Summary Mitoxantrone can be efficiently loaded into large unilamellar vesicles using a transmembrane pH gradient. Release studies indicate that these drug-loaded carriers are highly stable and even after dissipation of the residual pH gradient retain more than 85% of encapsulated mitoxantrone following dialysis at 370C for 5 days. In murine studies we have compared the plasma clearance and biodistribution of both mitoxantrone and liposomal lipid following intravenous administration of free drug or mitoxantrone encapsulated in either conventional or sterically stabilized liposomes. In contrast to the rapid blood clearance observed for free mitoxantrone, both liposomal systems provided extended circulation lifetimes, with over 90% of the drug present 1 h after administration and 15-30% remaining at 24 h. In agreement with previous reports, longer plasma half-lives were observed for sterically stabilized liposomes than for conventional systems. In addition, a strong correlation between drug and carrier biodistribution was seen, with uptake occurring mainly in the liver and spleen and paralleling plasma clearance. This would suggest that tissue disposition reflects that of drug-loaded liposomes rather than the individual components. Liposomal encapsulation also significantly reduced mitoxantrone toxicity, allowing administration of higher, more efficacious drug doses. In a murine Li 21 0 tumour model, for example, no long-term survivors were seen in animal groups treated with free drug, whereas at the maximum therapeutic dose of liposomal mitoxantrone survival rates of 40% were observed.

The polyethoxylated castor oil, Cremophor EL (Cremophor) is approved for human use as a vehicle for oral and intravenous administration of water-insoluble compounds. Cremophor has also previously been shown to reverse the multidrug resistance phenotype at clinically acceptable doses. This study demonstrates that doses of Cremophor in the range of 25-50 microliters/kg intravenously (i.v.) administered 1 day prior to near-lethal irradiation protected the regenerative capacity of the marrow, resulting in haematopoietic radioprotection and long-term survival of near-lethally-irradiated mice. In normal mice, Cremophor administration (1) markedly reduced the level of serum haematopoietic inhibitory activity 4-8 h following injection; (2) resulted in a transient decrease in femoral bone marrow cellularity and upregulated B220 (B cells), and 7/4 (neutrophils and activated macrophages), but not Thy-1 (T-cells) surface antigen expression in bone marrow cells within 24 h of injection; and (3) transiently elevated the incidence of both primitive and committed haematopoietic progenitor cells detected in clonal agar culture within 48 h of injection. Bone marrow progenitor cell content, and peripheral blood white cell, platelet and reticulocyte counts were unaffected. This suggests that the haematopoietic radioprotection and recovery observed in irradiated mice pretreated with Cremophor may be the result of accessory cell activation and/or modulation of accessory factors regulating haematopoietic progenitor cells. Our data suggest a potential clinical use of Cremophor as an adjunct to, or as a substitute for, cytokines to minimize myelosuppression following cytotoxic therapy.

Background:The viability stains propidium iodide (PI) and 7-amino-actinomycin D (7-AAD) are excited at 488 nm, as are the commonly used antibody conjugates fluorescein isothiocyanate (FITC), phycoerythrin (PE), and cyanine 5 dye covalently coupled to R-phycoerythrin (RPE-Cy5). When excited by a single laser, spectral overlap in the emission of PI and 7-AAD with RPE-Cy5 precludes the use of these viability stains for three-color immunophenotyping, particularly when evaluating low levels of marker expression in viable target cells. The ultraviolet excitable dye hydroxystilbamidine methanesulfonate (Fluoro-Gold, or FG) binds to DNA at the A-T-rich regions of the minor groove in permeabilized or dead cells. We assessed the suitability of this dye as a viability stain. Methods: The ability of FG to detect nonviable cells in fresh and cryopreserved human apheresed peripheral blood cells was compared with that of PI and 7-AAD. The stability of FG staining and the effects of dye and cell

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SummaryInfusions of ex vivo-expanded (EXE) mobilized blood cells have been explored to enhance haematopoietic recovery following high dose chemotherapy (HDT). However, prior studies have not consistently demonstrated improvements in trilineage haematopoietic recovery. Three cohorts of three patients with breast cancer received three cycles of repetitive HDT supported by either unmanipulated (UM) and/or EXE cells. Efficacy was assessed by an internal comparison of each patient's consecutive HDT cycles, and to 106 historical UM infusions. Twenty-one cycles were supported by EXE cells and six by UM cells alone. Infusions of EXE cells resulted in fewer days with an absolute neutrophil count (ANC) <0AE1 · 10 9 /l (median 2 vs. 4 d, P ¼ 0AE002) and 3 d faster ANC recovery to >0AE1 · 10 9 /l (median 5 vs.. This resulted in a major reduction in the incidence of febrile neutropenia compared with UM cycles (0% vs. 83%; P ¼ 0AE008) and in 66% of historical UM cycles (P ¼ 0AE01) and a marked reduction in hospital re-admission. There were also fewer platelet transfusions required (43% vs. 100%; P ¼ 0AE009). We conclude that EXE cells enhance both neutrophil and platelet recovery and reduce febrile neutropenia, platelet transfusion and hospital re-admission.