Part 1: Twelve patients are randomly assigned to one of two groups. Group 1 patients receive AZT for 7 days, followed by AZT plus L-697,661 with food for 56 days. Group 2 patients receive no drug for 7 days, followed by L-697,661 with food for 56 days. Antipyrine is administered 1 hour prior to study drug on days 8, 22, and 35.