Abstract 2925: Tandem targeting of poly (ADP-ribose) polymerase (PARP) and epidermal growth factor receptor (EGFR) as a novel strategy for enhancing radio- and chemosensitivity of refractory tumors

Abstract

Poly (ADP-ribose) polymerase (PARP) inhibitors are a novel therapeutic approach for the selective targeting of tumours with BRCA1/2 hereditary deficiencies. BRCA1/2 are two key proteins involved in homologous recombination (HR) repair. Although the therapeutic benefit of PARP inhibitors has now been proven in the clinic in patients with BRCA1/2 mutations, much effort has been deployed to expand the use of PARP inhibitors beyond tumours harbouring inherited deficiencies in HR- mediated DNA repair. Several combination modalities with agents that can induce HR deficiency and exploit the concept of “contextual synthetic lethality” have been reported for PARP inhibitors. Here we exploited the contextual synthetic lethality between PARP and the epidermal growth factor receptor (EGFR) to design and synthesize a novel dual EGFR targeted PARP inhibitor, termed ZSMR06. The results showed that: a) ZSMR06 is capable of inhibiting EGFR and PARP in whole cells in the nanomolar range (36-63 nM); b) it was selectively potent against BRCA2 mutant and EGFR expressing isogenic cells; c) as monotherapy, ZSMR06 was extremely potent with growth inhibitory activities superior to that of an equimolar combination of olaparib (a clinical PARP inhibitor) and gefitinib (a clinical EGFR inhibitor) in a large panel of tumour cell lines; d) ZSMR06 strongly potentiated the effect of temozolomide (TMZ) and induced significantly stronger (p<0.05-0.001) growth inhibition than olaparib + TMZ combination in cells expressing O6-methylguanine-DNA methyltransferase (MGMT), an enzyme that confers a robust resistance to TMZ; e) ZSMR06 selectively potentiated TMZ on EGFR expressing cells; f) it was able to strongly sensitize bladder cancer cells to radiation (DMF50= 2.96-9.5). These results in toto showed that ZSMR06 due to its dual mechanism of action is capable of behaving as a strong potentiator of TMZ and radiation in resistant cells. Its potency in non-BRCA1/2 mutant tumour cells indicates that it may be the first prototype of hybrid molecules capable of expanding the use of PARP inhibition beyond BRCA1/2 mutations. Citation Format: Martin Rupp, Zhor Senhaji Mouhri, Ursula Stochaj, Bertrand Jean-Claude. Tandem targeting of poly (ADP-ribose) polymerase (PARP) and epidermal growth factor receptor (EGFR) as a novel strategy for enhancing radio- and chemosensitivity of refractory tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2925.