Discovery of a novel, high affinity, small molecule alpha-v beta-6 integrin inhibitor for the treatment of idiopathic pulmonary fibrosis

R. J. Slack1, A. E. John2, E. J. Forty3, P. F. Mercer3, T. K. Pun1, E. Gower1, D. J. Flint4, S. Pyne4, J. C. Denyer1, A. J. Fisher5, R. C. Chambers3, G. R. Jenkins2, S. J. Macdonald1. 1Fibrosis and Lung Injury DPU, Respiratory TAU, GlaxoSmithKline, Stevenage, UNITED KINGDOM, 2Nottingham Respiratory Research Unit, University of Nottingham, Nottingham, UNITED KINGDOM, 3Centre for Inflammation and Tissue Repair, University College London, London, UNITED KINGDOM, 4Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UNITED KINGDOM, 5Tissue Fibrosis and Repair Group, Newcastle University, Newcastle upon Tyne, UNITED KINGDOM.

Introduction: Fibrosis is the formation of scar tissue due to injury or long-term inflammation and is a leading cause of morbidity and mortality in disorders that include idiopathic pulmonary fibrosis (IPF). The alpha-v beta-6 (αvβ6) integrin has been identified as playing a key role in the activation of transforming growth factor-β (TGFβ) that is hypothesised to be pivotal in the development of IPF [1]. Therefore, a drug discovery programme within GlaxoSmithKline to identify small molecule αvβ6 selective RGD-mimetics was initiated.

Method: As part of a medicinal chemistry programme GSK3008348 [2] was identified and profiled in a range of pre-clinical in vitro (radioligand binding [3], flow cytometry [4], functional TGFβ [5] and high content screening assays) and in vivo (bleomycin-induced lung injury mouse model (20 and 60 IU bleomycin treated male C57/Bl6 mice)) systems.

Results: GSK3008348 (1% DMSO) was shown to bind to the αvβ6 with high affinity (pKD 11.3±0.07, mean±SEM, n=6 donors) in membrane preparations generated from IPF human lung tissue. In primary human lung epithelial cells GSK3008348 (0.1% DMSO) induced rapid internalisation of αvβ6 (t1/22.6±0.5 min, mean±SEM, n=4) followed by a slow return of the integrin to the cell surface (t1/2 11.0±1.9 h, mean±SEM, n=4). It was shown that αvβ6 is degraded in lysosomes post-internalisation by GSK3008348 that would suggest the slow return of integrin to the surface and sustained duration of action is a consequence of new αvβ6 synthesis. GSK3008348 (1 mg/kg i.n. saline) was shown to engage with αvβ6 and inhibit the activation of TGFβ with a prolonged duration of action using in vivo mouse bleomycin lung fibrosis models measuring αvβ6 engagement (SPECT imaging [6]) and TGFβ signalling (pSMAD2 lung levels).

Conclusion: In summary, GSK3008348 displays the desirable pharmacological characteristics required for targeting a prolonged inhibition of TGFβ activation in the IPF lung via blockade of the αvβ6 integrin and is currently in Phase I trials for IPF [7].

References:

1. Goodwin A and Jenkins G (2009). Biochem Soc Trans 37: 849-854.

2. Anderson NA et al., (2016). Org Biomol Chem 14: 5992-6009.

3. Hall ER et al., (2016). Biochem Pharm (in press) doi:10.1016/j.bcp.2016.08.003.

4. Slack RJ et al., (2016). Pharmacology 97:114-125.

5. Xu MY et al., (2009) Am J Pathol 174: 1264-1279.

6. John AE et al., (2013) J Nucl Med 54:1-7.

7. NCT02612051 - First Time in Human (FTIH) Study of GSK3008348 in Healthy Volunteers and Idiopathic Pulmonary Fibrosis Patients https://clinicaltrials.gov/