Tanovea (rabacfosadine) Chemotherapy

What is Tanovea Chemotherapy and What Does It Do?

Rabacfosadine is known by the brand name Tanovea.^®,2 Tanovea chemotherapy is an injectable cytotoxic agent given in the veterinary hospital over the course of several weeks (see below).

Tanovea is a prodrug³, which means that it is inactive in its initial form. Specific canine cancer cells, particularly lymphoma, contain enzymes that convert rabacfosadine into the active agent.^3,5,8 This allows Tanovea to specifically target the cancer cells, while leaving normal cells unharmed.

Like many chemo drugs, Tanovea chemotherapy is given by injection into the dog’s vein. The infusion takes about 30 minutes³ and is done at the vet hospital.

Brand Names

Tanovea-CA1 is the very first FDA-approved treatment for lymphoma in dogs.⁷

How Tanovea Affects Cancer

After being injected into a vein, rabacfosadine travels through the body. Rabacfosadine itself is inactive, and does not damage cells that it encounters.

Except when it encounters lymphoma cells. Inside lymphoma cells, it goes through a couple of conversions before reaching its final form, PMEG diphosphate. PMEG diphosphate is cytotoxic, and inhibits DNA synthesis and triggers apoptosis (programmed cell death).⁵

How do we know it doesn’t harm normal cells? Most cells do not have the two enzymes needed to convert Tanovea from its initial form to the cytotoxic drug that kills the cancer cells. Lymphocytes are the primary cell type that has these enzymes.

Tanovea Chemotherapy Success Rates

Tanovea chemotherapy is only used for cancer treatment in dogs, and so far it only shows promise for a couple of cancer types (see below).

In vitro studies looking at other cancers have not shown a response.

Lymphoma

Rabacfosadine is fully FDA-approved to treat canine lymphoma as of July 2021.⁷

How long does Tanovea last? Given alone, it has a 73% response rate with remission generally lasting 4-6 months.⁸ That means that 73% of dogs taking Tanovea went into remission, and that remission generally last 4-6 months.

Tanovea can be used as a first-line treatment for lymphoma, or it can be used a second-line treatment or rescue therapy.¹⁰

As of early 2022, studies are underway to evaluate how Tanovea does when combined with other chemotherapy drugs or protocols.

• • An initial study that alternated Tanovea with doxorubicin (treatments once every three weeks for a total of six, with three of each drug) yielded response rates and remission duration about the same as a full CHOP protocol.⁵ A confirmatory study is underway.
  • Colorado State University, University of Wisconsin-Madison, and University of California-Davis are testing a protocol that uses rabacfosadine as part of CHOP.

We will update this article with results as they are released.

Multiple Myeloma

Early studies in dogs with multiple myeloma show promising results.⁹ A confirmatory study was completed in 2021 but has not been published yet. We will update this article with results as they are released.

Lymphoid Leukemia

Early studies using Tanovea chemotherapy in dogs with lymphoid leukemia have shown promising results, but more study is needed.

This episode of DOG CANCER ANSWERS has a lot of information about Tanovea from one of the veterinarians involved in its use right from the beginning of its interesting history.

Tanovea Side Effects

Rabacfosadine can cause similar side effects to many other chemo agents but does have potential to cause some unique ones.

The majority of side effects are mild⁹, and either resolve on their own or with symptomatic treatment at home.

Side effects of Tanovea include:^7.8

• Gastrointestinal signs such as vomiting and diarrhea
• Decreased white blood cell count
• Thinning hair coat
• Reddened skin
• Skin and ear infections
• Pulmonary fibrosis

Dogs undergoing treatment with Tanovea should be monitored closely for changes in the skin and ears to catch any potential infections as early as possible. Depending on how bad the side effects are, the next dose of Tanovea can be delayed to give the skin extra time to heal.⁷

Pulmonary fibrosis is the most concerning potential side effect observed so far with rabacfosadine, but thankfully it is rare.⁷

• Changes in the lungs are delayed and may not be apparent for several months after treatment.
• Pulmonary fibrosis has been fatal in about 2% of dogs treated with Tanovea at this point. Researchers are reviewing the literature to try to identify risk factors, but so far this side effect appears to be idiosyncratic (due to individual differences that aren’t common to most dogs).
• It is generally recommended to avoid Tanovea for dogs who already have lung problems or who are of a breed or mix that has a genetic predisposition to developing pulmonary fibrosis (most notably West Highland White Terriers).⁷

When to Not Use Tanovea

There are some situations in which Tanovea chemotherapy should either not be used at all or used with caution.

Risk factors include:²

• West Highland White Terriers have a potential genetic predisposition to developing pulmonary fibrosis (which can be fatal) and should not use Tanovea
• Terrier breeds and mixes also have a potential genetic predisposition to developing pulmonary fibrosis and should not use Tanovea
• Dogs who have already been diagnosed with pulmonary fibrosis
• Dogs who have undergone half-body radiation in the past, as these dogs are already at risk of developing pulmonary fibrosis
• Dogs who are pregnant, lactating, or being used for breeding, due to risk of birth defects

Known drug interactions include:

• None known at this time
• Rabacfosadine is safe for dogs with the MDR1 mutation¹

Known supplement interactions include:

• None known at this time

How Is Tanovea Administered?

Tanovea is an injectable cytotoxic agent, so it is given at veterinary facilities. It is given once every three weeks for a total of five treatments.⁹

When used with doxorubicin, the two drugs are alternated, with a treatment being given once every three weeks for a total of six treatments.⁶

Dose frequency may vary if Tanovea is used as part of another chemo protocol.

If the patient experiences side effects, treatment can be and usually is postponed to give the dog extra time to recover.⁷

What If I Miss a Tanovea Chemotherapy Dose?

If your dog misses a dose of rabacfosadine, contact your veterinarian or oncologist to determine the best time to reschedule. Doses postponed due to scheduling or travel difficulties can be given as soon as possible, while doses postponed due to side effects can be scheduled according to the dog’s needs.

Storage and Handling of Tanovea

Tanovea is a cytotoxic chemotherapy agent, so personal protective equipment must be used when handling and administering it. It is always given in the hospital setting by veterinary professionals.