Effect of Losartan in Cystic Fibrosis (CF)-NIH Grant #133240

Inclusion Criteria: * CF patients with any known mutation combination not on CFTR augmentation therapy * ≥18 years of age * Severity of the Disease: Suitable patients will have mild to moderate lung disease, as defined by: * Pulmonary Function: Each patient must have an FEV1 ≥40% of predicted at the screening visit. * Hemoglobin saturation: Patients must have an oxygen saturation of \>92% on room air as determined by pulse oximetry at the screening visit. * Produces sputum regularly (daily basis, at minimum) * FEV1 ≥ 40% of predicted at screening visit * Able to sign Informed consent * Negative COVID-19 test within 72 hours prior to MCC testing Exclusion Criteria: * When enrolling female patients * Not willing to adhere to strict birth control (combination of two methods) * If female, patient must be non-pregnant and non-lactating, and those of childbearing potential must be using an acceptable method of birth control (i.e., an Intrauterine Contraceptive Device with a failure rate of \<1%, hormonal contraceptives or a barrier method). If a female patient is abstinent, she must agree to use one of the acceptable methods if she becomes sexually active. * Unstable lung disease: As defined by a change in medical regimen during the preceding 2 weeks or an FEV1 ≥15% below value within 3 months * Received an investigational drug or therapy during the preceding 30 days * Active or former smokers with less than 1 year since quitting, or \>10 pack-year smoking history * Unabl…