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ARCT-165

Phase 1

COVID-19 | Monoclonal antibody | Infectious Disease |Arcturus Therapeutics Holdings Inc.|Last Updated: Oct 15, 2025

Success Probability

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Market & Valuation

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Trial Design

RandomizedDouble-BlindCONTROLLED
Total Trials1
Total Enrollment72

FDA Designations

No designations recorded

Clinical trial landscape

ARCT-165 · 1 trial · 3 indications

Phase 1 1
NCT05037097A Trial Evaluating the Safety and Immunogenicity of 3 COVID-19 SARS-CoV-2 RNA Vaccines in Healthy AdultsCOVID-19
COMPLETED72 Analytics
PHASE1COMPLETED
A Trial Evaluating the Safety and Immunogenicity of 3 COVID-19 SARS-CoV-2 RNA Vaccines in Healthy Adults
COVID-19Unlock trial analytics

Study Endpoints

Primary Endpoints

Number of Participants Reporting Solicited Local or Systemic Adverse Events (AEs)
Up to Day 8 (7 days after first vaccine administration for Cohorts A1, A2 and B), and up to Day 36 (7 days after second vaccine administration for Cohorts A1 and A2)

Solicited local AEs were defined as injection site erythema, injection site pain, injection site induration, and injection site tenderness. Solicited systemic AEs were defined as arthralgia, chills, diarrhea, dizziness, fatigue, fever (categorized by measured body temperature), headache, myalgia, nausea and vomiting. Data are reported for the number of participants with solicited local and solicited systemic AEs. A summary of all Serious Adverse Events and Other Adverse Events (nonserious) regardless of causality is located in the 'Reported Adverse Events' Section.

Number of Participants Reporting Unsolicited AEs
Up to Day 29 (28 days after vaccine administration for Cohort B), and up to Day 57 (up to 28 days after each vaccine administration for Cohorts A1 and A2)

Unsolicited AEs were defined as any spontaneously reported or discovered AE. Data are reported for the number of participants with unsolicited AEs. A summary of all Serious Adverse Events and Other Adverse Events (nonserious) regardless of causality is located in the 'Reported Adverse Events' Section.

Number of Participants Reporting Medically Attended Adverse Events (MAAEs), AEs Leading to Discontinuation From Study Vaccine/Study Withdrawal, or Serious Adverse Events (SAEs)
Through Final Visit (365 days after last study vaccine dose); up to a maximum of approximately 394 days

An MAAE was an AE that led to an unscheduled visit (including a telemedicine visit) with a health care provider (HCP) (e.g., nurse, nurse practitioner, physician's assistant, physician), including visits to a study site for unscheduled assessments (e.g., rash assessment, abnormal laboratory follow up, coronavirus disease 2019 \[COVID-19\]) and visits to HCPs external to the study site (e.g., urgent care, primary care physician). An SAE was defined as any event that resulted in death, was immediately life-threatening, required inpatient hospitalization or prolongation of existing hospitalization, resulted in persistent or significant disability/incapacity, or was a congenital anomaly/birth defect. A summary of all Serious Adverse Events and Other Adverse Events (nonserious) regardless of causality is located in the 'Reported Adverse Events' Section.

Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2) Serum Neutralizing Antibody Levels, Expressed as Geometric Mean Concentration (GMC)
Baseline, Days 29, 57, 209, Final Visit (approx. Day 394) for Cohorts A1 and A2; Baseline, Days 15, 29, 91, 181, 271 and Final Visit (approx. Day 366) for Cohort B

Blood samples were collected to assess participants' immune response. GMC data are reported for the pseudoviral D614G variant. Data are reported in international units per milliliter (IU/mL).

SARS-CoV-2 Serum Neutralizing Antibody Levels, Expressed as GMC
Baseline, Days 29, 57, 209, Final Visit (approx. Day 394) for Cohorts A1 and A2; Baseline, Days 15, 29, 91, 181, 271 and Final Visit (approx. Day 366) for Cohort B

Blood samples were collected to assess participants' immune response. GMC data are reported for the pseudoviral B.1.351 (beta) variant. Data are reported in arbitrary units per milliliter (AU/mL).

