According to the company, its DARRT-1 clinical study ended with a 27% incidence of abscopal response in soft-tissue lesions, using a combination of its Veyonda cancer drug and low-dose radiotherapy. An abscopal response involves radiation directed at a single tumor, triggering shrinkage of tumors well outside of the field of radiation.
A growing use of immuno-oncology drugs in combination with radiotherapy reportedly has led to increasing reports of abscopal responses in various cancers, including lung, breast, and urogenital cancers and melanoma.
However, before now, no such reports have come from studies in prostate cancer with checkpoint inhibitors either alone or in combination with radiotherapy, leading to this cancer gaining a reputation as a “non-immunological” cancer.
The DARRT-1 study involved 15 men with mCRPC post-taxane and ADT therapy; these patients received Veyonda, an experimental sphingosine-1-phosphate inhibitor, along with a palliative dose of external beam radiotherapy to a single tumor, typically a lymph node cluster. An abscopal response was determined on the basis of scans of other nonirradiated soft tissue lesions.
Graham Kelly, executive chairman and CEO of Noxopharm, told Outsourcing-Pharma that the results of the trial are promising and informative.
“While the mechanism behind it is yet to be fully explained, the growing evidence is that it has an immune basis,” he said. “It appears to stem from use of a low dose of radiation (such as is commonly used in palliative therapy) which inflames rather than destroys the irradiated tumor. That inflammation then triggers an immune response that surges throughout the body, seeking out and destroying all other cancer cells.”
Kelly added that to his knowledge, this study marks the first time that researchers have been successful in obtaining a meaningful abscopal response rate in prostate cancer.
“Prostate cancer has developed a reputation as a cancer with poor immune responsiveness, but this outcome suggests that this isn’t the case when a drug with the appropriate effect on the immune system is used. Today’s result positions Veyonda at the forefront of this emerging area of oncology and suggests that we have an exciting new prospective treatment for end-stage prostate cancer,” he said.