Abstract
Synthetic lethality, first proposed more than two decades ago, has long held immense promise for targeted cancer therapy. Although the clinical success of PARP inhibition in BRCA-mutant cancers stands as proof of concept, few other synthetic lethal interactions have been translated from preclinical findings into effective therapies. This slow pace of translation stems in part from the difficulty of developing drugs against genetic dependencies, but also reflects the cell- and tissue-specific nature of these interactions. In this Review, we outline recent advances in the discovery and validation of synthetic lethal pairs, from their discovery in large-scale genetic screens to the development of drugs for the clinic. We discuss how alternative CRISPR-based approaches — including combinatorial screens, base editing and saturation mutagenesis — are now being used to discover new tractable interactions. We also examine how machine learning models can enable prioritization of candidate pairs and the identification of biomarkers for patient stratification. Finally, we highlight alternative phenotypic readouts, such as high-content imaging and single-cell profiling, which enable the dissection of phenotypes beyond simple cell growth or fitness. Together, these developments are refining the synthetic lethality paradigm and advancing its potential for cancer therapy.
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Acknowledgements
E.G. work is supported by FCT (Fundação para a Ciência e Tecnologia), under projects UIDB/50021/2020 (DOI:10.54499/UIDB/50021/2020), 2024.07252.IACDC (https://doi.org/10.54499/2024.07252.IACDC, through RE-C05-i08.M04) and grant number 15030 (https://doi.org/10.54499/LISBOA2030-FEDER-00868200). C.J.R. is funded by Research Ireland under grant number 20/FFPâ€P/8641. D.J.A. is supported by the Wellcome Trust, CR-UK and the UKRI, Medical Research Council.
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Glossary
- Assay miniaturization
-
The process of reducing the volume of reagents and samples in laboratory assays, enabling high-throughput screening with increased efficiency and reduced costs.
- Collateral lethality
-
Deletion of a gene, for example, a tumour suppressor gene, that inadvertently leads to the loss of neighbouring genes, known as passenger genes, resulting in a therapeutic vulnerability that can be exploited for targeted cancer treatment.
- Epistasis
-
A genetic interaction in which the effect of one gene is modified by one or more other genes.
- HAP1 LIG4-null cells
-
A genetically engineered variant of the human HAP1 cell line in which the LIG4 gene, encoding DNA ligase IV, has been knocked out, disrupting the non-homologous end joining DNA repair pathway, promoting DNA repair via homologous recombination, important for the insertion of specific DNA edits.
- Metabolic flux coupling
-
The interdependence of metabolic reaction rates within a network, whereby the flux through one reaction constrains or affects the flux through another. This coupling can arise from stoichiometric relationships, shared intermediates or regulatory mechanisms.
- Microsatellite instability
-
(MSI). A condition characterized by the accumulation of insertion or deletion mutations in microsatellite regions of DNA, typically caused by defects in the mismatch repair system.
- Paralogues
-
Genes that arise from a duplication event within the genome of a species.
- PROTACtable
-
Proteins with features (ubiquitylation site, long half-life) that indicate that they may be suitable for degradation using proteolysis-targeting chimeras (PROTACS).
- Saturation mutagenesis
-
A technique in molecular biology in which specific regions of a gene are systematically mutated to all possible variations.
- Undruggable
-
Proteins currently not yet targetable with existing pharmacological strategies. Targets previously deemed undruggable, such as the oncoprotein KRAS, now have available inhibitors and so this category is continually evolving, especially as new modalities, such as proteolysis-targeting chimeras (PROTACs) and molecular glues, expand the targetable proteome.
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Gonçalves, E., Ryan, C.J. & Adams, D.J. Synthetic lethality in cancer drug discovery: challenges and opportunities. Nat Rev Drug Discov (2025). https://doi.org/10.1038/s41573-025-01273-7
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DOI: https://doi.org/10.1038/s41573-025-01273-7
