Self-amplifying RNA vaccine for Crimean-Congo hemorrhagic fever in healthy adults
Official title: A Phase 1, Open Label, Dose-Escalation Study to Evaluate the Safety, Reactogenicity and Immunogenicity of a Nanoparticle Carrier-Formulated Self-Amplifying RNA Vaccine Against Crimean-Congo Hemorrhagic Fever (HDT-321) in Healthy Adults
Run by HDT Bio · NCT06799013 · Data updated 2026-11-12
This will test whether different doses and a one- or two-dose schedule of the experimental HDT-321 vaccine are safe and trigger immune responses in healthy adults aged 18–64.
Quick facts
| Phase | Phase 1 |
|---|---|
| Study type | Interventional |
| Ages | 18 Years to 64 Years |
| Sex | All |
| Enrollment | 48 (estimated) |
| Sponsor | HDT Bio Industry-sponsored |
| Drugs / interventions | prednisone |
| Locations | 1 site (San Antonio, Texas) |
| Status | Recruiting |
| Started | July 10, 2025 |
| Main results expected | December 2026 |
| Study ends | July 2027 |
| Registry record updated | July 28, 2025 |
| Trial ID | NCT06799013 on ClinicalTrials.gov |
Is this trial a fit for you?
✓Likely a good fit
Healthy adults aged 18–64 with BMI 17–35 who are HIV/HBV/HCV negative, not pregnant, and willing to follow contraception and study visit requirements are ideal candidates.
✕Probably not a fit
People who are immunocompromised, pregnant, younger than 18 or older than 64, or with significant uncontrolled medical conditions are unlikely to benefit or be eligible.
A plain-English reading of the study's rules. Only the study team can confirm whether you qualify.
What this trial studies
This is a first-in-human, open-label, dose-escalation study enrolling about 48 healthy adults to examine safety, reactogenicity, and immune responses to HDT-321. Participants are assigned across four groups at three dose levels (10, 25, 50 μg), with most groups receiving two doses and one group receiving a single dose. Small sentinel cohorts in each dose group are monitored for 7 days before full enrollment and dose escalation proceeds only if predefined safety rules are met. Blood samples, memory aids for 7-day symptom recording after each injection, clinic visits, and phone follow-ups are used to collect safety and immunogenicity data.
Why it matters
Potential benefit: If successful, HDT-321 could induce protective immune responses and help prevent Crimean-Congo hemorrhagic fever in exposed populations.
How similar studies have gone: While conventional mRNA vaccines have shown strong results in humans, self-amplifying RNA vaccines like HDT-321 are early-stage with limited human data to date.
Who can join: the full rules
Show full inclusion / exclusion criteria
Inclusion Criteria: 1. Males and non-pregnant females 18 to 64 years of age at the time of signing the ICF. 2. Body mass index (BMI) 17 to 35 inclusive at screening. 3. Considered by the PI or designee to be in good general health as determined by medical history, physical examination, vital sign measurements\*, and clinical laboratory assessments conducted no more than 30 days prior to the first study injection administration. 4. Screening laboratory values within the laboratory reference ranges or considered non-clinically significant (NCS) if within Grade 1 severity on the toxicity grading scale. 5. Negative human immunodeficiency virus (HIV) 1/2 antibody, hepatitis B surface antigen (HBsAg), and hepatitis C virus (HCV) antibody. 6. Women of childbearing potential must agree to use or have practiced true abstinence or use at least one acceptable primary form of contraception3 for at least 30 days prior to the first injection and for 60 days after the last injection. Female participants of childbearing potential must have a negative serum pregnancy test at screening and a negative urine pregnancy test on the day of and prior to each study injection. 7. Able to understand and comply with planned study procedures and willing to be available for all study required procedures, visits, and telephone calls for the duration of the study. 8. Provide written informed consent before initiation of any study procedures. 9. Willing to abstain from donating whole blood or blood derivatives 30 days prior to screening and for the duration of the study. 10. Willing to refrain from receiving any licensed vaccine within 28 days prior to and after scheduled study injections. Exclusion Criteria: 1. Any medical disease or condition that, in the opinion of the participating site PI or appropriate sub-investigator, precludes study participation. Including Acute, subacute, intermittent, or chronic medical diseases or conditions that would place the subject at an unacceptable risk of injury, render the subject unable to meet the requirements of the protocol, or may interfere with the evaluation of responses or the subject's successful completion of the trial. Significant respiratory disease (COPD) requiring daily medications, asthma that is not well controlled, significant cardiovascular disease, history of myocarditis or pericarditis, myocardial infarction, coronary artery bypass surgery or stent placement, or uncontrolled cardiac arrhythmia, Neurological or neurodevelopmental conditions, ongoing malignancy or recent diagnosis of malignancy in the last five years excluding basal cell and squamous cell carcinoma of the skin, blood dyscrasias or significant disorder of coagulation, chronic liver disease, including fatty liver, autoimmune disease, including localized or history of psoriasis or hypothyroidism without a defined non-autoimmune cause and Immunodeficiency of any cause. 2. Abnormal screening electrocardiogram (ECG) 3. History of hypersensitivity or severe reactions to previous vaccinations 4. History of hypersensitivity or severe reactions to products known to contain polyethylene glycol (PEG). 5. Allergy to antibiotics structurally similar to kanamycin (including but not limited to neomycin, streptomycin, tobramycin, and gentamycin). 6. Chronic administration (defined as more than 14 days in total) of immunosuppressants or other immunemodifying drugs within 6 months prior to the first study injection (for corticosteroids: prednisone ≥20 mg/day or equivalent). Intra-articular, inhaled, nasal, and topical steroids are allowed. 7. Received immunoglobulins or any blood products within 60 days prior to enrollment/Day 1. 8. Donated blood products within 30 days prior to enrollment/Day 1. 9. Received an investigational or non-registered medicinal product within 30 days prior to screening. 10. Currently enrolled, or plan to participate, in another clinical trial with an investigational agent to be received during the study period. 11. Received or plans to receive any non-study vaccine within 28 days before and after each study injection. 12. Febrile illness\*, as determined by the participating site PI or appropriate sub-investigator, with or without fever (oral temperature ≥38.0°C/100.4°F), within 24 hours prior to each study injection. 13. Current heavy smoking/vaping (defined as 1 pack or more of cigarettes a day or vaping equivalent\*). \*1-2 mL of 20 mg/mL of nicotine salt 14. Known or suspected alcohol or illicit drug abuse within the past 12 months prior to Study Day 1. 15. Breastfeeding or plans to breastfeed from the time of the first vaccination through 60 days after the last study injection. 16. Participants unlikely to cooperate with the requirements of the study protocol.
Where it's running
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Flourish Research San Antonio (Clinical Trials of Texas)
San Antonio, Texas, United States Recruiting
Study contacts
- Study coordinator: James Keary
- Email: james.keary@hdt.bio
- Phone: 206-567-8230
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How to take part
- Review the eligibility criteria above with your treating physician.
- Check the official listing on ClinicalTrials.gov for the latest contact details and recruitment status.
- Contact the study coordinator or principal investigator to ask for pre-screening. Pre-screening is free and never obligates you to enroll.