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ARCT-2304

Phase 1

Influenza, Human | Monoclonal antibody | Infectious Disease |Arcturus Therapeutics Holdings Inc.|Last Updated: Sep 4, 2026

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Trial Design

RandomizedDouble-BlindACTIVE_CONTROLLEDDMC
Total Trials1
Total Enrollment212

FDA Designations

No designations recorded

Clinical trial landscape

ARCT-2304 · 1 trial · 1 indication

Phase 1 1
NCT06602531Safety and Immunogenicity Study of Self-Amplifying RNA Pandemic Influenza Vaccine in AdultsInfluenza, Human
COMPLETED212 Analytics
PHASE1COMPLETED
Safety and Immunogenicity Study of Self-Amplifying RNA Pandemic Influenza Vaccine in Adults
Influenza, HumanUnlock trial analytics

Study Endpoints

Primary Endpoints

Number of Participants With Solicited Adverse Events (AEs) Within 7 Days After Each Vaccination
7 days post each dose

The following solicited local and systemic AEs were recorded from Day 1 to 7 days after each vaccination (dose): Injection site pain, Erythema, Swelling, Fatigue, Headache, Myalgia, Arthralgia, Dizziness, Nausea, Chills, Fever (≥100.4 °Fahrenheit \[F\] /≥38.0 °Celsius \[C\]). A summary of all Serious Adverse Events and Other Adverse Events (non-serious) regardless of causality is located in the 'Reported Adverse Events' Section.

Number of Participants With Unsolicited AEs Within 28 Days After Each Vaccination
D1,29 Cohorts: up to Day 29 and up to Day 57 (28 days post each dose), D1,57 Cohorts: up to Day 29 and up to Day 85 (28 days post each dose)

An AE was any untoward medical occurrence in a participant or participant administered a medicinal product, whether or not considered related to the trial vaccine. An unsolicited AE was defined as any AE not included in the list of solicited AEs (i.e., any event other than injection site pain, erythema, swelling, fatigue, headache, myalgia, arthralgia, dizziness, nausea, chills, or fever (≥100.4 °F / ≥38.0 °C). Solicited AEs that lasted for more than 7 days were considered as unsolicited AEs. Unsolicited AEs were recorded from Day 1 up to 28 days after each vaccination (dose). A summary of all Serious Adverse Events and Other Adverse Events (non-serious) regardless of causality is located in the 'Reported Adverse Events' Section'.

Number of Participants With Serious Adverse Events (SAEs), Medically Attended AEs (MAAEs), AEs of Special Interest (AESIs), and AEs Leading To Early Termination From Day 1 to 28 Days After Second Vaccination
D1,29 Cohorts: up to Day 57, D1,57 Cohorts: up to Day 85

An SAE was defined as any AE that resulted in death, was life-threatening, resulted in persistent disability/incapacity, or required inpatient hospitalization or prolongation of existing hospitalization. AEs potentially associated with messenger ribonucleic acid (mRNA) vaccines and influenza vaccines were reported as AESIs. MAAEs were defined as AEs with medically attended visits including hospital, emergency room, urgent care clinic, or other visits (including phone/telehealth visits) to or from medical personnel for any reason but did not fulfil seriousness criteria. A summary of all Serious Adverse Events and Other Adverse Events (non-serious) regardless of causality is located in the 'Reported Adverse Events' Section'.

Geometric Mean Titer of Antibody Response to Hemagglutinin (HA) Glycoprotein Measured By Hemagglutinin Inhibition (HAI) Assay
D1,29 Cohorts: Day 1, Day 29 (28 days post dose 1), Day 36 (7 days post dose 2), and Day 57 (28 days post dose 2), D1,57 Cohorts: Day 1, Day 57 (56 days post dose 1), Day 64 (7 days post dose 2), and Day 85 (28 days post dose 2)

A serum HAI assay was used for measuring HA-specific antibodies against the A/H5N1/Indonesia/5/2005 influenza strain. Antibody titers were expressed as Geometric Mean Titers.

