A PET-CT scan indicates one patient’s partial response to the in situ vaccination after six months. as shown in pre-vaccine, left, and six months post-vaccine.
Researchers at the Icahn School of Medicine at Mount Sinai are pioneering two novel approaches to cancer immunotherapy that are promising for patients with non-Hodgkin lymphoma and other solid tumors, which have been stubbornly resistant to therapies such as checkpoint blockade.
One new approach is an in situ vaccination that worked so well in patients with advanced-stage lymphoma that it is now undergoing trials for breast cancer, as well as head and neck cancers. The other therapy captures the synergy of checkpoint blockade and stem cell transplantation in the form of a highly promising treatment known as immunotransplant. Joshua Brody, MD, Director of the Lymphoma Immunotherapy Program and Assistant Professor of Medicine (Hematology and Medical Oncology) at The Tisch Cancer Institute at Mount Sinai, is the lead investigator for both therapies.
The In Situ Vaccination
This vaccination approach involves injecting immune stimulants directly into a single tumor site, which “teaches” the immune system to recognize and destroy cancer cells at that site and throughout the body. “We’re teaching dendritic cells—the generals of the immune system army—to specifically recognize tumor antigens, which then instruct the T cells, the immune system’s soldiers, to go forth and kill the cancer cells while sparing non-cancer cells,” says Dr. Brody.
As reported in the April 2019 issue of Nature Medicine, this therapy involves several steps that begin with injection of a small molecule that calls the dendritic cells to action, followed by low-dose radiation to kill the tumor cells. These dying cells, in turn, release antigens into the immune system that are recognized by the dendritic cells and presented to the T cells as part of the “coaching” process.
The results were encouraging among a cohort of 11 patients with non-Hodgkin lymphoma. In earlier tests with lab mice, the vaccine was able to cure about 40 percent of lymphoma tumors, Dr. Brody says. When combined with checkpoint blockade, the cure rate nearly doubled. Dr. Brody reports that when testing the therapy in patients, “We saw some who had profound regressions of their entire tumor burden. After treating one site, tumors throughout the body melted away.”
The next step in the development of the vaccine began last spring when Mount Sinai began recruiting patients for a clinical trial that combines the vaccine therapy with checkpoint blockade—a widely used treatment that effectively removes the brakes from T cells so they are free to attack cancer cells. This trial will target lymphomas, as well as breast cancer and head and neck cancers.
Immunotransplant Therapy
While PD-1 blockade has been effective for some lymphoma patients, its ability to help those with non-Hodgkin lymphoma has been more challenging. Even anti-PD-1/anti-CTLA4 dual checkpoint blockade has yielded limited efficacy, perhaps due to insufficient T cell activation.
Recently, Dr. Brody and his team found that combining immunotherapy and stem cell transplantation may be beneficial. In this first-of-its-kind approach, reported in Cancer Discovery, the researchers were able to increase the cancer-killing immune response tenfold when tested in the lab, making it effective against not just non-Hodgkin lymphoma but also melanoma and lung cancer.
“In the lab, immunotransplant either prolonged survival greatly compared to immunotherapy alone or actually cured a significant portion of mice with melanoma and lung cancer,” Dr. Brody says.
Immunotransplant works through the principle of homeostatic proliferation: when T cells are put into an empty organism or body, they become activated and begin to wildly multiply. In immunotransplant, T cells are withdrawn from the blood through apheresis, clearing the way for their reintroduction as infused immune cells. As they proliferate, these reinvigorated T cells build the immune system back up, become activated, and enable checkpoint blockade to achieve its full cancer-fighting potential.
The fact that checkpoint blockade has become the standard of care for treating melanoma, kidney cancer, lung cancer, and other diseases underscores the promise of immunotransplant. “We’ve shown we can increase the power of checkpoint blockade immunotherapy to prolong survival and induce cures in aggressive cancers, and that means not just lymphomas but solid tumor types,” says Dr. Brody.