In Search of Beautiful Molecules: A Perspective on Generative Modeling for Drug Design.

Generative modeling with artificial intelligence (GenAI) offers an emerging approach to discover novel, efficacious, and safe drugs by enabling the systematic exploration of chemical space and to design molecules that are synthesizable while also having desirable drug properties. However, despite rapid progress in other industries, GenAI has yet to demonstrate clear and consistent value in prospective drug discovery applications. In this Perspective, we argue that the ultimate goal of generative chemistry is not just to generate "new" or "interesting" molecules, but to generate "beautiful" molecules─those that are therapeutically aligned with the program objectives and bring value beyond traditional approaches. We focus on five essential considerations for the successful applications of GenAI for drug discovery (GADD): 1) chemical synthesizability (accounting for time/cost constraints); 2) favorable ADMET (absorption, distribution, metabolism, excretion, and toxicity) properties; 3) desirable target-specific binding to modulate the biological mechanism of interest; 4) the construction of appropriate multiparameter optimization (MPO) functions to drive the GenAI toward the project objectives; and 5) human feedback from experienced drug hunters. Interestingly, defining the beauty of a molecule in a drug discovery program is not always obvious, being context-dependent as data emerge and priorities shift, making the role of expert human input indispensable. While MPO frameworks using complex desirability functions or Pareto optimization can help operationalize multifaceted project objectives, they cannot yet fully capture the nuanced judgment of experienced drug hunters. Reinforcement learning with human feedback (RLHF) offers a path to guide the GenAI toward therapeutically aligned molecules, just as RLHF played a pivotal role in training large language models (LLMs) like ChatGPT, especially in aligning the model's behavior with human expectations. While not responsible for the model's base knowledge, RLHF is essential in shaping how the model responds. In addition to RLHF, future progress in GADD will depend on better property prediction models and explainable systems that provide insights to expert drug hunters. "Beauty is in the eyes of the beholder"─for drug discovery, beauty is judged by experienced drug hunters and clinical success.