Geometric Mean Titer of Antibody Response to Neuraminidase (NA) Glycoprotein Measured By Enzyme-linked Lectin Assay (ELLA)
D1,29 Cohorts: Day 1, Day 29 (28 days post dose 1), Day 36 (7 days post dose 2), and Day 57 (28 days post dose 2), D1,57 Cohorts: Day 1, Day 57 (56 days post dose 1), Day 64 (7 days post dose 2), and Day 85 (28 days post dose 2)

A serum ELLA assay was used for measuring NA-specific antibodies against the A/H5N1/Indonesia/5/2005 influenza strain. Antibody titers were expressed as Geometric Mean Titers.

Geometric Mean Fold Rise of Antibody Response to HA Glycoprotein Measured By HAI Assay
D1,29 Cohorts: Day 29 (28 days post dose 1), Day 36 (7 days post dose 2), and Day 57 (28 days post dose 2), D1,57 Cohorts: Day 57 (56 days post dose 1), Day 64 (7 days post dose 2), and Day 85 (28 days post dose 2)

A serum HAI assay was used for measuring HA-specific antibodies against the A/H5N1/Indonesia/5/2005 influenza strain. Geometric Mean Fold Rise was reported as a ratio to Day 1.

Geometric Mean Fold Rise of Antibody Response to NA Glycoprotein Measured By ELLA
D1,29 Cohorts: Day 29 (28 days post dose 1), Day 36 (7 days post dose 2), and Day 57 (28 days post dose 2), D1,57 Cohorts: Day 57 (56 days post dose 1), Day 64 (7 days post dose 2), and Day 85 (28 days post dose 2)

A serum ELLA assay was used for measuring NA-specific antibodies against the A/H5N1/Indonesia/5/2005 influenza strain. Geometric Mean Fold Rise was reported as a ratio to Day 1.

Percentage of Participants With Seroconversion of Antibody Response to HA Glycoprotein Measured By HAI Assay
D1,29 Cohorts: Day 29 (28 days post dose 1), Day 36 (7 days post dose 2), and Day 57 (28 days post dose 2), D1,57 Cohorts: Day 57 (56 days post dose 1), Day 64 (7 days post dose 2), and Day 85 (28 days post dose 2)

A serum HAI assay was used for measuring HA-specific antibodies against the A/H5N1/Indonesia/5/2005 influenza strain. Seroconversion was recorded if participant had pre-vaccination antibody titer \< Lower Limit Of Quantitation (LLOQ) and a post-vaccination antibody titer ≥ 4 x LLOQ, or a pre-vaccination antibody titer ≥LLOQ and a ≥4-fold increase in post-vaccination antibody titer.

Percentage of Participants With Seroconversion of Antibody Response to NA Glycoprotein Measured By ELLA
D1,29 Cohorts: Day 29 (28 days post dose 1), Day 36 (7 days post dose 2), and Day 57 (28 days post dose 2), D1,57 Cohorts: Day 57 (56 days post dose 1), Day 64 (7 days post dose 2), and Day 85 (28 days post dose 2)

A serum ELLA assay was used for measuring NA-specific antibodies against the A/H5N1/Indonesia/5/2005 influenza strain. Seroconversion was recorded if participant had pre-vaccination antibody titer \< LLOQ and a post-vaccination antibody titer ≥ 4 x LLOQ, or a pre-vaccination antibody titer ≥LLOQ and a ≥4-fold increase in post-vaccination antibody titer.

Percentage of Participants With HAI Titers Above or Equal to Prespecified Thresholds
D1,29 Cohorts: Day 57 (28 days post dose 2), D1,57 Cohorts: Day 85 (28 days post dose 2)

A serum HAI assay was used for measuring HA-specific antibodies against the A/H5N1/Indonesia/5/2005 influenza strain. The prespecified antibody threshold levels were as follows: ≥1:10, ≥1:20, ≥1:40, ≥1:80, ≥1:160, and ≥1:320.

