High activity and incomplete cross resistance of nucleoside analogues cladribine and fludarabine versus Ara-C on leukemic cells from patients with AML

Efficacy and toxicity of cladribine for the treatment of refractory acute myeloid leukemia: a meta-analysis

Purpose: To investigate the overall efficacy and toxicity of cladribine and cladribine-based chemotherapy in the treatment of patients with refractory acute myeloid leukemia (AML) based on meta-analysis. Methods: PubMed, EMBASE database, and the Cochrane Library were searched for relevant studies. Eligible studies were clinical trials of refractory AML assigned to cladribine with data on efficacy including complete remission (CR) rate, overall response rate (ORR) and overall survival. Toxicity was evaluated based on the early death rate and the incidence of grade 3 and 4 adverse events (AEs). Results: A total of 10 clinical trials including 422 refractory AML patients were analyzed. The overall CR rate was 42.2% (95% CI: 31.0-54.3%). And the ORR of seven trials including 235 patients was 49.7% (95% CI: 33.5-66.0%). The overall early death rate of 260 patients enrolled in five trials was 6.8% (95% CI: 4.3-10.6%). Thrombocytopenia, anemia, neutropenia, and infection were the most common grade 3 and 4 AEs. Conclusion: Cladribine is effective for refractory AML, and its efficacy can be increased with the combination of cladribine, cytarabine, and granulocyte-colony stimulating factor regimen.

Comparison of epigenetic versus standard induction chemotherapy for newly diagnosed acute myeloid leukemia patients ≥60 years old

Older patients with acute myeloid leukemia (AML) have poor outcomes with standard induction chemotherapy. We retrospectively reviewed our institute's experience with epigenetic (Epi) versus cytarabine- and anthracycline-based intensive chemotherapy (IC) as induction in newly diagnosed AML patients aged 60 years and older. One hundred sixty-seven patients (n = 84, IC; n = 83, Epi) were assessed; 69 patients received decitabine and 14 azacitidine. Baseline characteristics between the IC and Epi patient cohorts were not statistically different except for age, initial white blood cell count, and comorbidity index. Overall response rate (ORR, 50% vs. 28%, respectively, P < 0.01) and complete response rate (CRR, 43% vs. 20%, respectively, P < 0.01) were superior following IC vs. Epi. Although univariate analysis demonstrated longer overall survival after IC (10.7 vs. 9.1 months, P = 0.012), multivariate analysis showed no independent impact of induction treatment. Treatment-related mortality was not statistically different in the two groups. Outcomes of patients with secondary, poor cytogenetic risk, FLT-3 mutated AML, or relapsed/refractory disease after IC or Epi were not significantly different. Outcomes of patients receiving IC versus a 10-day decitabine regimen (n = 63) also were not significantly different. Our results suggest that IC and Epi therapy are clinically equivalent approaches for upfront treatment of older patients with AML and that other factors (feasibility, toxicity, cost, etc.) should drive treatment decisions. Prospective randomized trials to determine the optimal induction approach for specific patient subsets are needed.

Revisiting the role of cladribine in acute myeloid leukemia: an improvement on past accomplishments or more old news?

Originally studied in lymphoid diseases, cladribine (CdA) is an adenosine deaminase resistant analog of adenosine that was later discovered to induce myeloid cell apoptosis. The activity of CdA in myeloid malignancies was first reported in relapsed/refractory (RR) pediatric acute myeloid leukemia (AML) with complete response (CR) rates of up to 47%. Consequently, several studies have confirmed the efficacy of single agent CdA or CdA combination regimens in AML. Established CR rates for combination regimens in RR adults are approximately 50%, while CR rates for newly diagnosed (ND) adults are approximately 70% and show similar toxicity profiles to previously used regimens. Despite these promising data, many centers have yet to adopt CdA combination regimens for these difficult to treat populations. We review the pharmacology, pharmacokinetics, clinical data, and safety of CdA monotherapy and combination regimens for the management of pediatric and adult ND and RR-AML.

Drug cross-resistance and therapy-induced resistance in chronic lymphocytic leukaemia by an enhanced method of individualised tumour response testing

Previous results with individualised tumour response testing (ITRT) in vitro in chronic lymphocytic leukaemia (CLL) have consistently shown good correlation with patient response and survival. We describe here an improved test and report its use with samples from the Leukaemia Research Fund CLL4 randomised clinical trial and previously treated patients. ITRT was performed by the tumour response to anti-neoplastic compounds (TRAC) assay, a modification of the differential staining cytotoxicity (DiSC) assay. Improvements included drying drugs into wells before assay and using the Octospot system to cytocentrifuge eight spots of cells onto one microscope slide. We successfully tested 765/782 (98%) cellular blood samples received within 48 h of phlebotomy. Cross-resistance (Pearson's r > 0.7) in untreated CLL was found between similar drugs. Mitoxantrone (r = 0.31), cyclophosphamide (r = 0.35) and pentostatin (r = 0.29) had low cross-resistance with fludarabine. Treatment resulted in increased resistance to chlorambucil, cyclophosphamide, doxorubicin, mitoxantrone, corticosteroids, cladribine and fludarabine (P < 0.01) but not to pentostatin. These results provide further rationale for standard drug combinations such as fludarabine-mitoxantrone and fludarabine-mitoxantrone-cyclophosphamide and suggest possible pentostatin salvage in fludarabine-resistant patients. ITRT results could assist both in determining the best treatment for individual patients and in the design and rationale of future clinical trials.

Improvement of purine and pyrimidine antimetabolite-based anticancer treatment by selective suppression of mycoplasma-encoded catabolic enzymes

Most mycoplasmas are present as commensals, colonising the mucosa of our respiratory and gastrointestinal tract. Experimental data suggest that the long-term association of certain mycoplasma species with mammalian cells might favour host-cell transformation and malignancy. Moreover, increased mycoplasma infection has been noted in several cancers. Despite efforts to develop target-specific anticancer drugs, current cancer treatment still relies on the use of nucleobase or nucleoside-based analogues. Here, we provide experimental evidence that nucleoside-metabolising catabolic enzymes expressed by mycoplasmas substantially compromise the efficacy of nucleoside antimetabolites used in the treatment of cancer. We also suggest potential methods for improving future chemotherapy by suppressing mycoplasma-mediated catabolism of the anticancer nucleoside analogues.