Monoclonal Antibody Drugs Helping Millions of Dogs and Cats


Osteoarthritis is even more common in dogs and far more common in cats than previously thought. As any person with arthritis knows, the condition is painful, and it’s equally painful in pets as it is in people. A new kind of monoclonal antibody treatment became available for cats in 2022 called Solensia and last year in dogs, called Librela, which target what’s called nerve growth factor which simply prevents pain signaling to the brain. Both drugs are administered by a monthly injection.

European pets were using both compounds before they were approved and used in the U.S. Each was approved by the U.S. Food and Drug Administration Center for Veterinary Medicine specifically for the species which each was created.

A Wall Street Journal report from April 12 has created all sort of anxiety as the story reveals health regulators in the U.S. and Europe have received thousands of reports of side effects from the drugs. Zoetis, the drugs’ manufacturers, notes this is true but adverse events or side-effects remain under one percent of the more than 18 million shots of both drugs combined administered to date in the U.S. and abroad.

While adverse events should remain in the single digits, less than one percent is clearly very acceptable (unless it is your pet, of course). And according to one study (in human health) many adverse events are preventable. Is this another example of that?

Understandably, pet parents and veterinary professionals are desperate to prevent pets from suffering in pain. In dogs non-steroidal anti-inflammatory drugs (NSAID’s) may be a useful tool. However, the reality is adverse events are higher (at least – so far- based on what we know today) when compared to Librela. In cats, for various reasons, a NSAID may not even be a viable option.

While it turns out that osteoarthritis occurs in cats FAR more than previously was known and is common in dogs – the painful and often debilitating condition is mostly recognized  in older pets. And older pets are most likely to have comorbidities or other medical conditions.

When the monoclonal antibodies became available – due to their success in Europe, veterinary professionals were very excited about their prospects. And indeed, many veterinarians can show off before vs. after videos of dogs and cats, and the differences in mobility and playfulness are obvious. I have impressive videos for our own 16-year-old dog post Librela injections.

The Wall Street Journal story quotes a veterinarian who treated a dog using Librela with a neurological condition who lost energy and was less eager to move, while another couldn’t walk. Both dogs improved after stopping injections. The veterinarian reported those events to Zoetis.

Also, monthly injunctions are supposed to be given by a veterinary professional but wonder if at least some of adverse events include injections administered incorrectly by pet parents.

In 1997 when Rimadyl, the first NSAID for dogs, became available, veterinarians didn’t know to check for and periodically monitor kidney values. Similarly, neurologic conditions weren’t in the trials or testing when Librela and Solensia were trialed.

Also, many of the dogs and cats on these drugs are old or geriatric and fragile, and suffer other medical conditions. Are at least some or many of the presumed causes associated with adverse effects may not actually causing the adverse events. Correlation is not causation, which means that just because two things correlate does not necessarily mean that one causes the other.

And I do understand, being a pet parent, how angry and upset people can be. Our 16-year-old dog Hazel took a NSAID (just prior to Librela becoming available), and following that event suffered a bout of pancreatitis. The only way to possibly know if there was a connection was to create a report with the FDA (which our veterinarian refused to do at the time – and yes we do have a new veterinarian for several reasons). However, I also understand that the NSAID may not have caused inflammation of the pancreas which became so serious that our dog might have died.

The good news is that according to U.S. rules, anytime a consumer feels there is a concern – viable or not – a report can be made to the FDA Center for Veterinary Medicine.

In time, experts will separate out which reports of adverse events to the FDA are most credible and if there is a pattern. Meanwhile, literally millions of pets are celebrating less pain and a dramatically improved quality of life because of Librela and Solensia. This is a fact.

True enough, though, even at less than one percent if it is your pet suffering an adverse event, and one which allegedly contributes to a fatality – it doesn’t matter what the percent is.

I recall doing a story on the adverse events caused by Rimadyl, and noting that another NSAID has contributed to more deaths in humans when compared to the then all-new dog drug, and that human drug is called aspirin.

(Full disclosure: For years, I’ve spoken at veterinary meetings about dogs and cats in pain, and when Solensia was released included Solensia in the talk. And Zoetis recently was a sponsor of a April 13-14 pain symposium which I helped organize in conjunction with the EveryCat Health Foundation and Carolina State University College of Veterinary Medicine Feline Health Center, Raleigh, NC. And we use Librela for our dog.)