The enhanced potential use of recombinant alpha interferon in the treatment of AIDS-related Kaposi's sarcoma.
Alpha interferon has been extensively studied in the treatment of the epidemic form of Kaposi's sarcoma (KS) common in the acquired immunodeficiency syndrome (AIDS). Its safety and efficacy against KS have been well documented, with objective tumor responses seen in 25%-50% of cases. In a number of large uncontrolled studies, patients had a low incidence of opportunistic infections (OIs) during recombinant alpha interferon therapy. Although several factors may be involved, individuals responding to interferon have a distinct survival advantage over those not responding. Patients with better prognostic features, such as CD4 (T-4/T-helper cell)* counts greater than 200/mm3, no history of OIs, and no lymphoma-like "B" symptoms, are most likely to respond to interferon. Recent studies have identified a soluble growth factor produced by human immunodeficiency virus (HIV)-infected T-lymphocytes, which may be important in the propagation of KS cells in vitro. Studies demonstrating in vivo and in vitro HIV inhibitory effects of alpha interferon and the correlation of antiviral and antitumor responses now suggest that the antiretroviral action of this agent may be critical in the control of KS. Phase I trials of interferon alpha plus the antiretroviral drug zidovudine (azidothymidine, AZT) have shown the combination to be well-tolerated and to produce anti-KS responses at lower doses of each agent than is generally administered. Synergistic antiretroviral activity has been demonstrated with zidovudine and interferon alpha in vitro. Phase II trials of this combination currently are in progress.