Efficacy and safety of the nucleoside analog GS-441524 for treatment of cats with naturally occurring feline infectious peritonitis

Pedersen, Niels C; Perron, Michel; Bannasch, Michael; Montgomery, Elizabeth; Murakami, Eisuke; Liepnieks, Molly; Liu, Hongwei

It was important to follow simple biological markers of progress over the ⩾12 week treatment periods. PCV, serum total protein, globulin and albumin levels, and the A:G ratio were identified as useful markers. Based on these parameters, it appeared that cats had not completely recovered after 6-10 weeks of treatment. This finding validated the 12 week minimum treatment period determined by an earlier GC376 field trial. 6 Anemia of chronic disease (anemia of inflammation) affects 18-95% of people with acute and chronic infections and is normocytic/normochromic and not associated with iron deficiency. 18, 19 Plasma albumin levels were also a good measure of disease activity, and low albumin and low PCV are known to coincide in situations of chronic disease. 19 Hyperglobulinemia in cats with FIP has been classified as infectious/inflammatory and is caused by increases in all gamma globulin classes and variable increases in alpha-2 globulins. 20 The strong tendency for cats with FIP to have high serum globulin and low albumin levels makes the A:G ratio a particularly good indicator of disease activity. 21 An expectation was that the pedigreed cats would not respond as well to treatment because of a genetic weakness in their ability to respond immunologically to FIPV 22 and that younger cats with effusive FIP would be most responsive. 6 However, the pedigreed cats in the present trial responded equally well as the random-bred cats, and the breeds represented by the cats in the study mainly mirrored the breeds' current popularities. Older cats, and cats with pure non-effusive FIP, also responded as well to GS-441524 treatment as young cats and cats with effusive FIP. If a proportion of cats with ocular and neurological disease can also be successfully treated with GS-441524, no clinical manifestations of FIP should be considered untreatable.