A Phase 1/1b study of VET3-TGI given alone and with atezolizumab in patients with advanced solid tumors.
About the study
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
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
Schedules vary by group. Your study doctor will explain what participation involves before you decide.
Tests and a baseline scan to confirm the study is a good fit.
VET3-TGI weekly for 4 to 6 doses, depending on the group, sometimes with atezolizumab. Some visits include a tumor biopsy.
A scan at about week 8 to check how the cancer is responding.
Booster doses about every 2 weeks for patients who are benefiting, for up to 2 years, with scans every 8 to 12 weeks.
The study team continues to check on your health after treatment ends.
Eligibility
Key criteria only. The study team will review the full criteria with you and your doctor.
Locations
Not every site enrolls every cohort. Contact the study team to find the right site.
USC/Norris Comprehensive Cancer Center
Los Angeles, California
UC Irvine Health
Orange, California
University of Miami
Miami, Florida
Community Health Network
Indianapolis, Indiana
UPMC Hillman Cancer Center
Pittsburgh, Pennsylvania
Mary Crowley Cancer Research
Dallas, Texas
The University of Texas MD Anderson Cancer Center
Houston, Texas
Fred Hutch/University of Washington/Seattle Children’s Cancer Consortium
Seattle, Washington
Sites as listed on ClinicalTrials.gov, last updated April 2026.
FAQs
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.
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.
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.
KaliVir Immunotherapeutics, the developer of VET3-TGI, sponsors the study. It is registered on ClinicalTrials.gov under the identifier NCT06444815.
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
Ask whether STEALTH-001 may be an option, and talk with your oncologist about it.
Refer a patient, request the protocol synopsis or ask about becoming a site.
Important information
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.
STEALTH-001 is conducted under an Investigational New Drug application with the FDA.
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.
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.
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.
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.
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.
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.
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