CB-280

CB-280 is an orally administered, small molecule arginase inhibitor developed by Calithera Biosciences for the treatment of cystic fibrosis. It is a first-in-class approach designed to enhance airway nitric oxide (NO) levels by inhibiting arginase, an enzyme that converts arginine into urea and ornithine. Increased arginase activity in cystic fibrosis patients correlates with worsened lung function and decreased airway NO, which promotes pathogen colonization and chronic infections. By blocking arginase and raising systemic arginine levels, CB-280 aims to restore NO production in the airways, improve lung function, and reduce infection risk. Preclinical studies demonstrated improved lung function and reduced bacterial colonies in CF mouse models; early clinical data showed positive trends in disease biomarkers such as increased FeNO (fractional exhaled nitric oxide), decreased sweat chloride, and improved FEV1 (forced expiratory volume). The drug has been evaluated in Phase 1 trials for safety and pharmacokinetics[2][5][6][7][8].