A phase IA/IB trial of anti-CD3 murine monoclonal antibody plus low-dose continuous-infusion interleukin-2 in advanced cancer patients

Preclinical studies have shown that anti-CD3 antibodies can enhance the in vitro activation of human T lymphocytes in combination with low-dose interleukin-2 (IL-2) and induce the in vivo rejection of murine tumors. A Phase IA/IB trial combining a murine monoclonal antibody, anti-CD3 antibody (OKT3), with low-dose continuous-infusion IL-2 was conducted in cancer patients to define the toxicity and immunologic effects of this combination. OKT3 administered weekly as a 15-min infusion at dose levels of 10, 100, 200, 400, and 600 μg/m²was followed 18 h later by a 100-h infusion of IL-2 at 3 MIU/m²/day for 3 consecutive weeks. When feasible, patients also received the IL-2 course without OKT3 to assess the effects of OKT3 on the IL-2 regimen within the same patient. Thirty patients were enrolled onto the study, with 24 completing the OKT3/IL-2 course and 18 completing both OKT3/IL-2 and IL-2 alone courses. OKT3 administration was associated with acute hypotension with fevers of >40°C and in two patients cerebral vascular infarcts. At 600 μg/m²OKT3, these toxicities were dose limiting. In a dose-dependent manner, OKT3 induced the transient release of tumor necrosis factor (TNF) and IL-6 into the serum and a profound lymphopenia. OKT3 did not significantly enhance the toxicity of this schedule of IL-2 administration. All solid tumor patients treated at 100-600 μg/m²OKT3 showed induction of a human anti-murine antibody response prior to the third week of treatment. A patient with renal cell cancer treated at the 600-μg/m²OKT3 dose level experienced a 4-month partial remission, and two mixed responses were observed in a sarcoma and a melanoma patient treated at 100- and 400-μg/m²OKT3 dose levels, respectively. Most importantly, we were unable to demonstrate that the addition of OKT3 enhanced immune activation within peripheral blood based upon the magnitude of rebound lymphocytosis, increase in CD56+ or CD3 +, CD25+ lymphocytes, induction of natural killer, lymphokine activated killer, or cytolytic T lymphocyte cytotoxicity, or release of serum cytokines (TNF, IL-6) or soluble CD25 (as assayed 24 h following IL-2 infusion). Therefore, this approach was ineffective at enhancing the immunologic effects of a low-dose continuous-infusion IL-2 regimen and will not be pursued further in clinical trials.