TerminatedNCT04728347Updated Dec 30, 2024Results posted

Open Label Extension Study to Assess the Safety and Long-Term Immunogenicity of ARCT-021

A Phase 2 interventional study of ARCT-021 in SARS-CoV-2, sponsored by Arcturus Therapeutics, Inc.. Terminated at 1 site in Singapore. Open to participants aged 21 Years to 80 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2024-12-30.

Sponsored by Arcturus Therapeutics, Inc. · Phase 2, Interventional, and Treatment

Why this study was terminated

A decision was made to terminate the study for operational/business reasons. This study was not terminated for reasons of safety or immunogenicity.

Phase: Phase 2
Study type: Interventional
Enrollment: 65
Allocation: Non-randomized
Ages: 21 Years to 80 Years
Sex: All

Study summary

This is an open-label study enrolling healthy adults that participated in Study ARCT-021-01 (the Parent Study). Participants will receive either a single injection of ARCT-021 or no injection and be followed for up to 365 days.

Read the detailed description

This is a phase 2a, open-label study enrolling up to 106 healthy adults that participated in Study ARCT-021-01 (the Parent Study). Participants will enter this study approximately 3 months after their final study visit in the Parent Study. Participants that received placebo in the Parent Study or who are seronegative for SARS-CoV-2 neutralizing antibodies at screening will receive a single dose of ARCT-021 and will be followed for 365 days. Participants that received two injections of ARCT-021 in the Parent Study will not receive any further injections of ARCT-021 and will be followed for 281 days.

Conditions studied

SARS-CoV-2

In context

Lead sponsor

Arcturus Therapeutics, Inc. is the lead sponsor of 12 studies on the registry; 2 are open to participants now.

Of its 7 completed or terminated interventional studies of FDA-regulated products, 5 (71%) have results posted.

Counted across the registry records on this site, refreshed daily.

Who can participate

Ages eligible: 21 Years to 80 Years
Sexes eligible: All
Accepts healthy volunteers: Yes

Inclusion criteria

Individuals who:

are able to give consent
must have completed Study ARCT-021-01
agree to comply with all study visits and procedures
Only for subjects that will receive ARCT-021 in this study:
are healthy and medically stable
are not planning to donate blood or plasma until 28 days after the last dose of ARCT-021.
are willing to refrain from strenuous exercise/activity and alcohol for at least 72 hours prior to study visits and until 28 days after the last dose of ARCT-021.
are willing to adhere to contraception requirements if sexually active and/or are of child-bearing potential

Exclusion criteria

Exclusion Criteria:

Individuals who:

are unable to comply with the study visits or procedures in Study ARCT-021-01
received placebo in the Parent Study and who are not willing to receive ARCT-021 in this study.
Only for subjects that will receive ARCT-021 in this study:
have or will receive any of the SARS CoV-2 or another experimental coronavirus during this study.
have a diagnosis of new clinically significant abnormalities including but not limited to
- Respiratory disease requiring daily medications or oxygen currently or any treatment of respiratory disease exacerbations
- Significant heart conditions
- Significant neurological conditions
- Significant blood disorders
- Newly diagnosed autoimmune disease
- Major surgery
have abnormal screening laboratory results
have uncontrolled diabetes
use of any prescription or over-the-counter medications within 7 days prior to vaccination
have received immunoglobulins and/or any blood or blood products
have a bleeding disorder
have uncontrolled blood pressure
have been treated with another investigational drug, biological agent, or device since completion of the Parent Study
have received or plan to receive:
- A licensed, live vaccine within 4 weeks before or after study vaccination, or
- A licensed, inactivated vaccine within 2 weeks before or after study vaccination
have traveled outside of Singapore within 30 days before the vaccination or plans to travel outside of Singapore within 60 days after vaccination.
other restrictions may apply

Study design

Phase: Phase 2
Primary purpose: Treatment
Allocation: Non-randomized
Intervention model: Parallel assignment
Masking: None (open label)
Enrollment: 65 participants (actual)

Study arms

Experimental
ARCT-021
Participants will receive a single dose of ARCT-021 on Day 1
Biological: ARCT-021
No intervention
Long-term follow up from ARCT-021-01
Participants will not receive intervention but will be followed for safety.

