TO THE EDITOR: Lenalidomide is a novel immune modulating drug (IMiD) that has demonstrated impressive antitumor activity in previously treated multiple myeloma and International Prognostic Scoring System low-risk and intermediate-1 risk deletion 5q myelodysplastic syndromes. The antileukemic effects of lenalidomide in patients with relapsed or refractory chronic lymphocytic leukemia (CLL) were recently reported in two ongoing phase II studies. 1,2 In the first study by Chanan-Khan et al, lenalidomide was given orally with a cyclic 25-mg regimen (day 1 to 21 of a 28-day cycle) in 45 patients with relapsed or refractory CLL; the overall response rate (ORR) was 47% with 9% of the patients attaining complete remission. In the other study by Ferrajoli et al, oral lenalidomide was administered at 10 mg daily for 28 days and dose escalated up to a maximum of 25 mg daily, in 45 patients with relapsed CLL who had received at least one purineanalog based regimen. The first 35 patients assessable for response had an ORR of 38% with 9% attaining complete remission. In both studies notable adverse reactions included tumor flare reaction (TFR) and tumor lysis syndrome (TLS). In the study by Chanan-Khan et al, TFR occurred in 58% (grade Յ 2, 50% and grade Ն 3, 8%) and TLS in 5% (all grade 3) of the patients. Ferrajoli et al reported 37% of TFR (grade Յ 2, 30% and grade Ն 3, 7%) and no TLS.We summarize here the development of TLS and TFR during lenalidomide therapy in CLL. TFR during lenalidomide therapy has been observed in CLL and small lymphocytic lymphoma (SLL). TFR occurs in the majority of lenalidomide-treated CLL patients, and is usually not severe and generally well managed with nonsteroidal antiinflammatory agents or steroids.Seven TLS episodes were observed among 260 CLL patients treated with lenalidomide to date. All seven patients had onset of TLS of varying severity during the first 15 days of treatment. Two patients also had concomitant TFR characterized by severe back and bone pain. TLS was complicated by acute renal failure and/or cardiac arrhythmia in three patients. Metabolic abnormalities and renal dysfunction resolved with supportive therapy in five patients; however, two patients died. Bulky disease, moderate renal insufficiency, and increased uric acid levels before therapy distinguished these seven patients from those who did not have TLS.Due to these findings, Celgene Corporation (Summit, NJ) temporarily suspended enrollment to its sponsored CLL trial (CC-5013-CLL-001) and an independent data monitoring committee (DMC) reviewed the data. The DMC recommended that, given the evidence of lenalidomide's significant activity in CLL in this and other trials, 1,2,5 the CLL-001 study should continue, but with modifications to define a better-tolerated lenalidomide dosing regimen. The DMC noted that similar reactions occurred with other immune modulating agents in CLL. 3,4 The use of low-dose-intensity regimens at the initiation of therapy and aggressive TLS prophylaxis and monitoring decreased the incidence of TL...

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Small circular DNAs ranging in contour length from 0.06 to 3.5 ;&m have been isolated from bursas of 19.day chicken embryos and 4-to 5-week-old chickens. Small (4), and human warts (5). At present, the most extensive information regarding purified spcDNA relates to the material derived from HeLa (1), Drosophila (4), and BSC-1 (3) cells. Specifically, HeLa spcDNA appears to be predominantly cytoplasmic, present at a level of about 100400 circles per exponentially growing cell, of greater molecular complexity than its average molecular weight, and derived from chromosomal DNA; Drosophila spcDNA appears to be predominantly nuclear, present at a level of about 3-40 circles per cell, and composed of molecules with different sensitivities to restriction endonuclease digestion; BSC-1 spcDNA appears to be present at a level of about 1000-2000 circles per cell, resolvable into relatively distinct size classes by gel electrophoresis, of a greater molecular complexity (in the range of 1 X 108) than its average molecular weight (5 X 105) and derived, at least in part, from chromosomal DNA. It should be noted that no biological function has been assigned to any of these spcDNAs.In this communication we report the isolation and characterization of covalently closed (form I) small circular DNAs from the developing chicken bursa, an organ known to contain large numbers of B lymphocytes undergoing development to a committed state for the production of particular antibodies; in brief, small circular DNAs derived from the bursas of embryonic (19-day) and 4-to 5-week-old chickens differed markedly in both quantity and size distribution. It is proposed that these molecules may represent products of immunoglobulin gene rearrangements, which are known to occur during development of B cells (6)(7)(8) at 19 days (2 days before hatching), and livers and bursas were removed, frozen on dry ice, and stored at -20'C until use. Four-to 5-week-old chickens (White Leghorns, H and N strain, obtained from Truslow) were sacrificed, and organs were removed and frozen in the same way. In general, 200 embryos yielded 100 g of liver and 7 g of bursa, while 7-10 chickens, 4-5 weeks old, yielded 50 g of liver and 10 g of bursa. To prepare small circular DNA from these tissues, 5-10 g of bursa or 30-40 g of liver was thawed on ice, minced into cold (40C) 0.15 M EDTA at pH 8.0 (8 ml/g of tissue), and homogenized with two strokes of a Kontes Duall 25 homogenizer. Sodium dodecyl sulfate (NaDodSO4), 10% wt/vol, was then added to a final concentration of 0.5% and the preparation was titrated to pH 12.10 with 1.25 M NaOH, incubated for 10 min at room temperature, and neutralized with 6 M HCl to pH 7.8, a procedure known to selectively denature linear and noncovalently closed (form II) circular DNAs (9). This lysate was then extracted with 1/2 vol of redistilled phenol (equilibrated with 0.15 M EDTA), and nucleic acids in the aqueous phase were precipitated overnight at -20'C by the addition of 2 vol of cold 100% ethanol. After centrifugation and et...

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Trimetrexate represents one of a number of new antimetabolites that have been studied in malignant, rheumatological and infectious disease. Methotrexate, the classical antifolate agent, is active in a broad spectrum of clinical settings, but its use is limited ny pre-existing or acquired cellular resistance. Trimetrexate is an agent that does not require uptake by the folate carrier transport system, a major mechanism of cellular resistance both in vitro and in vivo. Both dihydrofolate reductase inhibition and high performance liquid chromatography (HPLC) assays can be used to determine drug concentrations. Clearance of trimetrexate has been reported to follow biphasic or triphasic patterns. Elimination is primarily by biotransformation with less than 5% of the drug excreted renally in an unchanged form. Both active and inactive metabolites have been found, but the precise metabolic pathways have yet to be defined. The role of trimetrexate in the treatment of Pneumocystis carinii pneumonia is limited to compassionate use, as clinical studies have shown cotrimoxazole (trimethoprim-sulfamethoxazole) to be superior to trimetrexate. However, in a wide spectrum of malignant processes, trimetrexate appears to have a role either as a high-dose single agent, with calcium folinate (leucovorin calcium) rescue, or in combination with other antineoplastic agents. However, further trials are needed to fully establish the efficacy of trimetrexate in these settings. Increased knowledge of the pattern of resistance for individual tumours and tumour types may result in trimetrexate becoming more widely used clinically.