Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Recombinant immunotoxins are fusion proteins which contain a ligand derived from the immune system fused to a toxin. The protein toxin is truncated to delete its binding domain, allowing selective ligand-directed binding. Growth factor fusion toxins are often considered immunotoxins. One of these molecules, containing the truncated diphtheria toxin and human IL-2 (Ontak), Ligand Pharmaceuticals), has been approved for the treatment of cutaneous T-cell lymphoma. Recombinant immunotoxins have also been produced containing the variable domains (Fv fragment) of monoclonal antibodies fused to toxins. These agents are relatively versatile with respect to the range of antigens possible. Several of these recombinant immunotoxins have showed clinical effectiveness in Phase I testing against haematological malignancies. One of these molecules, BL22, targets CD22 on hairy-cell leukaemia and has enabled patients to achieve complete remissions despite previous treatment and resistance to chemotherapy.
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PMID:Recombinant immunotoxins for the treatment of haematological malignancies. 1526 78

Denileukin diftitox, a genetically engineered fusion protein combining the enzymatically active domains of diphtheria toxin and the full-length sequence for interleukin-2 (IL-2), efficiently targets lymphoma cells expressing the high-affinity IL-2 receptor (IL-2R) consisting of the alpha/p55/CD25, beta/p75/CD122, and gamma/p64/CD132 chains. In vitro studies demonstrated that the retinoid X receptor (RXR) retinoid, bexarotene, at biologically relevant concentrations of 10(-6) M to 10(-8) M, upregulated both the p55 and p75 subunits of the IL-2R and enhanced 5- to 10-fold the susceptibility of T-cell leukemia cells to denileukin diftitox. To determine whether this biomodulatory effect could be recapitulated in vivo, we treated 14 patients with relapsed or refractory cutaneous T-cell lymphoma with escalating doses of bexarotene (75 mg/day-300 mg/day) and denileukin diftitox (18 mcg/kg per day x 3 days every 21 days) in a phase 1 trial. Overall response was 67% (4 complete responses, 4 partial responses). Modulation of IL-2R expression was observed at or above a bexarotene dose of 150 mg/day. Four patients experienced grade 2 or 3 leukopenia, and 2 had grade 4 lymphopenia. Our results demonstrate that the combination of denileukin diftitox and bexarotene is well tolerated and that even low doses (150 mg/day) of bexarotene are capable of in vivo upregulation of CD25 expression on circulating leukemia cells.
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PMID:A phase-1 trial of bexarotene and denileukin diftitox in patients with relapsed or refractory cutaneous T-cell lymphoma. 1581 59

Immunotoxins, composed of protein toxins connected to cell binding ligands including monoclonal antibodies and growth factors, have been developed for several decades to target hematologic malignancies. Protein toxins from either plants or bacteria are extremely potent based on their enzymatic inhibition of protein synthesis and induction of apoptosis. Plant toxins, particularly ricin, are useful for chemically conjugating to monoclonal antibodies, and have shown clinical activity in several types of lymphoma and leukemia. Their dose is generally limited by vascular leak syndrome. Bacterial toxins have been used to produce single chain fusions with either growth factors or recombinant antibody fragments. These agents are smaller in size (55-65 kDa) and exit the bloodstream much more rapidly than the chemical conjugates, and generally do not cause severe vascular leak syndrome. The only approved drug containing a protein toxin is denileukin diftitox, a fusion of human interleukin 2 with truncated diphtheria toxin. Denileukin diftitox has shown efficacy in cutaneous T-cell lymphoma, chronic lymphocytic leukemia, and non-Hodgkin's lymphoma. Recombinant immunotoxin BL22 is an anti-CD22 Fv fragment fused to truncated Pseudomonas exotoxin; it induces complete remissions in a high percentage of patients with chemoresistant hairy cell leukemia. The anti-CD25 recombinant immunotoxin LMB-2 is active in several CD25+ hematologic malignancies. Several other recombinant immunotoxins are undergoing preclinical development for other target antigens expressed on hematologic malignancies.
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PMID:Immunotoxins in the treatment of hematologic malignancies. 1707 92

Immunotoxins are fusion proteins of modified toxin conjugated to tumor cell selective ligand. Denileukin diftitox approved by FDA for treatment of CTCL is diphtheria toxin (DT)/IL2 fusion protein targeted to high affinity IL2R. Here, we have attempted to target the more uniquely expressed low affinity IL2R (IL2Ralpha). We designed four immunotoxins, SPRSV1 was designed to code for a single protein of DT (390) and IL2 (133) without any extra amino acids at the junction. SPRSV2 was designed to selectively target low affinity IL2R, it codes for DT (390) and IL2 (69). We also constructed SPRSV3 encoding for only DT (390) without any ligand, as negative control and SPRSV4 was designed similar to commercial equivalent denileukin diftitox, it codes for DT (387) and IL2 (133) with His at the junction. The cytotoxic activities of these immunotoxins were tested in various cell lines, cell lines lacking IL2R expression and healthy MNC were used as controls. The activities of SPRSV1 and SPRSV2 were comparable to that of SPRSV4. SPRSV2 exhibited potent cytotoxicity effectively targeted to alpha subunit of IL2R on various leukemia cell lines. Our studies also showed a negative correlation between CD25 expression and percentage cell viability after treatment with immunotoxins.
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PMID:Modified DT-IL2 fusion toxin targeting uniquely IL2Ralpha expressing leukemia cell lines - Construction and characterization. 2058 Jul 54