A Phase I/II, Dose-finding Study to Assess the Safety, Reactogenicity, and Immunogenicity of a Broadly Protective Sarbecovirus Vaccine (GBP511) in Healthy Adults.

NCT07280858 | Recruiting Phase 1 DMC

• 1 other identifier: GBP511_001
• Study Type: interventional
• Target: 368
• Locations: 1 country
• Sites: 2

Brief Summary

The purpose of this research study is to evaluate the safety of and the body's immune response to single and multiple vaccinations in healthy men and women. We want to find out what effects GBP511 has on you and your health. We are doing this study to find out: If the study drug has any side effects when given as single and multiple vaccinations. If reactogenicity, an indication that the immune systems is working and is preparing to protect the body against future infection, occurs. This is a normal physical inflammatory response that occurs after vaccination, manifesting as localised reactions that may include pain or redness at the injection site, or systemic symptoms such as headache or fever. If immunogenicity which is when GBP511 causes your body to make antibodies against the non-harmful viral proteins contained within GBP511, called 'neutralising antibodies (Nab),' occurs. And if GBP511 will cause the specialised cells of the body's immune system to mount a defence against the non-harmful viral proteins contained within GBP511, called 'cell-mediated immunity (CMI)'. In this study, GBP511 will be administered with and without adjuvant, CAS-1. An adjuvant is an ingredient used in some vaccines that help produce a stronger immune response in the people receiving the vaccine and thus helps the vaccine work better. This study will recruit approximately 368 participants in total and will be conducted in two stages: Stage 1 will look at two vaccinations with GBP511 when given with and without the CAS-1 adjuvant; and Stage 2 will look at either one or two vaccinations with two candidate GBP511 vaccines chosen from Stage 1 of the study. Participants will be required to attend Linear's clinical unit on two separate occasions to receive their two vaccinations. On the first day of dosing (Visit 2/Day 1) and second day of dosing (Visit 5/Day 29), we will be testing a single dose of the study drug in up to 168 healthy volunteers who will be divided into 3 groups. Group 1, Groups 2 and 3 will have 56 people each. These 3 groups will be divided into treatment subgroups, with a total of 6 test subgroups and 3 control subgroups. In all groups, neither you or the study doctor will know what subgroup you are part of, and therefore what treatment (GBP511 or Comirnaty+ placebo) you will receive.

Conditions

Healthy Participants; Sarbecovirus

Outcome Measures

Primary Outcomes (8)

• Percentage of participants experiencing any immediate reactions

  For stage 1

  30 minutes (2 hours for sentinel participants) following each study vaccination

• Percentage of participants reporting any solicited local AEs

  For stage 1

  during the 7 days following each study vaccination

• Percentage of participants reporting any solicited systemic AEs

  For stage 1

  during the 7 days following each study vaccination

• Percentage of participants experiencing any unsolicited AEs

  For stage 1

  during the 28 days following each study vaccination

• Percentage of participants experiencing any SAEs, MAAEs, AESIs, as well as AE leading to study withdrawal

  For stage 1

  1st Vaccination date, 1 week, 2 weeks, 4 weeks following the 1st study vaccination, and 2nd vaccination date, 1 week, 2 weeks, 4 weeks, 3 months, 6 months, and 12 months following the 2nd study vaccination.

• GMT of neutralizing antibody against each matched strain measured by a pseudo-virus neutralization assay at each time point.

  For stage 2

  At baseline, 2 weeks, 4 weeks following the 1st study vaccination, and 2 weeks, 4 weeks, 3 months, 6 months, and 12 months following the last study vaccination.

• GMR of neutralizing antibody against each matched strain measured by a pseudo-virus neutralization assay, from each pre-vaccination to subsequent time point.

  For stage 2

  At baseline, 2 weeks, 4 weeks following the 1st study vaccination, and 2 weeks, 4 weeks, 3 months, 6 months, and 12 months following the last study vaccination.

• Percentage of participants with ≥ 2-fold and 4-fold rises against each matched strain in pseudo-virus neutralizing antibody titer, from baseline to each subsequent time point

  For stage 2

  At baseline, 2 weeks, 4 weeks following the 1st study vaccination, and 2 weeks, 4 weeks, 3 months, 6 months, and 12 months following the last study vaccination.

Secondary Outcomes (15)

• Geometric mean titer (GMT) of neutralizing antibody against each matched strain measured by a pseudo-virus neutralization assay

  At baseline, 2 weeks, 4 weeks following the 1st study vaccination, and 2 weeks, 4 weeks, 3 months, 6 months, and 12 months following the 2nd study vaccination.

• Geometric mean ratio (GMR) of neutralizing antibody against each matched strain measured by a pseudo-virus neutralization assay

  From pre-vaccination to baseline, 2 weeks, 4 weeks following the 1st study vaccination, and 2 weeks, 4 weeks, 3 months, 6 months, and 12 months following the 2nd study vaccination.

