Phase 1 Study of Alvelestat, an Oral Neutrophil Elastase Inhibitor, in Patients with Bronchiolitis Obliterans Syndrome after Hematopoietic Cell Transplantation

Introduction Bronchiolitis Obliterans Syndrome (BOS) is a rare but devastating complication of chronic graft-versus-host disease (GVHD) after allogeneic hematopoietic cell transplantation (HCT) and is associated with a high morbidity and mortality. There is a dearth of treatment options for BOS and new strategies are needed. Airway neutrophilia is a hallmark of BOS, even in the absence of infection, and neutrophil elastase (NE) is an enzyme that has been implicated in the pathogenesis of BOS. We conducted a phase 1 study of an oral NE inhibitor, alvelestat, in patients with BOS after HCT. Methods Patients age ≥18 years with BOS and chronic GVHD after HCT were recruited to the National Cancer Institute protocol (NCT02669251). Patients had stable systemic immunosuppression and FEV1 ≥30% on pulmonary function tests (PFTs). This phase 1 study had 2 parts: 8-week intra-patient dose escalation period, followed by a continuation period that allowed for up to 6 months of treatment. Alvelestat was given orally starting at 60mg twice daily (the dose previously used in patients with chronic lung disease) and increased every 2 weeks as tolerated to 120mg twice daily, 180mg twice daily, and finally 240mg twice daily. Patients continued this dose until completion of the continuation phase, or occurrence of unacceptable toxicity, dose interruption >28 days, or progression of GVHD or BOS. Primary objective was to determine the maximum tolerated dose (MTD) based on dose-limiting toxicities. Secondary objectives included determining pharmacokinetics, markers of NE activity, and markers of inflammation in blood and sputum. PFTs and chronic GVHD evaluations were performed at baseline, 4 weeks and 8 weeks during the dose escalation period, and at 3 months and 6 months during the continuation period. Results Between 2016 and 2018, 7 patients were enrolled (3 men and 4 women). Median FEV1 after bronchodilator at time of enrollment was 44% (range 38-74). All 7 patients were able to tolerate dose escalation of alvelestat up to the maximum dose 240mg twice daily; MTD was not reached. The most common adverse events (AEs) that were possibly related to study treatment were all grade 2, and included increased creatinine (3 patients), ALT or AST elevation (3 patients), and upper respiratory infection (3 patients). The only grade 3 AEs that were possibly related to study drug were gastroenteritis and vomiting requiring hospitalization in 1 patient and pneumonia in 1 patient. Three patients completed the study with 8 weeks + 6 months of treatment. Four patients required dose interruptions, and only 1 of those required dose reduction for grade 3 gastroenteritis (resulting in dehydration and elevated creatinine). Four patients discontinued treatment prior to end of study: 2 patients had dose interruption of >28 days due to adverse events, 1 patient had a decline in FEV1 after pneumonia, and treatment was stopped in 1 patient due to investigator discretion. The median duration of treatment was 6.4 months. Based on NIH chronic GVHD consensus criteria, 6 patients had unchanged disease and 1 patient had progressive disease (decline in FEV1 after pneumonia). Although patients did not achieve the 10% improvement in FEV1 required for an organ response, 2 patients had improvement of 9% in FEV1 and 4 patients had improvement in the Lee chronic GVHD symptom scale lung score. Preliminary pharmacokinetic analyses of the 7 patients showed a linear dose-dependent increase in each exposure metric (steady-state trough and steady-state peak), despite some inter-patient variability. Bronchoalveolar lavage fluid and induced sputum samples are being analyzed for NE activity. Conclusion In this phase 1 study of the oral NE inhibitor, alvelestat, in patients with BOS after HCT, MTD was not reached and the study drug was well tolerated. Six patients had stable disease, while 1 patient had progression in the setting of pneumonia. Two patients notably had improvement in FEV1 of 9%, and 4 patients experienced improvement in symptoms. We have demonstrated that NE inhibition is well tolerated and shows a signal of stabilizing disease in patients with advanced BOS. Further study of the clinical efficacy of alvelestat in BOS after HCT is warranted, especially at an earlier stage of disease and longer duration of drug administration. Disclosures No relevant conflicts of interest to declare.