The ARCT-154 Self-Amplifying RNA Vaccine Efficacy Study (ARCT-154-01) (ARCT-154-01)

A Randomized, Observer-Blind, Controlled Study to Assess the Safety, Immunogenicity and Efficacy of the SARS-CoV-2 Self- Amplifying RNA Vaccine ARCT-154 in Adults

This is a Phase 1/2/3, randomized, placebo-controlled, observer-blind study designed to evaluate the safety, immunogenicity and efficacy of ARCT-154 in adult participants to be enrolled in Vietnam.

This study consists of four parts:

Part 1 (Phase 1) will evaluate the safety of the study vaccines in 100 healthy individuals.

Part 2 (Phase 2) will evaluate the safety and immunogenicity of the study vaccines in 300 healthy individuals.

Part 3 (Phase 3a) will evaluate the safety, immunogenicity, and efficacy of the study vaccines in 600 individuals with and without underlying medical conditions.

Part 4 (Phase 3b) will evaluate the safety and efficacy of the study vaccines in 16,000 individuals with and without underlying medical conditions.

Part 5 (Phase 3c) will evaluate the safety and non-inferiority in immunogenicity of ARCT-154 vaccine vs. Astra Zeneca COVID-19 vaccine (ChAdOx1 nCoV-19) in 2400 individuals with and without underlying medical conditions.

In Phase 1, healthy individuals 18 to < 60 years of age will be enrolled. In Phase 2, 3a, and 3b, individuals 18 years of age and older will be enrolled including individuals with underlying medical conditions that put them at higher risk of complications of COVID-19 disease.

Phase 1, Phase 2, Phase 3a and Phase 3b participants will be randomly assigned to a study group that will receive up to 2 vaccination series. Each vaccination series comprises two vaccinations at 28-day intervals: an initial vaccination series with vaccinations on Day 1 and Day 29 and an additional vaccination series around 2 months after the first series (on Day 92 and 120).

Participants of Phase 2, 3a who received 2 doses of ARCT-154 vaccine will be rerandomized to receive either dose 3 of ARCT-154 on Day 92 plus placebo on Day 120 or placebo on Day 92 plus placebo on Day 120.

For Phase 1, Phase 3b and participants in Phase 2 and 3a that received placebo in the first vaccination series, the participants will be switched over to the opposite vaccine in the second series.

There is no second vaccination series for Phase 3c as all participants receive active vaccine in the initial series.

Study Overview

• Status: Completed
• Conditions: COVID-19 Vaccines
• Intervention / Treatment: Biological: ARCT-154 Self-Amplifying RNA SARS-CoV-2 Vaccine; Other: Placebo (normal saline); Biological: Astra Zeneca COVID-19 vaccine

Detailed Description

Phase 1 will enroll 100 healthy participants that are randomly assigned 3:1 to receive ARCT-154 or placebo (75:25) for the initial series of vaccinations.

In Phase 2, 300 participants will be randomly assigned 3:1 to receive ARCT-154 or placebo for the initial series of vaccinations. Participants that received ARCT-154 in the initial series will be rerandomized 3:1 to receive ARCT or placebo on Day 92 followed by placebo on Day 120.

In Phase 3a, 600 participants will be randomly assigned 3:1 to receive ARCT-154 or placebo for the initial series of vaccinations. Participants that received ARCT-154 in the initial series will be rerandomized 3:1 to receive ARCT or placebo on Day 92 followed by placebo on Day 120.

In Phase 3b, ~16,000 participants will be randomly assigned 1:1 to receive ARCT-154 or placebo for the initial series of vaccinations.

In Phase 3c, ~2,400 participants will be randomly assigned 1:1 to receive ARCT-154 or Astra Zeneca COVID-19 vaccine. Blood samples will be collected and reserved for Immunogenicity evaluation for the first 1500 participants (3c-1) and assays for immunogenicity evaluation will be performed for the first 800 participants.

Phase 1 participants must be <60 years of age and healthy. Phase 2, 3a, and 3b and 3c participants will include elderly (≥60 years) and those with comorbidities.

