Osteoarthritis (OA) is the most common cause of chronic pain in dogs. It affects 80% of dogs over the age of 8 years old. And more than 20% of dogs that are over 1 year of age are estimated to be affected by osteoarthritis. It is also one of the most common age-related conditions in cats. And research suggests 30 to 90% of older cats show signs of OA.
Arthritis is a progressive and degenerative disease, there is no cure, and it is likely to get worse over time. It is also commonly not noticed by owners, as we find it hard to recognise the subtle signs of chronic pain in comparison to acute pain.
So, of course we are constantly looking for new treatments that help animals with OA to reduce their pain and improve their quality of life. Recently, a new type of treatment has become available. You may have heard about it, been offered it or even tried it for your pet; monoclonal antibody therapy.
This article aims to explain a little more about how they work.
Table of contents
To start, what are monoclonal antibodies?
Monoclonal antibodies are highly specific immune system proteins that target and neutralise molecules involved in certain diseases. They function like naturally occurring antibodies, (an antibody is a protein produced by the body’s immune system in response to antigens, which are harmful substances) in our pets’ bodies, but the treatment aims to specifically target very specific molecules involved in a specific disease process. They are eliminated from the body via normal protein degradation pathways in every cell, with minimal stress to the liver or kidneys, which can be a real positive for long term OA treatment.
Monoclonal antibodies have been used in human medicine for some time for various diseases such as Crohn’s Disease, rheumatoid arthritis and cancers.
In OA there is a specific target: Nerve Growth Factor (NGF)
NGF is a neurotrophic (nerve growing, hence the name!) factor discovered in 1950 for its properties of promoting growth and survival of peripheral sensory and sympathetic nerve cells of mammals, including humans, dogs and cats!
NGF is elevated in certain chronic pain conditions and is a sufficient stimulus to cause lasting pain in humans. But the actual mechanisms underlying the persistent effects of NGF aren’t fully understood yet.
In canine and feline osteoarthritic joints, NGF is elevated and, by binding to receptors on neuron and immune cells, NGF results in increased pain. It can also trigger the release of pro-inflammatory mediators (chemicals that promote more inflammation), the release of even more NGF, and neurogenic inflammation (inflammation arising from the local release by afferent neurons of inflammatory mediators).
How does it work?
The aim of the drugs is to ‘mop up’ excessive NGF (or more specifically stop it attaching to nerve receptors) to lower the levels and avoid this pain causing mechanism.
The active substance in the canine monoclonal antibody is bedinvetmab (note that we aren’t allowed to name specific brands under VMD regulations). This is a monoclonal antibody (a type of protein) designed to recognise and attach to the NGF protein. Once attached, it prevents NGF from attaching to its receptors on nerve cells and interrupts the transmission of pain signals. For cats, the active substance is frunevetmab, a felinised monoclonal antibody (a type of cat-specific protein). It works in the same way the canininised monoclonal antibody does, but is specific to cats only.
This interruption in the transmission of pain signals is how these drugs alleviate pain.
Are they safe?
At present we know that the canine monoclonal antibody on the market, Bedinvetmab, has demonstrated an overall positive safety profile in clinical trials, including few gastrointestinal side effects. The way it works also means it has minimal involvement of the liver or kidneys. So far it has no known interactions with other medications. In a clinical study, bedinvetmab was administered together with other commonly used medications, including parasiticides, antibiotics, and vaccines with no issues.
The cat monoclonal antibody Frunevetmab has also been shown to be very safe. However one of the most common side effects (which may affect up to 1 in 10 animals) are skin reactions (itching, skin inflammation and hair loss).
How is it given?
For cats and dogs, the monoclonal antibody therapy comes as an injectable from that we administer by subcutaneous injection, every 4 weeks.
Is it right for every animal?
As with anything, it is important to work closely with your wonderful veterinary team with regards to OA. OA is a constantly changing disease. We know we cannot cure it and we know it is likely to continue to get worse (at varying speeds). Many factors can cause changes to your pet’s pain condition, and this treatment may be a useful tool in your pet’s pain management.
It is not to be used in young animals (<12 months), or ones intended for breeding, pregnant or lactating due to NGFs involvement in development of the nervous system (it is involved in the regulation of growth, maintenance, proliferation, and survival of certain target neurons). However most other animals will be a good candidate for treatment (if they let you inject them once a month!).
Some pets respond incredibly well to the treatment, others may not. Some start off responding and then seem to become less effective. This could be due to several reasons. It could be a flare up in pain that requires short term support; it may be a decline in your pet’s condition which warrants more diagnostics, work ups or longer-term support; or it could be that, in uncommon cases, your pet has developed anti-drug antibodies to it. These may be transient or persistent anti-drug antibodies. The induction of such antibodies is uncommon and may have no effect or may result in a decrease in effectiveness of the medication in animals that responded to treatment previously. Having said that, many pets benefit from the treatment and it helps improve pain levels, mobility and quality of life. Talk to your veterinary team if you have any questions.
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