Chemokine receptors, common to both FIV and HIV, are essential for infecting cells. In vitro studies using bicyclams have shown inhibition of FIV replication. In this 6-week placebo-controlled, double-blinded clinical trial, the CXCR4 antagonist plerixafor was evaluated alone or in combination with adefovir. Forty naturally infected cats with FIV were randomly assigned (n = 10) to 1 of 4 groups: placebo only, adefovir and placebo, plerixafor and placebo, or adefovir and plerixafor. Signs, laboratory parameters, proviral and viral load, and cell counts were monitored.

At the study’s end, all cats were alive, and signs had improved in all groups. There was a significant improvement in stomatitis scores for cats receiving plerixafor and adefovir or plerixafor alone compared with placebo. No significant changes in CD4:CD8 ratios or viral load were found, nor evidence of FIV resistance to plerixafor. There was a significant difference in proviral load between placebo- and plerixafor-treated cats (decrease) and between cats receiving plerixafor and adefovir (relative increase) and just plerixafor. A decrease in RBC count and hematocrit was noted in cats treated with adefovir alone or in combination with plerixafor. These results suggested a role for plerixafor in FIV treatment, although it is not recommended in conjunction with adefovir.

Commentary
Few FIV management medications have successfully decreased viral replication in naturally occurring infection and increased quality of life without adverse effects. Zidovudine has been documented to decrease viral load but can result in significant anemia. Fozivudine can decrease experimentally infected viral load without causing anemia, but the effect in naturally occurring infection is unknown.1 This study showed that plerixafor only had a mild reduction in FIV viral load. It is unknown if this reduction results in improved signs when given long term. The standard of care for FIV management remains preventing infections, documenting infections, and providing aggressive antimicrobial therapy. Antiviral drugs remain second- or third-tier therapy, as research did not show a significant improvement in disease outcome.—J.D. Foster, VMD

Source
Efficacy and adverse effects of the antiviral compound plerixafor in feline immunodeficiency virus-infected cats. Hartmann K, Stengel C, Klein D, et al. J Vet Intern Med 26:483-490, 2012.

1. Fozivudine tidoxil as single-agent therapy decreases plasma and cell-associated viremia during acute feline immunodeficiency virus infection. Fogle JE, Tompkins WA, Campbell B, et al. J Vet Intern Med 25:413–418, 2011.