Can Oclacitinib treat COVID-19 infections?

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The SARS-CoV-2 (“COVID-19”) pandemic is a worldwide health emergency. Emerging mutations, including the delta variant, have resulted in increased numbers of infected individuals and a more rapid spread of the virus. There is no known cure for COVID-19, and because of this many patients and healthcare professionals have researched possible alternative treatments for this disease. The Janus kinase (“JAK”) inhibitors are one type of medication that has been studied as a potential treatment for COVID-19 infection.

JAK inhibitors are a class of drugs used to treat conditions affecting the immune system, including cancers, allergies, and autoimmune disorders. JAK inhibitors work by blocking specific signaling pathways in the human body that affect inflammation. By inhibiting these pathways, JAK inhibitors effectively reduce the body’s response to inflammation. Several JAK inhibitors, including tofacitinib (Xeljanz®), baricitinib (Olumiant®), and upadacitinib (Rinvoq®), are currently approved by the United States Food and Drug Administration (US FDA) to treat conditions such as rheumatoid arthritis and ulcerative colitis. Unlike many other prescription anti-inflammatory medications such as adalimumab (Humira®) and etanercept (Enbrel®), which are only available in injectable formulations, JAK inhibitors are available as pills or oral solutions. The ability to take these medications by mouth makes JAK inhibitors an attractive option for many patients who suffer from inflammatory or autoimmune conditions.

 COVID-19 infection can result in widespread inflammation throughout the human body, including the development of a condition called “cytokine storm” which can cause severe illness or death. Because of the severe inflammation that often accompanies severe COVID-19 infection, JAK inhibitors have been explored as a potential treatment for COVID-19. In patients hospitalized with moderate to severe COVID-19 infection, use of the JAK inhibitor baricitinib has been shown to improve lung function and shorten recovery times from the virus. In 2020, the US FDA granted an Emergency Use Authorization for baricitinib for patients aged 2 years and older who are hospitalized with oxygen-dependent COVID-19 infection.

JAK inhibitors are associated with significant side effects, including an increased risk of serious infections and blood clots. Patients who take JAK inhibitor drugs may also be at increased risk for developing certain types of cancers. Doctors who prescribe JAK inhibitor drugs will generally monitor their patients closely for these conditions, and order blood testing at regular intervals.

JAK inhibitors are not just used in humans; since animals can also experience inflammation and allergies, JAK inhibitor drugs have also been developed for use in the animal population. Oclacitinib (Apoquel®) is a JAK inhibitor used for the treatment of allergic skin conditions and itching in dogs. Oclacitinib is available in oral formulation for dogs, like the human JAK inhibitors, but oclacitinib has not been studied for use in humans and is not approved by the US FDA for use in humans. In dogs, oclacitinib is associated with serious side effects including vomiting, lethargy, seizures, cancers, and even death. Given the concerning side effect profile of oclacitinib in animals and the lack of human studies regarding this drug, it is recommended that humans avoid taking the animal formulation of oclacitinib. In addition, there is no evidence to suggest that oclacitinib is effective in treating or preventing COVID-19 infection.

Kelly Johnson-Arbor, MD
Medical Toxicologist