• Percentage of participants with ≥ 2-fold and 4-fold rises against each matched strain in pseudo-virus neutralizing antibody titer

  At baseline, 2 weeks, 4 weeks following the 1st study vaccination, and 2 weeks, 4 weeks, 3 months, 6 months, and 12 months following the 2nd study vaccination.

• GMT of RBD-binding IgG antibody against each matched strain measured by ECL assay at each time point.

  At baseline, 2 weeks, 4 weeks following the 1st study vaccination, and 2 weeks, 4 weeks, 3 months, 6 months, and 12 months following the 2nd study vaccination (following the last vaccination for stage 2)

• GMR of RBD-binding IgG antibody against each matched strain measured by ECL assay, from each pre-vaccination to subsequent time point.

  At baseline, 2 weeks, 4 weeks following the 1st study vaccination, and 2 weeks, 4 weeks, 3 months, 6 months, and 12 months following the 2nd study vaccination(following the last vaccination for stage 2).

Other Outcomes (6)

• GMT of neutralizing antibody against each strain measured by a pseudo-virus neutralization assay at each time point.

  At baseline, 2 weeks, 4 weeks following the 1st study vaccination, and 2 weeks, 4 weeks, 3 months, 6 months, and 12 months following the last study vaccination.

• GMR of neutralizing antibody against each strain measured by a pseudo-virus neutralization assay, from each pre-vaccination to subsequent time point.

  At baseline, 2 weeks, 4 weeks following the 1st study vaccination, and 2 weeks, 4 weeks, 3 months, 6 months, and 12 months following the last study vaccination.

• Percentage of participants with ≥ 2-fold and 4-fold rises against each strain in pseudo-virus neutralizing antibody titer, from baseline to each subsequent time point.

  At baseline, 2 weeks, 4 weeks following the 1st study vaccination, and 2 weeks, 4 weeks, 3 months, 6 months, and 12 months following the last study vaccination.

Study Arms (9)

Test Group 1-1 (GBP511)

EXPERIMENTAL

Low-dose of recombinant protein nanoparticle pan-Sarbecovirus vaccine (2µg of RBD/strain); a total injection volume of 0.5mL IM injections on Day 1, 29 (Visit 2, 5)

Biological: Test Drug 1-1 (GBP511 low dose)

Test Group 1-2 (GBP511+CAS-1)

EXPERIMENTAL

Low-dose of recombinant protein nanoparticle pan-Sarbecovirus vaccine (2µg of RBD/strain) adjuvanted with a standard dose of CAS-1; a total injection volume of 0.5mL IM injections on Day 1, 29 (Visit 2, 5)

Biological: Test Drug 2-1 (GBP511 low dose + CAS-1)

Control Group

ACTIVE COMPARATOR

Comirnaty (2025-26 or subsequent seasonal formulation, 30 mcg of SARS-CoV-2 LP.8.1 spike protein mRNA); a total injection volume of 0.3mL Normal saline; a total injection volume of 0.5mL Comirnaty: IM injection on Day 1 (Visit 2) Normal Saline: IM injection on Day 29 (Visit 5)

Biological: Comparator (Comirnaty); Biological: Placebo (Normal Saline)

Test group 1-3 (GBP511)

EXPERIMENTAL

Mid-dose of recombinant protein nanoparticle pan-Sarbecovirus vaccine (6µg of RBD/strain); a total injection volume of 0.5mL IM injections on Day 1, 29 (Visit 2, 5)

Biological: Test Drug 1-2 (GBP511 mid dose)

Test group 1-4 (GBP511+CAS-1)

EXPERIMENTAL

Mid-dose of recombinant protein nanoparticle pan-Sarbecovirus vaccine (6µg of RBD/strain) adjuvanted with a standard dose of CAS-1; a total injection volume of 0.5mL IM injections on Day 1, 29 (Visit 2, 5)

Biological: Test Drug 2-2 (GBP511 mid dose + CAS-1)

Test Group 1-5 (GBP511)

EXPERIMENTAL

High-dose of recombinant protein nanoparticle pan-Sarbecovirus vaccine (18µg of RBD/strain); a total injection volume of 0.5mL IM injections on Day 1, 29 (Visit 2, 5)

Biological: Test Drug 1-3 (GBP511 high dose)

Test Group 1-6 (GBP511+CAS-1)

EXPERIMENTAL

High-dose of recombinant protein nanoparticle pan-Sarbecovirus vaccine (18µg of RBD/strain) adjuvanted with a standard dose of CAS-1; a total injection volume of 0.5mL IM injections on Day 1, 29 (Visit 2, 5)

Biological: Test Drug 2-3 (GBP511 high dose + CAS-1)

Test Group 2-1 (Stage 2)

EXPERIMENTAL

Participants will receive 2 intramuscular injections of the test vaccine in stage 2. Injections on Day 1, 29 (Visit 2, 5), in line with the selected dose regimen in stage 1.

Biological: Test Drug 13 (Stage 2, GBP511-A or B)

Test Group 2-2 (Stage 2)

EXPERIMENTAL

Participants will receive 2 intramuscular injections of the test vaccine in stage 2. Injections on Day 1, 29 (Visit 2, 5), in line with the selected dose regimen in stage 1.

Biological: Test Drug 14 (Stage 2, GBP511-A or B)

Interventions

Test Drug 1-2 (GBP511 mid dose) BIOLOGICAL

injection volume of 0.5mililiter (mL) with 2-doses at 4 weeks interval in stage 1 and 1-dose or 2-doses at 4 weeks interval in stage 2. Low dose: 2μg/strain, Mid dose: 6μg/strain, High dose: 18μg/strain

Test group 1-3 (GBP511)

Test Drug 1-3 (GBP511 high dose) BIOLOGICAL

injection volume of 0.5mililiter (mL) with 2-doses at 4 weeks interval in stage 1 and 1-dose or 2-doses at 4 weeks interval in stage 2. Low dose: 2μg/strain, Mid dose: 6μg/strain, High dose: 18μg/strain

Test Group 1-5 (GBP511)

Test Drug 2-1 (GBP511 low dose + CAS-1) BIOLOGICAL

injection volume of 0.5mililiter (mL) with 2-doses at 4 weeks interval in stage 1 and 1-dose or 2-doses at 4 weeks interval in stage 2. GBP511 - Low dose: 2μg/strain, Mid dose: 6μg/strain, High dose: 18μg/strain CAS-1 standard adjuvant dose

Test Group 1-2 (GBP511+CAS-1)

Comparator (Comirnaty) BIOLOGICAL

injection volume of 0.3mililiter (mL) with single-dose at visit 2. 30 mcg of SARS-CoV-2 LP.8.1 spike protein mRNA per 0.3mL

Control Group

Test Drug 1-1 (GBP511 low dose) BIOLOGICAL

injection volume of 0.5mililiter (mL) with 2-doses at 4 weeks interval in stage 1 and 1-dose or 2-doses at 4 weeks interval in stage 2. Low dose: 2μg/strain, Mid dose: 6μg/strain, High dose: 18μg/strain

Test Group 1-1 (GBP511)

Test Drug 2-2 (GBP511 mid dose + CAS-1) BIOLOGICAL

injection volume of 0.5mililiter (mL) with 2-doses at 4 weeks interval in stage 1 and 1-dose or 2-doses at 4 weeks interval in stage 2. GBP511 - Low dose: 2μg/strain, Mid dose: 6μg/strain, High dose: 18μg/strain CAS-1 standard adjuvant dose

Test group 1-4 (GBP511+CAS-1)

Test Drug 2-3 (GBP511 high dose + CAS-1) BIOLOGICAL

injection volume of 0.5mililiter (mL) with 2-doses at 4 weeks interval in stage 1 and 1-dose or 2-doses at 4 weeks interval in stage 2. GBP511 - Low dose: 2μg/strain, Mid dose: 6μg/strain, High dose: 18μg/strain CAS-1 standard adjuvant dose

Test Group 1-6 (GBP511+CAS-1)

Placebo (Normal Saline) BIOLOGICAL

injection volume of 0.5mililiter (mL) with single-dose at visit 5.

Control Group

Test Drug 13 (Stage 2, GBP511-A or B) BIOLOGICAL

Participants will receive 2 intramuscular injections of the test vaccine in stage 2. Injections on Day 1, 29 (Visit 2, 5), in line with the selected dose regimen in stage 1.

Test Group 2-1 (Stage 2)

Test Drug 14 (Stage 2, GBP511-A or B) BIOLOGICAL

Participants will receive 2 intramuscular injections of the test vaccine in stage 2. Injections on Day 1, 29 (Visit 2, 5), in line with the selected dose regimen in stage 1.

