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Clinical Trial Tests New Combinations of Immunotherapy Drugs to Treat Osteosarcoma
Medications bring months more of life to dog Jelly Bean
May 6, 2022
Two-year-old Labrador Retriever cross, Jelly Bean

When Patricia and Zach Mendonca first noticed a bump on the back leg of their two-year-old Labrador Retriever cross, Jelly Bean, the trio began a string of appointments with their veterinarian and various specialists before she was diagnosed with osteosarcoma (bone cancer).

The Mendoncas followed the doctors’ recommendation to amputate Jelly Bean’s leg and start chemotherapy at Ocean State Veterinary Services in Rhode Island.

According to Patricia, “She bounced back from amputation so quickly, she practically ran to us after surgery.” Jelly Bean also tolerated chemotherapy well.

Osteosarcoma starts in the bone and can travel through the bloodstream. Despite chemotherapy treatment, within a few months x-rays revealed that the cancer had spread to Jelly Bean’s lungs. The doctors at Ocean State suggested looking into the clinical trials at Cummings School of Veterinary Medicine at Tufts University.

More than 35 veterinary clinical trials are in progress at Cummings School, exploring better treatment options for various forms of cancer, kidney disease, heart disease, arthritis, and neurological conditions.

Jelly Bean was accepted into the clinical trial, testing combinations of three immunotherapy medications to treat dogs with metastatic osteosarcoma with spread to the lungs. Cummings School jointly launched the trial with Colorado State University (running a parallel study) in 2018, funded by the National Cancer Institute’s Cancer Moonshot initiative.

“This clinical trial is entirely novel as there are few, if any, treatments that work in the setting of metastatic osteosarcoma,” explains Dr. Cheryl London, director of the Clinical Trials Office and associate dean for research and graduate education at Cummings School.

“In general, the response rate of osteosarcoma after it has failed standard chemotherapy is less than 10 percent. We have found that a triple drug combination of all oral medications has activity in about 60–70 percent of dogs with spread of osteosarcoma to the lungs.”

Typically dogs with osteosarcoma live only eight to ten weeks once the cancer spreads to the lungs, even with treatment.

“It’s devastating for owners to hear that their dog only has one or two months to live,” laments Natalie Smith, V20, specialty intern in Clinical Trials at Cummings School. “We’re trying to come up with treatment options to have more time—and more quality time—than eight to ten weeks.”

Smith explained that chemotherapy targets all the body’s rapidly dividing cells, impacting not just cancer cells, but cells in the bone marrow, stomach, and intestines too. 

“This is a unique combination of medicines that don’t kill cancer cells directly, but rather stimulates and retrains the dog’s immune system to kill the cancer cells itself,” Smith states.

The doctors closely monitor each dog’s response to the experimental medications. Dogs exit the trial if the drugs are not treating the cancer or make the dogs too sick.

“When a human gets cancer, the goal is to cure it whenever possible,” says Smith. “What’s unique about veterinary oncology is that you can’t tell animals what they’re going through and why. So the goal is always quality of life, even if it means potentially putting off quantity of life.”

To date, 43 dogs have participated in the study, with most lasting four months. Jelly Bean entered the trial in October 2020 and is now approaching her 18-month mark.

“I didn’t expect much to come of it,” Patricia admits. “But by December, it was our Christmas miracle.”

Within two months, the masses in Jelly Bean’s chest shrunk, and by March, they disappeared from her x-rays. 

“Jelly Bean has far exceeded the eight-to-ten week prognosis—that makes her an outlier in the best way possible,” Smith boasts. “She’s a long-term survivor with visible evidence that the medication is effectively killing the cells. I’m incredibly happy she’s doing so well, as she has entered uncharted territory.”

While the trial is still ongoing, the doctors reveal that the medications are stabilizing cancer in most of the dogs, giving them, on average, several more months of life, instead of several weeks.

“We’re hoping that the results of the trial will allow us to offer this combination of immunotherapy drugs as a widely available treatment option for dogs with metastatic osteosarcoma,” Smith contends.

This trial could potentially impact treatment for humans as well.

“We are transitioning this therapy to be used prior to the development of tumor spread to the lungs. Should it show activity in this setting, then it will likely be evaluated in human patients that develop osteosarcoma spread to the lungs,” London explains.

In the meantime, Jelly Bean continues with her monthly treatments. “Jelly Bean is a regular frequent flier there now,” says Patricia.

“We’re happy that Jelly Bean is feeling well and enjoying a good quality of life while we’re successfully treating her cancer,” says Smith.