Tumor efficacy and bone marrow-sparing properties of TER286, a cytotoxin activated by glutathione S-transferase.

TER286 is a latent drug activated by human glutathione S-transferase (GST) isoforms P1-1 and A1-1 to produce a nitrogen mustard alkylating agent. M7609 human colon carcinoma, selected for resistance to doxorubicin, and MCF-7 human breast carcinoma, selected for resistance to cyclophosphamide, both showed increased sensitivity to TER286 over their parental lines in parallel with increased expression of GST P1-1. In primary human tumor clonogenic assays, the spectrum of cytotoxic activity observed for TER286 was both broad and unusual when compared to a variety of current drugs. In murine xenografts of M7609 engineered to have high, medium, or low GST P1-1, responses to TER286 were positively correlated with the level of P1-1. Cytotoxicity was also observed in several other cell culture and xenograft models. In xenografts of the MX-1 human breast carcinoma, tumor growth inhibition or regression was observed in nearly all of the animals treated with an aggressive regimen of five daily doses. This schedule resulted in a 24-h posttreatment decline in bone marrow progenitors to 60% of control and was no worse than for a single dose of TER286. These studies have motivated election of TER286 as a clinical candidate.

Effects of retinoids on cell toxicity and apoptosis in leukemic blast cells from patients with non-M3 AML.

All-trans retinoic acid (ATRA) induces complete remission in acute promyelocytic leukemia (APL or M3). In this study we measured the effect of retinoids alone and in combination with daunorubicin (DNR) on cell growth and apoptosis in blast cells from patients with non-M3 AML. Cells from 21 patients were incubated in 0.2 microM daunorubicin for 1 h or in 1 microM ATRA or 9-cis-RA continuously and in the combinations of DNR with both retinoids. Cell toxicity and apoptosis were analyzed after 96 h. Both ATRA and 9-cis-RA reduced the viability significantly to 86 and 84%, respectively (P = 0.003 for ATRA and 0.02 for 9-cis-RA). The expression of CD34 correlated to a higher sensitivity to ATRA (P = 0.003). When retinoids were added to DNR the mean decrease in viability was 11 percentage points with ATRA (P = 0.003) and nine percentage points with 9-cis-RA (P = 0.02). Apoptosis was induced by both retinoids and the percentage of apoptotic cells was increased from 16% in the controls to 24% with ATRA (P = 0.03) and to 26% with 9-cis-RA (P = 0.04). When the retinoids were added to DNR the apoptotic rate increased from 41% with DNR alone to 51% with ATRA (P = 0.01) and to 49% with 9-cis-RA (P = 0.03). We conclude that ATRA and RA exert a slight but clear cytotoxic and apoptotic effect on AML blast cells after 96 h incubation and that retinoids can have an additive or synergistic effects on cell toxicity when added to daunorubicin.

Alteration of pharmacokinetics of cyclophosphamide and suppression of the cytochrome p450 genes by ciprofloxacin.

Recently, it has been reported that prophylactic administration of ciprofloxacin during cyclophosphamide (CY) conditioning was a high-risk factor for relapse in patients undergoing allogeneic BMT. In the present study, we investigated the possible mechanisms of this interaction in male Sprague-Dawley rats. The kinetics of CY and its active 4-OH-CY metabolite were determined, after 3 days pretreatment with ciprofloxacin (200 mg/kg) and compared to control rats without treatment. CY was administered as a high or low single intravenous dose (150 and 90 mg/kg, respectively). The expression of the CYP2B1, CYP2B2, CYP2C11, CYP3A1 and CYP3A2 genes was evaluated by SYBR Green I Dye real-time PCR for quantification of mRNA. The administration of ciprofloxacin resulted in a significant increase in the AUC (P=0.007) and a significant decrease in clearance (P=0.007) when CY was given as a high dose. In accordance, the metabolic ratio (AUC4-OH-CY/AUCCY) was significantly lower (P=0.007) compared to that found in the control group. Ciprofloxacin significantly suppressed gene expression of CYP2C11 (P=0.01) and CYP3A1 (P=0.04); however, no effect was observed on the gene expression of CYP3A2, CYP2B1 and CYP2B2. Our study revealed that ciprofloxacin interacts with CY and suppressed relevant cytochromes p450 at the transcriptional level. This study may have a great clinical impact when ciprofloxacin is used in therapy.