(666) Ivacaftor Boosts CFTR-Mediated Nasal Potential Difference in CFTR Knockout Mice Treated with hCFTR-mRNA Lipid Nanoparticle

Background: We have previously used lipid nanoparticles (LNP) to successfully deliver hCFTR mRNA that partially restored CFTR function in CFTRKO mice as well as CF cell models. This is important as 10% of CF patients who lack the specific mutations are not eligible for the treatment with highly-effective-modulator-therapy that has proven to be significantly beneficial and effective in person with F508del CFTR mutation. There are also some evidences of drug intolerability or low response to the modulator therapy within eligible patient population. Thus, alternate approaches to restore CFTR function are needed.


A limitation to mRNA LNP is reduced functional expression of CFTR protein compared to wild-type cells. Chloride ion transport is a function of the product of the number of CFTR channels at the cell-surface and the open probability of each channel. Thus, increasing either cell surface protein expression or enhancing hCFTR open probability is a viable therapeutic strategy to augment hCFTR-mRNA mediated chloride transport rescue in CF cell and animal models.

In this study we aimed to increase the net ion transport as measured by the nasal potential difference in vivo of mRNA mediated CFTR rescue by using a two approaches. First, we varied the LNP formulation to test whether the newer formulations result in increased CFTR protein expression in vitro and in vivo. Second, we tested the hypothesis that combining hCFTR mRNA delivery with CFTR potentiating small molecule drug Ivacaftor (VX-770), that increases CFTR open probability, will result in increased activity of the resultant hCFTR protein.

Methods: We performed western blot and immunofluorescence studies to test the efficacy of different LNP formulations for increasing CFTR protein expression in vitro and in vivo. Nasal potential difference (NPD) was measured in CFTRKO mice post instillation of different hCFTR mRNA-LNP formulations before and after treatment with Ivacaftor.

Results: We observe that the newer formulations lead to increased expression of protein in vitro. We also observe that Ivacaftor perfusion resulted in overall 130.51% ± 27.06 SEM, (n=11) increase hCFTR activity.

Conclusions: We observe that the newer formulations lead to increased expression of protein in vitro. We also observe that Ivacaftor perfusion resulted in overall 130.51% ± 27.06 SEM, (n=11) increase CFTR activity.

Acknowledgements: MUKHER21F0-BASBAUM

R01HL146736

References: