The TRIFLOW study: a randomised, cross-over study evaluating the effects of extrafine beclometasone/formoterol/glycopyrronium on gas trapping in COPD

Background The effects of triple therapy on gas trapping in COPD are not fully understood. We evaluated the effects of the long acting bronchodilator components of the extrafine single inhaler triple therapy beclometasone dipropionate/formoterol/glycopyrronium (BDP/F/G) pMDI on gas trapping. Methods This open-label, randomised, single centre, 2-way cross-over study recruited 23 COPD patients taking inhaled corticosteroid combination treatments and with residual volume (RV) > 120% predicted at screening. Inhaled BDP was taken during run-in and washout periods. Baseline lung function (spirometry, lung volumes, oscillometry) was measured over 12 h prior to randomisation to BDP/F/G or BDP/F for 5 days followed by washout and crossover. Lung function was measured prior to dosing on day 1 and for 12 h post-dose on day 5. Results Co-primary endpoint analysis: BDP/F/G had a greater effect than BDP/F on FEV1 area under the curve over 12 h (AUC0–12) (mean difference 104 mls, p = 0.0071) and RV AUC0–12 (mean difference − 163 mls, p = 0.0028). Oscillometry measurements showed a greater effect of BDP/F/G on the difference between resistance at 5 and 20 Hz (R5–R20) AUC0–12, which measures small airway resistance (mean difference − 0.045 kPa/L/s, p = 0.0002). Comparison of BDP/F with the baseline measurements (BDP alone) showed that F increased FEV1 AUC0–12 (mean difference 227 mls) and improved RV AUC0–12 (mean difference − 558 mls) and R5–R20 AUC0–12 (mean difference − 0.117 kPa/L/s), all p < 0.0001. Conclusions In COPD patients with hyperinflation, the G and F components of extrafine BDP/F/G improved FEV1, RV and small airway function. These long acting bronchodilators target small airway function, thereby improving gas trapping and airflow. Trial registration The study was retrospectively registered at ClinicalTrials.gov on 15th February 2019 (No.: NCT03842904, https://clinicaltrials.gov/ct2/show/NCT03842904).


Background
Chronic obstructive pulmonary disease (COPD) is characterised by persistent inflammation in the small airways, associated with remodelling and ultimately small airway destruction [1,2]. These pathological changes reduce airflow and increase gas trapping [3]. Inhaled treatment with a long acting beta-agonist (LABA) and/or a long Open Access *Correspondence: jdean@meu.org.uk 1 Medicines Evaluation Unit, Southmoor Road, Manchester M23 9QZ, UK Full list of author information is available at the end of the article acting muscarinic antagonist (LAMA) can bronchodilate the small airways to improve airflow, reduce air trapping and thereby improve dyspnoea and exercise capacity [4][5][6][7]. Inhaled corticosteroid (ICS) treatment can target small airway inflammation to improve clinical outcomes including exacerbation rates [8].
The triple combination inhaler containing beclometasone dipropionate/formoterol/glycopyrronium (BDP/ F/G) was developed as an extrafine formulation to enable efficient delivery of an ICS combined with a LABA and a LAMA to the small airways [9]. Phase 3 clinical trials have shown that this single inhaler triple therapy reduces exacerbation rates, and improves quality of life and lung function compared to double combination inhalers containing ICS/LABA or LAMA/LABA, and compared to LAMA monotherapy [10][11][12].
In order to further understand the effects of the bronchodilator components of extrafine BDP/F/G on the small airways and gas trapping, we conducted a clinical trial focusing on lung volumes and small airway physiology. To measure effects on gas trapping, we recruited patients with increased residual volume (RV) at study entry. The TRIFLOW study was a randomised, cross-over study evaluating the effects of the F and G components of BDP/F/G on lung volumes and small airway physiology (using oscillometry).

