Alkyl-lysophospholipid derivates (ALP) are currently being tested as bone marrow (BM) purging agents prior to autologous BM transplantation in different malignancies. We evaluated the toxicity of the ALP ET-18-OCH3 (ET-18; Edelfosine, 1-0-octadecyl-2-0-methyl-rac-glycero-3-phosphocholine) towards early hematopoietic precursors by testing progenitor regeneration of non-purged and ET-18-purged BM (75 mu g and 125 mu g ET-18/ml/2x10(7) BM cells) in autologous long-term bone marrow cultures (LTBMC) from 3 different patients in complete remission. LTBMC feeder layers were irradiated with 875 rad for complete elimination of hematopoietic progenitors and recharged with cryopreserved purged and non-purged BM. In weekly intervals, adherent layer and supernatant LTBMC cells were completely removed and evaluated in colony forming unit (CFU)-assays. We have seen sufficient CFU-regeneration out of ET-18-purged BM up to 8 weeks of LTBMC (>40 CFU/flask). Total CFU-counts from LTBMC with purged BM were slightly reduced compared to non-purged control. High dose purging with 125 mu g ET-18/ml partly inhibited initial CFU-proliferation, but demonstrated elevated CFU-counts after 4 and 8 weeks of LTBMC compared to control. In conclusion, in our LTBMC series ET-18-purging yielded tolerable toxicity towards committed BM-progenitors, but no remarkable decline of early hematopoietic precursors regenerating CFU-progenitors for up to 8 weeks of culture.

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