A 28-person company in Pittsburgh is teaching smallpox's cousin to do something new: travel through the bloodstream, find a tumor, and unload cancer therapy on arrival.
The virus that ended smallpox, photographed here as a corporate logo - now retrained, edited gene by gene, to hunt the disease vaccines never could.
Here is a fact that should be more famous than it is: the hardest problem in cancer virotherapy was never killing the tumor cell. Viruses are extraordinarily good at bursting cells open - that is, essentially, their entire job description. The hard part was getting the virus to the tumor in the first place. Inject an oncolytic virus into a vein and the body, which has spent a few hundred million years learning to clear viruses from the blood, clears it in minutes. So for years the field mostly gave up on the vein and used the needle instead, injecting viruses directly into tumors a doctor could see and reach.
Which is fine, if your cancer politely stays in one visible place. Cancer, notoriously, does not. It metastasizes. It hides. The tumors that kill people are frequently the ones you cannot get a needle into.
KaliVir Immunotherapeutics, founded in Pittsburgh in 2019, was built around solving the vein problem. Its platform - the Vaccinia Enhanced Template, or VET - is a set of genetic modifications layered onto vaccinia virus, the same viral family used in the vaccine that eradicated smallpox. The point of all that editing is to make a virus that survives systemic, intravenous delivery, replicates selectively once it reaches a tumor, and then - because vaccinia has an unusually large genetic cargo hold - expresses therapeutic payloads right there inside the cancer.
That tagline is doing real work. The company's lead internal candidate, VET3-TGI, doesn't just kill tumor cells. On the way out it delivers interleukin-12 (IL-12), a signal that wakes up the immune system, plus a TGF-β inhibitor, which stops the tumor from quietly putting that immune response back to sleep. It is, in effect, a coordinated three-part attack encoded into a single virus's DNA: destroy the cell, ring the alarm, and jam the snooze button. The elegance is in the combination, not any one part of it.
There is a nice conceptual trick underneath all of this. Cancer immunotherapy - the revolution that reshaped oncology over the past decade - only works when the immune system can actually find the tumor. Many tumors are "cold": immunologically invisible, ignored. KaliVir's whole thesis is to use the virus as a flare. Infect the tumor, trigger inflammation, turn the microenvironment "hot," and suddenly the immune system knows exactly where to look. Sometimes the breakthrough is not a new drug. It is a better spotlight.
The Vaccinia Enhanced Template integrates multiple genetic modifications to maximize viral replication, enable intravenous delivery, and express therapeutic transgenes matched to a tumor's immunophenotype.
KaliVir's internal lead. Destroys tumor cells while activating the immune system through a payload combining IL-12 and a TGF-β inhibitor. Now in the STEALTH-001 study for advanced solid tumors.
Formerly VET2-L2. A systemic oncolytic vaccinia virus delivered intravenously, expressing a Leptin-IL2 fusion protein payload. Licensed to and led by Astellas Pharma; cleared for Phase 1 in 2023.
A 28-person company partnered with both Astellas and Roche is, on its face, an anomaly. The explanation is platform depth. When you solve a problem the whole field is stuck on - systemic oncolytic delivery - the licensing calls come to you.
Holds a worldwide exclusive license to develop and commercialize KaliVir's initial lead candidate, VET2-L2 (now ASP1012), a systemic oncolytic vaccinia virus in Phase 1 trials.
Signed a May 2022 global exclusive licensing and collaboration agreement for VET-derived oncolytic viruses. In November 2025, agreed to evaluate VET3-TGI in combination with atezolizumab (Tecentriq).
CEO Helena Chaye holds both a Ph.D. and a J.D. and brings more than 23 years in virotherapy across Jennerex, MediGene and SillaJen. Co-founder and CSO Stephen Thorne has now co-founded four oncolytic virus companies - Jennerex, Western Oncolytics, BioEclipse and KaliVir. There is a pattern in biotech: the people who lived through the first generation's mistakes tend to build the second generation's winners.
Stephen Thorne co-founds KaliVir in Pittsburgh to develop oncolytic viral immunotherapies on the VET platform.
Closes a $15M Series A led by South Korean VCs in March, then signs a global exclusive licensing agreement with Roche in May.
FDA clears the IND for systemic oncolytic virus ASP1012, partnered with Astellas, for Phase 1 trials in solid tumors.
FDA clears the IND for lead candidate VET3-TGI, three new U.S. patents issue, and the STEALTH-001 study begins.
Announces a collaboration with Roche to test VET3-TGI in combination with atezolizumab (Tecentriq).
It is a clinical-stage biotech developing oncolytic viral immunotherapies for cancer using its proprietary Vaccinia Enhanced Template (VET) platform, which engineers vaccinia viruses to be delivered intravenously and to express therapeutic payloads inside tumors.
The Vaccinia Enhanced Template platform integrates multiple genetic modifications into vaccinia virus to maximize replication, enable systemic (intravenous) delivery, and express therapeutic transgenes matched to a tumor's immunophenotype.
KaliVir has global exclusive licensing and collaboration agreements with Astellas Pharma (for ASP1012) and Roche (for VET-derived oncolytic viruses, including a combination study of VET3-TGI with atezolizumab).
VET3-TGI is KaliVir's internal lead oncolytic immunotherapy candidate, designed to destroy tumor cells while activating the immune system through a payload combining interleukin-12 (IL-12) and a TGF-β inhibitor. It is in the Phase 1 STEALTH-001 study.
KaliVir closed a $15 million Series A financing in March 2022, led by a syndicate of South Korean venture capital firms including Premier Partners, Company K Partners and Quad Investment Management.