The Phase 3 clinical development program included two placebo-controlled studies (Studies 2 and 3) and one open-label study (Study 1), which randomized and dosed 157 and 517 patients, respectively, with a clinical diagnosis of cystic fibrosis, confirmed by quantitative pilocarpine iontophoresis sweat chloride test, well-characterized disease causing mutations in each CFTR gene, or abnormal nasal transepithelial potential difference characteristic of cystic fibrosis.
In the placebo-controlled studies, all patients were aged between 6 and 21 years old and had an FEV1 at screening within the range of 25% to 80% (inclusive) of predicted normal values for their age, sex, and height based upon Knudson criteria. In addition, all patients were infected with P. aeruginosa as demonstrated by a positive sputum or throat culture (or bronchoalveolar lavage) within 6 months prior to screening, and also in a sputum culture taken at the screening visit. Among the 76 patients treated with TOBI Podhaler, 37% were males and 63% were females. Thirty-six patients were between 6 and 12 years of age, and 40 patients were between 13 and 21 years of age. Patients had a mean baseline FEV1 of 56% of predicted normal value.
In both studies, >90% of patients received concomitant therapies for cystic fibrosis-related indications. The most frequently used other antibacterial drugs (any route of administration) were azithromycin, ciprofloxacin, and ceftazidime. Consistent with the population of cystic fibrosis patients, the most frequently used concomitant medications included oral pancreatic enzyme preparations, mucolytics (especially dornase alfa), and selective β2-adrenoreceptor agonists.
Study 2
Study 2 was a randomized, 3-cycle, 2-arm trial. Each cycle comprised of 28 days on treatment followed by 28 days off treatment. The first cycle was double-blind, placebo-controlled with eligible patients randomized 1:1 to TOBI Podhaler (4 times 28 mg capsules twice-daily) or placebo. Upon completion of the first cycle, patients who were randomized to the placebo treatment group received TOBI Podhaler for Cycles 2 and 3. The total treatment period was 24 weeks.
A total of 95 patients were randomized into Study 2 and received TOBI Podhaler (n=46) or placebo (n=49) in Cycle 1. All patients were less than 22 years of age (mean age 13.3 years) and had not received inhaled antipseudomonal antibiotics within four months prior to screening; 56% were female and 84% were Caucasian. This study was stopped early for demonstrated benefit and the primary analysis used the set of patients included in the interim analysis (n=79); 16 patients did not have data on the primary endpoint at that time. Of the 79 patients included in the interim analysis, 18 patients were excluded due to a failure to meet spirometry quality review criteria as determined by an external review panel. This resulted in a total of 61 patients, 29 in the TOBI Podhaler arm and 32 in the placebo arm, who were included in the primary analysis.
In the primary analysis, TOBI Podhaler significantly improved lung function compared with placebo as measured by the relative change in FEV1 % predicted from baseline to the end of Cycle 1 dosing. This analysis adjusted for the covariates of baseline FEV1 % predicted, age, and region, and imputed for missing data. Treatment with TOBI Podhaler and placebo resulted in relative increases in FEV1 % predicted of 12.54% and 0.09%, respectively (LS mean difference = 12.44%; 95% CI: 4.89, 20.00; p=0.002). Analysis of absolute changes in FEV1 % predicted showed LS means of 6.38% for TOBI Podhaler and -0.52% for placebo with a difference of 6.90% (95% CI: 2.40, 11.40). Improvements in lung function were achieved during the subsequent cycles of treatment with TOBI Podhaler, although the magnitude was reduced (Figure 1).
The percentage of patients using new antipseudomonal antibiotics in Cycle 1 was greater in the placebo treatment group (18.4%) compared with the TOBI Podhaler treatment group (13.1%). During the first cycle, 8.7% of TOBI Podhaler patients and 10.2% of placebo patients were treated with parenteral antipseudomonal antibiotics. In Cycle 1, two patients (4.4%) in the TOBI Podhaler treatment group required respiratory-related hospitalizations, compared with six patients (12.2%) in the placebo treatment group.
Figure 1 – Study 2: Mean Relative Change In Fev1 % Predicted From Baseline In Cycles 1 To 3 By Treatment Group (Image 05)
Figure 1 – Study 2: Mean Relative Change in FEV1 % Predicted from Baseline in Cycles 1 to 3 by Treatment GroupStudy 3
Study 3 was a randomized, double-blind, placebo-controlled trial, similar in design to Study 2. Eligible patients were randomized 1:1 to receive TOBI Podhaler (4 times 28 mg capsules twice-daily) or placebo for one cycle (28 days on-treatment and 28 days off-treatment).
A total of 62 patients were randomized into Study 3 and allocated to TOBI Podhaler (n=32) or placebo (n=30). All patients were less than 22 years of age (mean age 12.9 years) and had not received inhaled antipseudomonal antibiotics within 4 months prior to screening; 64.5% were female and 98.4% were Caucasian.
In this study, the results were not statistically significant for the primary lung function endpoint when adjusting for the covariates of age (<13 years, ≥13 years) and FEV1 % predicted at screening (<50%, ≥50%) and imputing for missing data. Improvement in lung function for TOBI Podhaler compared with placebo was evaluated using the relative change in FEV1 % predicted from baseline to the end of Cycle 1 dosing. Treatment with TOBI Podhaler (8.19%) compared to placebo (2.27%) failed to achieve statistical significance in relative change in FEV1 % predicted (LS mean difference = 5.91%; 95% CI: -2.54, 14.37; p=0.167). Analyses of absolute changes in FEV1 % predicted showed LS means of 4.86% for TOBI Podhaler and 0.48% for placebo with a difference of 4.38% (95% CI:-0.17, 8.94).
Study 1
Study 1 was a randomized, open-label, active-controlled parallel arm trial. Eligible patients were randomized 3:2 to TOBI Podhaler (4 times 28 mg capsules twice-daily) or TOBI (300 mg/5 mL twice-daily). Treatment was administered for 28 days, followed by 28 days off therapy (one cycle) for three cycles. The total treatment period was 24 weeks. The time to administer a dose of TOBI Podhaler (10th to 90th percentiles) ranged from 2 to 7 minutes at the end of the dosing period for Cycle 1, and 2 to 6 minutes at the end of the dosing period for Cycle 3.
A total of 517 patients were randomized in Study 1 and received TOBI Podhaler (n=308) or TOBI (n=209). Patients were predominantly 20 years of age or older (mean age 25.6 years) with no inhaled antipseudomonal antibiotic use within 28 days prior to study drug administration; 45% were female and 91% were Caucasian.
The primary purpose of Study 1 was to evaluate safety. Interpretation of efficacy results in Study 1 is limited by several factors including open-label design, testing of multiple secondary endpoints, and missing values for the outcome of FEV1 % predicted. The number (%) of patients with missing values for FEV1 % predicted at Weeks 5 and 25 in the TOBI Podhaler treated group were 40 (13.0%) and 86 (27.9%) compared to 15 (7.2%) and 40 (19.1%) in the TOBI treated group. Using imputation of the missing data, the mean differences (TOBI Podhaler minus TOBI) in the percent relative change from baseline in FEV1 % predicted at Weeks 5 and 25 were -0.87 (95% CI: -3.80, 2.07) and 1.62 (95% CI: -0.90, 4.14), respectively.