Recombinant soluble CD4 protein (rCD4) is a drug that has been produced by genetic engineering techniques. In laboratory studies, rCD4 binds to HIV and reduces its ability to enter the cell, thus inhibiting its reproduction. Before rCD4 can be tested for therapeutic effectiveness in HIV-infected patients, it is necessary to determine the maximum dose that can be tolerated by humans. AMENDED: To date, Biogen's original sequence recombinant soluble CD4 and Biogen's natural sequence recombinant soluble CD4 have both been referred to as recombinant soluble CD4 (rsCD4). In order to distinguish between these two products, a change in nomenclature has been made. In this protocol, whenever the original sequence CD4 molecule is referred to, it is called recombinant soluble T4 (rsT4). Whenever the natural sequence molecule (currently under study in this protocol) is referred to, it is called BG8962 or rCD4. Whenever the drug is discussed generically, it is referred to as rsCD4.

The initial dose level is the highest dose previously established with other patients in this trial to be safe when administered intramuscularly (IM). Dose escalation is by semilogarithmic steps. A shift from IM injection to continuous subcutaneous infusion (CSCI) is necessitated by the volume of drug which is administered as part of the escalation dose. Three groups of eight patients each are treated as follows. The first group of 8 patients receives BG8962 daily and consists of two cohorts of four patients each. One cohort receives BG8962 as an IM injection. The second cohort receives BG8962 as a continuous 24 hour infusion. All patients in this group are treated for 12 weeks. The second dosing group of 8 patients receive daily BG8962 by CSCI for 12 weeks. The third group of 8 patients receive BG8962 by CSCI for 6 weeks. Every two weeks during the study the following tests and evaluations are done: Blood chemistry, hematology, urinalysis with microscopic exam, and T-cells and T-cell subsets.