Non-steroidal anti-inflammatory drugs and cytotoxics

Pharmacokinetic basis for the comparative antitumour activity and toxicity of chlorambucil, phenylacetic acid mustard and beta, beta-difluorochlorambucil (CB 7103) in mice

This report describes the relationship between the pharmacokinetics, antitumour activity and toxicity of chlorambucil (CHL), phenylacetic acid mustard (PAAM) and beta, beta-difluorochlorambucil (beta-F2CHL) in mice. Pharmacokinetics were studied by HPLC, antitumour activity by a regrowth delay assay using the KHT murine sarcoma and toxicity by acute LD50. For both antitumour activity and acute toxicity the order of potency was: PAAM greater than CHL greater than beta-F2CHL. CHL and PAAM exhibited identical therapeutic indices, whereas that for beta-F2CHL was somewhat improved. CHL is metabolized by mitochondrial beta-oxidation to the 3,4-dehydro derivative (DeHCHL) and PAAM, and the latter is further metabolized to its monodechloroethylated derivative DeC-PAAM, presumably by hepatic microsomal enzymes. Administered PAAM gave only one metabolite, DeC-PAAM. Unexpectedly, despite beta, beta-disubstitution, beta-F2CHL was also beta-oxidized to give DeHCHL and PAAM, but at reduced rates. Further, metabolic switching was demonstrated with the appearance in large amount of 2 new, unidentified metabolites, which may be dechlorethylation products. The pharmacokinetics of administered CHL, PAAM and beta-F2CHL differ in that the plasma clearance was fastest for CHL, slowest for PAAM and intermediate for beta-F2CHL. For the metabolites, CHL produced peak plasma concentrations of DeHCHL and PAAM, respectively, 7-fold and 2-fold greater than those produced by beta-F2CHL. However, despite these differences, exposures to total bifunctional nitrogen mustards were similar following administration of the 3 drugs and therefore cannot account for their differential activity. In contrast, there was a good correlation between potency and PAAM exposure, which is highest after treatment with PAAM, intermediate after CHL and lowest after beta-F2CHL. In plasma, 3.2% of PAAM is present as nonprotein-bound free drug, compared to 1.3% for DeHCHL, 0.9% for CHL and 0.45% for beta-F2CHL. We propose the amount of free bifunctional nitrogen mustard, itself partly dependent on the extent of metabolism, to be of major importance for the in vivo potency of CHL analogues.

The modulating effects of flurbiprofen on adriamycin plus vincristine or vindesine in the treatment of advanced breast cancer

To assess the modulating effects of a non-steroidal anti-inflammatory drug on chemotherapeutic agents, 183 patients with advanced breast cancer have been treated in a randomised study with flurbiprofen or placebo and adriamycin plus a vinca alkaloid. To assess the efficacy of the new vinca alkaloid, vindesine, in breast cancer, patients were further randomised to receive vindesine or vincristine. The overall response rate in evaluable patients was 57%, and the median duration of response in the different treatment groups varied from 6 to 10 months. Response rates and toxicity in vindesine- and vincristine-treated patients were similar, although with vindesine neurotoxicity was slightly lower. Flurbiprofen did not improve the response rate or reduce the toxicity of adriamycin plus vinca alkaloid.

Increased survival of cancer-bearing mice treated with inhibitors of prostaglandin synthesis alone or with chemotherapy

In mice with a transplantable mammary carcinoma, treatment with the prostaglandin-synthesis inhibitors flurbiprofen or indomethacin produced various beneficial effects. Survival time after excision of the transplanted tumour was increase, particularly when the drugs were given with the chemotherapeutic agents methrotrexate and melphalan, and there were more disease-free survivors. The combined treatment with flurbiprofen also gave less tumour recurrence at the excision site. Flurbiprofen did not seem to alter the bioavailability of the chemotherapeutic agents.