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Morbidity and mortality in pulmonary arterial hypertension (PAH) remain high. Activation of platelet-derived growth factor receptor, colony stimulating factor 1 receptor, and mast or stem cell growth factor receptor kinases stimulates inflammatory, proliferative, and fibrotic pathways driving pulmonary vascular remodelling in PAH. Seralutinib, an inhaled kinase inhibitor, targets these pathways. We aimed to evaluate the efficacy and safety of seralutinib in patients with PAH receiving standard background therapy. The TORREY trial was a phase 2, randomised, multicentre, multinational, double-blind, placebo-controlled study. Patients with PAH from 40 hospital and community sites were randomly assigned 1:1 via interactive response technologies to receive seralutinib (60 mg twice daily for 2 weeks, then increased to 90 mg twice daily as tolerated) or placebo by dry powder inhaler twice daily for 24 weeks. Randomisation was stratified by baseline pulmonary vascular resistance (PVR; <800 dyne·s/cm5 and ≥800 dyne·s/cm5). Patients were eligible if classified as WHO Group 1 PH (PAH), WHO Functional Class II or III, with a PVR of 400 dyne·s/cm5 or more, and a 6 min walk distance of between 150 m and 550 m. The primary endpoint was change in PVR from baseline to 24 weeks. Analyses for efficacy endpoints were conducted in randomly assigned patients (intention-to-treat population). Safety analyses included all patients who received the study drug. TORREY was registered with ClinicalTrials.gov (NCT04456998) and EudraCT (2019-002669-37) and is completed. From Nov 12, 2020, to April 20, 2022, 151 patients were screened for eligibility, and following exclusions, 86 adults receiving PAH background therapy were randomly assigned to seralutinib (n=44; four male, 40 female) or placebo (n=42; four male, 38 female), and comprised the intention-to-treat population. At baseline, treatment groups were balanced except for a higher representation of WHO Functional Class II patients in the seralutinib group. The least squares mean change from baseline to week 24 in PVR was 21·2 dyne·s/cm5 (95% CI −37·4 to 79·8) for the placebo group and −74·9 dyne·s/cm5 (−139·7 to −10·2) for the seralutinib group. The least squares mean difference between the seralutinib and placebo groups for change in PVR was −96·1 dyne·s/cm5 (95% CI −183·5 to −8·8; p=0·03). The most common treatment-emergent adverse event in both treatment groups was cough: 16 (38%) of 42 patients in the placebo group; 19 (43%) of 44 patients in the seralutinib group. Treatment with inhaled seralutinib significantly decreased PVR, meeting the primary endpoint of the study among patients receiving background therapy for PAH. Gossamer Bio. [ABSTRACT FROM AUTHOR]

Seralutinib, an inhaled, small‐molecule tyrosine kinase inhibitor in clinical development for the treatment of pulmonary arterial hypertension (PAH), was evaluated for its potential as a perpetrator or victim of a metabolic and transporter‐based drug‐drug interactions in 2 phase 1 studies. In study 1, 24 participants received a cocktail of probe substrates: caffeine (CYP1A2), montelukast (CYP2C8), flurbiprofen (CYP2C9), midazolam (CYP3A), and pravastatin (OATP1B1/1B3), plus digoxin (P‐gp) with or without seralutinib. In study 2, 19 participants received seralutinib with/without itraconazole, a strong CYP3A inhibitor, or fosaprepitant, a weak CYP3A inhibitor. Geometric least‐squares mean ratios and 90% confidence intervals for maximum observed concentration (Cmax) and area under the plasma concentration‐time curve (AUC) were obtained. Safety was monitored throughout the studies. All adverse events were mild or moderate in severity. Seralutinib coadministration increased AUC for midazolam 3.03‐fold and caffeine 1.32‐fold. The coadministration increased digoxin Cmax 1.28‐fold. Seralutinib did not meaningfully alter Cmax and AUC for montelukast, flurbiprofen, or pravastatin. Fosaprepitant and itraconazole increased seralutinib AUC 1.08‐ and 1.84‐fold, respectively. Seralutinib is a moderate CYP3A inhibitor and a weak CYP1A2 inhibitor; it slightly inhibits P‐gp. Seralutinib exposure is minimally affected by a weak CYP3A inhibitor but is substantially increased by a strong CYP3A inhibitor. [ABSTRACT FROM AUTHOR]