This is a multi-dose study with RCT1100 and is designed to provide safety, tolerability and preliminary efficacy data for future clinical studies.

The primary objective of this study is to determine the impact of multiple doses of inhaled RCT1100, administered via nebulizer, on MCC with adult participants with Primary Ciliary Dyskinesia caused by pathogenic mutations in the DNAI1 Gene.

Major Inclusion Criteria:

• The participant is a male or female, 18 to 75 years of age, inclusive, at the time of consent.
• Participant has disease-causing (pathogenic and/or likely pathogenic) mutations in the DNAI1 gene.
• The participant has a percent predicted forced expiratory volume in 1 second (FEV1pp) of at least 40% predicted.

Exclusion Criteria:

• History or presence of clinically significant medical, surgical, clinical laboratory, or psychiatric condition or disease.

• History of cancer, with exception of adequately treated basal cell or squamous cell carcinoma of the skin.

• Predisposition to bleeding or clinically meaningful hemorrhagic event in the 12 months prior

• Medically significant hemoptysis.

• Anticoagulation therapy for the treatment of a pulmonary embolus or has had a pulmonary embolus in the last 6 months of screening.

• Active tuberculosis infection.

• 12-lead ECG with QT interval >450 msec (or >480 msec for BBB)

• Laboratory abnormalities in clinical laboratory tests at screening:

  1. Serum creatinine level
  2. Total bilirubin, aspartate aminotransferase or alanine aminotransferase values
  3. Hematological or coagulation values outside the normal reference range

• Any medical history of disease that has the potential to cause a rise in total bilirubin over the ULN.

• COVID-19 infection within 4 weeks of Screening or receipt of COVID-19 vaccine within 2 weeks prior to first dose of RCT1100.

• Receipt of vaccine with live virus, attenuated live virus, or live viral components within 2 weeks prior to first dose of RCT1100 or to receive these vaccines during treatment or within 8 weeks of completion of study treatment.

Other protocol defined inclusion/exclusion criteria may apply.