STEALTH-001
A Phase 1/1b study of VET3-TGI given alone and with atezolizumab in patients with advanced solid tumors.
About the study
A new approach for advanced solid tumors
STEALTH-001 is the first clinical study of VET3-TGI, an investigational oncolytic immunotherapy. VET3-TGI is a vaccinia virus that has been modified in the laboratory and is designed to infect and kill cancer cells while sparing healthy cells. It carries two genes, IL-12 and a TGF-β inhibitor, designed to help the immune system attack the cancer.
This first-in-human study is built to evaluate route, dose, and the potential of VET3-TGI alone and in combination. It is evaluating safety, tolerability, the maximum tolerated dose and early signs of antitumor activity. VET3-TGI is given by injection into a tumor or by infusion into a vein, alone or with atezolizumab, an approved checkpoint inhibitor.
Expansion cohorts now focus on Merkel cell carcinoma and melanoma in patients whose cancer progressed on or after checkpoint inhibitors. Intravenous dose escalation is ongoing.
Study design
Dose escalation, then expansion
Phase 1 finds the highest tolerated dose for each route. Phase 1b enrolls up to 15 patients per cohort at the recommended dose.
Injected into tumors weekly for 4 doses.
At the recommended intratumoral dose.
Given by infusion weekly for 6 doses.
At the recommended intravenous dose.
What to expect
Your path through the study
Schedules vary by group. Your study doctor will explain what participation involves before you decide.
Screening
Tests and a baseline scan to confirm the study is a good fit.
Treatment
VET3-TGI weekly for 4 to 6 doses, depending on the group, sometimes with atezolizumab. Some visits include a tumor biopsy.
First scan
A scan at about week 8 to check how the cancer is responding.
Maintenance
Booster doses about every 2 weeks for patients who are benefiting, for up to 2 years, with scans every 8 to 12 weeks.
Follow-up
The study team continues to check on your health after treatment ends.
Eligibility
Who may be able to join
Key criteria only. The study team will review the full criteria with you and your doctor.
You may be eligible if you have
- Adults 18 or older with an advanced, unresectable or metastatic solid tumor confirmed by pathology
- Cancer progressed after, or you could not tolerate or chose not to receive, standard treatments such as checkpoint inhibitors, targeted therapy or chemotherapy
- Measurable disease on scans (RECIST 1.1)
- At least one tumor that can be safely injected or biopsied
- Able to carry out daily activities (ECOG 0 or 1) with adequate organ function
You may not be eligible if you have
- Brain metastases not fully removed or treated with radiation
- Blood thinners or antiplatelet medicines that cannot be safely paused
- History of myocarditis
- Known HIV/AIDS or active hepatitis B or C
- High-dose immunosuppressive medicine or significant immunodeficiency, such as an organ transplant
Locations
Study sites
Not every site enrolls every cohort. Contact the study team to find the right site.
Sites as listed on ClinicalTrials.gov, last updated April 2026.
FAQs
Frequently asked questions
What does the STEALTH-001 trial study?
STEALTH-001 studies VET3-TGI, an investigational oncolytic immunotherapy built on an engineered vaccinia virus. VET3-TGI has not been approved by the FDA or any other regulatory authority. The study evaluates it alone and in combination with atezolizumab, an approved checkpoint inhibitor that blocks PD-L1.
Is STEALTH-001 limited to one type of cancer?
No. The study enrolls adults with a range of advanced solid tumors. Cancers listed for the study on ClinicalTrials.gov include melanoma, Merkel cell carcinoma, cutaneous squamous cell carcinoma, mesothelioma, non-small cell lung cancer, head and neck squamous cell carcinoma, kidney, cervical, bladder and microsatellite-stable colorectal cancers. Current expansion cohorts focus on skin cancers, and the study team can confirm which cohorts are open.
How is VET3-TGI given?
Depending on the study group, VET3-TGI is given either by injection directly into a tumor (intratumoral) or by infusion into a vein (intravenous). Some groups receive VET3-TGI alone, and others receive it together with atezolizumab given by intravenous infusion.
Who is sponsoring the trial?
KaliVir Immunotherapeutics, the developer of VET3-TGI, sponsors the study. It is registered on ClinicalTrials.gov under the identifier NCT06444815.
Where can patients enroll?
The study is recruiting at cancer centers across the United States; see Study sites above. To ask about eligibility or the nearest site, contact the study team, or see current site contacts on ClinicalTrials.gov.
Contact
Talk with the study team
Patients and caregivers
Ask whether STEALTH-001 may be an option, and talk with your oncologist about it.
clinicaltrials@kalivir.comPhysicians and referring sites
Refer a patient, request the protocol synopsis or ask about becoming a site.
medinfo@kalivir.comImportant information
About this study and this page
Investigational product
VET3-TGI is an investigational product. It has not been approved by the U.S. Food and Drug Administration or any other regulatory authority, and its safety and effectiveness have not been established. Nothing on this page should be read as a claim that VET3-TGI is safe or effective for any use.
Regulatory oversight
STEALTH-001 is conducted under an Investigational New Drug application with the FDA.
Not medical advice
This page provides general information about a clinical study. It is not medical advice and does not replace a conversation with your doctor. Decisions about your care and about joining a study should be made with your healthcare provider.
Eligibility and enrollment
The criteria shown are a summary. Eligibility is decided by the study doctor using the full protocol criteria. Meeting the criteria listed here does not guarantee enrollment, and not every site enrolls every cohort.
Voluntary participation
Taking part is voluntary. If you join, you may withdraw at any time without penalty or loss of benefits to which you are otherwise entitled. The possible risks and benefits, including the possibility that you may not benefit, will be explained to you during the informed consent process.
Your privacy
Information you share when contacting the study team is used to respond to your inquiry and, with your permission, to connect you with a study site. It is handled in accordance with our Privacy Policy. Please do not send detailed medical records by email. [Confirm with Privacy counsel.]
Medical emergencies
Do not use this page or the study contacts for urgent medical needs. If you have a medical emergency, call 911 or your local emergency number.
Source of information
Study details are summarized from the ClinicalTrials.gov record for NCT06444815 and are current as of October 26, 2026. For the most current information, see ClinicalTrials.gov.
Trademarks
TECENTRIQ® (atezolizumab) is a registered trademark of Genentech, Inc., a member of the Roche Group. VET™ is a trademark of KaliVir Immunotherapeutics, Inc.
Page last updated October 26, 2026