Participants
This study recruited male and female COPD patients from 40 to 75 years of age, with a post-bronchodilator forced expired volume in 1 s (FEV 1 ) of 30-80% predicted, a FEV 1 /forced vital capacity (FVC) ratio of < 0.70, and a RV > 120% predicted. Eligible patients were current or ex-smokers with a smoking history of ≥ 10 pack years. All patients were required to be currently taking ICS as part of treatment with ICS/LABA or ICS/LABA/LAMA (as separate inhalers or a single inhaler). Patients were excluded using the following criteria: known respiratory disorder other than COPD; COPD exacerbation within 8 weeks or hospitalisation within 12 months due to COPD; or abnormal clinically relevant findings on physical examination, laboratory or electrocardiogram (ECG) evaluations that in the investigator`s opinion made it unsafe for the patient to participate. All patients provided written informed consent using a protocol approved by the Health & Social Care Research Ethics Committee A (18/NI/0194).

Study design
The study was a randomised, open label, 2 way cross over design (ClinicalTrials.gov registration: NCT03842904). Eligible patients commenced a 10-28 day run-in period receiving BDP (Clenil Modulite) 200 µg twice daily in place of current ICS treatment. Long acting bronchodilator treatments were withdrawn, and replaced with short acting bronchodilators for use as needed. After ≥ 10 days of run-in, a baseline visit was completed, followed by two treatment periods of 5 days each, separated by a washout period of 7-21 days during which BDP and short acting bronchodilators were used (Fig. 1). Patients were randomised (with a 1:1 ratio), to receive triple therapy (Trimbow: BDP/F/G, 100/6/10 µg pMDI, 2 puffs, twice daily) followed by dual therapy (Fostair: BDP/F, 100/6 µg pMDI, 2 puffs, twice daily) or vice-versa. BDP/F/G or BDP/F treatment was commenced on the morning of day 1 and a final dose given on the morning of day 5 (total of 9 doses).
At the baseline visit, and on day 5 of each treatment period, impulse oscillometry (IOS), spirometry, and whole body plethysmography were performed (in that order) prior to the morning dose. IOS and spirometry were then repeated 30 min and 1, 2, 4, 6, 8, 10 and 12 h post-dose. Plethysmography was repeated at 1, 2, 4, 8 and 12 h post-dose. On day 1 of each treatment period, patients performed spirometry, IOS, and whole body plethysmography prior to the first administration of BDP/ F/G or BDP/F.

Statistical methods
The co-primary objectives were to compare the effects of BDP/F/G versus BDP/F on change in FEV 1 and RV on day 5 compared to day 1 pre-dose, by analysing area under the curve over 12 h (AUC 0-12 ). The secondary objectives were to compare the effect of BDP/F/G versus BDP/F on change in all other lung function measurements for AUC 0-12 and peak, while treatment differences for FEV 1 and RV peak and trough (12 h post-dose) were also determined. Additionally, the differences between AUC 0-12 for BDP/F/G and BDP/F at day 5 were compared to the AUC 0-12 for BDP alone at baseline visit (relative to baseline visit pre-dose value). A sample size of 20 patients was required to detect a mean difference > 0.23 L (FEV 1 AUC 0-12 ) between treatments. This corresponds to a 2-sided t-test with 80% power conducted at the 5% significance level, assuming a standard deviation of 0.17 L for the paired differences between treatment groups. The primary analysis was conducted using a mixed model. The model included fixed effects for treatment and period and a random effect for patient within treatment sequence. For the primary endpoint, the AUC 0-12 from the baseline visit was included as a covariate. The AUC 0-12 (normalised by time), peak and trough (defined as the 12 h measurement post-dose on day 5) values were analysed as change from within-period day 1 pre-dose measurement. All were analysed without any procedures to account for multiple comparisons.

Participants
Sixty-six patients were screened, with 23 randomised, as shown in Fig. 2. One patient was withdrawn due to lack of treatment compliance, leaving 22 patients analysed. Patient characteristics are shown in Table 1. The mean FEV 1 % predicted (post-bronchodilator) was 49%, and RV was 152% predicted.

