YourVaccx, a new type of cancer vaccine developed by ImmunSYS, is safe and shows promising effectiveness in patients with metastatic prostate cancer and other difficult-to-treat advanced solid tumors, a proof-of-concept study shows.
Study findings were presented in a poster titled, “Regression of metastatic cancer and abscopal effects following in situ vaccination by cryosurgical tumor cell lysis and intratumoral immunotherapy: A case series,” at the American Association for Cancer Research (AACR) 2020 Virtual Annual Meeting II, June 22-24.
YourVaccx uses a proprietary procedure developed by ImmunSYS that is designed to boost the activity of the immune system to fight cancer.
The therapy comprises two steps. First, a portion of the tumor is destroyed using a technique called local cryosurgical tumor cell lysis (disintegration), so that molecules found within the tumor are released to the exterior. These molecules will activate and instruct patients’ immune cells to attack the tumor.
A combination of three immunotherapy agents then are injected into the disrupted tumor, which is intended to block inhibitory signals from cancer cells that prevent the immune system from acting and to promote the proliferation of immune cells and their migration into cancer sites.
The combination of both techniques is expected to create a local, self-directed vaccine that triggers an abscopal effect — a phenomenon in which shrinkage of a tumor treated with local therapy results in the shrinkage of tumors found elsewhere in the body.
The company now has announced data from a proof-of-concept study (NCT03695835), where YourVaccx was used to treat 27 patients with metastatic cancers.
Most patients (21 of the 27 enrolled) had metastatic prostate cancer, while the remaining six had other types of equally advanced cancers, including bladder, colon, and pancreatic cancer.
All patients completed at least one treatment cycle that consisted of cryosurgical lysis of the tumor, followed by a local injection of a triple combination of immunotherapy medications — Yervoy (ipilimumab), Keytruda (pembrolizumab) or Opdivo (nivolumab), and Leukine (sargramostim) — into the disrupted tumor.
Opdivo, Yervoy, and Keytruda are immune checkpoint inhibitors that target proteins involved in the processes used by cancer cells to escape the immune system. Opdivo and Keytruda target the PD-1 protein on T-cells — immune cells with the ability to fight tumors — and prevent its interaction with PD-L1 in tumors, boosting anti-cancer responses. Yervoy targets the CTLA-4 protein also on T-cells, causing them to expand and become activated.
Leukine also is designed to boost immune system activity. It acts by stimulating the bone marrow to produce more white blood cells — the main cell type of the immune system — and typically is given to patients to restore cell numbers following chemotherapy.
The triple combo treatment was followed by a 30-day period in which patients received under-the-skin (subcutaneous) injections of Leukine.
All patients were assessed after completing the therapy, which varied from one to three cycles of treatment, spaced by intervals of at least one month. Three prostate cancer patients were excluded from the analysis due to lack of follow-up imaging data.
From the 24 eligible patients, 10 (42%) achieved significant reductions in tumor volume, including nine (38%) attaining a complete response (complete tumor elimination).
Among the 18 metastatic prostate cancer patients eligible for treatment efficacy analyses, nine (50%) achieved a complete response. Six additional patients (33%) experienced disease stabilization after receiving the treatment.
Most responses were durable, with five of the nine patients who responded to treatment maintaining responses that lasted from one to more than 4.5 years.
Treatment also was found to lower the levels of the prostate specific antigen (PSA), a marker of prostate cancer, by at least 50% in more than half (62%) of the patients who participated in the study.
The therapy was generally safe and well-tolerated. Three patients with prostate cancer experienced six severe or life-threatening adverse events (side effects). No treatment-related deaths were reported during the study.
“We are pleased to present these encouraging findings at the AACR virtual annual meeting II,” Eamonn Hobbs, chairman and CEO of ImmunSYS, said in a press release.
“These results demonstrate long-term, durable responses, ranging from 1 to 4.5 years, and a favorable tolerability profile in tough-to-treat patient populations. There is an unmet need for effective treatment options for patients with metastatic cancers and these data demonstrate the potential that YourVaccx has to significantly improve the lives of patients,” Hobbs said.