Development of a small molecule that corrects misfolding and increases secretion of Z α ₁ ‐antitrypsin

Abstract

Severe α1‐antitrypsin deficiency results from the Z allele (Glu342Lys) that causes the accumulation of homopolymers of mutant α1‐antitrypsin within the endoplasmic reticulum of hepatocytes in association with liver disease. We have used a DNA‐encoded chemical library to undertake a high‐throughput screen to identify small molecules that bind to, and stabilise Z α1‐antitrypsin. The lead compound blocks Z α1‐antitrypsin polymerisation in vitro, reduces intracellular polymerisation and increases the secretion of Z α1‐antitrypsin threefold in an iPSC model of disease. Crystallographic and biophysical analyses demonstrate that GSK716 and related molecules bind to a cryptic binding pocket, negate the local effects of the Z mutation and stabilise the bound state against progression along the polymerisation pathway. Oral dosing of transgenic mice at 100 mg/kg three times a day for 20 days increased the secretion of Z α1‐antitrypsin into the plasma by sevenfold. There was no observable clearance of hepatic inclusions with respect to controls over the same time period. This study provides proof of principle that “mutation ameliorating” small molecules can block the aberrant polymerisation that underlies Z α1‐antitrypsin deficiency.

Hepatic and Extrahepatic Sources and Manifestations in Endoplasmic Reticulum Storage Diseases

“…Recent observations on small molecules predicted to bind Z AAT [117][118][119] or mutant fibrinogen at the interface of the aggregation sites, thus increasing degradation and inhibiting intracellular accumulation, appear to be promising and in line with the observations from the present study.…”

The molecular species responsible for α1‐antitrypsin deficiency are suppressed by a small molecule chaperone

“…We have developed a small molecule inhibitor of polymerisation, c716, that is active in vivo and that prevents the formation of M* in vitro [44]. To investigate its behaviour under the experimental conditions considered here, CHO K1 cells were seeded in the presence of DMSO or c716 and subsequently induced to produce Z a 1 -antitrypsin for 48 h before being starved, pulsed and processed as described in Fig 1 . Intra-Z a 1antitrypsin and extracellular Z a 1 -antitrypsin were sequentially immunoprecipitated with 2C1 and 3C11 mAbs.…”

Association between circulating alpha-1 antitrypsin polymers and lung and liver disease

“…However, to the best of our knowledge, no other studies have related CP concentrations with LSM or ELF and this is important since transient elastography is increasingly used for the screening and follow-up of liver disease in patients with AATD [ 30 , 31 ], and ELF is a systemic biomarker of liver fibrosis [ 18 ]. The importance of the polymerisation of mutated AAT in the pathogenesis of liver and lung disease in AATD has stimulated the development of new strategies of treatment for AATD based on the blockade of polymer formation [ 32 , 33 ].…”