Profiling the CFTR Variant Selectivity and Off-Target Interactions of VX-121

Area of Science:

• Biochemistry
• Genetics
• Pharmacology

Background:

• Cystic fibrosis (CF) is a genetic disorder caused by over 1,200 variants of the cystic fibrosis transmembrane conductance regulator (CFTR) gene.
• While common CFTR variants like F508del have targeted therapies, rare variants exhibit variable responses to existing treatments.
• VX-121, a component of Alyftrek, presents a potential new option for rare CF variants, but its efficacy across all variants is not fully understood.

Purpose of the Study:

• To evaluate the impact of VX-121 on the plasma membrane expression of 232 rare CFTR variants using deep mutational scanning (DMS).
• To compare the efficacy of VX-121 against VX-445 for various rare CFTR variants.
• To investigate the molecular mechanisms underlying VX-121's interactions with CFTR variants.

Main Methods:

• Deep mutational scanning (DMS) to assess plasma membrane expression of 232 rare CFTR variants.
• Computational docking to analyze protein-ligand interactions.
• Photo-crosslinking to identify off-target interactions.

Main Results:

• VX-121 generally enhanced CFTR variant expression more effectively than VX-445, particularly for variants in the first membrane spanning domain (MSD1).
• The Y1032C variant demonstrated reduced response to VX-121 compared to VX-445, with computational docking suggesting altered coordination due to mutation.
• VX-121 was shown to avoid a significant off-target interaction associated with VX-445.

Conclusions:

• VX-121 shows broad potential for enhancing rare CFTR variant expression, offering a promising therapeutic avenue.
• Understanding variant-specific responses and molecular interactions is crucial for optimizing CFTR modulator therapy.
• VX-121's distinct interaction profile compared to VX-445 may offer therapeutic advantages and a better safety profile.