Activity of 2-chloro-2'-deoxyadenosine in chronic lymphocytic leukemia, hairy cell leukemia, and autoimmune hemolytic anemia

Cladribine prolongs progression-free survival and time to second treatment compared to fludarabine and high-dose chlorambucil in chronic lymphocytic leukemia

We conducted a randomized phase III trial to compare the efficacy and safety of two purine analogs, cladribine and fludarabine, with high-dose chlorambucil, in patients with previously untreated chronic lymphocytic leukemia (CLL). Between 1997 and 2004, 223 patients with CLL were randomly assigned to cladribine, fludarabine or chlorambucil, for six cycles of therapy with frequent health-related quality of life assessments. There was no statistical difference for the primary endpoint of overall response with cladribine (70%), fludarabine (67%) and chlorambucil (59%), or complete remission (12%, 7% and 8%), respectively. However, the median progression-free survival (25, 10, 9 months) and median time to second treatment (40, 22, 21 months) were superior with cladribine. There was no significant difference in overall survival (96, 82 and 91 months), nor in toxicity or HRQoL assessments. Monotherapy with cladribine gives superior PFS and longer response duration than fludarabine and chlorambucil as first-line treatment of CLL.

Ernest Beutler: his life and contribution to medical science

Ernest Beutler was one of the preeminent haematologists of the last half of the 20th and the early 21st century. In a career that spanned six decades, his research interests included such diverse areas as red cell metabolism, blood preservation, glycolipid storage diseases, leukaemias and iron metabolism. Indeed, he was quite different from most of his contemporaries in that his knowledge encompassed not only haematology and not only the medical sciences, but the biological sciences as a whole. He was among the first to describe X chromosome inactivation, and he established the critical link between glucose-6-phosphate dehydrogenase deficiency and drug-induced haemolysis. He was a skilled and innovative clinician, and an early advocate of bone marrow transplantation for the treatment of acute leukaemia. He was a prolific author, with over 800 publications; a long time member of the Editorial Board of Blood; founder of the journal Blood Cells Molecules and Diseases; and an editor of Williams Haematology from the time of its inception. He bequeathed $1 million to the American Society of Haematology to recognise and reward outstanding basic research and its clinical application: a pursuit to which he had committed his life. Indeed, he became an extraordinary exemplar of the bench-to-bedside ethos, which holds that even today, an MD researcher, working with limited means and independent of pharmaceutical companies, can have a great impact on the practice of medicine.

Uncommon tumors and exceptional therapies: paradox or paradigm?

Why does it seem that, repeatedly, when a new treatment with a striking effect is discovered in the cancer field, it is effective for a very rare cancer type? For example, groundbreaking therapeutic discoveries have been made for extremely uncommon malignancies such as hairy cell leukemia, chronic myelogenous leukemia, seminoma, gastrointestinal stromal tumor, (del)5q myelodysplastic syndrome, and acute promyelocytic leukemia. In contrast, progress in the most common and most intensively studied tumors - lung, breast, prostate, and colon cancer - has been slow and incremental. We hypothesize that the reason for this phenomenon is that the pathophysiologic basis for a tumor being rare is one and the same as the reason that it may ultimately be so treatable. That is, if a cancer can be derived only via a single aberrant molecular genetic aberration, then it should be both rare and easily targeted by a molecular cancer therapeutic approach. If, on the other hand, many distinct pathways can lead to the development of a specific tumor type, it should occur much more commonly and be significantly more difficult to treat. The corollary to our hypothesis is the prediction that new therapies will continue to show their most salutary effects in rare cancers. Furthermore, only by stratifying the common tumors, especially when using targeted agents, into the molecular subsets of diseases that compose them are we likely to achieve a substantial effect in these disorders.

Oral antilymphocyte activity and induction of apoptosis by 2-chloro-2'-arabino-fluoro-2'-deoxyadenosine

2-Chlorodeoxyadenosine (CdA) is active in chronic lymphocytic leukemia, hairy-cell leukemia, and low-grade lymphomas. In part, this spectrum of activity may be attributable to the selective toxicity of CdA to nondividing lymphocytes and monocytes. However, CdA is unstable at acidic pH and is degraded by bacterial nucleoside phosphorylases. The present experiments demonstrate that the 2'-arabino-fluoro derivative of CdA, designated CAFdA, is also directly toxic to quiescent lymphocytes and macrophages. Unlike CdA, CAFdA was stable at pH 2 and resisted degradation by Escherichia coli nucleoside phosphorylase. Cell killing was preceded by the formation of DNA strand breaks and could be prevented by supplementation of the medium with deoxycytidine. The initial DNA damage initiated the pattern of oligonucleosomal DNA fragmentation characteristic of apoptosis. Mutant lymphoblasts, deficient in deoxycytidine kinase, with elevated cytoplasmic 5'-nucleotidase, or with expanded deoxynucleotide pools secondary to increased ribonucleotide reductase activity, were cross-resistant to both CAFdA and CdA toxicity. One-week oral treatment with CAFdA (1 mg/ml in drinking water) achieved an average plasma concentration of 0.56 microM and eliminated 90% of chronic lymphocytic leukemia cells transplanted into severe combined immunodeficiency (scid) mice. Under the same conditions, CdA was much less active. Collectively, these results suggest that CAFdA could be effective as an oral agent in indolent lymphoproliferative diseases and in autoimmune diseases where lymphocyte and monocyte depletion is desirable.