Adeno‐associated virus‐vectored erythropoietin gene therapy for anemia in cats with chronic kidney disease

BACKGROUND: A treatment of chronic kidney disease (CKD)‐associated anemia in cats is needed. SB‐001 is an adeno‐associated virus‐vectored (AAV)‐based gene therapeutic agent that is administered intramuscularly, causing the expression of feline erythropoietin. HYPOTHESIS/OBJECTIVE: We hypothesized that SB‐001 injection would lead to a sustained increase in PCV in cats with CKD‐associated anemia. ANIMALS: Twenty‐three cats with International Renal Interest Society (IRIS) Stage 2 to 4 CKD‐associated anemia were enrolled at 4 veterinary clinics. METHODS: In a prospective clinical trial, cats were treated with 1 of 3 regimens of SB‐001 (Lo 1.2 × 10(9) genome copies [GCs] on Day 0; Lo ± Hi [supplemental 2nd dose of 3.65 × 10(9) GC on Day 42]; Hi 3.65 × 10(9) GC IM on Day 0) and followed for 70 days. RESULTS: A response to SB‐001 at any time between Day 28 and Day 70 was seen in 86% (95% confidence interval 65, 97%) of all cats. There was a significant (P < .003) increase in PCV from Day 0 to Day 28 (mean increase 6 ± 6 percentage points [pp]; n = 21), Day 42 (8 ± 9 pp; n = 21), Day 56 (10 ± 11 pp; n = 17), and Day 70 (13 ± 14 pp, n = 14). Twelve cats were hypertensive at baseline, 4 of which developed encephalopathy during the study. An additional 6 cats became hypertensive during the study. CONCLUSIONS AND CLINICAL IMPORTANCE: Results of this study suggest that SB‐001 therapy represents a suitable single injection treatment that can address nonregenerative anemia in cats with CKD. It was generally well tolerated; however, hypertension and encephalopathy developed in some cats as previously described in association with erythropoiesis‐stimulating agent therapy.