Merck’s Dr. Laura Greene Leads Final 2025 Summer Webinar
Two years ago, when Dr. Laura Greene, DVM, DACVIM, Senior Professional Services Veterinarian for Merck Animal Health, spoke about immunotherapy as part of the ACCC Summer Webinar Series, she reported that eight checkpoint inhibitors had been approved by the FDA for cancer therapy in humans. Today, 14 different checkpoint inhibitor therapies are approved to treat over 20 different types of cancer in humans.
Merck Animal Health has received a USDA conditional license for the checkpoint inhibitor drug, gilvetmab, for the treatment of mast cell tumors and melanoma in dogs. Immunotherapy, explained Dr. Greene, is an incredibly powerful modality for treating cancer as it utilizes the body’s own immune defenses to precisely target and destroy cancers. Increasingly, the branch of immunotherapy is becoming a key pillar of therapy not only for humans but also for veterinary medicine.
The concept of checkpoint inhibitors centers on the body’s own response to pathogens, such as an infection. To fight against this foreign substance, T cells identify and then destroy the bad cells. As a result, those T cells increase until the pathogen is gone. Checkpoint molecules then move in to remove (or turn off) the T-cells that are no longer needed. Cancer cells, however, often know how to make their own ligand (molecules that bind to other molecules) to suppress T-cells, allowing the cancer cells to multiply. Checkpoint inhibitors prevent that process and make sure the T-cells continue to grow and fight off the cancer.
“Checkpoint inhibitors are monoclonal antibodies that help T cells to fight cancer,” said Dr. Greene. “The antibodies do not target the cancer specifically; rather, they prevent the cancer from turning off the immune system.”
Although the extent of the use of immunotherapy in animals has not caught up to human medicine yet, Dr. Greene expressed optimism about the future of cancer treatment as research continues to uncover more opportunities. The influence of a diverse gut microbiome, for example, is one area that may help improve the efficacy of checkpoint inhibitors. “The power of a diverse gut microbiome,” she said, “has interesting promises.”
She also explained the value of combining various treatment options to achieve maximum results. “Adding immunotherapy to the traditional pillars of treatment – chemotherapy, radiation, and surgery – gives dog owners a promising fourth option,” she said. “When we treat cancer, we’re always looking for a hero. We have so many more options today to provide a spectrum of care.”
She encouraged the veterinarians on the webinar to have honest and straightforward conversations with pet owners that go beyond the science and are inclusive of pet owner needs and the needs of the pet as an individual. Because as many as 45% of pet owners believe cancer treatment will be painful for their pet, there is an opportunity to reframe the conversation. She stressed the importance of discussing all factors related to each individual situation, including the pet’s lifestyle, how it reacts to vet visits, what is the owner’s work and personal schedule, what are the family’s priorities, and past experiences with and understanding of cancer. With all of these factors taken into account, the pet owner can have a clear view of their priorities for themselves and for their pet, which increases the value of the evidence-based medicine conversation they can have with a specially trained veterinary oncologist.
For more detailed information on immunotherapy, view Dr. Greene’s presentation HERE.