Treatment of myelodysplastic syndromes with low-dose oral 6-thioguanine

Repurposing existing agents as adjunct therapies for glioblastoma

Numerous non-oncologic medications have been found in the last decade to have anti-cancer properties. While the focus in oncology research should clearly remain on deriving new therapeutic strategies, repurposing these existing medications may offer the potential to rapidly enhance the effectiveness of treatment for resistant cancers. Glioblastoma, the most common and lethal brain cancer, is highly resistant to standard therapies and would benefit from even minor improvements in treatment. Numerous agents already in the clinic for non-cancer applications have been found to also possess potential against cancer or specifically against glioblastoma. These include agents with activities affecting oxidative stress, the immune reponse, epigenetic modifiers, cancer cell metabolism, and angiogenesis and invasiveness. This review serves as a guide for potential ways to repurpose individual drugs alongside standard glioblastoma therapies.

Standard and low-dose chemotherapy for the treatment of myelodysplastic syndromes

The myelodysplastic syndromes (MDS) are a heterogeneous group of disorders with an invariably fatal outcome. Other than bone marrow transplantation, no treatment has been able to alter the natural history of MDS. As a result, there has been an interest in identifying new and more effective chemotherapeutic agents. Many of the drugs that have been evaluated in an attempt to increase remissions and prolong survival were selected because of their activity in acute myeloid leukemia. Thus cytarabine has been the most widely studied drug. Although numerous studies suggested activity for low-dose cytarabine (LoDAC), a careful analysis of the data identified a complete remission (CR) rate of less than 20%, without meaningful clinical benefit. The issue of LoDAC was finally put to rest by a randomized trial in which survival was no better than with supportive care. 5-Azacytidine induces cellular differentiation by hypomethylation of DNA. Phase II trials noted CRs in fewer than 10% of patients, with response rates under 30%, although additional patients appeared to experience hematologic and clinical benefit. A randomized trial of 5-azacytidine versus supportive care failed to demonstrate a survival benefit. One of the most promising new agents is the topoisomerase inhibitor topotecan, which achieves CRs in more than 30% of patients. Combinations of this drug with other active agents are in development. Obviously, new treatment strategies are needed to improve the outcome of MDS patients. Combination approaches incorporating new, active agents should have sound scientific rationale, targeting biological differences among the various MDS subtypes.

Combined differentiating therapy for myelodysplastic syndromes: a phase II study

An in vitro synergism between different inducers of AML cell differentiation has been previously observed. Therefore, we treated 53 myelodysplastic (MDS) patients with a low dose combination of cis-retinoic acid (cRA, 20-40 mg/day) and 1,25 alpha (OH)2 cholecalciferol [(OH)2D3, 1-1.5 micrograms/day] +/- intermittent 6-thioguanine (30 mg/m2/day). The latter was reserved for patients with bone marrow (BM) blast excess (> or = 5%). The treatment was well tolerated, without major toxicity. Among 25 patients with BM blasts less than 5%, we observed one complete, eight partial and four minor responses (response rate 52%) with a median response duration of 8 months (2 +/- 24). Median survival, which did not correlate with response, is projected at 76 months. Thirty-one patients with BM blast excess (> or = 5%), including three of the previous group who progressed to refractory anemia with excess of blasts (RAEB), were treated with the three-drug protocol. One complete, 12 partial and six minor responses were obtained (response rate 61%) with a median response duration of 6 months (2-29+). A significant difference in survival (P < 0.005) was observed between the 19 responders (median 25 months) and the 12 non-responders (median 9 months). A reduction in the transfusion need was observed in 41% of the transfusion-dependent patients with blast excess and in 53% of those without blast excess. Therefore, combined differentiating therapy seems more effective than previously reported single agent treatments and should be considered for a larger randomized study to assess its actual impact on survival of MDS patients.