Test Group 2-2 (Stage 2)

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Age
• For Stage 1, participant must be 18 to 55 years of age inclusive, at the time of signing the informed consent.
• For Stage 2, participant must be 18 years of age and older, at the time of signing the informed consent.
• Type of Participant and Disease Characteristics
• Participants who are healthy as determined by medical evaluation including medical history, vital signs, physical examination, clinical laboratory tests, and medical judgement of the investigator.
• Participants who are willing and able to attend all scheduled visits and comply with all study procedures.
• Body mass index (BMI) within the range of 18.5-32.0 kg/m2 (revised) at screening
• Participants who received a primary series and at least one booster dose of an authorized COVID-19 vaccine at least 24 weeks prior to the 1st study vaccination.
• Sex and Contraceptive/Barrier Requirements
• All participants must agree to be abstinent from heterosexual intercourse or agree to consistently use at least one acceptable method of contraception from at least 4 weeks prior to the 1st study vaccination to 12 weeks after the last study vaccination (See Appendix 10.4 for detailed contraceptive methods).
• Women of childbearing potential (WOCBP) with a negative urine or serum pregnancy test at screening.
• \* Female participants who are surgically sterile (e.g., having undergone a full hysterectomy, bilateral salpingectomy, or bilateral oophorectomy) or postmenopausal with at least 12 months amenorrhoea not considered to be caused by any other medical condition, are not subject to a pregnancy test.
• Informed Consent
• Participants who are capable of giving signed informed consent as described in Appendix 10.1.3 which includes compliance with the requirements and restrictions listed in the informed consent form (ICF) and in this protocol before initiation of any trial-specific procedures.

You may not qualify if:

• Medical Conditions
• Any clinically significant respiratory symptoms (e.g., cough, sore throat), febrile illness (tympanic temperature \>38°C), or acute illness within 24 hours prior to the 1st study vaccination. Prospective participants with these conditions cannot be included until 24 hours after resolution.
• Concurrent or a history of virologically or serologically confirmed SARS-CoV-2 infection, or suspected SARS-CoV-2 infection as determined by the investigator, within 24 weeks prior to the 1st study vaccination.
• History of virologically or serologically confirmed SARS-CoV-1, or MERS disease.
• History of congenital, hereditary, acquired immunodeficiency, or autoimmune disease.
• Any positive test results for hepatitis B surface antigen, hepatitis C antibody, or human immunodeficiency virus (HIV) at screening.
• History of bleeding disorder or thrombocytopenia which is contraindicating intramuscular vaccination in the investigator's opinion.
• History of hypersensitivity and severe allergic reaction (e.g., anaphylaxis) to any vaccines or components of the study intervention.
• History of neurologic diseases (e.g., Guillain-Barre syndrome, myelitis, or encephalomyelitis).
• History of myocarditis, pericarditis or myopericarditis, as assessed by the investigator, indicating probable or possible myocarditis, pericarditis, or myopericarditis, or demonstrating clinically significant abnormalities that could affect participant safety or the interpretation of study findings.
• History of malignancy within 1 year prior to first study vaccination, except for cutaneous non-melanoma malignancy, melanoma-in-situ, or cervical carcinoma in situ that have been fully treated with completed follow-up prior to screening. Malignancy considered to carry minimal risk of recurrence may also be permitted at the discretion of the investigator.
• Significant unstable chronic or acute illness that, in the opinion of the investigator, might pose a health risk to the participant if enrolled, or could interfere with the protocol-specified activities, or interpretation of study results.
• Any other conditions which, in the opinion of the investigator, might interfere with the evaluation of the study objectives (e.g., alcohol or drug abuse, neurologic or psychiatric conditions).
• Female participants who are pregnant or breastfeeding.
• Prior/Concomitant therapy

Sponsors & Collaborators

• SK Bioscience Co., Ltd.: lead

Study Sites (2)

Linear

Joondalup, Western Australia, 6027, Australia

NOT YET RECRUITING

Linear

Nedlands, Western Australia, 6009, Australia

RECRUITING

MeSH Terms

Interventions

BNT162 Vaccine; Saline Solution

Intervention Hierarchy (Ancestors)

mRNA Vaccines; Nucleic Acid-Based Vaccines; Vaccines, Synthetic; Recombinant Proteins; Proteins; Amino Acids, Peptides, and Proteins; Vaccines; Biological Products; Complex Mixtures; COVID-19 Vaccines; Viral Vaccines; Antigens; Biological Factors; Crystalloid Solutions; Isotonic Solutions; Solutions; Pharmaceutical Preparations

Central Study Contacts

Hoon Lee

CONTACT

82-2-2008-2200; hoon.lee@sk.com

Jungeun Song

CONTACT

82-2-2008-2200; jungeun@sk.com

Study Design

• Study Type: interventional
• Phase: phase 1
• Allocation: RANDOMIZED
• Masking: QUADRUPLE
• Who Masked: PARTICIPANT, CARE PROVIDER, INVESTIGATOR, OUTCOMES ASSESSOR
• Purpose: PREVENTION
• Intervention Model: SEQUENTIAL
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Model Details: Stage 1: sequential, Stage 2 : parallel

Study Record Dates

• First Submitted: November 26, 2025
• First Posted: December 12, 2025
• Study Start: January 28, 2026
• Primary Completion (Estimated): December 9, 2026
• Study Completion (Estimated): September 12, 2028
• Last Updated: February 12, 2026

Record last verified: 2026-02

Locations

AU (2)