For Phase 2, 3a, 3b and 3c, prior to randomization, participants will be stratified by age (< 60 or ≥ 60 years of age) and for participants < 60 years of age by risk of severe COVID 19. Participants will be followed up for approximately 1 year after completion of the initial vaccination series.

An independent Data and Safety Monitoring Board (DSMB) will perform ongoing review of blinded and unblinded data.

An independent blinded adjudication committee will adjudicate all suspected COVID-19 cases to determine if they meet the primary endpoint requirements.

• Study Type: Interventional
• Enrollment (Actual): 19474
• Phase: Phase 2; Phase 3

Contacts and Locations

Study Locations

• Vietnam
  • Hanoi
    • Hanoi, Hanoi, Vietnam, 00000
      • Hanoi Medical University
    • Hanoi, Hanoi, Vietnam, 00000
      • Military Medical University
  • Ho Chi Minh
    • Ho Chi Minh City, Ho Chi Minh, Vietnam, 00000
      • Pasteur Institute

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 14 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

Individuals who:

1. are able to provide consent
2. agree to comply with all study visits and procedures
3. are of childbearing potential and sexually active must be willing to adhere to contraceptive requirements
4. are male or female ≥18 years of age (or, for Phase 1, 18 to < 60 years of age)
5. are at higher risk of developing COVID-19 based on where they work or live

Exclusion Criteria:

Individuals who:

1. Significant infection or other acute illness, including body temperature >100.4°F (>38.0°C) on the day prior to or Day 1. Participants meeting this criterion may be rescheduled within the relevant window periods. Afebrile participants with minor illnesses can be enrolled at the discretion of the investigator.
2. Pregnant or breastfeeding.
3. Known history of COVID-19 (asymptomatic SARS-CoV-2 infection and/or nucleocapsid positive test is not exclusionary).
4. Close contact with a person known to be SARS-CoV-2 positive or with a clinical diagnosis of COVID-19 within 7 days prior to enrollment. Participants meeting this criterion who remain asymptomatic for 7 days may be rescheduled for enrollment within the relevant windows.
5. Known history of anaphylaxis, urticaria, or other significant adverse reaction to the vaccine or its excipients.
6. Known history of anaphylaxis to other vaccines.
7. Bleeding disorder considered a contraindication to intramuscular (IM) injection or phlebotomy.
8. Immunosuppressive or immunodeficient state, asplenia, recurrent severe infections, or known to be HIV positive.

9. An underlying clinically significant acute or chronic medical condition or physical examination findings for which, in the opinion of the investigator, participation would not be in the best interest of the participant (eg, compromise the well-being) or that could prevent, limit, or confound the protocol-specified assessments.

   Prior/Concomitant Therapy

10. Has previously received investigational or approved MERS-CoV, SARS-CoV, SARS-CoV-2 vaccines or who have plans to receive off-study COVID-19 vaccines.
11. Has received a live replicating vaccine within 28 days prior to each study vaccination or a licensed inactivated or non-replicating vaccine within 14 days prior to first study vaccination.
12. Has received treatment with immunosuppressive therapy, including cytotoxic agents or systemic corticosteroids, eg, for cancer or an autoimmune disease, within 6 months prior to Screening, or planned receipt throughout the study. If systemic corticosteroids have been administered short term (<14 days) for treatment of an acute illness, participants should not be enrolled into the study until corticosteroid therapy has been discontinued for at least 28 days prior to first study vaccine administration. Inhaled/nebulized, intra-articular, intrabursal, or topical (skin or eyes) corticosteroids are permitted.

13. Has received systemic immunoglobulins or blood products within 3 months prior to first study vaccine administration or plans to receive such products during the study.

    Other Exclusions

14. Demonstrated inability to comply with the study procedures.
15. Investigator site staff members, employees of the Sponsor or the 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.
16. Other restrictions apply to Phase 1 participants to ensure they are healthy.

