Unmodified antiTac monoclonal antibodies

Nineteen patients with ATL (11 acute, 4 lymphoma, and 4 chronic) were treated with an unmodified murine anti-Tac monoclonal antibody.115 Nine patients were previously untreated. Therapy was relatively well tolerated. Three of six responding patients developed human antimurine antibodies (HAMA) against the anti-Tac antibody. An OR rate of 32% (CR 11%; PR 21%) was achieved with response durations of 9 weeks to over 3 years. Responses were seen in patients with lymphoma (n = 2), chronic (n = 3), and acute (n = 1) subtypes; only two were previously treated and four had soluble IL-2R levels of less than 10,000 U/mL. To overcome limitations with murine antibodies, including a short circulating half-life in humans, increased immunogenic-ity with repeated dosing, and relatively ineffective recruitment of host antibody-dependent cellular cyto-toxicity, a humanized anti-Tac antibody (daclizumab) was developed.116117 Anecdotal reports of remissions in patients with chronic and smouldering forms of ATL treated with daclizumab have been observed.118 Therefore, single-agent daclizumab is currently being evaluated in patients with ATL in a phase I/II study.

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