sponsor decided to withdrawn the study as development strategy has changed

This is a phase 2, randomized, controlled, observer-blind study to evaluate the immunogenicity and safety of different formulations of the investigational adjuvanted recombinant SARS-CoV-2 trimeric S-protein (from B.1.351 variant) subunit vaccine (SCB-2020S), when administered as 2-dose vaccination series 21 days apart to adults ≥ 18 years of age.

Clover has developed a second candidate vaccine, SCB-2020S, that contains S protein from the dominant B.1.351 variant. The purpose of clinical study CLO-SCB-2020-001 is to assess the immunogenicity and safety of different formulations of the SCB-2020S compared to the prototype SCB-2019 vaccine, and to select a formulation of SCB-2020S for further clinical development. The protocol plans to enroll 150 participants. There will be 5 study arms and participants will receive two intramuscular (i.m.) injections, one at Day 1 and one at Day 22.

Inclusion Criteria:

• 1. Male or female ≥18 years of age
• 2. Individuals are willing and able to comply with study requirements, including all scheduled visits, vaccinations, laboratory tests and other study procedures.
• 3.Individuals are willing and able to give an informed consent, prior to screening
• 4. Healthy participants or participants with pre-existing medical conditions* who are in a stable medical condition. (*A stable medical condition is defined as disease not requiring significant change or hospitalization for worsening disease during the 3 months before enrollment.)
• 5. Female participants of childbearing potential may be enrolled in the study, if the participant has practiced adequate contraception for 30 days prior to vaccination and has a negative pregnancy test on the day of vaccination and has agreed to continue adequate contraception for 3 months after the last vaccination
• 6. Male participants must agree to employ acceptable contraception from the day of the first dose of the study vaccine until 6 months after the last dose of the study vaccine and also refrain from donating sperm during this period.

Exclusion Criteria:

• 1. Individuals with body temperature >37.5°C (axillary), or any acute illness at baseline (Day 1) or within 3 days prior to randomization. Participants meeting this criterion may be rescheduled within the relevant window. Febrile participants with minor illnesses can be enrolled at the discretion of the investigator.
• 2. Individuals with laboratory-confirmed SARS-CoV-2 infection [as defined by reverse transcriptase polymerase chain reaction (RT-PCR) assay or Rapid COVID Antigen Test or an equivalent at Visit 1] or with history of COVID-19.
• 3. Individuals seropositive at Baseline for SARS-CoV-2.
• 4.Individuals who have received an investigational or authorized COVID-19 vaccine prior to Day 1, or plan to receive COVID-19 vaccine during the study period.
• 5. Any confirmed or suspected immunosuppressive or immunodeficient condition resulting from disease [e.g., malignancy, human immunodeficiency virus (HIV) infection] or immunosuppressive/cytotoxic therapy (e.g., systemic corticosteroids, medications used for cancer chemotherapy, organ transplantation or to treat autoimmune disorders) within 3 months prior to Day 1.
• 6. Individuals with any progressive unstable or uncontrolled clinical conditions.
• 7. Individuals who are pregnant, or breastfeeding, or planning to become pregnant while enrolled in this study or during the study period.
• 8. Individuals who have a history of severe adverse reaction associated with a vaccine or severe allergic reaction [e.g., anaphylaxis to any component of the study vaccines (CpG 1018, aluminum), or SCB-2020S/SCB-2019 components ].
• 9. Individuals who have a history of malignancy within 1 year before screening (exceptions are squamous and basal cell carcinomas of the skin and carcinoma in situ of the cervix which have been cured, or other malignancies with minimal risk of recurrence).
• 10. Individuals who have received any other investigational product within 30 days prior to Day 1 or intend to participate in another clinical study at any time during the conduct of this study.
• 11. Individuals who have received any other licensed vaccines within 14 days prior to enrollment in this study or who are planning to receive any vaccine up to 21 days after the second vaccination.
• 12. Individuals with known bleeding disorder that would, in the opinion of the investigator, contraindicate intramuscular injection.
• 13. Individuals who have received treatment with Rituximab or any other anti-CD20 monoclonal antibodies within 9 months prior to Day 1 or planned during the study period.
• 14. Administration of intravenous immunoglobulins and/or any blood products within 3 months prior to enrollment or planned administration during the study period.
• 15. Individuals with positive test result for hepatitis B surface antigen, hepatitis C virus antibody, or human immunodeficiency virus types 1 or 2 antibodies at Screening.
• 16. Individuals with safety laboratory test results (hematology, chemistry, and coagulation) with a toxicity score of Grade ≥2 at Screening (see Laboratory Manual for laboratory-specific normal ranges and associated toxicity grades). The inclusion of subjects with non-clinically significant (NCS) Grade 1 laboratory abnormalities is allowed based on the Investigator's discretion.
• 17. The subject has a reported or documented history of alcohol abuse or drug addiction or nonmedicinal recreational drug use (excluding nonprescription health supplements and herbal remedies) within 1 year before the planned day of dose administration.
• 18. The subject has a positive test result for drugs of abuse at Screening.
• 19. Individuals with any condition that, in the opinion of the investigator, would interfere with the primary study objectives or pose additional risk to the participant.