This was a first-time-in-human, randomised, double-blind, single ascending-dose study of nebulised GSK3008348 (NCT02612051). GSK3008348 was formulated as a solution, administered via nebulisation over approximately 10 min using a Philips Respironics Inno Spire Delux Nebuliser with a Philips side stream mouthpiece. Informed consent was obtained from all individual participants in the study.
Two cohorts of eight healthy participants each were randomised 3:1 to receive GSK3008348 (n = 6) or placebo (n = 2) in each period of a 4-period crossover. Within each cohort, participants were randomised to receive up to three ascending doses of GSK3008348 and one of placebo. In case it was necessary to repeat any doses to obtain more PK or safety data, a third cohort with the same design was also included in the study. Sentinel dosing was used throughout: on day 1, two subjects were dosed one active and one placebo, the remaining subjects in the dosing group were dosed the following day. Once each dose group had been completed, there was a blinded review of the safety and PK before proceeding to the next dose (Fig. 1).
In each period, participants were admitted to the clinical unit before dosing and were discharged 48 h after their dose. There was a washout period of at least 6 days between doses. This was based on non-clinical PK observations predicting an effective half-life of less than 12 h and human in vitro studies indicating a modestly extended pharmacodynamic effect. GSK3008348 demonstrates a receptor dissociation half-life of ~ 9 h and induces rapid internalisation of αvβ6 (minutes) followed by a slow return of the integrin to the cell surface (hours) due to integrin degradation [13, 14]. Non-clinical PK studies demonstrated rapid absorption of the drug from the lung into the systemic circulation with no evidence of significant lung retention. After the final dose, there was a follow-up period for 7–14 days.
Cohort 1 received 1, 3, 10, and 30 mcg GSK3008348, and cohort 2 received 100, 300, 1000, and 3000 mcg GSK3008348. Cohort 3 received a repeat of the highest dose levels, 1000 and 3000 mcg GSK3008348, to obtain additional information on safety and PK. The 1 mcg starting dose of GSK3008348 was predicted to engage approximately 15% of the αvβ6 in healthy lungs at lung peak concentrations, and the free systemic concentrations were predicted to be below the KD at maximum plasma concentration (Cmax). This was a deliberately conservative approach given the novel mechanism. Dose escalation was continued, using half log steps, to a maximum of 3000 mcg in order to explore sustained higher occupancies (predicted > 90%) where downstream biomarker modulation and efficacy may be expected based on pre-clinical evidence . In addition, 3000 mcg was the maximum dose supported by non-clinical toxicological studies. No systemic toxicity was identified at all doses tested in the 4-week inhalation toxicity studies. The human systemic exposures achieved across the dose range were within the systemic nonclinical safety margins.
The objectives of the study were achieved after the first two dosing periods in cohort 3; therefore, the study was terminated and the final two dosing periods in cohort 3 were not required.
Healthy male or female participants aged ≥ 18 years, with body weight ≥ 50 kg and body mass index ≥ 19.0–≤ 35.0 kg/m2, were eligible to participate in the study. Female participants were eligible if they were of non-childbearing potential. Participants were determined as healthy based on medical history, physical examination, clinical laboratory tests (haematology, clinical chemistry, urinalysis, HIV and hepatitis B and C screen, and drug, alcohol and smoking screening tests), 12-lead electrocardiogram (ECG), continuous cardiac telemetry, vital signs and pulmonary function tests.
Current smokers and participants with current or history of liver disease, known hepatic or biliary abnormalities, current or history of photosensitivity, current respiratory tract infection or history of excessive alcohol consumption were excluded.
Participants were under continuous medical supervision during each admission period (up to 48 h post-dose), and safety assessments were made at regular intervals throughout each period and until the end of follow-up. Assessment of safety was conducted by monitoring AEs, clinical laboratory tests (haematology, clinical chemistry and urinalysis), vital signs (including pulse oximetry), 12-lead ECGs, telemetry, physical examinations and pulmonary function tests (forced expiratory volume in 1 s [FEV1], FVC, diffusing capacity of the lung for carbon monoxide).
Blood samples for the measurement of plasma GSK3008348 concentrations were taken up to 24 h after each dose administration and up to 30 h after dose administration in cohort 3. Analysis was conducted using a validated analytical method based on protein precipitation, followed by high-performance liquid chromatography (Waters Acquity Chromatograpy System) and mass spectrometry detection via an electrospray interface with multiple reaction monitoring (Waters Xevo TQ-S). The lower limit of quantification for GSK3008348 was 50 pg/mL using a 50-μL aliquot of human plasma with a higher limit of quantification of 50,000 pg/mL. The overall assay accuracy (% deviation from nominal) was ± 3.5% and precision (% coefficient of variation) was ≤ 8.4%.
Safety data was summarised descriptively and presented in tabular format. PK parameters were determined by non-compartmental analysis of GSK3008348 plasma concentration-time data. The following parameters were generated where data permitted: Cmax, time of maximum concentration (Tmax), terminal half-life (T½), area under the plasma concentration-time curve from zero hours to time (AUC0-t) and area under the plasma concentration-time curve from 0 h to infinity (AUC0-inf).
An assessment of dose proportionality was made for Cmax and AUC0-inf using the power model . Both parameters were loge-transformed, and a mixed-effect model was fitted for each parameter with loge (dose) as a fixed effect and subject specific intercepts as a random effect. For each parameter, the exponent of the power model and corresponding 90% confidence intervals (CIs) were estimated. Further dose proportionality analyses were performed using the analysis of variance method. Dose-normalised, loge-transformed AUC0-inf and Cmax were analysed separately using a mixed-effect model as described above but with dose as a categorical variable. Pairwise comparisons were made with respect to each dose versus the chosen reference dose of 300 mcg.