This is a double-blind, randomized, placebo-controlled study of CMTX-101 in pwCF who are 18 years of age or older and chronically infected with P. aeruginosa. This study will evaluate the safety and tolerability, PK, immunogenicity, reduction of pulmonary P. aeruginosa burden, and exploratory endpoints of CMTX-101 in up to 41 participants. This study has 2 parts.