Therapeutic reactivation of mutant p53 protein by quinazoline derivatives

The human tumour suppressor protein p53 is mutated in nearly half of human tumours and most mutant proteins have single amino acid changes. Several drugs including the quinazoline derivative 1 (CP-31398) have been reported to restore p53 activity in mutant cells. The side chain of 1 contains a styryl linkage that compromises its stability and we wished to explore the activity of analogues containing more stable side chains.

Reactivation of p53 function was measured by flow cytometry as the ability to potentiate radiation-induced G(1)-phase cell cycle arrest and by western blotting to determine expression of p21(WAF1). DNA binding was measured by competition with ethidium and preliminary pharmacological and xenograft studies were carried out.

Screening of analogues for potentiation of radiation-induced G(1)-phase cell cycle arrest using NZOV11, an ovarian tumour cell line containing a p53(R248Q) mutation, demonstrated that the (2-benzofuranyl)-quinazoline derivative 5 was among the most active of the analogues. Compound 5 showed similar effects in several other p53 mutant human tumour cell lines but not in a p53 null cell line. 5 also potentiated p21(WAF1) expression induced by radiation. DNA binding affinity was measured and found to correlate with p53 reactivation activity. Plasma concentrations of 5 in mice were sufficient to suggest in vivo activity and a small induced tumour growth delay (7 days) of NZM4 melanoma xenografts was observed.

Compound 5 restores p53-like function to a human tumour cells lines expressing a variety of mutant p53 proteins, thus providing a basis for the design of further new drugs.