VX809 is primarily used in the treatment of cystic fibrosis, a genetic disorder that affects the lungs and digestive system. It functions as a corrector of the defective CFTR protein, which is responsible for the condition. By facilitating the proper folding and trafficking of the CFTR protein to the cell surface, VX809 helps improve chloride ion transport, thereby alleviating symptoms associated with cystic fibrosis. It is often used in combination with other CFTR modulators to enhance its therapeutic efficacy. This targeted approach has shown promise in improving lung function and overall quality of life for patients with specific mutations of the disease.