Evolution-informed rescue drug design: exploiting acquired resistance to develop more selective and resistance-durable targeted therapies

Acquired resistance to targeted anticancer drugs presents an evolutionary paradox: mutations that allow cancer cells to escape an initial inhibitor may simultaneously create molecular vulnerabilities that enable the development of more selective and potentially more resistance-durable successor drugs. This review examines whether such mutations can resolve a fundamental conflict in drug design: functionally indispensable protein regions are attractive targets for limiting resistance, but their conservation across normal proteins can make selective inhibition difficult. We propose a two-drug strategy in which Drug 1 is the initial anticancer inhibitor and Drug 2 is a rescue inhibitor designed against resistance mutations anticipated before clinical emergence. Drug 2 would exploit a structural feature created by resistance to Drug 1 for selective recognition, while deriving most of its binding strength from experimentally verified, functionally constrained contacts that cannot readily mutate without compromising essential protein function. Published studies of substrate-envelope design, prospective resistance screening, mutant-selective inhibitors, and EGFR resistance mechanisms provide the scientific foundation for this hypothesis, although none of the studies examined establishes the proposed combination. Accelerated resistance evolution, mutagenesis, and CRISPR-based editing could deliberately generate and characterize resistant variants in vitro, allowing Drug 2 to be developed and evaluated in parallel with Drug 1 rather than after clinical treatment failure. This prospective approach could also introduce an evolution-informed pharmaceutical development and patenting paradigm in which rescue inhibitors are designed against experimentally characterized molecular targets before those resistance states appear in patients. The hypothesis requires experimental validation of mutant-specific selectivity, functional anchoring, and protection against subsequent resistance. Its central proposition is that the evolutionary process responsible for failure of an initial treatment may itself create the molecular conditions for a more effective successor therapy.