• Adults ≥18 years of age at the time of screening.

• If enrolled in the CFF Patient Registry, must provide registry information.

• Confirmed CF diagnosis based on current CF Foundation (CFF)-sponsored guidelines.

• For participants on modulator therapy, they must be on a stable dose of modulator therapy for at least 3 months.

• Willing and capable of providing induced sputum for evaluation at defined study timepoints.

• Positive P. aeruginosa growth of ≥104 CFU/gram from a sample of induced sputum at the screening visit.

• FEV1 ≥50% (Part1) or ≥35% (Part 2) of predicted normal value at screening.

• Currently receiving inhaled antibiotic therapy, either tobramycin or aztreonam alone, or as part of CAT. At least one 28-day cycle completed within 8 weeks prior to screening visit.

• Women of childbearing potential (WOCBP) must have a negative serum beta-human chorionic gonadotropin test during screening and agree to use an effective method of contraception for the duration of the study and for 4 months after the last infusion of study drug. A female participant is considered of childbearing potential unless postmenopausal or surgically sterilized and at least 3 months has passed since sterilization procedure. Female surgical sterilization procedures include tubal ligation, bilateral salpingectomy, hysterectomy, or bilateral oophorectomy. A female participant is considered postmenopausal if she has had spontaneous amenorrhea for at least 2 years with an appropriate clinical profile (e.g., age appropriate, history of vasomotor symptoms).

• • Effective methods of contraception include (a) abstinence, (b) partner vasectomy, (c) intrauterine devices, (d) hormonal implants (such as Implanon), or (e) other hormonal methods (birth control pills, injections, patches, vaginal rings).

⁃ Male participants with a female partner must use a medically accepted contraceptive regimen during his participation in the study and for 4 months after study drug infusion.

⁃ • Acceptable methods of contraception for male participants include condoms with spermicide, surgical sterilization of the participant (i.e., vasectomy) at least 26 weeks before screening, or sexual abstinence (i.e., refraining from heterosexual intercourse) if that is the preferred and usual lifestyle of the participant.

⁃ \- Males with infertility documentation are not required to use contraception.

⁃ Male participants must agree to abstain from sperm donation through 4 months after study drug administration.

⁃ Capable of providing informed consent.

⁃ Capable and willing to complete all study visits and perform all procedures required by the protocol.