Investigational drug PV-10 decreases melanoma cells in tumors

An investigational drug being studied for the treatment of melanoma has demonstrated a decrease of melanoma cells in both injected tumors and non-injected bystander tumors in mice.

PV-10, a 10 percent solution of rose bengal being studied by Provectus Biopharmaceuticals, was tested in eight patients with melanoma, according to a news release. Researchers with Moffitt Cancer Center found significant decreases in melanoma cells not only in the injected tumors, but also in the non-injected bystander tumors at seven to 10 days after PV-10 was injected. The decrease was confirmed by pathologic evaluation with immunohistochemical staining of biopsy specimens for melA.

The changes in the tumors were also accompanied by increased populations of CD3+, CD4+ and CD8+ T cells, as well as NKT cells in peripheral blood.

PV-10 was also found to be cytotoxic to B16 mouse melanoma cells, with minimal cytotoxicity to normal fibroblasts. Using PV-10 to treat B16 tumors in mice led to a release of HMGB1, a soluble damage associated molecule pattern crucial to activation of dendritic cells, according to the company. The dendritic cells from the mice were selectively active against B16 tumor cells. Treating the B16 tumors in mice with PV-10 led to an infiltration of dendritic cells to the lymph nodes draining the treated tumors.

“Ironically, the original aim of the trial to assess tumor-infiltrating lymphocytes was thwarted when biopsies of patient tumors collected just seven to 14 days after PV-10 injection no longer contained viable tumor tissue,” Shari Pilon-Thomas, Ph.D., a researcher at Moffitt, said in the news release. “We are following up both the human data and continuing to design more experiments in mice to better explain the systemic immune effects elicited by PV-10 ablation.”

The findings were presented recently in a poster presentation at the annual meeting of the American Association for Cancer Research in San Diego.