Safety of short-term valacyclovir as an anti-sickling agent in sickle-cell anemia.

To assess safety and tolerability, we administered valacyclovir, an oral anti-viral medication that inhibits erythrocyte sickling in vitro, to 14 subjects with sickle-cell anemia for 1 week at a standard dose of 1,000 mg every 8 hr. No clinically significant adverse effects occurred. In 11 subjects in steady state, the mean hemoglobin concentration was almost constant while the absolute reticulocyte count decreased in eight (P = 0.1) and the overall mean fell slightly although not significantly (10%, P = 0.2). These results suggest that valacyclovir is safe and well tolerated in patients with sickle-cell anemia and that a longer duration of therapy merits investigation.

Inhibition of sickling in vitro by three purine-based antiviral agents: an approach to the treatment of sickle cell disease.

As a result of an in vitro screening effort the antiviral agent acyclovir was found to inhibit aggregation of hemoglobin S and the sickling of erythrocytes from individuals with sickle cell disease. Sickling of the erythrocytes was significantly inhibited at 200 microg/ml under essentially anaerobic conditions, considerably more hypoxic than the conditions in which sickling occurs in sickle cell patients. The structurally related guanine-based antiviral agents ganciclovir, valacyclovir, and penciclovir were also tested. Valacyclovir and ganciclovir showed comparable anti-sickling activity at concentrations similar to that of acyclovir. An examination of the shared structural characteristics of the four guanine derivatives linked anti-sickling activity to the presence of an oxygen atom alpha to the N9 of the guanine moiety. These findings suggest a new approach in the search for new agents for the treatment of patients with sickle cell disease.