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 are conducting a phase 1b study of an oral NE inhibitor, alvelestat, in patients with BOS after HCT . Biomarkers, including the elastin breakdown peptides desmosine/isodesmosine (DES/IDES), and stimulated neutrophil elastase assess direct effect on NE activity. Neo-epitope by-products of collagen type 3 and 6 synthesis (PRO-C3 and PRO-C6) and degradation (C3M and C6M) are measured as biomarkers of fibrosis/tissue modelling


Patients age ≥18 years with BOS and chronic GVHD after HCT were recruited to the National Cancer Institute protocol (NCT02669251). 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, increased every 2 weeks to 120mg twice daily, 180mg twice daily, and finally 240mg twice daily. Peripheral blood samples were collected at baseline and at the end of each dose-escalation stage.

Plasma DES/IDES was measured by isotopic dilution liquid chromatography-tandem mass spectrometry (Huang et al Thorax 2012;67:502-508). Ex vivo zymosan stimulated neutrophil elastase activity was measured by ProteaseTag® immunoassay (ProAxsis Ltd, Northern Ireland). PRO-C3, PRO-C6, C3M and C6M were measured by competitive ELISA. (Nordic Biosciences, Denmark). Results are presented as Mean and Standard Error Mean (SEM).


Between 2016 and 2018, 7 patients were enrolled (3 men and 4 women). Median FEV 1 after bronchodilator at time of enrollment was 44% predicted (range 38-74). All 7 patients were able to tolerate dose escalation of alvelestat up to the maximum dose 240mg twice daily. Preliminary clinical results were previously presented.

DES/IDES was elevated at baseline (mean 0.464 (SEM 0.0508) ng/ml, with 6 of 7 subjects above the Upper Limit of Normal (ULN, 0.280 ng/ml)). Levels progressively declined during the dose escalation period to 0.380 (SEM 0.0419) ng/ml by week 8, representing a mean within subject % change from baseline (CFB) of -16.2% (SEM 6.794, Figure 1a)

Ex vivo zymosan stimulated elastase activity also showed progressive decrease over the dose escalation period, with some subjects demonstrating 100% suppression (Figure 1b).

Collagen synthesis as measured by PRO-C3 and PRO-C6 was increased above ULN at baseline and declined with alvelestat treatment (Figure 1c and 1d). There was no consistent change in collagen degradation biomarkers (C3M, C6M)

There was consistency of a suppressive effect on biomarkers of elastase activity and collagen turnover in 6 of 7 treated patients, all of whom had improved or stable lung disease (ranging from change in FEV1 % predicted at end of treatment from +9% to -6%).


NE can damage lung tissue due to elastin breakdown, pro-inflammatory and pro-fibrotic effects (Sallenave J-M, J Leuk Biol 2015;98:137-139). This is the first evidence of elevated elastase activity as detected by elastin breakdown in patients with BOS and chronic GVHD.

Treatment with the selective NE inhibitor, alvelestat was associated with progressive reduction of plasma desmosine levels over 8 weeks of within-subject dose escalation and reduction stimulated neutrophil elastase activity.

The consistent suppression of elastase and of collagen synthesis/turnover biomarkers following alvelestat treatment is encouraging for its potential to impact progressive lung fibrosis in BOS and chronic GVHD.


Parkin:Mereo BioPharma Group: Current Employment. Moore:Mereo BioPharma Group: Current Employment. Pavletic:Center for Cancer Research: Research Funding; National Cancer Institute: Research Funding; National Institutes of Health: Research Funding; Celgene: Research Funding; Actelion: Research Funding; Eli Lilly: Research Funding; Pharmacyclics: Research Funding; Kadmon: Research Funding.

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