Fine scale structural information substantially improves multivariate regression model for mRNA in-vial degradation prediction.

The success of COVID-19 mRNA vaccines has made optimizing mRNAs for in-vial stability a key objective. However, we still lack a complete understanding of the sequence metrics that influence mRNA stability in solution. RNA secondary structure plays a central role in protecting against hydrolysis, the primary degradation pathway under storage conditions. Yet, the structural metrics that best guide stability-focused mRNA design remain unclear. Global metrics like minimum free energy and average unpaired probability have improved mRNA stability but fail to capture local structural variation relevant to degradation. We show that base-pairing probability, in terms of log odds, provide fine-scale, orthogonal insight that complements global metrics and improves stability modeling. By combining local and global features into a four-feature regression model, dubbed STRAND (Stability Regression Analysis using Nucleotide-Derived features), we achieve substantial gains in predictive performance over current methods. This compact and interpretable model provides a practical framework for designing mRNAs with enhanced in-solution stability.