by: Krystal Harris, DVM, DACVIM (Oncology)
Ranger is a 7yr old MN Bloodhound, that developed pneumonia, lethargy, and diffuse erythematous lesions over most of his body. He started vomiting and then became anorexic losing ~10lbs rapidly.
After starting antibiotic therapy for pneumonia, three punch biopsies confirmed a diagnosis of Cutaneous Epitheliotropic T-cell Lymphoma (CETL). Prednisone was started while awaiting results without notable improvement in his condition.
Upon presentation to the Oncology service, he received a single dose of Lomustine; 1 week later mild improvement was reported by the owner but minimal improvement on physical exam.
Image: 1-week post lomustine/prednisone
Image: 1-week post lomustine/prednisone
At this time, Ranger had an asymptomatic Grade 4 neutropenia and little improvement in his skin. Due to his low neutrophil count, we were unable to proceed with additional cytotoxic therapy so started a 2-week trial of oclacitinib while waiting for his bone marrow to recover.
After 2-weeks on oclacitinib, his skin lesions were almost fully resolved and his appetite was great! He has continued on oclacitinib and a tapering dose of prednisone for 3 months to date and remains in clinical remission in the absence of any other chemotherapy intervention.
Oclacitinib (Apoquel) is a tyrosine kinase inhibitor selective for JAK1; it also inhibits JAK2, JAK3 and TYK2. The JAK/STAT pathways are essential for T-cell function, and oclacitinib has been shown to cause apoptosis of CD4+ and CD8+ T cells in vitro. In humans, alterations in JAK/STAT signaling have been described in most T-cell lymphoproliferative disorders including CETL. Ruxolitinib, a JAK1/2 inhibitor, is approved for the treatment of myeloproliferative neoplasms in humans, and preliminary results in human CETL patients have shown positive outcomes, with a greater and more durable response in patients with documented JAK/STAT alterations.
The use of oclacitinib to treat canine CETL was published in VetDermatol 2021. The dog in this case study started to show clinical improvement in his skin, energy, and appetite after 4 days of oclacitinib. Repeat punch biopsies obtained on Day 14 of oclacitinib showed an 80% reduction in neoplastic T-cell infiltrate.
Ideally, we would submit biopsies in cases of CETL for genetic sequencing to help with case selection.
Aslan J, Shipstone MA, Sullivan LM. Treatment of canine cutaneous epitheliotropic T-cell lymphoma with oclacitinib: a case report. Vet Dermatol. 2021 Aug;32(4):398-e113. doi: 10.1111/vde.12976. Epub 2021 May 25. PMID: 34033147.