NCT07280858

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

A 2-Stage, Phase I/II, Active-controlled, Randomized, Observer-blinded, Dose-finding Study to Assess the Safety, Reactogenicity, and Immunogenicity of a Broadly Protective Sarbecovirus Vaccine (GBP511) in Healthy Adults (Aged 18 Years and Older)

• Status: Recruiting
• Phase: Phase 1 / Phase 2
• Study type: Interventional
• Enrollment: 368 (estimated)
• Sponsor: SK Bioscience Co., Ltd. · Industry
• Sex: All
• Age: 18 Years
• Healthy volunteers: Accepted

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

Interventions

Type	Name	Description
BIOLOGICAL	Test Drug 1-1 (GBP511 low dose)	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
BIOLOGICAL	Test Drug 1-2 (GBP511 mid dose)	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
BIOLOGICAL	Test Drug 1-3 (GBP511 high dose)	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
BIOLOGICAL	Test Drug 2-1 (GBP511 low dose + CAS-1)	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
BIOLOGICAL	Test Drug 2-2 (GBP511 mid dose + CAS-1)	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
BIOLOGICAL	Test Drug 2-3 (GBP511 high dose + CAS-1)	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
BIOLOGICAL	Comparator (Comirnaty)	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
BIOLOGICAL	Placebo (Normal Saline)	injection volume of 0.5mililiter (mL) with single-dose at visit 5.
BIOLOGICAL	Test Drug 13 (Stage 2, GBP511-A or B)	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)	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.

Timeline

• Start date: 2026-01-28
• Primary completion: 2026-12-09
• Completion: 2028-09-12
• First posted: 2025-12-12
• Last updated: 2026-02-12

Locations

2 sites across 1 country: Australia