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The Daily Vet by petMD

The Daily Vet is a blog featuring veterinarians from all walks of life. Every week they will tackle entertaining, interesting, and sometimes difficult topics in the world of animal medicine – all in the hopes that their unique insights and personal experiences will help you to understand your pets.

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I’ve just returned from Minneapolis after attending the Veterinary Cancer Society’s (http://www.vetcancersociety.org) annual conference and wanted to share an exciting new treatment option for dogs with cancer.

The Veterinary Cancer Society (VCS) is a professional organization dedicated towards advancing cancer care for pets and includes a membership of over 800 specialists in medical, surgical, and radiation oncology plus internists, pathologists, pharmacologists, general practitioners, interns, and residents. Once a year we all gather to attend dozens of presentations on the ongoing research studies at various institutions throughout the world for pets with cancer.

Topics vary, but typically include clinical trials, retrospective studies, and basic science experiments. This year’s conference was heavily centered on the latter. For oncologists such as myself working in private practice, science experiments, though interesting, are hardly practical for me in my day-to-day endeavors. It takes a great deal of time to translate what goes on in petri dishes to practical use in the veterinary hospital, but it’s good to keep current, nonetheless.

However, such research is exactly what led to the development of this new treatment I am excited to discuss, highlighting its importance, even when the immediate relevance is not apparent.

One of the most interesting take-home points I had from the conference (other than figuring out how to get from my hotel to the conference site without ever having to step outside, using the city’s strange, but useful, skywalk system!) was the development of a promising new therapeutic option for B-cell lymphoma in dogs. This treatment is modeled off of a similar drug used in people with non-Hodgkin’s lymphoma called Rituximab.

I’ve discussed lymphoma in dogs in previous articles on this site, but as a quick recap, lymphoma is a cancer of lymphocytes, which are immune cells usually responsible for fighting off infections.

In people, lymphoma is usually classified as being Hodgkin-like (HL) or Non-Hodgkin-like (NHL), with NHL being the most common form. Diffuse large B-cell lymphoma (DLBCL) is the most common form of NHL in people. Though many different forms of lymphoma exist in dogs, the most common form we diagnose in our canine patients is very similar to the DLBCL seen in humans.

Traditionally, in both people and animals, NHL is treated with chemotherapy with cytotoxic drugs in what is known as the “CHOP” protocol. For the most part, the chemotherapy drugs in this protocol, though effective in controlling disease, are not specific for cancer cells, and this is the main reason for the adverse side effects seen with treatment.

The idea of developing “targeted therapies” for treating cancer has been around for decades, but it wasn’t until the late 1990s before this idea became a reality. Targeted therapies are designed to do exactly what their name implies: specifically target cancer cells while sparing healthy cells, thereby reducing side effects and hopefully also increasing efficacy.

Rituximab is an example of a targeted therapy; it is a “manufactured” antibody directed against a protein located on the outer surface of B-lymphocytes called CD20. After administration, one end of the Rituximab antibody binds to the CD20 protein while the other end “sticks out” and signals the patient’s immune system to attack the lymphocyte and destroy it. Rituximab will bind to both cancerous and normal B-lymphocytes, but not to cells of other healthy tissues, making it a very specific form of treatment for cancers (and other disorders) of B-lymphocytes, with limited toxicity to other tissues.

For humans with DLBCL, the addition of Rituximab to traditional CHOP chemotherapy regimens essentially resulted in achievable cure in many cases, and this combination is now accepted worldwide as standard of care for treating this form of lymphoma in people. Adding Rituximab to combination chemotherapy during the initial treatment of less aggressive variants of B-cell lymphoma (other than DLBCL) has also been documented in multiple clinical trials over the past decade.

A logical question would be, why not try Rituximab to treat canine lymphoma? This exact experiment was performed several years ago. However, results were disappointing, as it was hypothesized that the engineered antibody was specific only for human CD20 and did not appear to recognize the canine version of this same protein. Since that time, the veterinary oncology world has anxiously awaited an animal-approved version of Rituximab to be discovered and developed.

The upshot from the conference is it appears that day is coming soon, possibly even as soon as the “very near future,” although frustratingly we were not offered specifics as to the “when and where” of an anticipated release date or even much information as to the efficacy of the product in dogs. It’s important to note that rituximab will likely not replace traditional chemotherapy for dogs with lymphoma, but will be an additional option we can use to extend the lives of our patients.

It’s difficult to remain patient knowing this option is “out there” but is not something I can immediately prescribe, but I am looking forward to being able to offer this treatment for my patients, and will certainly keep my eyes and ears open for its release.

Dr. Joanne Intile

Image: Thinkstock

Comments  8

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  • Exciting News!
    10/23/2013 07:05pm

    Exciting news indeed!

    Do animal drugs need to go through the painstaking approval protocol as human drugs that takes years and years? Or will smaller clinical trials suffice?

    This article makes me wonder if lymphocytic (small-cell) lymphoma is far behind. Could this type of medication translate?

    I have a great interest in lymphocytic lymphoma in kitties because my Winston (RIP) fought the good fight for quite awhile.

  • 10/25/2013 09:09pm

    Hi

    Drugs for animals do have to go through testing - I do not know the specifics of the timeline, but it definitely is time consuming.

    Yes- this drug could have a role in lymphocytic lymphomas but only if they are of B-cell origin. Most are T-cell. Also this drug is specific for dogs, but I imagine a kitty version would come very soon after....

    Joanne

  • Any news?
    01/01/2015 05:42am

    Have there been any updates or advances toward being able to use this new drug since the article was written? I read somewhere else that the drug company shelved it.

  • 01/01/2015 10:29am

    There is actually a monoclonal antibody therapy that is now currently available with conditional licensure for dogs with T-cell lymphoma at a few select institutions (my hospital is one) and the B-cell monoclonal has a more limited availability for trials right now. There have been some changes in the ownership of the B-cell monoclonal, which I think may have slowed down it's more widespread release. The upshot is both are available, but not everywhere, so owners need to seek out a veterinary oncologist for more information.

  • 01/01/2015 05:04pm

    Thank you so much for responding to my question. My dog has B Cell Lymphoma. Our oncologist hasn't made mention of the possibility of using B-cell monoclonal- she is on traditional CHOP therapy. Is it only available through vet schools or trials? What should I ask him to look into for us so I don't sound nuts- just say "B-cell monoclonal therapy"? We live in Las Vegas. I'm really very interested in trying anything and everything that might be more promising than just the typical protocol. She had a bone marrow transplant in June but relapsed at the beginning of December and just started CHOP again :-(

  • 01/02/2015 02:34pm

    Hi

    I am not sure of the specific locations for the B-cell treatment - I'm having trouble tracking that info down myself. I also don't think it's being used on relapsed cases right now either, but not 100% sure. Certainly worth having your oncologist take a look to see if there are places closer to you offering it.

  • 01/07/2015 01:57pm

    I thought you might be interested- I received the following email today regarding the B-Cell therapy:

    "AT-004 was granted full license by USDA on January 5, 2015. This therapy is marketed by our partner, Novartis Animal Health. Further inquiries should be directed to the Novartis Technical Products Support Group at 1-800-637-0281."

    I'm hoping this means it will be available to us! I will be asking her oncologist to look into it for us today!

  • Donations welcome
    01/17/2015 02:25pm

    My dogs going through some hard times any help would be appreciated

    http://www.gofundme.com/kboux4

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