Secondary endpoints BDP/F/G versus BDP/F
BDP/F/G caused larger improvements than BDP/F for most of the lung function AUC 0-12 parameters ( Table 2). Using IOS, the change in small airway resistance, measured by R5-R20 AUC 0-12 , was greater with BDP/F/G compared to BDP/F (mean difference − 0.045 kPa/L/s; p = 0.0002). There were also significantly greater treatment differences in favour of BDP/F/G for Fres, AX and X5, while ∆X5 failed to reach statistical significance (p = 0.06). IC, TLC and FRC AUC 0-12 measurements did not show statistically significant differences between treatments, although TLC and FRC showed numerical changes in favour of BDP/F/G. sGaw AUC 0-12 change was greater with BDP/F/G (p = 0.01).
Change in peak FEV 1 was greater for BDP/F/G versus BDP/F (mean difference 120 mls; p = 0.0016), while for peak RV the difference was not significant (mean difference − 79 mls; p = 0.11). Other peak lung function results are shown in the Additional File 1; R5-R20 peak change with BDP/F/G was greater compared to BDP/F (mean difference − 0.036 kPa/L/s; p = 0.0022), while there were also significant differences for Fres, AX and X5, but not ∆X5. Lung volume peak measurements did not show statistically significant differences between treatments, while sGaw changes were in favour of BDP/F/G.

Safety
There were no serious AEs (adverse events) leading to withdrawal from the study or discontinuation of treatment. Further safety information is described in the Additional File 1.

