ALBERT

Description: The active form of vitamin D3 [1 alpha, 25-dihydroxyvitamin-D3 (1 alpha, 25(OH)2D3)] modulates the proliferation and differentiation of hematopoietic cells. Analogs of 1 alpha, 25(OH)2D3 that have greater potency may have the potential as adjuvant therapy for high-risk patients in remission for acute myelogenous leukemia (AML) and myelodysplastic syndromes. A new generation of 11 analogs of 1 alpha, 25(OH)2D3 has been synthesized, and we examined their effects on the human leukemic cell line HL-60. This cell line provides a sensitive monitor of activity of the 1 alpha, 25(OH)2D3 analogs. All the compounds were potent, producing a 50% clonal inhibition (ED50) in the range of 10(-8) to 10(-11) mol/L; nine of the 11 analogs had ED50s at concentrations that were at least 10-fold lower than those for the parental 1,25(OH)2D3. The most active compound [cmpd LA, (22R)-1 alpha, 25-(OH)2–16,22,23-triene-D3] had an ED50 of 2 x 10(-11) mol/L; it was also tested on clonogenic cells from patients with AML, and it achieved an ED50 of approximately 6 x 10(-11) mol/L, while 1 alpha, 25(OH)2D3 produced an ED50 of approximately 10(-8) mol/L on the same population of cells. Five different cell surface markers were examined on HL-60 cells exposed to the 1 alpha, 25(OH)2D3 analogs: HLA-DR and CD11b were induced by all of the compounds; CD13 was induced by six of the 12 compounds, including 1,25(OH)2D3; CD14 was strongly induced by all compounds; and CD38 was induced rather weakly by nine of 12 analogs. WAF1/CIP1/p21, a cyclin-dependent kinase inhibitor (CDKI), which is important in blocking the cell cycle, was examined by Western blot and was found to be induced by all of the compounds, suggesting a possible mechanism by which these analogs inhibit leukemic growth. The induction of WAF1 occurred at concentrations of vitamin D analogs as low as 10(- 10) mol/L. This structure-function study showed that a new series of 1 alpha, 25(OH)2D3 analogs was active in clonal inhibition, as well as induction of differentiation and WAF1 expression of HL-60 cells. The key structural motifs included C-16 double bond, double and/or triple bonds in the side chain, lengthening of the side chain, 20-epi- conformation of the side chain, replacement of six hydrogens at the end of the side chain with fluorines, and the removal of C-19. Consideration should be given to further in vivo testing of toxicity and efficacy to move toward a clinical trial, especially in a setting of minimal residual disease.

Description: We conducted a multicenter trial of treatment with all-trans retinoic acid (ATRA) for newly diagnosed acute promyelocytic leukemia (APL) in the AML-92 study and compared it with our previous study with standard intensive chemotherapy, the AML-89 study, in the view of complete remission (CR) rate, incidence of early death, and event-free survival (EFS). Patients were scheduled to receive oral ATRA 45 mg/m2 daily until CR. If patients had leukocyte counts above 3 x 10(9)/L at the start of therapy, they received daunorubicine (DNR) 40 mg/m2 for 3 days and behenoyl cytosine arabinoside (BHAC) 200 mg/m2 for 5 days in addition to ATRA. During the ATRA therapy, if patients showed myeloblast plus promyelocyte counts higher than 1 x 10(9)/L in the peripheral blood, they received additional DNR and BHAC in the same schedule, as well. A total of 110 patients were entered into the study. Median age was 43 years (range, 16 to 74). Twenty-eight (26%) of 109 patients (one died before the start of therapy) received ATRA alone. Ninety-seven patients (89%) achieved CR; 48 of 49 (98%) aged less than 40 years, 44 of 52 (84%) aged between 40 and 69, and 5 of 8 (63%) aged above 70 achieved CR, respectively; 25 of 28 (89%) with ATRA alone, 46 of 51 (90%) with ATRA plus initial chemotherapy and 26 of 30 (87%) with ATRA plus later chemotherapy attained CR, respectively. Nine (8%) patients died within 28 days after the start of therapy. In contrast, 44 of 62 patients (71%) attained CR, and 13 (21%) died within 28 days in the AML-89 study with the combination of DNR, BHAC, 6-mercaptopurine and prednisolone. Seven developed retinoic acid syndrome and one died of it in the present study. Other toxicities associated with this drug included cheilitis, desquamation, muscle pain, and hypertriglyceridemia. Predicted 23 months EFS for all ATRA-treated patients and disease-free survival (DFS) in the CR cases were 75% and 81%, respectively, in a median follow-up period of 21 months. Compared to the AML-89 study, there was a highly significant difference in remission rate (P = .004), EFS (P = .0007), and also early mortality rate (P = .02). Present results demonstrated that ATRA with or without chemotherapy gives a statistical improvement in CR rate and early mortality rate, as well as superior survival in newly diagnosed APL.