28th of February, 2026
A novel immunotherapy medication has demonstrated potential for effectively addressing prostate cancer, according to findings from a phase I trial.
Promising Immunotherapy Results
Nearly half of the participants in the trial who were assessable showed a reduction in their tumors after using the medication, and most of the individuals noted a significant decrease in a prostate cancer marker. The researchers were encouraged to find that the vast majority of patients only faced very mild adverse effects.
The phase I study encompassed 8 locations globally and is directed by Professor Johann de Bono at The Institute of Cancer Research in London and The Royal Marsden NHS Foundation Trust.
T cell activator
Phase I Trial Overview
The findings from the study, which received funding from Vir Biotechnology, are showcased at the American Society of Clinical Oncology (ASCO) Genitourinary Cancers Symposium.
The study evaluated the efficacy of the new VIR-5500 medication in 58 individuals suffering from advanced prostate cancer that had ceased to respond to previous therapies. The purpose of the study was to assess the drug’s safety and identify the optimal dosage for administration to patients.
The groundbreaking medication functions as a T-cell engager, connecting to the immune T-cells in the body as well as to prostate-specific membrane antigen (PSMA), which is found on the exterior of cancerous cells.
Patient Outcomes and Side Effects
Stealth technology
It attaches to cancer cells throughout the body and brings T-cells into proximity with them, enhancing their ability to attack. Additionally, it features a cloaking mechanism that keeps it concealed and inactive until it reaches the tumor, which helps minimize side effects. Furthermore, it enables the medication to remain in the bloodstream longer, potentially reducing the number of doses required for patients.
T-cell engagers have previously caused significant inflammatory reactions in patients with prostate cancer, as they stimulate the immune system throughout the body. However, due to the cloaking mechanism, 88 percent of patients did not face the typical treatment-related side effects associated with T-cell engagers.
Research Leadership and Funding
Prostate-specific antigen (PSA) serves as a disease marker that may be elevated in individuals with prostate cancer. Among the 17 patients who were evaluated and received the highest dose of VIR-5500, 82 percent (14 patients) experienced a reduction in their PSA levels by half, while 53 percent (nine patients) saw a 90 percent decrease in their PSA levels.
Reduces the size of tumors
Among the 11 patients who received the highest dose and were assessable, 45 percent (five patients) showed a reduction in their tumours following treatment. Imaging revealed that tumours had diminished in various locations throughout the body, including within the internal organs.
Research suggests that over 75% of the 10,000 men diagnosed annually with advanced prostate cancer have tumors exhibiting elevated PSMA levels, making them likely candidates for the treatment.
'The final blow'
Professor Johann de Bono, the Regius Professor of Cancer Research at The Institute of Cancer Research in London and a Consultant Medical Oncologist at The Royal Marsden NHS Foundation Trust, remarked:
“T-cell engagers enable the immune system to target cancer cells effectively, delivering a lethal blow. It’s truly astonishing to observe early indications that this T-cell engager medication may significantly benefit patients with advanced prostate cancer, who are in urgent need of innovative therapies.
“It’s encouraging to note that only a small number of patients have encountered significant side effects, as this has historically been a major hurdle in the delivery of immunotherapies for prostate cancer treatment.”
“This clinical study is currently in progress, and the medication will advance to larger trials to examine its impact on the long-term outcomes for patients. There is certainly optimism that treatments like this could enhance the chances of a cure, even for advanced prostate cancer that has already metastasized, in the near future.”
Professor Kristian Helin, the Chief Executive of The Institute of Cancer Research in London, remarked:
“Immunotherapy has revolutionized outcomes for numerous individuals battling cancer, yet its advantages have frequently been elusive for those with prostate cancer. It is heartening to witness this groundbreaking method demonstrating encouraging results in preliminary clinical trials, and I eagerly anticipate its ongoing progress. I am hopeful that VIR-5500 could provide a new therapeutic option for patients with advanced prostate cancer, who are in dire need of more effective treatments.”