PREreview of On-target mutations confer resistance to WRN helicase inhibitors in Microsatellite Unstable Cancer Cells

Picco et al. present a framework for monitoring and designing treatment strategies to respond to WRN inhibitor resistance as it emerges, using screening and co-treatment approaches to dissect the distinct mechanisms of action underlying resistance. The comparison of resistance arising from genetic knockdown versus pharmacological inhibition provides an essential resource for distinguishing mechanisms underlying global WRN function from those specific to the inhibited WRN. Additionally, the base editing approach across multiple cancer cell lines and patient-derived xenograft models focuses the work on biologically accessible mutations, providing a valuable tool for understanding mechanisms of action. This work is a substantial resource applicable across treatment paradigms and will inform clinical decision-making as WRN inhibitors advance.

Minor points:

1. The base editing screen showed broad coverage for WRN. Among the identified hits, were any mutations tested in a homozygous background? Whether the rescue effect is sufficient to replace wild-type activity would be relevant to assess. Similarly, do all in vivo and in vitro resistant samples harbor a single mutant allele while maintaining the wild-type allele, or do dual mutations emerge in the same clone?

2. In Figure 4B, the effects of C727R in the top panel do not appear to confer resistance to the covalent inhibitor VVD-133214, with no increase in relative IC₅₀ across different cell lines. However, the bottom panel shows some effect. This discrepancy makes the figure difficult to interpret. Clarification in the figure legend of what the top versus bottom panels represent, along with additional detail in the text or methods on how the over 150 assay conditions are summarized in this heatmap, would improve interpretability.

Editorial points:

1. The visualization of the binding pocket in Figure 4A does not clearly illustrate the proposed changes in the hydrophobic cage. The supplementary figure images are clearer. An improved comparison of the pocket changes between wild-type and mutant structures would strengthen the interpretability of the structural predictions.

Another preprint (https://www.biorxiv.org/content/10.64898/2026.01.22.700152v1 ) has some similar analyses and both strongly implicated SMARCAL1. But they differ in the specifics of DNA damage response/NEHJ pathway genes implicated in resistance with implications for companion therapies. They also differ in the discussion of the importance of P53. The authors may wish to comment about these differences and whether they result from different cell backgrounds, analyses, or other factors.

Competing interests

The authors declare that they have no competing interests.

Use of Artificial Intelligence (AI)

The authors declare that they did not use generative AI to come up with new ideas for their review.