Phase I studies of 2',3'-dideoxycytidine in severe human immunodeficiency virus infection as a single agent and alternating with zidovudine (AZT).

Five dose regimens of 2',3'-dideoxycytidine (ddC) were administered, intravenously for 2 weeks then orally for 4 or more weeks, to 20 patients with acquired immunodeficiency syndrome (AIDS) or AIDS-related complex (ARC). ddC was well absorbed from the gut and crossed the blood-brain barrier. 10 of the 15 patients who received 0.03-0.09 mg/kg every 4 h had increases in their absolute number of T4+ T cells at week 2 (p less than 0.05), though in many these rises were not sustained. 11 of 13 evaluable patients had a fall in their serum human immunodeficiency virus (HIV)p24 antigen by week 2 of therapy (p less than 0.01); in 4 patients the p24 antigen subsequently rose to baseline while in others the decline was sustained. Dose-related toxic effects included cutaneous eruptions, fever, mouth sores, thrombocytopenia, and neutropenia. A reversible painful peripheral neuropathy developed in 10 patients after 6-14 weeks' treatment. These results suggest that ddC has activity against HIV in vivo and has a different toxicity profile from that of zidovudine (AZT). 6 patients with AIDS or ARC were given an alternating regimen of oral AZT (200 mg every 4 h for 7 days) and oral ddC (0.03 mg/kg every 4 h for 7 days). The regimen was well tolerated, and the 5 patients who completed 9 or more weeks of treatment had sustained rises in their T4+ T cells and/or falls in p24 antigen.