Clinical use of streptolysin-O to facilitate antisense oligodeoxyribonucleotide delivery for purging autografts in chronic myeloid leukaemia.

Antisense oligodeoxyribonucleotides (ODN) targeted against the breakpoint in BCR-ABL mRNA will specifically decrease BCR-ABL mRNA, provided cells are first permeabilised with streptolysin-O (SL-O). We used 18-mer chimeric methylphosphonodiester: phosphodiester linked (4-9-4) ODN complementary to 9 bases either side of the BCR-ABL junction to purge harvests ex vivo in three CML patients who remained completely Ph positive after multiple chemotherapy courses. After CD34+ cell selection and SL-O permeabilisation, harvests were purged with 20 microM ODN. After purging, all individual CFU-GM colonies grown from the two b3a2 breakpoint cases remained positive for BCR-ABL mRNA. In contrast, all 24 colonies grown from the b2a2 breakpoint case were BCR-ABL mRNA negative. Patients were conditioned with busulphan 16 mg/kg. The initial post-transplant course was uneventful, although the time to return to 0.5 x 10(9)/l neutrophils was slow at 25-51 days. Both chronic phase patients remain in haematological remission at +724 and +610 days, although each has cytogenetic evidence of relapse. The b2a2 accelerated phase patient died of myeloid blast transformation at day +91. The present SL-O-facilitated ODN purging strategy appears to be without significant toxicity, and offers considerable improvements in ODN delivery to the cytosol.

Previous treatment predicts the efficiency of blood progenitor cell mobilisation: validation of a chemotherapy scoring system.

Following mobilising chemotherapy and myeloid growth factors, some heavily pretreated patients do not mobilise adequate numbers of peripheral blood progenitor cells (PBPC). It would be clinically useful to identify such patients in advance. A recent scoring system based on previous therapy may be useful in predicting CD34-positive cell yield. In this study we validated this scoring system on an independent group of 99 patients undergoing 103 harvesting episodes. In 61 patients mobilised with cyclophosphamide 1.5 g/m2 and G-CSF, those with treatment scores less than 21 yielded significantly more CD34-positive cells than patients with scores greater than 63 (P = 0.0012). Previous treatment with melphalan or carmustine was associated with a significantly lower yield of CD34-positive cells (P= 0.0001). No relationship was seen between the time from previous chemoradiotherapy and harvest outcome. Patients with treatment scores less than 21 required a shorter duration of G-CSF therapy (P = 0.05). Similar findings were seen in 42 further mobilisation cycles undertaken with alternative mobilisation schedules. The present data suggest that a score summarising previous treatment can be used to predict CD34 yields, and could be of clinical use to identify poor PBPC mobilisers in advance.