Studies leading to the identification of ZD1839 (IRESSA): an orally active, selective epidermal growth factor receptor tyrosine kinase inhibitor targeted to the treatment of cancer.

This paper describes the development of the epidermal growth factor receptor tyrosine kinase inhibitor ZD1839 from a lead series of 4-anilinoquinazoline compounds. ZD1839 has suitable properties for use as a clinically effective drug and shows activity against human tumours. In particular, the use of pharmacokinetic data in the development of ZD1839 is discussed.

Nonsteroidal progestins and antiprogestins related to flutamide.

From the dual progestin/antiandrogenic properties of certain synthetic steroids (e.g. cyproterone acetate), it was apparent that the progesterone (P) and androgen (A) receptors must have some common ligand binding features. The nonsteroidal antiandrogen (aA) hydroxyflutamide was therefore considered a possible starting point for medicinal chemistry aimed at antiprogestin (aP) activity. Various modifications to the side chain and aryl ring substituents of flutamide yielded both P and aP activity, but always coupled with varying degrees of A or aA activity. Mineralocorticoid activity was present in some structures, but glucocorticoid and antiglucorticoid activities were not detected. Species (rat, rabbit and monkey) and chiral differences presented formidable difficulties in developing simple structure activity patterns, and low ( < 1%) in vitro uterine receptor binding belied in vivo potency of some aPs. One of the most active aPs, ZM172406, the R enantiomer of ZM150271, N-(3-chloro-4-cyanophenyl)-3,3, 3-trifluoro-2-hydroxy-2-methylpropanamide, had comparable oral potency to mifepristone in rats and monkeys. The racemate ZM150271 was an effective abortifacient during early pregnancy in pigtailed monkeys (3 x 10 mg/kg) but less effective in cynomolgus monkeys. One of the most active progestins (Pn), ZM182345, N-(4-nitro-3-trifluoromethylphenyl)-4-phenyl-2-hydroxy-2-trifluoromet hyl-pentanamide, was at least as potent as P in rats and rabbits but also possessed A activity.

The epidermal growth factor receptor and its inhibition in cancer therapy.

Much effort has been expended in the search for inhibitors of signalling molecules that may prove to be important therapeutically in cancer. The epidermal growth factor receptor (EGFR) family and their associated ligands has been one such area extensively investigated. The complex nature of EGFR biology allows for potential opportunities for EGFR inhibitors in a number of areas of cancer therapy, including proliferative, angiogenic, invasive, and metastatic aspects. Much positive evidence of likely benefit has already been gathered from a multiplicity of laboratory experiments. Clinical trials are now urgently required to further evaluate the advantages of such agents.

Specific inhibition of epidermal growth factor receptor tyrosine kinase by 4-anilinoquinazolines.

Since the mitogenic action of EGF is mediated by ligand-induced autophosphorylation of the EGF receptor (EGFR), and EGFR is commonly overexpressed in solid human tumours, inhibitors of receptor tyrosine kinase activity (RTK) could prove to be effective antitumour agents. Screening of a compound library using an EGF-RTK enzyme prepared from human tumour derived A431 cells identified a series of potent (IC50 < 1 microM) enzyme inhibitors. These inhibitors are quinazolines bearing a variety of substituted anilines at the 4-position. The most potent 4-anilinoquinazolines (IC50 approximately equal to 20 nM) have small non-polar meta substituents on the aniline ring, and are competitive with ATP and non-competitive with substrate. The growth inhibitory activity of these agents was assessed in vitro using KB cells (human oral squamous tumour) grown in the absence or presence of EGF. A selected compound, 4-(3-chloroanilino)quinazoline (CAQ), inhibited EGF-stimulated growth in a concentration dependent manner and complete blockade was observed at concentrations (1-10 microM) which had no effect on basal growth. Selectivity of growth inhibition by CAQ was further exemplified in IGF1-stimulated KB cells where no effect was detected at concentrations which completely blocked EGF-stimulated growth. Similarly, CAQ blocked TGF alpha-stimulated growth in MCF-7 human breast cancer cells without affecting insulin-stimulated growth. These studies define a novel class of EGF-RTK inhibitors which are also potent and selective inhibitors of EGF-stimulated human tumour cell growth in vitro.