Additional Exclusion Criteria for Phase 3c Participants Only:

No contraindications (as specified in the prescribing information) to receiving the ChAdOx1 vaccine.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: ARCT-154; Each participant is planned to receive a two-dose vaccination series of ARCT-154 at a dose of 5 µg with 28 day interval in the first vaccination series.	Biological: ARCT-154 Self-Amplifying RNA SARS-CoV-2 Vaccine; ARCT-154 Self-Amplifying RNA SARS-CoV-2 Vaccine
Placebo Comparator: Placebo; Each participant is planned to receive a two-dose vaccination series of placebo (normal saline) with 28 day interval in the first vaccination series.	Other: Placebo (normal saline); Normal saline with the same volume as of ARCT-154
Active Comparator: Astra Zeneca COVID-19 vaccine; Each participant is planned to receive a two-dose vaccination series of Astra Zeneca COVID-19 vaccine with 28 day interval in the first vaccination series.	Biological: Astra Zeneca COVID-19 vaccine; Astra Zeneca COVID-19 vaccine (ChAdOx1 nCoV-19)

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Number of Participants Reporting Solicited Local Adverse Reactions (ARs)	Solicited local ARs included injection site erythema, injection site pain, injection site induration/swelling, and injection site tenderness. A summary of serious and all other non-serious adverse events regardless of causality is located in the Reported Adverse Events module.	Within 7 days after Dose 1 and Dose 2 (up to Day 7 and 36)
Number of Participants Reporting Solicited Systemic ARs	Solicited systemic ARs included arthralgia, chills, diarrhea, dizziness, fatigue, fever (categorized by measured body temperature), headache, myalgia, and nausea/vomiting. A summary of serious and all other non-serious adverse events regardless of causality is located in the Reported Adverse Events module.	Within 7 days after Dose 1 and Dose 2 (up to Day 7 and 36)
Number of Participants Reporting Unsolicited Adverse Events (AEs)	Unsolicited AEs were defined as any spontaneously reported or discovered AE. A summary of serious and all other non-serious adverse events regardless of causality is located in the Reported Adverse Events module.	Approximately 28 days after Dose 1 and Dose 2 (Day 1 to Day 29 and Day 29 to Day 57)
Number of Participants Reporting Medically Attended Adverse Events (MAAEs), Serious Adverse Events (SAEs) and AEs Leading to Discontinuation	An MAAE was defined as an AE that led to an unscheduled visit (including a telemedicine visit) with a healthcare provider ([HCP], e.g., nurse, nurse practitioner, physician's assistant, 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 arising from a pregnancy conceived after receipt of study vaccine. A summary of serious and all other non-serious adverse events regardless of causality is located in the Reported Adverse Events module.	Day 1 to Day 92
Number of Participants With Neutralizing Antibody (NAb) Responses	Data are presented for the number of participants with a NAb seroconversion response as determined by the surrogate virus neutralization test (sVNT). Seroconversion was defined as a ≥4-fold increase in antibody concentration from baseline.	Day 57
Number of Participants With a First Occurrence of Coronavirus Disease 2019 (COVID-19)	COVID-19 was defined as a positive SARS-CoV-2 test and at least one of the following that was a new or worsening finding: ⦁ Fever or chills ⦁ Cough ⦁ Shortness of breath or difficulty breathing ⦁ Fatigue ⦁ Muscle or body aches ⦁ Headache ⦁ New loss of taste or smell ⦁ Sore throat ⦁ Congestion or runny nose ⦁ Nausea or vomiting ⦁ Diarrhea Data are presented for the number of participants with a first occurrence of COVID-19 with no evidence of prior infection.	Day 36 to Day 92

