For three decades, central nervous system (CNS) drug development was a tough space for investors, scarred by failed bets on Alzheimer's disease, plateauing first-generation antidepressants, and setbacks in safety and efficacy.   But advances in receptor-selective chemistry and so-called “biased agonism” – steering toward therapeutic pathways and away from areas that cause side effects – are reviving interest in the field.   Successes such as esketamine for depression or cannabinoids for epilepsy have shown ...