Pancreatic secretory trypsin inhibitor stimulates the growth of rat pancreatic carcinoma cells.

Pancreatic secretory trypsin inhibitor was examined for growth-promoting activity on five cell lines using standard cell culture techniques. One cell line, AR4-2J, derived from a rat pancreatic acinar cell carcinoma, responded with significantly increased incorporation of [3H]thymidine and colony formation. Pancreatic secretory trypsin inhibitor stimulated the incorporation of [3H]thymidine in liquid culture; the maximal increase was 61 +/- 10% above control (P less than 0.001) and was seen at a concentration of 10(-9) mol/L. Using a soft agarose clonogenic assay, pancreatic secretory trypsin inhibitor also consistently stimulated (3 assays) colony formation: the peak activity occurred at a concentration of 10(-10) mol/L which caused a 150 +/- 55% (mean +/- SE, P less than 0.05) increase above control. Aprotinin had no effect on the growth of AR4-2J cells and pancreatic secretory trypsin inhibitor did not bind to the epidermal growth factor receptor. AR4-2J cells were shown to produce pancreatic secretory trypsin inhibitor. The study raises the possibility that pancreatic secretory trypsin inhibitor provides autocrine stimulation of tumor cell growth.

Conformationally restrained cyclic peptides as antagonists of luteinizing hormone-releasing hormone.

Using minimum energy calculations and molecular dynamics techniques the preferred conformational states of LHRH and its analogues have been reported to involve a modified beta-bend between residues 5 to 8. Based on some of these models cyclic peptide analogues of LHRH antagonists were synthesised using solid phase peptide synthesis methodology. The analogues were tested for their ability to inhibit ovulation in normal cycling rats. Some analogues were also tested in receptor binding and in vitro LH release assays. The most potent cyclic peptide analogue, Ac-D-Phe(p-C1)-D-Phe(p-C1)-D-Trp-Ser-Glu-D-Arg-Leu-Lys-Pro-D-Ala-NH2 (V), had an ED50 value of 91.9 micrograms/kg in the inhibition of ovulation test. The corresponding linear peptide (IV) was about three times less potent. Analogues with smaller or larger ring sizes or with modifications within the ring were also prepared but these were either less potent or inactive, up to a dose of 1000 micrograms/kg, in inhibiting ovulation in normal cycling rats.

ICI 176,334: a novel non-steroidal, peripherally selective antiandrogen.

Pure antiandrogens, like flutamide, antagonize androgen action both peripherally and centrally at the hypothalamic-pituitary axis, which leads to an increase in LH and testosterone secretion. A new non-steroidal antiandrogen ICI 176,334 [2RS)-4'-cyano-3-(4-fluorophenylsulphonyl)-2-hydroxy-2-methyl-3'- trifluoromethyl)propion-anilide) has now been discovered which causes regression of the accessory sex organs but does not increase serum concentrations of LH and androgens. ICI 176,334 binds to rat prostate androgen receptors with an affinity around fourfold that of hydroxyflutamide. When administered s.c. concurrently with testosterone propionate (200 micrograms/kg) for 7 days to immature castrated rats, ICI 176,334 (10 mg/kg) significantly (P less than 0.001) inhibited growth of the seminal vesicles and ventral prostate gland. Oral administration of ICI 176,334 at doses of 1, 5 and 25 mg/kg for 14 days to adult rats caused a dose-related reduction in accessory sex organ weights but had no effect on the testes. None of these doses caused a significant increase in serum LH and testosterone. Flutamide was around fourfold less potent and significantly increased serum LH and testosterone at the higher doses. ICI 176,334 was well tolerated. ICI 176,334 should, therefore, prove useful for the treatment of androgen-responsive benign and malignant diseases.