Conflict of interest statement
There is no conflict of interest related to this work.
ABSTRACT (248 words; max 250)
Background and Purpose:Despite progress in developing pharmacotherapies to rescue F508del-CFTR,
the most prevalent Cystic Fibrosis (CF)-causing mutation, individuals
homozygous for this mutation still face several disease-related
symptoms. Thus, more potent compound combinations are still needed.
Here, we investigated the mechanism of action (MoA) of RDR01752, a novel
F508del-CFTR trafficking corrector.
Experimental approach: F508del-CFTR correction by RDR01752 was
assessed by biochemical, immunofluorescence microscopy and functional
assays in cell lines and in intestinal organoids. To determine the MoA
of RDR01752, we assessed its additive effects to those of genetic
revertants of F508del-CFTR, the FDA-approved corrector drugs VX-809 and
VX-661, and low temperature.
Key Results: Our data demonstrated that RDR01752 rescues
F508del-CFTR processing and plasma membrane (PM) expression to similar
levels of VX-809 in cell lines, although RDR01752 produced lower
functional rescue. However, in functional assays using intestinal
organoids (F508del/F508del), RDR01752, VX-809 and VX-661 had similar
efficacy. RDR01752 demonstrated additivity to revertants 4RK and G550E,
but not to R1070W, as previously shown for VX-809. RDR01752 was also
additive to low temperature. Co-treatment of RDR01752 and VX-809 further
increased F508del-CFTR function compared to each corrector alone, but
not PM expression.
Conclusion and Implications: The lack of additivity of RDR01752
with the genetic revertant R1070W suggests that this compound has the
same effect as the insertion of tryptophan at 1070, i.e., filling the
pocket at the NBD1:ICL4 interface in F508del-CFTR, similarly to VX-809.
Combination of RDR01752 with correctors mimicking the rescue by
revertants G550E or 4RK could thus maximize rescue of F508del-CFTR.
Keywords: cystic fibrosis, protein trafficking, revertants, low
temperature, intestinal organoids, drug discovery.