrative expense was $11 million, compared with $10.3 million a year earlier.
Mulroy attributed lower revenue to reduced revenue recognition under the CSL collaboration as the agreement moved toward termination. Lower research and development spending reflected reduced expenses for salaries, benefits and facilities, he said.
The company said its cash runway extends more than two and a half years, through the end of 2028, as it pursues clinical and regulatory milestones for ARCT-032 and ARCT-810.
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.
This instant news alert was generated by narrative science technology and financial data from MarketBeat in order to provide readers with the fastest reporting and unbiased coverage. Please send any questions or comments about this story to contact@marketbeat.com.
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