NCT06810934 · Kara Chew
A Phase 1/2A, Randomized Study of a T Follicular Helper (TFH)-Targeting Genetic Vaccine Strategy Designed to Induce Broad, Durable Immune Responses
(CONTENDER)
What this study is about
The goal of this clinical trial is to test two experimental COVID-19 booster vaccines, called CoTend-s3BXBB and CoTend-BXBB, in healthy volunteers ages 40-64. The CoTend-s3BXBB vaccine includes a component called "s3", which was designed to improve the body's response to the vaccine. CoTend-BXBB is the same vaccine without s3.
View original scientific description
The goal of this clinical trial is to test two investigational COVID-19 booster vaccines, called CoTend-s3BXBB and CoTend-BXBB, in healthy volunteers ages 40-64. The CoTend-s3BXBB vaccine includes a component called "s3", which was designed to improve the body's response to the vaccine. CoTend-BXBB is the same vaccine without s3.
Interventions
BIOLOGICAL
CoTend-BXBB (SARS2-30404)
Ad35-vectored SARS-CoV-2 RBD (XBB.1.5) vaccine
BIOLOGICAL
CoTend-s3BXBB (SARS2-17032)
Ad35-vectored s3-SARS-CoV-2 RBD (XBB.1.5) vaccine
BIOLOGICAL
Placebo
Sterile sodium chloride 0.9% for injection, preservative free
Primary outcome measures
Frequency of solicited local reactogenicity adverse events (AEs) within 7 days after dosing.
Time frame: 7 days
Number of participants with solicited local reactogenicity AEs (injection site pain, erythema, or swelling) within 7 days after dosing. An AE is any untoward medical occurrence in a clinical investigation of a patient administered a pharmaceutical product and that does not necessarily have a causal relationship with the treatment.
Frequency of solicited systemic reactogenicity AEs within 7 days after dosing.
Time frame: 7 days
Number of participants with solicited systemic reactogenicity AEs (malaise, participant-measured body temperature, fatigue, headache, chills, nausea, muscle aches/pain, joint pain) within 7 days after dosing.
Frequency of unsolicited AEs within 28 days after dosing.
Time frame: 28 days
Number of participants with unsolicited AEs within 28 days after dosing. Unsolicited AEs are AEs that were not pre-defined as solicited.
Frequency of serious adverse events (SAEs) within 28 days after dosing.
Time frame: 28 days
Number of participants with an SAE within 28 days after dosing. An SAE is defined as any adverse event that results in any of the following outcomes: death during a period of surveillance defined by the protocol, a life-threatening adverse experience, inpatient hospitalization or prolongation of existing hospitalization, a persistent or significant disability/incapacity, or a congenital anomaly/birth defect. The following are also considered SAEs for this study: severe COVID-19, defined as COVID-19 requiring hospitalization or supplemental oxygen, myocarditis or pericarditis within 6 weeks of study vaccination, and acute or new onset thrombosis or thromboembolism within 60 days of vaccination.
Frequency of adverse events of special interest (AESIs) within 28 days after dosing.
Time frame: 28 days
Number of participants with AESIs. AESIs defined as: thrombotic or thromboembolic events, thrombosis with thrombocytopenia syndrome, immune thrombocytopenia, or capillary leak syndrome occurring within 60 days; new thrombocytopenia \<150 x 10\^9/L or below the lower laboratory limit of normal or worsening in grade of thrombocytopenia within 60 days after study vaccination; new D-dimer elevation \>2000 ng/mL within 60 days; laryngospasm, bronchospasm, or anaphylaxis assessed as at least possibly related; generalized urticaria assessed as related; any other grade allergic/ hypersensitivity reaction within 7 days; any ulceration, abscess, or necrosis at injection site assessed as possibly related; myocarditis or pericarditis occurring within 6 weeks; new diagnosis of Guillain-Barré syndrome occurring within 60 days; any new or worsened immune mediated medical condition; grade 3+ lab abnormality for which there is a reasonable possibility of causal relationship to study treatment.
Frequency of medically attended adverse events (MAAEs) within 28 days after dosing.
Time frame: 28 days
Number of participants with MAAEs (MAAE defined as an AE resulting in a hospitalization, emergency room visit, or otherwise unscheduled visit with medical personnel for any reason) within 28 days after dosing.
Geometric mean titers (GMTs) of serum anti-XBB.1.5 neutralizing antibodies (NAb) through week 8.
Time frame: 8 weeks
Serum anti-XBB.1.5 NAb GMT
Proportion of participants achieving serum anti-XBB.1.5 NAb titers of 1:250 or better through week 8.
Time frame: 8 weeks
Proportion of participants achieving serum anti-XBB.1.5 NAb titers of 1:250 or better
Geometric mean fold rise (GMFR) from pre-dose to week 8 in serum anti-XBB.1.5 NAb responses.
Time frame: Pre-dose to 8 weeks
Geometric mean fold rise (GMFR) in serum anti-XBB.1.5 NAb levels
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
Inclusion criteria
- Individuals 40 - 64 years of age 2. Received at least two doses of a COVID-19 mRNA vaccine (Moderna or Pfizer) \> 120 days before study entry 3. Nasal SARS-CoV-2 negative by molecular (polymerase chain reaction, PCR) testing at screening 4. The following laboratory criteria must be met at screening: 1. Total white blood cell (WBC) count \> 3500 cells/mm3 2. Absolute neutrophil count (ANC) \> 1500 cells/mm3 3. Hemoglobin \> 13.5 g/dL if male sex and \> 12.0 g/dL if female sex 4. Platelet count \> 140,000/uL 5. Estimated creatinine clearance (CrCl) \> 50 mL/min by Cockroft-Gault equation 6. Total bilirubin ≤ 1.1x upper limit of normal (ULN) 7. Aspartate aminotransferase (AST) ≤ 1.3x ULN 8. Alanine aminotransferase (ALT) ≤ 1.3x ULN 5. Individuals of reproductive potential must have a negative serum or urine beta-human chorionic gonadotropin (ß-HCG) test at screening and within 48 hours prior to entry. Reproductive potential is defined a
Where
- Los Angeles, California
- San Francisco, California
Collaborators
University of California, San Francisco, University of California, Davis, Tendel Therapies, Inc., National Institute of Allergy and Infectious Diseases (NIAID)
Related conditions & keywords
Frequently asked questions
What is a clinical trial?
A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.
Is it safe to participate?
Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.
Will I be compensated?
Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.
Will I receive a placebo instead of treatment?
When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.
Can I leave a trial if I change my mind?
Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.
How long does a clinical trial last?
Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.
Data: ClinicalTrials.gov · synced Oct 31, 2025 · Source of record for eligibility and locations