7-Azaindole, 2,7-diazaindole, and 1H-pyrazole as core structures for novel anticancer agents with potential chemosensitizing properties

Chemoresistance of cancer cells is a hallmark of treatment failure and the poor patient prognosis. The mechanism of resistance is often connected to the overexpression of specific kinases involved in DNA damage response cascade. Contrary, selected kinase inhibition can augment cancer cell sensitization to conventional therapy, enabling more efficient treatment. Among those kinases, ataxia-telangiectasia and Rad3-related kinase (ATR), the major responder to replication stress, stands out as one of the most attractive targets. Inspired by clinical candidates targeting ATR, we designed and prepared a small, focused library of 40 novel compounds building on 7-azaindoles, 2,7-diazaindoles, and 1H-pyrazoles as core structures. All the compounds alone or combined with cisplatin (CDDP) were screened against a panel of nine cancer cell lines and one healthy cell line. Three highlighted compounds (3, 22, and 29) were selected for broad oncology panel screening containing 104 kinases. Only compound 29, the 2,7-diazaindole representative, showed ATR inhibitory efficacy with the IC50 around 10 μM. In contrast, the compound 22, 7-azaindole congener with the most pronounced cytotoxicity profile exceeding CDDP alone or in combination with CDDP, expressed the multi-kinase activity. Highlighted representatives, including compound 29, were also effective alone against primary glioblastoma. Overall, we showed that 7-azaindole, and 2,7-diazaindole scaffolds could be considered novel pharmacophores delivering anticancer activity.