https://www.selleckchem.com/ g., histamine, serotonin, and proteases) and reduced mediator release upon degranulation, and 4) engraftment of MC-deficient Kit W-sh/W-sh mice with adult male, female, or perinatally androgenized female MCs results in MC-mediated anaphylaxis response that reflects the MC sex and not host sex. Together, these data present evidence that sex differences in MC phenotype and resulting disease severity are established in early life by perinatal androgens. Thus, factors affecting levels of perinatal androgens could have a significant impact on MC development and MC-associated disease risk across the life span.Duchenne muscular dystrophy is a genetic disorder that shows chronic and progressive damage to skeletal and cardiac muscle leading to premature death. Antiinflammatory corticosteroids targeting the glucocorticoid receptor (GR) are the current standard of care but drive adverse side effects such as deleterious bone loss. Through subtle modification to a steroidal backbone, a recently developed drug, vamorolone, appears to preserve beneficial efficacy but with significantly reduced side effects. We use combined structural, biophysical, and biochemical approaches to show that loss of a receptor-ligand hydrogen bond drives these remarkable therapeutic effects. Moreover, vamorolone uniformly weakens coactivator associations but not corepressor associations, implicating partial agonism as the main driver of its dissociative properties. Additionally, we identify a critical and evolutionarily conserved intramolecular network connecting the ligand to the coregulator binding surface. Interruption of this allosteric network by vamorolone selectively reduces GR-driven transactivation while leaving transrepression intact. Our results establish a mechanistic understanding of how vamorolone reduces side effects, guiding the future design of partial agonists as selective GR modulators with an improved therapeutic index.We formulate a general method to ex