Early data from a St. Louis clinical trial are giving one of medicine's toughest cancers a rare bit of good news, as researchers report that a made-to-order DNA vaccine for glioblastoma appears safe and may be nudging outcomes in the right direction.
Last Tuesday, investigators released first-in-human results showing that a personalized vaccine could reliably stir up immune responses against glioblastoma, a notoriously aggressive brain cancer with few effective options. The phase 1 study was small, and no one is calling it a cure, but one participant is still recurrence-free nearly five years after surgery, and the overall numbers were strong enough to get the field's attention.
Small Trial, Big Signals
The GT-20 phase 1 trial enrolled nine adults with newly diagnosed glioblastoma whose tumors had an unmethylated MGMT promoter, a group that typically responds poorly to standard treatment. Each participant received a custom-built DNA vaccine called GNOS-PV01 that can encode up to 40 tumor-specific neoantigens.
Investigators reported six-month progression-free survival and 12-month overall survival in two-thirds of patients. Median progression-free survival was 8.5 months, and median overall survival was 16.3 months, with 24-month survival at 33 percent. The safety profile showed no unexpected serious side effects, which is critical for a treatment layered on top of surgery, radiation and chemotherapy. Full details appear in a paper published last Tuesday in Nature Cancer.
How The Vaccine Works
The approach leans into extreme personalization. Researchers sequence each patient's tumor, then use that information to design a bespoke DNA plasmid that encodes dozens of neoantigens unique to that cancer. The plasmid is delivered into muscle with the help of electroporation. Patients also receive a second plasmid that encodes the immune-stimulating molecule interleukin-12 to amplify the response.
"We are extremely encouraged by these results," said lead author Tanner M. Johanns, MD, PhD, in a news release from WashU Medicine. Study authors say that by targeting up to 40 neoantigens at once, the vaccine gives the immune system many different ways to recognize and attack cancer cells, which in theory makes it harder for tumors to slip away by losing a single target.
A St. Louis Patient's Long Survival
One story out of the trial hits especially close to home for the local team. Kim Garland, who lives in Kirkwood, Missouri, had a 6.5-centimeter brain tumor removed in 2021 and later received the personalized vaccine as part of GT-20. She remains without recurrence nearly five years after surgery.
Before her diagnosis, Garland was noticing subtle but unsettling lapses. "I was forgetting things, things that should have been very obvious," she told WashU Medicine, recalling the early symptoms that eventually led to imaging and surgery. Investigators are quick to point out that her experience is a single long-term outcome in a very small, early-stage trial, not proof that the vaccine can reliably deliver similar results.
What's Next
Researchers and outside experts alike are stressing caution. GT-20 was a phase 1 study built to test safety and feasibility, not to settle questions about survival. The results now need to be checked in larger, randomized trials and in combination with other immunotherapies.
WashU has already opened a follow-up phase 1 trial that pairs the personalized vaccine with the PD-1 antibody retifanlimab, listed on ClinicalTrials.gov. In the Nature Cancer report, the team also flags a practical hurdle that will have to be solved for any future rollout: making highly customized vaccines quickly enough and at scale for real-world use.
They are not the only ones chasing better glioblastoma treatments. Multiple companies have pushed new programs into early testing, including BioLineRx with its agent GLIX1 and EnGeneIC with an EGFR-targeted EDV therapy, signaling a busy and competitive early-stage landscape for brain cancer immunotherapy.
Cautious Optimism
For patients and clinicians who live in the shadow of glioblastoma's grim statistics, the message from St. Louis is cautiously hopeful. The GT-20 data show that a fully personalized DNA vaccine can be manufactured, given safely and used to generate immune responses against a long list of tumor-specific targets. What it does not do, at least not yet, is change the standard of care.
Even so, the story has escaped the confines of academic journals. Coverage of the findings, including a short segment by CBS News New York, has put a spotlight on the St. Louis research team and on the broader effort to finally make immunotherapy pay off for brain tumors. For a disease that rarely gets to celebrate wins, even early ones, that attention is part of the impact.
