Researchers praise ‘stunning’ results of new prostate cancer treatment | Prostate cancer

A new drug for advanced prostate cancer has shown promise in early trials, with the drug shrinking tumors in some patients, experts say.

Prostate cancer is the most common cancer among men in many countries, including the United States and the United Kingdom. Around 1.5 million men are diagnosed each year worldwide.

The new drug has generated excitement because it is a type of treatment called immunotherapy. This approach uses the body’s immune system to fight disease and has already been shown to be beneficial for some cancers. However, experts note that its impact has not yet been the same on prostate cancer.

Today, scientists reported results from a preliminary trial of an immunotherapy drug called VIR-5500, suggesting it could offer hope to men with advanced prostate cancer.

“We believe that such treatments could, in the long term, lead to cures,” said Professor Johann de Bono of the Institute of Cancer Research and the Royal Marsden NHS Foundation Trust, who led the work.

De Bono said VIR-5500 was an artificial antibody that brought together the body’s killer T cells with tumor cells trying to escape them. This type of drug, called a T cell engager, allowed the killer cells to eliminate those in the tumor.

What’s special about VIR-5500, De Bono added, is that it was designed to be activated only within the tumor. This not only minimized side effects – an important consideration because other T-cell activators have been shown to trigger severe inflammatory responses in prostate cancer patients – but also allowed the drug to persist in the bloodstream, meaning fewer doses may be needed.

In the phase one clinical trial, funded by Vir Biotechnology, 58 men with advanced prostate cancer who were no longer responding to other treatments received VIR-5500.

Researchers found that the majority of patients – 88% – experienced only very mild side effects.

They then looked at the level of prostate-specific antigen (PSA) in the men’s blood – a biomarker that higher levels may be a sign of prostate conditions.

De Bono noted that the trial began with low doses, with the dose increasing in stages. When the team looked at data from 17 men who received the highest dose, they found that 14 (82%) had their PSA levels drop by at least half after treatment, nine (53%) saw their PSA levels drop by at least 90%, and five (29%) experienced a drop of at least 99%.

De Bono described the results as unprecedented for a disease previously thought to be “immune-cold,” meaning resistant to immunotherapy.

The team added that of 11 patients who received the highest dose and whose tumors were measurable, five had tumor shrinkage. In one case involving a 63-year-old man whose cancer had spread to his liver, the team found 14 liver cancer lesions “completely resolved” after six cycles of treatment.

The findings, which have not yet been peer-reviewed, were presented at the American Society of Clinical Oncology’s Genitourinary Cancers Symposium in San Francisco.

De Bono said further clinical trials were now planned. “We need more data, but the results are stunning,” he said.

Charlotte Bevan, professor of cancer biology at Imperial College London, who was not involved in the work, said advances in the use of immunotherapy for prostate cancer were potentially very exciting, paving the way for a new class of drugs. But, she added, it was important for studies to be done with patients of different ethnicities because there are disparities in prostate cancer outcomes.

Simon Grieveson, deputy director of research at Prostate Cancer UK, described the early phase trial as exciting.

“With more than 12,000 men dying from prostate cancer in the UK each year, we urgently need new and innovative ways to treat this disease,” he said.

“These initial results are extremely promising, with a number of men in the study responding positively to the treatment with minimal side effects. I look forward to seeing this now tested in larger trials, in the hope that this treatment will offer men more valuable time with their loved ones.”