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Completed

NCT Number: NCT05037097

A Trial Evaluating the Safety and Immunogenicity of 3 COVID-19 SARS-CoV-2 RNA Vaccines in Healthy Adults

This is a Phase 1/2, randomized, observer-blind study in healthy adults. The study will evaluate the safety, reactogenicity, and immunogenicity of 3 SARS-CoV-2 self-amplifying RNA vaccine candidates against COVID-19 in adults previously vaccinated and not previously vaccinated against SARS-CoV-2.

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Key information

Conditions

COVID-19 Corona Virus Infection Coronaviridae Infections Coronavirus Infections Infections Lung Diseases Nidovirales Infections Pneumonia Pneumonia, Viral RNA Virus Infections Respiratory Tract Diseases Respiratory Tract Infections Sars-CoV-2 Infection Virus Diseases

Age range

21 year–80 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 1 / Phase 2

Primary location

Arcturus Investigational Site 101, Singapore

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About this study

The study will initially enroll approximately 72 adult participants into 2 cohorts (A and B). Cohort A is further sub-divided into two sub-cohorts which include 12 participants who are seronegative, not previously vaccinated at screening (Sub-cohort A1) and 24 participants who are seropositive, not previously vaccinated at screening (Sub-cohort A2).

Within the first cohort (Cohort A), Sub-cohort A1 will include a total of 12 adult participants ≥21 to ≤65 years of age who have not been previously vaccinated with a SARS-CoV-2 vaccine. Sub-cohort A2 will include a total of 24 adult participants ≥21 to ≤65 years of age who have not been previously vaccinated with a SARS-CoV-2 vaccine. Study vaccines will be given as 2 doses separated by 28 days.

The second cohort (Cohort B) will include a total of 36 adult participants ≥21 to ≤65 years of age who have been previously vaccinated (5 months or longer prior to study enrollment) with SARS-CoV-2 vaccine. Study vaccines will be given as single doses.

Additional cohorts may increase the age range of participants up to 80 years of age.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

Individuals who:

  • Are able to provide consent
  • Agree to comply with all study visits and procedures
  • Are willing and able to adhere to study restrictions
  • Are sexually active and willing to adhere to contraceptive requirements
  • Are male, female, or transgender ≥21 to ≤80 years of age
  • For the previously vaccinated groups only, received 2 doses of SARS-CoV-2 vaccine 5 months or longer prior to study enrollment

Exclusion criteria

Individuals who:

  • For the unvaccinated groups only, previously received any investigational or authorized MERS-CoV, SARS-CoV, and SARS-CoV-2 vaccines (including ARCT-021)
  • For the previously vaccinated groups only, previously received BNT162b2 but have not received 2 doses within at least 5 months prior to study enrollment
  • Are planning to receive other COVID-19 vaccines during the study period
  • Recently received other vaccines
  • Have a fever or are feeling sick close to the time of the first study vaccination
  • Have a known history of COVID-19 disease or asymptomatic SARS-CoV-2 infection
  • Are pregnant or breastfeeding
  • Have had a severe reaction to previous vaccines
  • Have a severe or uncontrolled disease(s) that may interfere with the interpretation of the study
  • Have some respiratory diseases
  • Have some significant heart diseases
  • Have some neurological conditions
  • Have sickle cell disease or some other blood disorders
  • Have had a major surgery within the past 6 months
  • Have a history of chronic liver disease
  • Have a history of autoimmune disease or immunodeficiency
  • Have received allergy injections, interferon, immunomodulators, cytotoxic drugs or other similar toxic drugs.
  • Have received blood products
  • Have a positive test for hepatitis B or C or human immunodeficiency virus
  • Have uncontrolled hypertension
  • Have had cancer except for cancers that were treated and that have low risk of returning
  • Are obese
  • Are Investigator site staff members, employees of Arcturus or the contract research organization (CRO) directly involved in the conduct of the study, or site staff members otherwise supervised by the Investigator or immediate family members of any of the previously mentioned individuals

Treatment and study plan

ARCT-165

Biological

Dose 3

ARCT-154

Biological

Dose 2

ARCT-021

Biological

Dose 1

Primary outcomes

  1. Number of Participants Reporting Solicited Local or Systemic Adverse Events (AEs)

    Time frame: 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.

  2. Number of Participants Reporting Unsolicited AEs

    Time frame: 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.

  3. Number of Participants Reporting Medically Attended Adverse Events (MAAEs), AEs Leading to Discontinuation From Study Vaccine/Study Withdrawal, or Serious Adverse Events (SAEs)

    Time frame: 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.

  4. Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2) Serum Neutralizing Antibody Levels, Expressed as Geometric Mean Concentration (GMC)

    Time frame: 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).

  5. SARS-CoV-2 Serum Neutralizing Antibody Levels, Expressed as GMC

    Time frame: 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).

  6. SARS-CoV-2 Serum Neutralizing Antibody Levels, Expressed as Geometric Mean Fold Rise (GMFR)

    Time frame: 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.

  7. SARS-CoV-2 Serum Neutralizing Antibody Levels, Expressed as GMFR

    Time frame: 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.

  8. 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)

    Time frame: 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.

  9. 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)

    Time frame: 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.

  10. GMC Ratio (ARCT-165 vs ARCT-154 and ARCT-021 vs ARCT-154)

    Time frame: 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).

  11. GMC Ratio (ARCT-021 vs ARCT-165 Cohorts A1 and B)

    Time frame: 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).

  12. SARS-CoV-2 Full-length Spike and Receptor-binding Domain (RBD) Binding Antibody Levels, Expressed as GMCs

    Time frame: 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.

  13. Changes in SARS-CoV-2 Full-length Spike and RBD Binding Antibody Levels, Expressed as GMFRs

    Time frame: 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.

  14. 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

    Time frame: 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.

Sponsors and collaborators

Lead sponsor

Arcturus Therapeutics, Inc.

Industry

Registry information

Official study title

A Phase 1/2 Randomized, Observer-Blind Study of the Safety, Reactogenicity, and Immunogenicity of 3 SARS-CoV-2 RNA Vaccine Candidates in Adults Previously Vaccinated and Not Previously Vaccinated Against SARS-CoV-2

Important dates

Study start
2021
Primary completion
2023
Study completion
2023
First posted
Sep 8, 2021
Registry last updated
Oct 15, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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