What is Keytruda used for in dogs?

In this article:

• What is Keytruda used for in dogs?
• Is Keytruda safe for dogs?
• Keytruda dosage for dogs
• Keytruda alternatives for dogs
• Summary

In this article

• What is Keytruda used for in dogs?
• Is Keytruda safe for dogs?
• Keytruda dosage for dogs
• Keytruda alternatives for dogs
• Summary

Keytruda (pembrolizumab) is a cancer immunotherapy drug used to treat human cancer, including melanoma, small-cell lung cancer, lymphoma, breast cancer, stomach cancer, esophageal cancer, cervical cancer, and many other types of cancer. The active ingredient in Keytruda is a monoclonal antibody. As an immune checkpoint inhibitor, pembrolizumab prevents cancer cells from blocking the immune system’s ability to kill off cancer cells. Veterinarians do not use Keytruda in dogs because it won’t work. However, the Food and Drug Administration has conditionally licensed a drug that works similarly called gilvetmab. The drug can be used by veterinary specialists in dogs with melanoma or mast cell tumors.

What is Keytruda used for in dogs?

Keytruda is not used in dogs. 

Instead, veterinarians can use a similar drug called gilvetmab, which works like Keytruda. The FDA has conditionally approved the use of gilvetmab in dogs with stage 2 or stage 3 melanoma or stage 1, stage 2, or stage 3 mast cell tumors. Cancer stages are determined by the depth of invasion (DOI) of the tumor and the spread of the cancer to the rest of the body (metastases). Higher stages represent deeper invasions and wider spread. 

Gilvetmab is still being studied in dogs, but clinical studies so far suggest it is highly effective and safe. At this time, gilvetmab can only be used by researchers and veterinary cancer specialists (oncologists). Regular veterinarians do not have access to this drug.

Pembrolizumab, the active ingredient in Keytruda, is a monoclonal antibody designed for humans and humans alone. It won’t work in other species. 

Monoclonal antibodies are designed to glue themselves to molecules on the surface of cells. They are big molecules, but only one part of the drug is designed to do the gluing. The rest is engineered to look like an antibody that a human body would produce. In that way, the immune system doesn’t attack the drug as if it were a foreign invader.

If Keytruda were injected into a dog’s bloodstream, the dog’s immune system would eventually destroy all the pembrolizumab in the injection. To work in dogs, the part of Keytruda that works has to look like a dog antibody. 

Researchers at Merck have done that. They’ve developed an antibody similar to pembrolizumab called gilvetmab. Like pembrolizumab, it is a PD-1 inhibitor. Both Keytruda and gilvetmab attach to a molecule called PD-1 that sits on the surface of immune cells called T cells. These are the immune cells that fight and destroy infections and cancers. This PD-1 receptor, however, works like an “off” button. Some cancers produce molecules that attach to PD-1 and shut down those killer immune cells. That’s good for the cancer but not so good for the person with cancer. By attaching to PD-1 receptors on immune cells, Keytruda and gilvetmab prevent cancer cells from turning these immune cells off, so the immune response against cancer remains robust. 

The good news is that researchers in veterinary medicine are working on producing canine versions of some of the best antibody drugs used in humans, like Humira or Cosentyx. Gilvetmab is one of the drugs. Though still in clinical trials, it works so well that veterinary oncologists can prescribe it for canine mast cell tumors and melanoma.

Is Keytruda safe for dogs?

Veterinarians do not use Keytruda in dogs. 

The veterinary version of Keytruda is gilvetmab. It is currently in clinical trials for dogs but has been made conditionally available to veterinary oncologists. At this point, the FDA considers it both effective and safe in dogs. In two studies, gilvetmab was found to be well-tolerated without any genuinely severe side effects or complications.

Side effects of Keytruda in dogs

Keytruda is not used in dogs, but Merck has developed a similar drug called gilvetmab.

In early rounds of clinical studies, the most common effects of gilvetmab were:

• Lethargy, lack of energy, fatigue
• Decreased appetite
• Gastrointestinal upset
• Weight loss
• Elevated liver enzymes
• Diarrhea
• Vomiting

No severe or life-threatening adverse effects were recorded in the two earliest clinical studies.

Interactions of Keytruda with other pet meds

Keytruda is not used in dogs, and gilvetmab, a veterinary version still in clinical trials, has not been studied in dogs taking other drugs.

Keytruda dosage for dogs

Keytruda is not used in dogs.

A veterinary version of Keytruda is in clinical trials. 

Doses are administered by veterinary specialists in oncology. Gilvetmab doses are given as a 30-minute intravenous infusion every two weeks for 10 treatments. About 15 to 30 minutes before the infusion, the veterinary oncologist will give the dog a shot of diphenhydramine, the active ingredient in Benadryl. After each infusion, the dog will need to be monitored for at least one hour.

Can dogs overdose on Keytruda?

Dogs are not given Keytruda. 

Gilvetmab, a new drug for dogs that works like Keytruda, has never been given as an overdose to dogs.

Can I give my dog Keytruda every day?

Keytruda is not given to dogs. 

A new veterinary drug similar to Keytruda is injected every two weeks.

How to give your dog Keytruda

Keytruda is not given to dogs.

Merck has a similar drug called gilvetmab that is still in clinical trials. Because it has worked so well in early clinical trials, the FDA has conditionally released it for use by veterinary oncologists.

To get treatment, take the dog to a veterinary cancer specialist. To locate a veterinary oncologist, visit the Veterinary Cancer Society or the ACVIM Vet Specialists site. Ask for a veterinary oncologist who is registered to order gilvetmab from Merck. Dog owners can also look for open clinical trials in their area.

The doses will be administered as intravenous injections by the veterinary specialist. Expect to spend at least two hours at the clinic, not including any waiting room time.

Keytruda alternatives for dogs

Keytruda is not used in companion animals. 

The alternative to Keytruda is a veterinary version still in clinical trials called gilvetmab. However, it may be hard to locate a nearby veterinary oncologist who can administer injections. The cost might also be a deterrent.

The standard cancer therapy for malignant melanoma in dogs is surgery. Dogs most commonly get malignant melanomas in their mouth (oral melanoma) or toes. When the toes are involved, amputation may be required. Surgery is followed by radiation therapy, chemotherapy, or immunotherapy treatment. Gilvetmab would be used as part of post-surgical treatment.

The standard cancer treatment for mast cell tumors in canine patients is surgical removal of the tumor cells, radiation therapy, and, if the cancer has spread, corticosteroids, chemotherapy, and targeted therapy with kinase inhibitors. Another treatment option is Stelfonta (tigilanol tiglate). Again, a dog would receive gilvetmab after surgery. 

Summary

Keytruda is not used in dogs, but dog owners can have their companion treated with a similar drug called gilvetmab. Clinical trials so far have shown it to be an effective and safe treatment for canine melanomas and mast cell tumors. It will take some work and investment. Only veterinary cancer specialists or veterinary cancer centers can purchase and administer the drug. Finding one might be difficult. There is currently no established price for gilvetmab, so the cost may vary between veterinary cancer centers.