A vaccine designed to wake up the immune system against cancers that already exist
In a quiet but consequential shift in the long war against cancer, a Paris-based biotech has moved from laboratory promise to human trial with a vaccine designed not to prevent HPV-related cancers, but to confront them after they have already taken root. TheraVectys enrolled its first patient in October 2024, testing Lenti-HPV-07 across U.S. cancer centers with 36 patients whose tumors have resisted prior treatment. The effort draws on two decades of immunological research at the Pasteur Institute, asking whether the immune system — properly awakened — can still turn the tide against cancers it once failed to stop.
- Patients with recurrent or metastatic HPV cancers who have exhausted standard treatments, including immunotherapy, now represent the trial's most urgent test case — people for whom few options remain.
- Preclinical results were striking enough to accelerate human trials: 100% tumor elimination across all animal models, with metastases cleared and immune memory sustained long after treatment.
- The vaccine's lentiviral delivery system — refined over nearly two decades and previously tested in an HIV trial without serious side effects — offers a safety profile that regulators and researchers are watching closely as doses escalate.
- A key tension runs through the trial design: the vaccine must prove it can do what checkpoint inhibitors alone could not, while also showing it amplifies their effect when the two are combined.
- Early immune response data is expected within months of final injections, and those numbers will determine whether this approach advances — or joins the long list of promising therapies that did not survive contact with human biology.
A Paris-based biotech called TheraVectys has enrolled its first patient in a human trial of a vaccine built not to prevent cancer, but to treat it. Lenti-HPV-07 targets cancers caused by human papillomavirus — responsible for nearly all cervical cancers and many throat and anal cancers — and is designed to activate the immune system against tumors that have already formed. The trial, which began in early October 2024, will include 36 patients at multiple U.S. cancer centers.
This is a therapeutic vaccine, not a preventive one, and the distinction matters. The HPV vaccines most people know train the immune system to block infection before it begins. Lenti-HPV-07 is aimed at a harder problem: waking up an immune system that has already failed to stop a growing cancer. It targets two patient groups — those with recurrent or metastatic disease who have tried and failed multiple prior treatments, and newly diagnosed patients with locally advanced cancers who have not yet begun standard care.
The vaccine's underlying technology was developed over nearly two decades at the Pasteur Institute. It uses a modified lentiviral vector — stripped of its ability to cause disease — to deliver genetic instructions into dendritic cells, the immune system's messengers. Those cells are then prompted to display fragments of HPV proteins from the two strains most linked to cancer, triggering cytotoxic T cells to seek out and destroy cells carrying those same viral markers.
In animal studies published in 2023 and 2024, a single injection eliminated tumors completely in every treated subject, cleared metastases, and produced lasting immune memory. When paired with anti-PD1 immunotherapy drugs, effectiveness increased roughly fourfold over the drug alone — a synergy the human trial is designed, in part, to explore.
The trial will proceed through careful dose escalation, monitoring safety before advancing to higher doses. TheraVectys has prior safety data from a five-year HIV vaccine trial using similar lentiviral technology, which found no serious side effects or genetic damage. The current vaccine uses a non-integrative vector, meaning it does not insert itself into the patient's DNA. Preliminary safety and immune response data are expected within months of the final injections in each patient group — and what those early numbers show will determine what comes next.
A Paris-based biotech company called TheraVectys has enrolled its first patient in a human trial of a vaccine designed not to prevent cancer, but to treat it. The vaccine, called Lenti-HPV-07, targets cancers caused by human papillomavirus—the virus responsible for nearly all cervical cancers and many throat and anal cancers. The trial began in early October 2024 and will eventually include 36 patients across multiple cancer centers in the United States.
What makes this moment significant is the shift in approach. The HPV vaccines most people know—the ones given to teenagers—work by preventing infection in the first place. They train the immune system to recognize and block the virus before it takes hold. Lenti-HPV-07 does something different. It is meant to wake up the immune system against cancers that already exist, tumors that have already formed and grown inside the body. This is a therapeutic vaccine, not a preventive one, and it targets a population with few good options: people whose HPV-related cancers have come back after treatment, or who have never been treated at all but have advanced disease.
The trial is structured in two arms. One group consists of patients with recurrent or metastatic cancers who have already tried multiple treatments, including immunotherapies, and failed. These patients will receive two injections of the vaccine, spaced a month apart. The second group will be newly diagnosed patients with locally advanced cancers who have not yet received any treatment. They will receive a single injection, then move on to standard care—often including anti-PD1 drugs, a class of immunotherapy that has become common in cancer treatment.