Discussion
This study focused on COPD patients with evidence of gas trapping, measured by RV. For the primary endpoint analysis (AUC 0-12 ), BDP/F/G had greater effects compared to BDP/F on FEV 1 and RV (mean treatment differences; 104 mls and − 163 mls respectively). This demonstrates that the G component of extrafine BDP/F/G reduced gas trapping in COPD patients. Furthermore, the greater improvement in R5-R20 AUC 0-12 for BDP/F/G compared to BDP/F demonstrates that G also reduced small airway resistance. Overall, these results indicate that G had a beneficial effect on small airway physiology leading to improvements in gas trapping.
A secondary analysis, comparing BDP/F versus BDP, showed that F improved FEV 1 , RV and IOS measurements including R5-R20 AUC 0-12 . This demonstrates benefits of F on small airway physiology which are associated with decreases in gas trapping. The effect sizes observed showed that F treatment for 5 days caused 558 mls improvement in RV AUC 0-12 and a 227 mls improvement in FEV 1 AUC 0-12 . This comparison to baseline analysis also showed the extra benefit of the addition of G for 5 days, as BDP/F/G versus BDP treatment differences were 678 mls for RV AUC 0-12 and 320 mls for FEV 1 AUC 0-12 . Overall, these results indicate a greater effect of the addition of the first bronchodilator (BDP/F versus BDP) than the addition of the second bronchodilator (BDP/F/G versus BDP/F). This smaller effect of the second bronchodilator has been observed in many previous studies [5,18,19], and may be due to reaching near to the maximum improvement that may be achieved with these bronchodilator drug classes.
The primary and secondary outcomes, describing improvements in different components of lung mechanics, provide insights into the physiological effects of the long acting bronchodilators within BDP/F/G. Gas trapping is associated with an increased burden of symptoms in COPD [20,21], and pharmacological interventions to reduce gas trapping can improve exercise performance [22,23]. The primary endpoint analysis showed that using BDP/F/G can reduce gas trapping to a greater degree compared to BDP/F. This physiological effect may be extremely useful in clinical practice, in order to optimise the reduction of gas trapping and hence associated symptoms. The short treatment duration, and   limited sample size of the current study means that we could not properly assess changes in symptoms or exercise capacity. Nevertheless, the TRILOGY phase 3 study, conducted over one year, provided evidence of greater improvements at many of the time-points for symptoms and quality of life for treatment with BDP/F/G compared to BDP/F [10]. The peak lung function changes on day 5 (for the comparison of BDP/F/G versus BDP/F) followed the same pattern of results as AUC 0-12 , except RV showed a lower numerical difference (65 mls) that was not statistically significant (p = 0.08). This might be due to the reduction in gas trapping by the first bronchodilator (F) being relatively large at peak, leaving little room for improvement by the addition of the second bronchodilator (G). For both the AUC 0-12 and peak measurements, RV had the greatest sensitivity out of all the lung volume measurements to measure differences between BDP/F/G versus BDP/F; this is likely related to the enrichment of the study population for individuals with RV > 120% predicted at screening.
Using IOS allowed measurements of airway resistance and reactance to be collected. R5-R20 is a well accepted measurement of small airway resistance, and previous papers have shown that bronchodilators improve R5-R20 in COPD patients [4,24]. In this study, the concurrent improvements in R5-R20 and RV imply that bronchodilator related improvements in small airway function enabled reduced gas trapping. IOS reactance measurements (X5, Fres, AX) reflect lung compliance and elasticity, and here we observed consistent improvements in these parameters for the G and F components of extrafine triple therapy.
Small airway closure can prevent low frequency oscillometric signals from reaching the distal lung [7]. Small airway closure can therefore operate as regional "choke points" during expiration but not inspiration, which has been called expiratory flow limitation (EFL). This can cause marked differences in reactance measurements during tidal breathing, and is measured by ∆X5, which is an oscillometry measurement of EFL. It has been reported that EFL measurements are associated with greater airflow limitation and gas trapping, greater symptoms, more exacerbations and increased mortality [21,25,26]. The comparisons of BDP/F/G or BDP/F versus BDP (baseline) both showed large improvements in ∆X5, and consequently the BDP/F/G versus BDP/F Table 2  comparison yielded a small treatment difference that was not statistically significant. The design of the study, using the same inhaler device delivering extrafine formulations for all treatments, allowed the contributions of F and G on small airway function and gas trapping to be determined. We did not study a non-extrafine formulation with less peripheral lung deposition compared to BDP/F/G; this would be an interesting future study to compare changes in small airway function and gas trapping between treatments. While this was an open study, the objective nature of the endpoints (lung function measurements) restricted any bias that could be introduced by lack of treatment blinding. The main advantage of blinding is for patient reported outcomes which are more subjective. A potential limitation of the study was the relatively small sample size. However, the sample size was very similar to other crossover design studies investigating long acting bronchodilator effects on lung function [27,28], and the enrichment for individuals with gas trapping (RV > 120% predicted) increased the homogeneity of the population thereby decreasing the potential variability in lung function data.
The mean CAT score at screening was 19.6, suggesting this was a very symptomatic population. However, 13 out of the 22 patients had mMRC scores < 2 at study entry. The majority of patients (20 out of 22) were already receiving triple therapy in real life at study entry, which likely reduced the burden of dyspnoea. The differences between CAT and mMRC scores likely reflect the broader range of disease components assessed by the former, as previously reported [29]. All patients were using ICS at study entry; these drugs should be used in patients with a history of exacerbations [30], but often are inappropriately given to patients who do not have a history of exacerbations. While some of our study population had no exacerbations in the last year, this may reflect a positive treatment response to ICS initiation [31].
Late phase studies with large sample sizes often require statistical approaches to account for multiple testing. This smaller study was more exploratory in nature, providing information on the usefulness of a broad range of lung  function tests. This information can be used to select the most appropriate tests to be used in future studies comparing inhaled treatments. Multiple testing correction is often not performed in smaller clinical trials with a more exploratory nature [32]. Nevertheless, many of the p values reported were highly significant, arguing against the presence of false positives due to multiple testing. In summary, this study focused on COPD patients with gas trapping, and demonstrated that the G and F components of extrafine BDP/F/G improved FEV 1 , RV and small airway function. It can be concluded that these long acting bronchodilators target small airway function, thereby improving gas trapping and airflow.