Preclinical activity of taxotere (RP 56976, NSC 628503) against freshly explanted clonogenic human tumour cells: Comparison with taxol and conventional antineoplastic agents

Taxotere (TER) and taxol (TA) are new antitumour agents currently undergoing clinical evaluation. We studied the antineoplastic effects of these agents (final concentrations: 4.0, 0.4, 0.04 μmol/l) on the in vitro proliferation of clonogenic cells from freshly explanted human tumours using a capillary soft agar cloning system. We also compared the activity of these new compounds to conventional antineoplastic agents (bleomycin, cisplatin, dacarbazine, doxorubicin, etoposide, 5-fluorouracil, vinblastine, interferon-α2). Using a 21-28-day continuous drug exposure, 5481 specimens (67%) were evaluable for comparisons, and using a 1-h drug exposure followed by 21-28 days incubation, 5080 specimens (63%) were similarly evaluable. With both schedules, TA and TER showed concentration-related antitumour activity. At 0.4 μmol/l, median colony survival was 0.61 × control (range 0.09-0.96) for TA and 0.51 × control (0.15-0.81) for TER in the 1-h incubation (P = 0.0002). Median colony formation was also reduced significantly more by TER as compared to TA in the long-term incubation schedule. Statistical analysis indicated that TER but not TA was significantly more active than cisplatin (P = 0.02), doxorubicin (P = 0.01), 5-fluorouracil (P = 0.01) and interferon-α2 (P = 0.01). We conclude that TER and TA are more active against in vitro tumour colony formation from freshly explanted human tumours. TER appears to be slightly more active than taxol and promises to be active against tumours resistant to conventional antineoplastics.