Percentage of Participants With ELLA Titers Above or Equal to Prespecified Thresholds
D1,29 Cohorts: Day 57 (28 days post dose 2), D1,57 Cohorts: Day 85 (28 days post dose 2)

A serum ELLA assay was used for measuring NA-specific antibodies against the A/H5N1/Indonesia/5/2005 influenza strain. The prespecified antibody threshold levels were as follows: ≥1:10, ≥1:20, ≥1:40, ≥1:80, ≥1:160, and ≥1:320.

Secondary Endpoints

Number of Participants With SAEs, MAAEs, AESIs, and AEs Leading To Early Termination From Day 1 to Day 240
Day 1 to Day 240
Geometric Mean Titer of Antibody Response To HA Glycoprotein Measured By HAI Assay at Day 240
Day 240
Geometric Mean Titer of Antibody Response to NA Glycoprotein Measured By ELLA at Day 240
Day 240
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Study Design & Arms

AllocationRANDOMIZED
MaskingQUADRUPLE
ModelPARALLEL
PurposePREVENTION

Treatment Arms

ArmTypeDescription
Low dose of ARCT-2304, Schedule 1, Young AdultsEXPERIMENTALLow dose of ARCT-2304 administered through intramuscular injection in the deltoid muscle. Interventions: 2-dose regimen, schedule 1 Investigational Vaccine: ARCT-2304
Mid dose of ARCT-2304, Schedule 1, Young AdultsEXPERIMENTALMid dose of ARCT-2304 administered through intramuscular injection in the deltoid muscle. Interventions: 2-dose regimen, schedule 1 Investigational Vaccine: ARCT-2304
High dose of ARCT-2304, Schedule 1, Young AdultsEXPERIMENTALHigh dose of ARCT-2304 administered through intramuscular injection in the deltoid muscle. Interventions: 2-dose regimen, schedule 1 Investigational Vaccine: ARCT-2304
Control, Schedule 1, Young AdultsACTIVE_COMPARATORControl Vaccine (dose 1) and placebo (dose 2) administered through intramuscular injection in the deltoid muscle. Interventions: 2-dose regimen, schedule 1 Investigational Vaccine: Comparator vaccine younger adult and saline placebo vaccine
Low dose of ARCT-2304, Schedule 1, Older AdultsEXPERIMENTALLow dose of ARCT-2304 administered through intramuscular injection in the deltoid muscle. Interventions: 2-dose regimen, schedule 1 Investigational Vaccine: ARCT-2304
Mid dose of ARCT-2304, Schedule 1, Older AdultsEXPERIMENTALMid dose of ARCT-2304 administered through intramuscular injection in the deltoid muscle. Interventions: 2-dose regimen, schedule 1 Investigational Vaccine: ARCT-2304
High dose of ARCT-2304, Schedule 1, Older AdultsEXPERIMENTALHigh dose of ARCT-2304 administered through intramuscular injection in the deltoid muscle. Interventions: 2-dose regimen, schedule 1 Investigational Vaccine: ARCT-2304
Control, Schedule 1, Older AdultsACTIVE_COMPARATOROlder Adults Control Vaccine (dose 1) and placebo (dose 2) administered through intramuscular injection in the deltoid muscle. Interventions: 2-dose regimen, schedule 1 Investigational Vaccine: Comparator vaccine older adult and saline
Low dose of ARCT-2304, Schedule 2, Young AdultsEXPERIMENTALLow dose of ARCT-2304 administered through intramuscular injection in the deltoid muscle. Interventions: 2-dose regimen, schedule 2 Investigational Vaccine: ARCT-2304
Mid dose of ARCT-2304, Schedule 2, Young AdultsEXPERIMENTALMid dose of ARCT-2304 administered through intramuscular injection in the deltoid muscle. Interventions: 2-dose regimen, schedule 2 Investigational Vaccine: ARCT-2304
High dose of ARCT-2304, Schedule 2, Young AdultsEXPERIMENTALHigh dose of ARCT-2304 administered through intramuscular injection in the deltoid muscle. Interventions: 2-dose regimen, schedule 2 Investigational Vaccine: ARCT-2304
Control, Schedule 2, Young AdultsACTIVE_COMPARATORYoung Adults Control Vaccine (dose 1) and placebo (dose 2) administered through intramuscular injection in the deltoid muscle. Interventions: 2-dose regimen, schedule 2 Investigational Vaccine: Comparator vaccine younger adult and saline placebo vaccine
Low dose of ARCT-2304, Schedule 2, Older AdultsEXPERIMENTALLow dose of ARCT-2304 administered through intramuscular injection in the deltoid muscle. Interventions: 2-dose regimen, schedule 2 Investigational Vaccine: ARCT-2304
Mid dose of ARCT-2304, Schedule 2, Older AdultsEXPERIMENTALMid dose of ARCT-2304 administered through intramuscular injection in the deltoid muscle. Interventions: 2-dose regimen, schedule 2 Investigational Vaccine: ARCT-2304
High dose of ARCT-2304, Schedule 2, Older AdultsEXPERIMENTALHigh dose of ARCT-2304 administered through intramuscular injection in the deltoid muscle. Interventions: 2-dose regimen, schedule 2 Investigational Vaccine: ARCT-2304
Control, Schedule 2, Older AdultsACTIVE_COMPARATOROlder Adults Control Vaccine (dose 1) and placebo (dose 2) administered through intramuscular injection in the deltoid muscle. Interventions: 2-dose regimen, schedule 2 Investigational Vaccine: Comparator vaccine older adult and saline placebo vaccine

