Phase I trial of a ligand fusion-protein (DAB389IL-2) in lymphomas expressing the receptor for interleukin-2.

The purpose of this study was to evaluate the safety, tolerability, pharmacokinetics, and possible antitumor activity of a ligand fusion-protein, DAB389IL-2, in a phase I trial. This was a multicenter, open-label, dose-escalation trial. Patients with preserved organ function and histologically confirmed relapsed cutaneous T-cell lymphoma (CTCL), other non-Hodgkin's lymphomas (NHL), or Hodgkin's disease (HD) were eligible if their cancer was shown to express the interleukin (IL)-2 receptor by an immunohistochemical assay for the p55 or the p75 subunit. Patients received up to eight courses of DAB389IL-2 given as a short intravenous infusion daily for 5 days with subsequent courses every 21 days. The maximum tolerated dose (MTD) and tumor response was determined according to standard criteria. Seventy-three patients (44 men/29 women), aged 16 to 81 years (mean, 50.7) with CTCL (n = 35), NHL (n = 17), and HD (n = 21) were enrolled. The patients were extensively treated, failing 0 to 15 previous therapies (median, 4). Patients received one to six courses (mean, 3.3) of DAB389IL-2 over a range of 3 to 31 micrograms/kg/day. The dose-limiting toxicity was asthenia, establishing the maximum tolerated dose of 27 micrograms/kg/day. Approximately half of all patients had significant titers of antibody to diphtheria toxin or to DAB389IL-2 at the time of enrollment compared with 92% with titers at the end of treatment. The presence of antibody did not preclude clinical response. There were five complete (CR) and eight partial (PR) remissions in patients with CTCL with one CR and two PR occurring in NHL. The median time to response was 2 months and the duration of response was 2 to 39+ months. No responses were documented in patients with HD. DAB389IL-2 is well tolerated with an MTD of 27 micrograms/kg/day. This ligand fusion-protein showed antitumor effects in patients with IL-2 receptor expressing CTCL and NHL. Additional trials in these diseases are warranted.