This is an urgent call for Medicines Agencies to impose a moratorium on the approval and/or commercial release of Lenivia and Portela – Zoetis’ new longer acting anti-NGF monoclonal antibodies.
We urge veterinary medicines agencies across the world to fulfil their responsibility to protect the safety of our dogs and cats, and the welfare of their families. We ask medicines agencies to delay the approval and/or commercial release of Lenivia (izenivetmab) and Portela (relfovetmab), until the full risks of these drugs in real-world clinical patients are understood.

Medicines agencies must ensure that history does not repeat itself (or worse) and that the safety of dogs and cats is given priority over commercial interests and profit

Shockingly, despite the growing evidence of the harmful effects of Librela and Solensia, Zoetis are currently gaining marketing approval from Medicines Agencies for two new longer-acting anti-NGF monoclonal antibodies  - Lenivia for dogs and Portela for cats. In view of the known adverse reactions and increasing confirmation of foreseeable risks of Librela and Solenisa, we are calling for delays in the approval and/or launch of Lenivia and Portela until
1) Zoetis’ clinical studies for Lenivia and Portela are scrutinised and the risks vs benefits assessed
2) post-marketing data for Librela and Solensia are carefully analysed to ascertain predictable class effects of anti-NGF monoclonal antibodies in dogs and cats.  Additionally, if Lenivia and Portela still make it to market - the responsible Medicines Agencies must ensure that the drug labels fully disclose the potential risks of these new longer acting anti-NGF monoclonal antibodies.

Like Librela and Solensia, Lenivia and Portela are indicated for the alleviation of pain caused by osteoarthritis. All are anti-NGF monoclonal antibodies, which  putting it simply,  bind to the neurotrophic protein complex Nerve Growth Factor/NGF, preventing attachment to its cellular receptors. NGF is vital for the nervous system and most other systems and organs – anti-NGF monoclonal antibodies deplete the systemic amount of NGF throughout the body. Unlike Librela and Solensia, one injection of these new drugs lasts for 3 months. Many thousands of dogs and cats suffered serious harm or died as a result of Librela or Solensia – “death” is listed as a potential adverse reaction for Librela in the Canadian and US product information, and for Solensia, in the Canadian product information. 
Due to the already long-acting nature of Librela and Solensia, recovery from adverse reactions takes weeks or months – if at all. How long would it take for dogs and cats to recover from adverse reactions caused by Lenivia and Portela which last three times longer?

The risks of Librela and Solensia were known by Zoetis and the EMA at the time they were approved - The EMA CVMP Assessment Reports for Librela and Solensia highlighted the risks to the nervous system and also stated that these drugs have the “reasonably high" potential  to cause harmful off-target effects in the following systems and organs-“heart/cardiovascular, immune, inflammation response/control, intestine, kidney, endocrine (pancreatic islet cells, adrenal gland, pituitary gland), and energy allocation and metabolism, to name a few.” It was also stated that there was further potential for harm – for example skin disorders.
Link to  EMA CVMP assessment report for Librela

Despite this knowledge the EMA and Zoetis failed to provide any information in the Summary of Product Characteristics regarding these “reasonably high risks” - instead Librela and Solensia were, and still are, marketed to vets and the public as being completely safe - despite the addition of numerous adverse reactions to the US, UK and Canadian labels. As of 17 September 2025, the EMA database of suspected adverse drug reaction reports holds 35,372 reports of dogs affected by Librela, including 11,774 neurological adverse reactions such as ataxia and paralysis and 4,962 deaths. There have been 14,966 reports of cats affected by Solensia, including 2,181 neurological adverse reactions, 6,210 skin and appendage disorders and 1,217 deaths. Behind these statistics are suffering dogs and cats, traumatised and heartbroken families, and distressed veterinarians.
Link to  EMA data base https://www.adrreports.eu/vet/en/index.html

Pressure must be applied upon Zoetis to be completely transparent about the potential risks - since without pressure, Zoetis have neither acknowledged nor disclosed the many and serious risks of anti-NGF drugs. Medicines agencies must act so that the information sheets in all countries fully disclose the risks of Zoetis’ entire portfolio of anti-NGF monoclonal antibodies. 

Unlike Human medicines, clinical studies for veterinary medicines involve very small populations –the total number of dogs treated with Lenivia during the 9 month field study was 289. Zoetis have intimated that Lenivia and Portela are safer than Librela and Solensia – suggesting that this is due to them binding to a different site on the NGF molecule - but even with such a small population of carefully selected dogs - the EMA have highlighted the following side-effects, “ataxia, polydipsia, polyuria (uncommon), and lethargy and anorexia (rare)”.
Link to Lenivia EMA CMVP Summary of positive opinion

Additionally the adverse reaction rates and details released in the Canadian product information are very worrying, and include the death of a dog which occurred “unexpectedly” during the field study -  5 days after a “staggering episode”, which was categorised  by Zoetis’ research team as ‘ataxia’. The dog had received Lenivia.
Link to   Canadian PI (draft)  (scroll past the Client Info.)

Veterinary medicines rely on post-marketing surveillance and the pharmacovigilance process to identify adverse reactions, contraindications and potential drug interactions. This is a slow and inefficient process, which is contingent upon the co-operation of the manufacturers - many animals suffer or die before any information regarding risks and adverse reactions is communicated to vets and the public. In the case of Lenivia and Portela, medicines agencies already have global data regarding the adverse reactions and risks associated with their predecessors, Librela and Solensia. If medicines agencies and Zoetis do value the safety of dogs and cats, and the welfare of their families - this data should also be included in the labels for Lenivia and Portela, along with warnings that due to the longer-acting nature of these drugs, recovery takes months.

We urge veterinary medicines agencies across the world to fulfil their responsibility to protect the health and welfare our dogs and cats, and their families.

• We ask veterinary medicines agencies to delay veterinary access to Lenivia and Portela, until the full risks of these drugs are assessed and disclosed.
• We ask veterinary medicines agencies to fully assess and disclose the risks of Zoetis’ entire portfolio of anti-NGF monoclonal antibodies and that these risks are included in all product information in all countries.