Kenneth Atz, Small Molecule AI Scientist, Roche
Accurate estimation of conformational strain in small-molecule ligands is critical for successful structure-based drug design. While torsional strain in acyclic bonds is readily assessed, evaluating strain in saturated ring systems currently necessitates conformational sampling and compute-intensive quantum-mechanical calculations. To address this limitation, RingAnalyzer is introduced, i.e., a machine learning framework predicting conformational strain directly from single three-dimensional molecular geometries. The method introduces a ring-centric 3D equivariant neural network trained on a rigorously curated dataset of 4,226 drug-like molecules and 27,581 conformations. Calculated at the high-fidelity $\omega$B97XD/Def2TZVP level of theory, this dataset captures diverse stereoelectronic effects. Following extensive data augmentation strategies yielding 76,636 conformations, the computational model accurately predicts strain energies with a mean absolute error of 0.54 kcal/mol, demonstrating robustness to structural artifacts and incomplete structures. Prospective application of RingAnalyzer across diverse structural repositories, including small-molecule conformer generators, 3D generative models, co-folding architectures, docking datasets, the Protein Data Bank, and the Cambridge Structural Database, highlights a widespread occurrence of high-energy ring artifacts. As a computationally efficient and quantum-accurate geometric filter, RingAnalyzer enables the rapid identification and elimination of strained ring systems to streamline structure-based molecular design.