The discovery of the allosteric WRN helicase inhibitor HRO761 illustrates how systematic analysis of structure–property relationships (SAR) can guide medicinal chemistry in challenging beyond–rule‑of‑five (bRo5) space. Targeting WRN as a synthetic lethal vulnerability required balancing high molecular weight and polarity with sufficient permeability, cellular activity, and in vivo efficacy.
Central to this approach was the prospective use of physics‑based property prediction, systematic data capture, and collaborative idea triaging to define target property windows and to support rapid decision‑making. Within this framework, matched molecular pair analysis (MMPA) played a key role in extracting robust medicinal chemistry insights from developing datasets. Single structural modifications were quantitatively linked to changes in potency, permeability, and cellular efficacy, enabling design hypotheses to be tested rapidly and effectively while establishing robust SAR.
MMPA revealed pronounced chameleonic effects, where subtle substitutions—such as a methyl group addition—led to non‑intuitive improvements in permeability and cellular activity without increasing lipophilicity. These effects are consistent with conformation‑dependent modulation of exposed polarity rather than simple logP‑driven behavior.
Overall, this case study demonstrates how consistent application of MMPA enables the derivation of actionable design rules, supporting rational optimization of inhibitors for difficult targets operating in bRo5 space.

[1] S. Ferretti, J. Hamon, J. et al., Nature, 2024, 629, 443-449.
[2] H. Moebitz, V. Bordas et al., ACS Spring, 2024, American Chemical Society