Foscarnet is active in vitro (test tube) against herpes viruses, including CMV, by inhibiting the virus DNA polymerases, enzymes necessary for virus replication, without affecting cellular DNA polymerases. Opportunistic CMV disease in AIDS is usually seen as retinitis, colitis, esophagitis, hepatitis, pancreatitis, encephalitis, or pneumonia. Ganciclovir has been used to treat AIDS patients with CMV disease but can cause severe neutropenia (very low neutrophil cell counts). Foscarnet does not suppress the production of neutrophils or other leukocytes (myelosuppression) and has shown in vitro activity against HIV.
Treatment is given for a total of 10 weeks with a 2-week induction regimen followed by randomization to daily maintenance foscarnet for 8 weeks. If induction therapy is tolerated without unexpected toxicity, patients are allowed to self-administer foscarnet at home via central venous catheter and may receive up to 11 days of induction therapy by self-administration on an outpatient basis. Foscarnet will be administered in open-label fashion so that both investigator and patient will know the dose. Within the study, there are 8 patients who upon entering the 2nd week of maintenance foscarnet therapy are treated with zidovudine (AZT).