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Prior treatments T—X included interferon (IFN), cladribine (CdA), and pentostatin (DCF). Patients with absent spleens had prior splenectomy. The presence absence (+ or —) of cytopenias is also listed to indicate whether patients had ANC <1500/mm3, platelets <100,000/mm3, or Hb <11 g/dL on enrollment. Neutralizing antibodies (Neut ABs) were + if the serum neutralized 1000 ng/mL of the cytotoxic activity of LMB-2 toward CD25 + SP2/Tac cells. Peak levels indicate the highest plasma level achieved with any of the doses of LMB-2 administered, as measured by cytotoxicity assay of plasma on SP2/Tac cells using pure LMB-2 for a standard curve. Responses included partial response (PR) or complete remission (CR). The percent decrease in circulating HCL count (% Decr HCL) as a result of LMB-2 treatment is shown.

Prior treatments T—X included interferon (IFN), cladribine (CdA), and pentostatin (DCF). Patients with absent spleens had prior splenectomy. The presence absence (+ or —) of cytopenias is also listed to indicate whether patients had ANC <1500/mm3, platelets <100,000/mm3, or Hb <11 g/dL on enrollment. Neutralizing antibodies (Neut ABs) were + if the serum neutralized 1000 ng/mL of the cytotoxic activity of LMB-2 toward CD25 + SP2/Tac cells. Peak levels indicate the highest plasma level achieved with any of the doses of LMB-2 administered, as measured by cytotoxicity assay of plasma on SP2/Tac cells using pure LMB-2 for a standard curve. Responses included partial response (PR) or complete remission (CR). The percent decrease in circulating HCL count (% Decr HCL) as a result of LMB-2 treatment is shown.

The most common first-cycle toxicity at the MTD (40 ^g/kg q.o.d. X 3) in nine patients was transaminase (aspartate transaminase and alanine transaminase) elevations. Nausea, fever, and weight gain were also common toxicities. Symptomatic pulmonary edema or other features of dose-limiting vascular leak syndrome (VLS) were not seen, although hypoalbumine-mia was common. Reversible anaphylaxis to LMB-2 was observed in one patient who had been pretreated with anti-Tac mAb and had developed nonneutraliz-ing anti-idiotype antibody prior to LMB-2 enrollment. The median half-life of LMB-2 was about 4 h at the MTD. After cycle 1, only 6 of 35 patients (17%) made neutralizing antibodies at high enough levels to disqualify them from further treatment. Thus, patients were retreated for a total of two to six cycles. None of eight CLL patients receiving a total of 16 cycles developed any trace of neutralizing antibodies. PRs were observed in one patient with ATL, HD, CTCL, and CLL.

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