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ARCT-2303

Phase 3

COVID-19 | Monoclonal antibody | Infectious Disease |Arcturus Therapeutics Holdings Inc.|Last Updated: Dec 12, 2025

Success Probability
Approval Probability 71%
TA Base Rate26%
Adjusted LOA41%
ML RiskLOW_RISK
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Market & Valuation
rNPV $3.2B
Market Size $9.4B
Revenue Basis $1.6B
Competitors 6
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Trial Design
RandomizedDouble-BlindACTIVE_CONTROLLEDDMC
Total Trials1
Total Enrollment1,514
FDA Designations
No designations recorded
Clinical Trials (1)
NCT IDTitlePhaseStatusEnrollmentVelocityDesignStartCompletionLast UpdatedSitesCountries
NCT06279871Immunogenicity and Safety Study of Self-amplifying mRNA COVID-19 Vaccine Administered With Influenza Vaccines in AdultsPHASE3 COMPLETED 1,514Mar 27, 2024Nov 21, 2024Dec 12, 202529 Australia, Costa Rica +2
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Study Endpoints
Primary Endpoints
Groups 2a and 2b and ARCT-154-J01 Historical Control: Geometric Mean Titers (GMT) of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Neutralizing Antibody Titers Against Omicron XBB.1.5 Subvariant at Day 29
Day 29
Groups 2a and 2b and ARCT-154-J01 Historical Control: Number of Participants With Seroconversion to SARS-CoV-2 Neutralizing Antibody Against Omicron XBB.1.5 Subvariant at Day 29
Day 29

Seroconversion was defined as either a pre-vaccination titer below the lower limit of quantitation (LLOQ) and a postvaccination titer ≥4xLLOQ; or a pre-vaccination titer ≥LLOQ and a ≥4-fold increase in post-vaccination titer.

Groups 1a and 3a: Adjusted Hemagglutination Inhibition (HI) GMTs Against Influenza Vaccine Strains at Day 29
Day 29

Influenza vaccine strains were A/H1N1, A/H3N2, B/Victoria, and B/Yamagata.

Groups 1a and 2a: Adjusted GMTs of SARS-CoV-2 Neutralizing Antibody Against Omicron XBB.1.5 Subvariant at Day 29
Day 29
Secondary Endpoints
Groups 1a and 2a: GMT of SARS-CoV-2 Neutralizing Antibodies Against Omicron XBB.1.5 Subvariant at Days 1, 29 and 181
Group 1a: Days 1 and 29; Group 2a: Days 1, 29, and 181
Groups 1a and 2a: Geometric Mean Fold Rise (GMFR) of SARS-CoV-2 Neutralizing Antibodies Against Omicron XBB.1.5 Subvariant at Days 29 and 181
Group 1a: Day 29; Group 2a: Days 29 and 181
Groups 1a and 2a: Number of Participants With Seroconversion of SARS-CoV-2 Neutralizing Antibodies Against Omicron XBB.1.5 Subvariant at Day 29
Day 29
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Study Design & Arms
AllocationRANDOMIZED
MaskingQUADRUPLE
ModelPARALLEL
PurposePREVENTION
Treatment Arms
ArmTypeDescription
Group 1a (ARCT-2303/Influenza vaccine)EXPERIMENTALParticipants will receive one 0.5-mL IM (intramuscular) dose of ARCT-2303 and one 0.5-mL IM dose of influenza vaccine on Day 1 followed by a 0.5-mL IM dose of placebo on Day 29.
Group 2a (ARCT-2303)EXPERIMENTALParticipants will receive one 0.5-mL IM dose of ARCT-2303 and one 0.5-mL IM dose of placebo on Day 1 followed by a 0.5-mL IM dose of influenza vaccine on Day 29.
Group 3a (Influenza vaccine)ACTIVE_COMPARATORParticipants will receive one 0.5-mL IM dose of influenza vaccine and one 0.5-mL IM dose of placebo on Day 1 followed by a 0.5-mL IM dose of ARCT-2303 on Day 29.
Group 1b (ARCT-2303/ Influenza vaccine)EXPERIMENTALParticipants will receive one 0.5-mL IM dose of ARCT-2303 and one 0.5-mL IM dose of influenza vaccine on Day 1 followed by a 0.5-mL IM dose of placebo on Day 29.
Group 2b (ARCT-2303)EXPERIMENTALParticipants will receive one 0.5-mL IM dose of ARCT-2303 and one 0.5-mL IM dose of placebo on Day 1 followed by a 0.5-mL IM dose of influenza vaccine on Day 29.
Group 3b (Influenza vaccine)ACTIVE_COMPARATORParticipants will receive one 0.5-mL IM dose of influenza vaccine and one 0.5-mL IM dose of placebo on Day 1 followed by a 0.5-mL IM dose of ARCT-2303 on Day 29.
Interventions
NameTypeDescription
ARCT-2303BIOLOGICALSelf-Amplifying RNA COVID-19 vaccine (Omicron XBB.1.5)
Influenza vaccineBIOLOGICALLicensed cell-based influenza vaccine
Influenza vaccine, adjuvantedBIOLOGICALLicensed influenza vaccine, adjuvanted
PlaceboOTHER0.9% saline
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Eligibility Criteria
Age Range18 Years — N/A
SexALL
Healthy VolunteersYes
Study Sites29

Inclusion Criteria: 1, Individuals are male, female, or transgender adults ≥18 years of age. 2\. Healthy participants or participants with pre-existing stable medical conditions. 3\. Participant or legally authorized representatives must freely provide documented informed consent prior to study p...

Countries:AustraliaCosta RicaHondurasPhilippines
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