The vaccine itself is built on technology developed over nearly two decades at the Pasteur Institute in Paris. It uses a lentiviral vector—a modified virus stripped of its ability to cause disease but still capable of delivering genetic instructions into cells. The vector is designed to interact with dendritic cells, which are the immune system's messengers. Once inside these cells, the vector causes them to display fragments of HPV proteins, specifically the E6 and E7 antigens from HPV-16 and HPV-18, the two strains most commonly linked to cancer. This display triggers a strong response from cytotoxic T cells, the immune system's assassins, which then hunt down and kill cancer cells bearing those same viral proteins.
In preclinical studies published in 2023 and 2024, the vaccine performed remarkably well in animal models. A single injection eliminated tumors completely in 100 percent of treated animals, regardless of tumor size. It also cleared metastases—cancer that had spread to other parts of the body—in every case. The immune response lasted a long time, reducing the risk of relapse, which accounts for a large share of cancer deaths. When combined with anti-PD1 drugs in animal studies, the vaccine's effectiveness increased roughly fourfold compared to the drug alone.
The human trial will unfold in two phases. First comes dose escalation, where researchers will gradually increase the amount of vaccine given to successive groups of patients, carefully monitoring safety after each dose before moving to the next. Once 18 patients in each arm have received treatment and safety looks acceptable, the trial will expand to treat 18 additional patients at what researchers call the optimal biological dose. In total, 72 patients with HPV-positive cancer will eventually be enrolled.
TheraVectys has some safety data to draw on. The company previously conducted a five-year clinical trial of a similar lentiviral vaccine targeting HIV-1. That trial found no serious side effects or genetic damage. The current HPV vaccine uses a non-integrative lentiviral vector, meaning it does not insert itself into the patient's DNA, which adds another layer of safety assurance.
The trial represents the culmination of more than two and a half years of preparation—regulatory discussions with the FDA, vaccine manufacturing, preclinical testing, and site selection. Christian Bréchot, the medical director of TheraVectys and a former leader of the Pasteur Institute, called the enrollment of the first patient a key milestone. Pierre Charneau, the founder and head of the joint laboratory at Pasteur, said the company expects preliminary safety and immune response data a couple of months after all patients in one group receive their final injection. What happens next depends on what those early results show.
Citas Notables
The inclusion of the first patient represents a key milestone for TheraVectys. It is the achievement of more than 2.5 years of preparation, from first interaction with the FDA, production of the vaccine, performance of the preclinical studies, review and approval by the regulatory authorities till sites preparation.— Christian Bréchot, Medical Director of TheraVectys
With the launch of this study, we are proud to bring our product to a new phase of its development. We expect the preliminary results on safety and immunogenicity a couple of months after all patients in one group will have received their last injection.— Pierre Charneau, head of the Pasteur-TheraVectys Joint Laboratory
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Why does a therapeutic vaccine for existing cancer matter when we already have preventive vaccines?
The preventive vaccines work brilliantly for people who haven't been infected yet. But they do nothing for the millions of people who already have chronic HPV infection or established tumors. This vaccine is for them—it's trying to teach the immune system to recognize and kill cancer cells that are already there.
The preclinical data sounds almost too good—100 percent tumor elimination. What's the catch?
Animal models are not human bodies. The immune system in mice behaves differently than in people. What works perfectly in a controlled lab setting often faces unexpected obstacles in real patients—other diseases, medications, individual variation in immune response. That's why this trial exists.
Why use a lentiviral vector instead of something newer, like mRNA?
The company's own research suggests lentiviral vectors are more effective against large, established tumors. mRNA vaccines showed promise in preclinical work, but they struggled with bigger tumors and had high relapse rates. The lentiviral approach seems to create a longer-lasting immune memory, which matters for preventing cancer from coming back.
What happens to the patients in Group A—the ones who've already failed multiple treatments?
They're the hardest cases. Their cancers have already outsmarted conventional chemotherapy and immunotherapy. If this vaccine works for them, it would be genuinely transformative. If it doesn't, they're no worse off than they were before, but they've contributed to understanding whether the approach has merit.
How long until we know if this actually works?
The trial will follow patients for a year. Preliminary safety and immune response data should come within a couple of months after the last patient in a group receives their final injection. But real efficacy—whether tumors actually shrink or disappear—will take longer to assess and will likely require follow-up beyond the formal trial period.