A Cross-over Study of OligoG in Subjects With Cystic Fibrosis. Fibrosis

Inclusion Criteria: * Male or female with a confirmed diagnosis of cystic fibrosis defined by: * Clinical features consistent with the diagnosis of CF \[(Rosenstein BJ and Cutting GR 1998)\]; AND * Sweat chloride ≥60 mmol/L by pilocarpine iontophoresis; OR * Genotypic confirmation of CFTR mutation * Aged 18 years or older * Ability to provide samples for microbiological evaluation throughout the study. Note: sputum samples are preferred however cough swabs may be performed on occasions where sputum cannot be collected. * Positive microbiological finding of Pseudomonas aeruginosa in expectorated sputum or cough swab documented within 24 months prior to Screening (Visit 1). * FEV1 must, at Screening (Visit 1), be between 35%-80% of the predicted normal value following adjustment for age, gender, and height according to the Knudson equation \[(Knudson RJ., Lebowitz MD., et al 1983)\]. * At Screening (Visit 1), no clinical or laboratory findings suggestive of significant pulmonary illness, other than CF, which in the opinion of the investigator would preclude participation in the study. * Female subjects of child bearing potential and male subjects participating in the study who are sexually active must use acceptable contraception. Female subjects documented as being of non child-bearing potential (Section 4.2.8) are exempt from the contraceptive requirements. For the purpose of this study acceptable contraception is defined as: * oral, injected or implanted hormonal methods of contraception;OR * placement of an intrauterine device (IUD) or intrauterine system (IUS);OR * barrier methods of contraception: condom or occlusive cap (diaphragm or cervical/vault caps) with spermicidal foam/gel/film/cream/suppository * Provision written informed consent Exclusion Criteria: * Changes in underlying therapy (e.g., pulmonary massage therapy, bronchodilators, NSAIDs, antibiotic agents, pancreatic enzyme preparations, nutritional supplements and DNase within the 21 days prior to Day 1 (Visit 2). Subjects must be willing to remain on the same underlying stable therapy regimens for the duration of the study until the final follow-up visit at Day 111. * Changes in physiotherapy technique or schedule within 14 days prior to Day 1 (Visit 2). * Prohibited medications within 7 days prior to Day 1 (Visit 2). Prohibited medications are described in Section 5.6 * Pulmonary exacerbation within 28 days of Screening (Visit 1). * Positive microbiological finding of Burkholderia sp. in expectorated sputum or cough swab documented within 12 months prior to Screening (Visit 1). * On-going acute illness. Subjects must not have needed an outpatient visit, hospitalization or required any change in therapy for other pulmonary disease between Screening (Visit 1) and Day 1 (Visit 2). * History of, or planned organ transplantation. * Allergic bronchopulmonary aspergillosis (ABPA) in the last 12 months prior to Screening (Visit 1), defined as having received treatment for ABPA. * Requirement for continuous (24 hour/day) oxygen supplementation. * Concomitant administration of inhaled mannitol or hypertonic saline within 7 days prior to Day 1 (Visit 2). * Initiation of cycled, inhaled tobramycin (TOBI) less than 4 months prior to Screening (Visit 1). Note: Chronic TOBI users are allowed to participate in this study, but subjects who have recently initiated chronic TOBI should have at least 2 cycles of TOBI in the preceding 4 months before being enrolled in this study. Chronic TOBI subjects should be starting an 'off- TOBI' period at Day 1 (Visit 2) so there will be no concomitant dosing of TOBI and assigned study medication. * Clinically significant abnormal findings on haematology or clinical chemistry. In addition, any value ≥ 3 x the upper limit of normal will exclude the subject from participating in the study. * Subjects unable to perform pulmonary function tests according to the ATS/ERS criteria. * Pregnant or breast-feeding women. A negative urine pregnancy test must be demonstrated in females of child-bearing potential (Section 4.2.8) at Screening (Visit 1). * Subjects who have participated in any interventional clinical trial within the 28 days prior to Day 1 (Visit 2). * Subjects with documented or suspected, clinically significant, alcohol or drug abuse. The determination of clinical significance will be determined by the Investigator. * Known allergies or intolerance to alginates (e.g., foods and food additives based on seaweed extracts). * Current malignant disease (with the exception of basal cell carcinoma; BCC). * Any serious or active medical or psychiatric illness, which in the opinion of the Investigator, would interfere with subject treatment, assessment, or compliance with the protocol.