Interventions

BiologicalARCT-021
ARCT-021 single dose

What researchers measure

Primary outcomes

Number of Participants With Solicited Local and Systemic Adverse Events
Solicited local adverse events were defined as pain, tenderness, erythema, or swelling at the injection site. Solicited systemic adverse events were defined as fever, fatigue, headache, chills, nausea, vomiting, diarrhoea, myalgia, and arthralgia. A summary of serious and all other non-serious adverse events regardless of causality is located in the Reported Adverse Events module.
Time frame: Up to Day 7 (7 days after vaccine administration)
Number of Participants With Unsolicited Adverse Events
Unsolicited adverse events were defined as any spontaneously occurring adverse event (serious and non-serious). A summary of serious and all other non-serious adverse events regardless of causality is located in the Reported Adverse Events module.
Time frame: Up to Day 29 (28 days after vaccine administration)
Number of Participants With Serious Adverse Events (SAEs), Unsolicited Adverse Events Associated With New Onset of Chronic Disease (NOCD) or Medically Attended Adverse Events (MAAEs)
SAEs were defined as any event that resulted in death, was life threatening, required inpatient hospitalization or prolongation of existing hospitalization, resulted in a persistent or significant incapacity or substantial disruption of the ability to conduct normal life functions, a congenital anomaly or birth defect, or was an important medical event. A NOCD was defined as a MAAE that led to the new diagnosis of a chronic medical condition that was not present or suspected prior to enrollment. A MAAE was an adverse event that led to an unscheduled visit (including a telemedicine visit) to a healthcare practitioner. A summary of serious and all other non-serious adverse events regardless of causality is located in the Reported Adverse Events module.
Time frame: Up to a maximum of approximately 12 months

Secondary outcomes

Geometric Mean Titer (GMT) of Serum Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Neutralizing Antibodies
Time frame: Cohorts 1a and 1b: Days 1, 29, 57, Cohort 2: Day 29
Geometric Mean Fold Rise (GMFR) in SARS-CoV-2 Neutralizing Antibody Titers
Time frame: Cohort 1a: Days 29, 57, Cohort 1b: Days 1, 29, 57, and Cohort 2: Day 29
Number of ARCT-021-naïve Participants (Cohort 1a) With Seroconversion (Neutralizing Antibodies)
Seroconversion was defined as a 4-fold increase in antibody titer/concentration from baseline. Data is presented for the number of participants seroconverting for neutralizing antibodies and immunoglobulin G (IgG) antibodies against the full-length SARS-CoV-2 recombinant spike protein antigen and spike protein receptor binding domain of the SARS-CoV-2 spike glycoprotein (RBD). ARCT-021-naïve participants were those participants whose first ARCT-021 vaccine administration occurred in this study (Cohort 1a). As pre-specified, data is presented for participants in Cohort 1a only.
Time frame: Days 29, and 57
Geometric Mean Concentration (GMC) of Serum SARS-CoV-2 Binding Antibodies
GMC data are reported for the S (spike binding antibodies) analyte.
Time frame: Cohorts 1a and 1b: Days 1, 29, 57, Cohort 2: Day 29
GMFR in SARS-CoV-2 Binding Antibody Titers
GMFR data are reported for the S (spike binding antibodies) analyte.
Time frame: Cohort 1a: Days 29, 57, Cohort 1b: Days 1, 29, 57, and Cohort 2: Day 29
Number of ARCT-021-naïve Participants (Cohort 1a) With Seroconversion (Binding Antibodies)
Seroconversion was defined as a 4-fold increase in antibody titer/concentration from baseline. Data is presented for the number of participants seroconverting for binding antibodies and immunoglobulin G (IgG) antibodies against the full-length SARS-CoV-2 recombinant spike protein antigen and spike protein receptor binding domain of the SARS-CoV-2 spike glycoprotein (RBD). ARCT-021-naïve participants were those participants whose first ARCT-021 vaccine administration occurred in this study (Cohort 1a). As pre-specified, data is presented for participants in Cohort 1a only.
Time frame: Days 29, and 57

