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

The safety profile of GS-441524 was impressive. No systemic sign of toxicity based on CBC and serum chemistry values was observed over total treatment periods from 12-30 weeks, with one possible exception. One cat (CT53) had a mild rise in BUN and SDMA 8 weeks into a third round of treatment and prompting a halt as a precautionary measure. Based on a previous experience with GC376, 6 there was concern about the effect of GS-441524 on the development of permanent dentition. Three cats (CT52, CT74, CT77) in the present study were 4 months of age or younger and still had their juvenile dentition, and none showed any subsequent dental abnormalities. Injection site reactions were observed with GS-441524, but these were remarkably low in number and were easily treated. It was not determined whether the drug, diluent or both were at fault. The 1.5 pH of the diluent was well below the minimum Food and Drug Administration (FDA) threshold of 4.5, but drugs of this type are difficult to solubilize and stabilize at more physiologic pH. Nonetheless, more physiologic diluents should be evaluated.