SARS-CoV-2 Serum Neutralizing Antibody Levels, Expressed as Geometric Mean Fold Rise (GMFR)
Days 29, 57, 209, Final Visit (approx. Day 394) for Cohorts A1 and A2, and Days 15, 29, 91, 181, 271 and Final Visit (approx. Day 366) for Cohort B

Blood samples were collected to assess participants' immune response. GMFR data are reported for the pseudoviral D614G variant.

SARS-CoV-2 Serum Neutralizing Antibody Levels, Expressed as GMFR
Days 29, 57, 209, Final Visit (approx. Day 394) for Cohorts A1 and A2, and Days 15, 29, 91, 181, 271 and Final Visit (approx. Day 366) for Cohort B

Blood samples were collected to assess participants' immune response. GMFR data are reported for the pseudoviral B.1.351 (beta) variant.

Number of Participants Achieving Greater Than or Equal to 4-fold Rise From Before Vaccination in SARS-CoV-2 Serum Neutralizing Antibody Levels (Pseudoviral D614G Variant)
Days 29, 57, 209, Final Visit (approx. Day 394) for Cohorts A1 and A2, and Days 15, 29, 91, 181, 271 and Final Visit (approx. Day 366) for Cohort B

Blood samples were collected to assess participants' immune response. Data are reported for the pseudoviral D614G variant.

Number of Participants Achieving Greater Than or Equal to 4-fold Rise From Before Vaccination in SARS-CoV-2 Serum Neutralizing Antibody Levels (Pseudoviral B.1.351 [Beta] Variant)
Days 29, 57, 209, Final Visit (approx. Day 394) for Cohorts A1 and A2, and Days 15, 29, 91, 181, 271 and Final Visit (approx. Day 366) for Cohort B

Blood samples were collected to assess participants' immune response. Data are reported for the pseudoviral B.1.351 (beta) variant.

GMC Ratio (ARCT-165 vs ARCT-154 and ARCT-021 vs ARCT-154)
Days 29, 57, 209, Final Visit (approx. Day 394) for Cohorts A1 and A2, and Days 15, 29, 91, 181, 271 and Final Visit (approx. Day 366) for Cohort B

Blood samples were collected to assess participants' immune response. Data are reported for the pseudoviral D614G Variant, B.1.351 Variant, B.1.617.2 Variant, BA.1 Variant for the GMC ratio of ARCT-165 vs ARCT-154 and ARCT-021 vs ARCT-154. Data are reported for the ARCT-165 and ARCT-021 arms (vs ARCT-154 values).

GMC Ratio (ARCT-021 vs ARCT-165 Cohorts A1 and B)
Days 29, 57, 209, Final Visit (approx. Day 394) for Cohort A1, and Days 15, 29, 91, 181, 271 and Final Visit (approx. Day 366) for Cohort B

Blood samples were collected to assess participants' immune response. Data are reported for the pseudoviral D614G Variant, B.1.351 Variant, B.1.617.2 Variant, BA.1 Variant for the GMC ratio of ARCT-021 vs ARCT-165. Data are reported for the ARCT-021 arm (vs ARCT-165 values).

SARS-CoV-2 Full-length Spike and Receptor-binding Domain (RBD) Binding Antibody Levels, Expressed as GMCs
Baseline and Day 57 for Cohorts A1 and A2, Baseline and Day 15 for Cohort B

Spike binding antibody levels expressed as GMCs are reported for ancestral, D614G, and B.1.351 variants and RBD binding antibodies for ancestral strain.

Changes in SARS-CoV-2 Full-length Spike and RBD Binding Antibody Levels, Expressed as GMFRs
Day 57 for Cohorts A1 and A2, Day 15 for Cohort B

Spike binding antibody levels expressed as GMFRs are reported for ancestral, D614G, and B.1.351 variants and RBD binding antibody levels expressed as GMFR for ancestral strain.

Number of Participants Achieving Greater Than or Equal to 4-fold Rise From Before Vaccination in SARS-CoV-2 Full-length Spike and RBD Binding Antibody Levels
Day 57 for Cohorts A1 and A2, Day 15 for Cohort B

Data are reported for ancestral, D614G, and B.1.351 variants for Spike binding antibodies and ancestral for RBD binding antibodies.