Results

Posted Dec 30, 2024

Participant flow

Participant flow — Overall Study
Milestone	Cohort 1a	Cohort 1b	Cohort 2 Younger Adults	Cohort 2: Older Adults
Started	12	12	25	16
Received study drug in this study	12	12	0	0
Completed	12	12	24	16
Not completed	0	0	1	0
Withdrew: Sponsor decision	0	0	1	0

Outcome measures

PrimaryNumber of Participants With Solicited Local and Systemic Adverse Events

Solicited local adverse events were defined as pain, tenderness, erythema, or swelling at the injection site. Solicited systemic adverse events were defined as fever, fatigue, headache, chills, nausea, vomiting, diarrhoea, myalgia, and arthralgia. A summary of serious and all other non-serious adverse events regardless of causality is located in the Reported Adverse Events module.

Time frame:: Up to Day 7 (7 days after vaccine administration)
Reported as:: Count of participants · Participants

Number of Participants With Solicited Local and Systemic Adverse Events
Participants	Cohort 1a	Cohort 1b
Solicited Local	11	10
Solicited Systemic	11	8

PrimaryNumber of Participants With Unsolicited Adverse Events

Unsolicited adverse events were defined as any spontaneously occurring adverse event (serious and non-serious). A summary of serious and all other non-serious adverse events regardless of causality is located in the Reported Adverse Events module.

Time frame:: Up to Day 29 (28 days after vaccine administration)
Reported as:: Count of participants · Participants

Number of Participants With Unsolicited Adverse Events
Participants	Cohort 1a	Cohort 1b
Number of Participants With Unsolicited Adverse Events	3	2

PrimaryNumber of Participants With Serious Adverse Events (SAEs), Unsolicited Adverse Events Associated With New Onset of Chronic Disease (NOCD) or Medically Attended Adverse Events (MAAEs)

SAEs were defined as any event that resulted in death, was life threatening, required inpatient hospitalization or prolongation of existing hospitalization, resulted in a persistent or significant incapacity or substantial disruption of the ability to conduct normal life functions, a congenital anomaly or birth defect, or was an important medical event. A NOCD was defined as a MAAE that led to the new diagnosis of a chronic medical condition that was not present or suspected prior to enrollment. A MAAE was an adverse event that led to an unscheduled visit (including a telemedicine visit) to a healthcare practitioner. A summary of serious and all other non-serious adverse events regardless of causality is located in the Reported Adverse Events module.

Time frame:: Up to a maximum of approximately 12 months
Reported as:: Count of participants · Participants

Number of Participants With Serious Adverse Events (SAEs), Unsolicited Adverse Events Associated With New Onset of Chronic Disease (NOCD) or Medically Attended Adverse Events (MAAEs)
Participants	Cohort 1a	Cohort 1b	Cohort 2: Younger Adults
SAEs	0	1	0
Unsolicited Adverse Events Associated with NOCD	0	1	0
MAAEs	2	5	3

SecondaryGeometric Mean Titer (GMT) of Serum Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Neutralizing Antibodies

Time frame:: Cohorts 1a and 1b: Days 1, 29, 57, Cohort 2: Day 29
Reported as:: Geometric mean · Titer

Geometric Mean Titer (GMT) of Serum Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Neutralizing Antibodies
Titer	Cohort 1a	Cohort 1b	Cohort 2: Younger Adults	Cohort 2: Older Adults
Day 1	5.0 (5.00 to 5.00)	7.3 (3.14 to 16.99)	—	—
Day 29	6.1 (4.46 to 8.41)	38.6 (12.10 to 123.12)	9.7 (4.28 to 21.75)	5.0 (5.00 to 5.00)
Day 57	5.7 (4.28 to 7.45)	23.5 (7.65 to 71.98)	—	—

SecondaryGeometric Mean Fold Rise (GMFR) in SARS-CoV-2 Neutralizing Antibody Titers

Time frame:: Cohort 1a: Days 29, 57, Cohort 1b: Days 1, 29, 57, and Cohort 2: Day 29
Reported as:: Geometric mean · Ratio

Geometric Mean Fold Rise (GMFR) in SARS-CoV-2 Neutralizing Antibody Titers
Ratio	Cohort 1a	Cohort 1b	Cohort 2: Younger Adults	Cohort 2: Older Adults
Day 1	—	0.9 (0.71 to 1.07)	—	—
Day 29	1.2 (0.89 to 1.68)	4.3 (1.71 to 10.88)	1.6 (0.49 to 5.48)	1.0 (1.00 to 1.00)
Day 57	1.1 (0.86 to 1.49)	3.6 (1.42 to 9.33)	—	—