Interventions

NameTypeDescription
ARCT-2304BIOLOGICALEach participant will receive 2-dose regimen intramuscular (IM) dose into the deltoid muscle.
Control vaccine younger adultsBIOLOGICALEach participant will receive one intramuscular (IM) dose into the deltoid muscle.
Control vaccine older adultsBIOLOGICALEach participant will receive one intramuscular (IM) dose into the deltoid muscle.
Placebo VaccineOTHEREach participant will receive one intramuscular (IM) dose into the deltoid muscle.
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Eligibility Criteria

Age Range18 Years to 80 Years
SexALL
Healthy VolunteersYes
Study Sites4

Main Inclusion Criteria: * Individuals are male or female adults 18-80 years of age. * Healthy participants or participants with pre-existing stable medical conditions. * Individuals of childbearing potential must be willing to adhere to contraceptive requirements. Main Exclusion Criteria: * Indi...

Countries:United States
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Frequently asked questions about ARCT-2304

What is ARCT-2304 used for?

ARCT-2304 is an investigational vaccine being developed for the prevention of influenza in humans. It is currently in Phase 1 clinical development and is being studied for its safety and immunogenicity in adults.

Who makes ARCT-2304?

ARCT-2304 is being developed by Arcturus Therapeutics Holdings Inc., a biopharmaceutical company. The company is conducting clinical trials to evaluate the vaccine's safety and immune response in adults.

What phase is ARCT-2304 in?

ARCT-2304 is in Phase 1 clinical development. It is an investigational vaccine and has not been approved by regulatory authorities. A Phase 1 trial has been completed to assess its safety and immunogenicity.

What clinical trials is ARCT-2304 in?

ARCT-2304 has one completed Phase 1 clinical trial, NCT06602531, titled 'Safety and Immunogenicity Study of Self-Amplifying RNA Pandemic Influenza Vaccine in Adults.' The trial enrolled 212 participants in the United States and was randomized, double-blind, and active-controlled.

Is ARCT-2304 the same as a self-amplifying RNA vaccine?

ARCT-2304 is a self-amplifying RNA vaccine, as indicated by the clinical trial title. It is designed to encode antigens that elicit an immune response against influenza. The vaccine is administered to healthy adult volunteers.