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Study Design & Arms

AllocationRANDOMIZED
MaskingQUADRUPLE
ModelPARALLEL
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
Study Group 1, Adult Participants Seronegative, Not Previously Vaccinated randomized to ARCT-165EXPERIMENTALParticipants will receive one dose of ARCT-165 on Day 1 and one dose of ARCT-165 on Day 29
Study Group 2, Adult Participants Seronegative, Not Previously Vaccinated randomized to ARCT-154EXPERIMENTALParticipants will receive one dose of ARCT-154 on Day 1 and one dose of ARCT-154 on Day 29
Study Group 3, Adult Participants Seronegative, Not Previously Vaccinated to receive ARCT-021EXPERIMENTALParticipants will receive one dose of ARCT-021 on Day 1 and one dose of ARCT-021 on Day 29
Study Group 4, Adult Participants Seropositive, Not Previously Vaccinated to receive ARCT-021EXPERIMENTALParticipants will receive one dose of ARCT-021 on Day 1 and one dose of ARCT-021 on Day 29
Study Group 5, Adult Participants Seropositive, Not Previously Vaccinated randomized to ARCT-154EXPERIMENTALParticipants will receive one dose of ARCT-154 on Day 1 and one dose of ARCT-154 on Day 29
Study Group 6, Adult Participants Previously Vaccinated randomized to receive ARCT-165EXPERIMENTALParticipants will receive one dose of ARCT-165 on Day 1
Study Group 7, Adult Participants Previously Vaccinated randomized to receive ARCT-154EXPERIMENTALParticipants will receive one dose of ARCT-154 on Day 1
Study Group 8, Adult Participants Previously Vaccinated randomized to receive ARCT-021EXPERIMENTALParticipants will receive one dose of ARCT-021 on Day 1

Interventions

NameTypeDescription
ARCT-165BIOLOGICALDose 3
ARCT-154BIOLOGICALDose 2
ARCT-021BIOLOGICALDose 1
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Eligibility Criteria

Age Range21 Years to 80 Years
SexALL
Healthy VolunteersYes
Study Sites4

Inclusion Criteria: Individuals who: 1. Are able to provide consent 2. Agree to comply with all study visits and procedures 3. Are willing and able to adhere to study restrictions 4. Are sexually active and willing to adhere to contraceptive requirements 5. Are male, female, or transgender ≥21 to ...

Countries:United StatesSingaporeSouth Africa
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Frequently asked questions about ARCT-165

What is ARCT-165 used for?

ARCT-165 is an investigational COVID-19 vaccine being developed for the prevention of COVID-19, which is caused by the SARS-CoV-2 virus. It is designed to be administered to healthy adults to generate an immune response against the virus. The vaccine is currently in clinical development and has not been approved for use.

Who makes ARCT-165?

ARCT-165 is being developed by Arcturus Therapeutics Holdings Inc., a biopharmaceutical company traded on the NASDAQ under the ticker symbol ARCT. The company is conducting clinical trials to evaluate the safety and immunogenicity of this COVID-19 vaccine candidate.

What phase is ARCT-165 in?

ARCT-165 is in Phase 1 clinical development. It is an investigational COVID-19 vaccine that has completed a Phase 1 trial. The vaccine is not yet approved by regulatory authorities and remains under investigation for safety and immunogenicity in healthy adults.

What clinical trials is ARCT-165 in?

ARCT-165 was evaluated in a Phase 1 clinical trial with the identifier NCT05037097. This trial assessed the safety and immunogenicity of three COVID-19 SARS-CoV-2 RNA vaccines in healthy adults. The study enrolled 72 participants and was conducted in the United States, Singapore, and South Africa. The trial has been completed.

Is ARCT-165 a monoclonal antibody?

ARCT-165 is classified as a monoclonal antibody modality, but it is being developed as a COVID-19 vaccine. It is designed to elicit an immune response against SARS-CoV-2. The vaccine is administered to healthy adults and is currently in Phase 1 clinical development.