Novel and emerging drugs for acute lymphoblastic leukemia

Over the past several decades the important progress has been made in the management of acute lymphoblastic leukemia (ALL), especially among children. However, in adult patients reported cure rates seldom exceeded 40%, despite the use of hematopoietic stem-cell transplantation in many cases. Conventional chemotherapy is toxic and ineffective. Therefore, new treatment options and risk-adapted therapies are needed to improve the outcome of ALL patients. This review is focused on new systemic treatment modalities, such as nucleoside analogues, purine synthetase inhibitors, monoclonal antibodies, tyrosine kinase inhibitors and other agents targeting molecular pathways that are aimed to benefit patients and improve the outcome of their treatment.

Pharmacological and clinical studies on purine nucleoside analogs--new anticancer agents

More recently, three novel purine nucleoside analogs, including clofarabine, nelarabine and immucillin H, have been introduced into clinical trials. These agents have different metabolic properties, novel mechanism of action, and are undergoing phase I-II clinical studies for the treatment of hematopoietic malignancies. Pharmacology and anticancer activity of PNA are the subjects of this review.

The interaction of gemcitabine and cytarabine on murine leukemias L1210 or P388 and on human normal and leukemic cell growth in vitro

BACKGROUND AND OBJECTIVE

Gemcitabine (dFdC) is a new nucleoside antimetabolite of deoxycytidine that resembles cytarabine (Ara-C) in both its structure and metabolism. Little is known about dFdC efficacy in hematologic malignancies, either as a single drug or in combination with other drugs. In this study we have tried to determine whether the cytotoxic effect of Ara-C can be increased by using it in combined therapy with dFdC.

DESIGN AND METHODS

In the in vivo part of our study, mice bearing L1210 or P388 leukemia were treated with dFdC and Ara-C. The drugs were administered alone and in combination according to the following schedules: Ara-C and dFdC at the same time, dFdC before Ara-C, and Ara-C before dFdC. The efficacy of the therapy against leukemia (defined as the increase in lifespan, ILS) was assessed as the percentage of the median survival time (MST) of the treated group (T) in relationship to that of the control group (C): ILS=[(MST(C)/MST(T)) -1]x100. In the in vitro part of our study, normal granulocyte-macrophage colony-forming unit (CFU-GM) cells as well as CFU-GM cells obtained from patients with chronic myeloid leukemia (CML) were incubated either with dFdC or Ara-C alone or with adequate concentrations of a combination of these drugs.

RESULTS

The in vivo experiment revealed that in both leukemias tested, combined therapy with dFdC given before Ara-C and dFdC given at the same time with Ara-C were more effective than monotherapy with either dFdC or Ara-C. The other treatment schedule (Ara-C before dFdC) did not significantly prolong the survival time of the treated mice bearing L1210 or P388 leukemia as compared with the treatment with dFdC alone. The in vitro experiments showed that dFdC used together with Ara-C acted additively on normal as well as CML CFU-GM cells. Furthermore, the drugs used jointly inhibited the growth of colonies formed by CML CFU-GM cells to a significantly higher degree than normal CFU-GM and the differences were statistically significant in the case of the combination of highest concentrations.

INTERPRETATION AND CONCLUSIONS

Gemcitabine increased the activity of Ara-C. As these agents incorporate into DNA blocking chain elongation, and moreover, dFdC influences the cytotoxicity of Ara-C, our results could be explained by the drugs acting at these levels. dFdC used jointly with Ara-C may have an important clinical implication in the treatment of CML and other hematologic malignancies in future.