SecondaryNumber of ARCT-021-naïve Participants (Cohort 1a) With Seroconversion (Neutralizing Antibodies)

Seroconversion was defined as a 4-fold increase in antibody titer/concentration from baseline. Data is presented for the number of participants seroconverting for neutralizing antibodies and immunoglobulin G (IgG) antibodies against the full-length SARS-CoV-2 recombinant spike protein antigen and spike protein receptor binding domain of the SARS-CoV-2 spike glycoprotein (RBD). ARCT-021-naïve participants were those participants whose first ARCT-021 vaccine administration occurred in this study (Cohort 1a). As pre-specified, data is presented for participants in Cohort 1a only.

Time frame:: Days 29, and 57
Reported as:: Count of participants · Participants

Number of ARCT-021-naïve Participants (Cohort 1a) With Seroconversion (Neutralizing Antibodies)
Participants	Cohort 1a
Day 29	1
Day 57	0

SecondaryGeometric Mean Concentration (GMC) of Serum SARS-CoV-2 Binding Antibodies

GMC data are reported for the S (spike binding antibodies) analyte.

Time frame:: Cohorts 1a and 1b: Days 1, 29, 57, Cohort 2: Day 29
Reported as:: Geometric mean · Arbitrary units per milliliter (AU/mL)

Geometric Mean Concentration (GMC) of Serum SARS-CoV-2 Binding Antibodies
Arbitrary units per milliliter (AU/mL)	Cohort 1a	Cohort 1b	Cohort 2: Younger Adults	Cohort 2: Older Adults
Day 1	47.3 (24.06 to 93.12)	310.6 (90.06 to 1071.18)	—	—
Day 29	1629.3 (770.41 to 3445.89)	5319.8 (1817.81 to 15568.32)	802.8 (349.23 to 1845.44)	713.2 (178.25 to 2853.69)
Day 57	1013.5 (501.13 to 2049.58)	3088.1 (1172.00 to 8136.75)	—	—

SecondaryGMFR in SARS-CoV-2 Binding Antibody Titers

GMFR data are reported for the S (spike binding antibodies) analyte.

Time frame:: Cohort 1a: Days 29, 57, Cohort 1b: Days 1, 29, 57, and Cohort 2: Day 29
Reported as:: Geometric mean · Ratio

GMFR in SARS-CoV-2 Binding Antibody Titers
Ratio	Cohort 1a	Cohort 1b	Cohort 2: Younger Adults	Cohort 2: Older Adults
Day 1	—	7.2 (3.83 to 13.45)	—	—
Day 29	34.4 (16.76 to 70.69)	136.5 (46.58 to 400.08)	13.3 (3.94 to 44.75)	29.6 (15.80 to 55.33)
Day 57	20.4 (10.59 to 39.24)	104.9 (34.62 to 317.74)	—	—

SecondaryNumber of ARCT-021-naïve Participants (Cohort 1a) With Seroconversion (Binding Antibodies)

Seroconversion was defined as a 4-fold increase in antibody titer/concentration from baseline. Data is presented for the number of participants seroconverting for binding antibodies and immunoglobulin G (IgG) antibodies against the full-length SARS-CoV-2 recombinant spike protein antigen and spike protein receptor binding domain of the SARS-CoV-2 spike glycoprotein (RBD). ARCT-021-naïve participants were those participants whose first ARCT-021 vaccine administration occurred in this study (Cohort 1a). As pre-specified, data is presented for participants in Cohort 1a only.

Time frame:: Days 29, and 57
Reported as:: Count of participants · Participants

Number of ARCT-021-naïve Participants (Cohort 1a) With Seroconversion (Binding Antibodies)
Participants	Cohort 1a
Day 29	10
Day 57	9

Adverse events

Collected over Up to a maximum of approximately 12 months. Non-serious events are listed at a 0% frequency threshold.