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Geometric Mean Titers of SARS-CoV-2 Neutralizing Antibodies		Days 1, 29, 57 and 92
Geometric Mean Fold Rise in SARS-CoV-2 Neutralizing Antibody Titers		Days 29, 57, 92
Number of Participants Seroconverting for Neutralizing Antibodies	Seroconversion was defined as a ≥4-fold increase in antibody concentration from baseline as measured by the sVNT test. Data are presented for the number of participants seroconverting for neutralizing antibodies.	Days 29, 57 and 92
Geometric Mean Concentration of Spike Protein Immunoglobulin G (IgG) Binding Antibodies		Days 1, 29, 57, 92
Geometric Mean Fold Ratio of Spike Protein IgG Binding Antibodies		Days 29, 57, 92
Number of Participants Seroconverting for Spike Protein IgG Binding Antibodies	Seroconversion was defined as a ≥4-fold increase in antibody concentration from baseline. Data are presented for the number of participants seroconverting for spike protein IgG binding antibodies.	Days 29, 57, 92
Number of Participants Seroconverting on Neutralizing Antibody Responses by Plaque Reduction Neutralization Test at 50% Reduction (PRNT50)	The plaque reduction neutralization test (PRNT) is a live virus assay. Neutralizing antibody titers were calculated as the highest serum dilution that resulted in 50% reduction in the number of virus plaques (PRNT50). Data presented is for the ancestral-clinical isolate variant. Data are presented for the number of participants that demonstrated seroconversion (as defined by 4-fold increase in neutralizing antibody concentration from baseline) on PRNT50.	Days 29 and 57
Number of Participants With a First Occurrence of Severe COVID-19	Number of participants with a first occurrence of severe COVID-19 in participants with no evidence of prior infection. Severe COVID-19 was defined as a positive SARS-CoV-2 test, symptoms per protocol-defined COVID-19 and any of the following: Clinical signs at rest indicative of severe systemic illness: - Respiratory rate ≥30 per minute, - Heart rate ≥125 per minute, - Oxygen saturation (SpO2) ≤93% on room air at sea level or partial pressure of oxygen (PO2)/fraction of inspired oxygen (FiO2) <300 millimeter of mercury (mm Hg) - Respiratory failure (defined as needing high flow oxygen, noninvasive ventilation, mechanical ventilation or extracorporeal membrane oxygenation [ECMO]); Evidence of shock: - Systolic blood pressure (SBP) <90 mm Hg, or - Diastolic blood pressure (DBP) <60 mm Hg, or requiring vasopressors, - Significant acute renal, hepatic, or neurologic dysfunction - Admission to an intensive care unit (ICU) - Death	Day 36 to Day 92
Number of Participants With Death Due to COVID-19	Number of participants with death due to COVID-19 in participants with no evidence of prior infection.	Day 36 to Day 92
Number of Participants With a First Occurrence of COVID-19 Irrespective of Prior Infection	Number of participants with a first occurrence of COVID-19 irrespective of prior infection.	Day 36 to Day 92
Number of Participants With a First Occurrence of COVID-19	Number of participants with a first occurrence of COVID-19 in participants with no evidence of prior infection.	Day 1 to Day 92

Collaborators and Investigators

• Sponsor: Vinbiocare Biotechnology Joint Stock Company
• Collaborators: Arcturus Therapeutics, Inc.

Study record dates

Study Major Dates

• Study Start (Actual): August 15, 2021
• Primary Completion (Actual): January 18, 2023
• Study Completion (Actual): January 18, 2023

Study Registration Dates

• First Submitted: August 13, 2021
• First Submitted That Met QC Criteria: August 13, 2021
• First Posted (Actual): August 19, 2021

Study Record Updates

• Last Update Posted (Estimated): November 6, 2025
• Last Update Submitted That Met QC Criteria: October 16, 2025
• Last Verified: October 1, 2025

More Information

Terms related to this study

• Keywords: SARS-CoV-2; Efficacy; COVID-19; Immunogenicity; ARCT-154
• Additional Relevant MeSH Terms: Respiratory Tract Infections; Infections; RNA Virus Infections; Virus Diseases; Respiratory Tract Diseases; Lung Diseases; Pneumonia, Viral; Pneumonia; Coronavirus Infections; Coronaviridae Infections; Nidovirales Infections; COVID-19; Pharmaceutical Preparations; Crystalloid Solutions; Isotonic Solutions; Solutions; Saline Solution
• Other Study ID Numbers: ARCT-154-01

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: IPD is the sole property of VinBioCare. VinBioCare may share a copy of the study IPD with their collaborative partners if requested.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: Yes