Treosulfan is an alkylating agent that is structurally related to busulfan. It is used in the treatment of ovarian carcinoma and currently considered in clinical trials as a conditioning agent prior to autologous and allogeneic stem cell transplantation (SCT). While high-dose busulfan is associated with severe dose-limiting adverse effects such as interstitial pneumonia, hemorrhagic cystitis, convulsion, mucositis and an increased risk for venoocclusive disease, high-dose treosulfan has been found to be less toxic on non-hematological tissues. In addition, treosulfan combines favorably myeloablative and immunosuppressive efficacy and might be a preferential agent in combination with the immunosuppressive drugs fludarabine or cyclophosphamide for conditioning protocols. Therefore, it seems an ideal candidate to replace busulfan in myeloablative therapy for allogeneic SCT. First successful results in adult hematological malignancies have been reported by Casper et al.. Although childhood and adult leukemias are biologically different, treosulfan might be of interest for the treatment of childhood leukemia as well, because of both its very low nonhematological toxicity and its broad spectrum of antineoplastic activity against various cancers. To date, the prognosis of children with relapsed or therapy refractory leukemia remains still dissatisfactory despite multimodal chemotherapy and SCT. This is necessitating optimization of high-dose chemotherapy (HDC) protocols similar to the approach of Den Boer et al. for patient stratification based on drug resistance profiles in children with leukemia. Accordingly, the development of new HDC protocols requires several stages of pre-clinical and clinical investigations including in vivo and in vitro studies.
There is little data available describing in vitro and in vivo efficacy of treosulfan compared to busulfan in leukemic cells, and literature lacks such in vitro data in leukemic cells of pediatric patients. Lanvers-Kaminsky et al. show a high sensitivity of adult leukemic cell lines towards treosulfan, which has been superior, compared to busulfan incubation. Most importantly, xenograft mouse models described by Fichtner et al. Yielded promising in vivo results for three childhood leukemias when comparing treosulfan with busulfan.
We, therefore, sought to evaluate the cytotoxic effect and dose response of treosulfan and busulfan on both freshly isolated leukemic pediatric cell samples and normal hematological cells like stem cells, T cells and natural killer (NK) cells. The nucleoside-analogue fludarabine was added in some experiments to evaluate possible interactions, because fludarabine is commonly combined with busulfan. Additionally, the rapid cell apoptosis was accessed by increased cleavage of pro-caspase 3 in the high active parts of this proteinase to detect the apoptotic action in leukemic cells.
Munkelt, Doreen, et al. “Cytotoxic effects of treosulfan and busulfan against leukemic cells of pediatric patients.” Cancer chemotherapy and pharmacology 62.5 (2008): 821-830.