Adverse event summary by group
Group	Deaths	Serious	Other
Cohort 1a	0/12 (0%)	0/12 (0%)	3/12 (25%)
Cohort 1b	0/12 (0%)	1/12 (8.3%)	1/12 (8.3%)
Cohort 2: Younger Adults	0/25 (0%)	0/25 (0%)	3/25 (12%)
Cohort 2: Older Adults	0/16 (0%)	0/16 (0%)	0/16 (0%)

Most frequent serious events

Most frequent serious events
Event	Cohort 1a	Cohort 1b	Cohort 2: Younger Adults	Cohort 2: Older Adults
Ischaemic strokeNervous system disorders	0/12	1/12	0/25	0/16

Most frequent other events

Most frequent other events
Event	Cohort 1a	Cohort 1b	Cohort 2: Younger Adults	Cohort 2: Older Adults
Blood creatine phosphokinase increasedInvestigations	1/12	0/12	0/25	0/16
Decreased appetiteMetabolism and nutrition disorders	1/12	0/12	0/25	0/16
Rhinitis allergicRespiratory, thoracic and mediastinal disorders	1/12	0/12	0/25	0/16
Vessel puncture site bruiseGeneral disorders	0/12	1/12	0/25	0/16
Lip dryGastrointestinal disorders	0/12	0/12	1/25	0/16
Ligament sprainInjury, poisoning and procedural complications	0/12	0/12	1/25	0/16
Tendon ruptureInjury, poisoning and procedural complications	0/12	0/12	1/25	0/16
Rotator cuff syndromeMusculoskeletal and connective tissue disorders	0/12	0/12	1/25	0/16
HeadacheNervous system disorders	0/12	0/12	1/25	0/16

Baseline characteristics

Data presented for all enrolled participants. As pre-specified, baseline characteristics are presented per sub-cohort (younger and older adults) for Cohort 2.

Age, Continuous
Age, Continuous(years)	Cohort 1a	Cohort 1b	Cohort 2: Younger Adults	Cohort 2: Older Adults	Total
Mean	45.1 ± 14.99	48.3 ± 16.17	39.7 ± 8.34	63.7 ± 4.13	48.2 ± 14.28

Sex: Female, Male
Sex: Female, Male(Participants)	Cohort 1a	Cohort 1b	Cohort 2: Younger Adults	Cohort 2: Older Adults	Total
Female	3	2	9	4	18
Male	9	10	16	12	47

Ethnicity (NIH/OMB)
Ethnicity (NIH/OMB)(Participants)	Cohort 1a	Cohort 1b	Cohort 2: Younger Adults	Cohort 2: Older Adults	Total
Hispanic or Latino	0	0	0	0	0
Not Hispanic or Latino	12	12	25	16	65
Unknown or Not Reported	0	0	0	0	0

Race (NIH/OMB)
Race (NIH/OMB)(Participants)	Cohort 1a	Cohort 1b	Cohort 2: Younger Adults	Cohort 2: Older Adults	Total
American Indian or Alaska Native	0	0	1	0	1
Asian	12	11	22	16	61
Native Hawaiian or Other Pacific Islander	0	0	0	0	0
Black or African American	0	0	0	0	0
White	0	1	1	0	2
More than one race	0	0	0	0	0
Unknown or Not Reported	0	0	1	0	1

Study locations

1 site

SingHealth Investigational Medicine Unit (IMU), Singapore General Hospital
Singapore, 169608, Singapore

References and documents

Study documents

Study protocol · Jan 13, 2021
Statistical analysis plan · Nov 15, 2021

Documents are hosted by the registry — open the source record to download them.

Individual participant data

Plan to share: No

Updates

Tracking since Sep 25, 2026

No changes since tracking began. The registry record was last updated on Dec 30, 2024, before this site started recording changes on Sep 25, 2026. Its history is on ClinicalTrials.gov ↗

Registry details

Key details

Study ID: NCT04728347
Lead sponsor: Arcturus Therapeutics, Inc.
Responsible party: Sponsor
First posted: Jan 28, 2021
Start date: Jan 4, 2021
Primary completion: Dec 28, 2021
Completion: Dec 28, 2021
Results posted: Dec 30, 2024
Last update: Dec 30, 2024

Oversight

Data monitoring committee: No
FDA-regulated drug: Yes
FDA-regulated device: No

View the source record on ClinicalTrials.gov ↗

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