Rescue of Mutant CFTR Trafficking Defect by the Investigational Compound MCG1516A

Abstract

Although some therapeutic progress has been achieved in developing small molecules that correct F508del-CFTR defects, the mechanism of action (MoA) of these compounds remain poorly elucidated. Here, we investigated the effects and MoA of MCG1516A, a newly developed F508del-CFTR corrector. MCG1516A effects on wild-type (WT) and F508del-CFTR were assessed by immunofluorescence microscopy, and biochemical and functional assays both in cell lines and in intestinal organoids. To shed light on the MoA of MCG1516A, we evaluated its additivity to the FDA-approved corrector VX-661, low temperature, genetic revertants of F508del-CFTR (G550E, R1070W, and 4RK), and the traffic-null variant DD/AA. Finally, we explored the ability of MCG1516A to rescue trafficking and function of other CF-causing mutations. We found that MCG1516A rescues F508del-CFTR with additive effects to VX-661. A similar behavior was observed for WT-CFTR. Under low temperature incubation, F508del-CFTR demonstrated an additivity in processing and function with VX-661, but not with MCG1516A. In contrast, both compounds promoted additional effects to low temperature to WT-CFTR. MCG1516A demonstrated additivity to genetic revertant R1070W, while VX-661 was additive to G550E and 4RK. Nevertheless, none of these compounds rescued DD/AA trafficking. Both MCG1516A and VX-661 rescued CFTR processing of L206W- and R334W-CFTR with greater effects when these compounds were combined. In summary, the absence of additivity of MCG1516A to genetic revertant G550E suggests a putative binding site for this compound on NBD1:NBD2 interface. Therefore, a combination of MCG1516A with compounds able to rescue DD/AA traffic, or mimicking the actions of revertant R1070W (e.g., VX-661), could enhance correction of F508del-CFTR defects.

One Size Does Not Fit All: The Past, Present and Future of Cystic Fibrosis Causal Therapies

“…In cell models, additivity of c407 with VX-809 suggests these compounds might represent a complementary MoA with existing CFTR corrector types. Other pharmacological chaperones targeting NBD1 are phenylhydrazones [ 166 ], such as RDR-1 [ 130 ], which enhanced CFTR currents in differentiated human bronchial epithelial cell (HBE) cultures synergistically with VX-809 and MCG1516A [ 167 ], and which, since then, have been proposed to bind at the NBD1:NBD2 interface [ 168 ].…”

Advances in Preclinical In Vitro Models for the Translation of Precision Medicine for Cystic Fibrosis

“…epithelial) have been generated and optimized to help in enhancing our knowledge of CFTR biology [ 14 , 15 ]. These include baby hamster kidney (BHK) [ 18 , 31 , 32 ], Chinese hamster ovary (CHO) [ 33 , 34 , 35 , 36 ], African green monkey kidney (Cos-7) [ 37 , 38 , 39 , 40 ], embryonic Swiss mouse (3T3) [ 17 , 35 , 41 ], human embryonic kidney (HEK) [ 36 , 41 , 42 , 43 , 44 ], Madin-Darby canine kidney (MDCK) [ 43 , 45 , 46 ], Fischer rat thyroid (FRT) [ 16 , 47 , 48 , 49 ] and CF bronchial epithelial (CFBE41o − ) cell lines [ 32 , 43 , 49 , 50 , 51 , 52 ] ( Table 1 ). These cells are easy to be cultured and expanded, making them suitable models for the usage in different methods and assays [ 14 ].…”

“…Indeed, the existing cell models have some liabilities due to immortalization processes that can cause genome instability, karyotypic alterations and modifications in gene expression [ 14 , 60 , 61 ]. Furthermore, cell background has a strong influence on the pharmacological rescue of CFTR mutations, as it has been previously demonstrated for F508del-CFTR when the same compound is assessed in different cell models [ 31 , 52 , 62 , 63 , 64 ]. Validation of several hit compounds (or combinations thereof) on primary cells (i.e., human bronchial epithelial (HBE) cells) may be nevertheless unfeasible, as these are a limited resource and usually require invasive procedures to be obtained (bronchoscopy or explants from lung transplantation).…”

Molecular mechanisms of cystic fibrosis – how mutations lead to misfunction and guide therapy

“…Other potential binding sites are likely to exist for other correctors. For instance, MCG1516A, a corrector additive to VX-661, was proposed to target the interface between NBD1 and NBD2 principally as it is not additive to the G550E revertant, in contrast to the R1070W one (at the interface between ICL4 and NBD1) [ 106 ]. Other corrector binding sites have been proposed within NBD1 [ 107 ] and at the NBD1:ICL4 interface [ 108–110 ].…”

“…Strategies aimed at other channels and transporters (discussed and reviewed in [ 106 ]) are under development or clinical trial focusing on the inhibition of the epithelial sodium channel (ENaC), the modulation of the calcium activated channel TMEM16A (or anoctamin 1) or of the solute carrier family member 26A member 9 (SLC26A9). Some attention has also been given to the identification of synthetic anionophores, able to restore transmembrane chloride transport.…”