Personalized CFTR Modulator Therapy for G85E and N1303K Homozygous Patients with Cystic Fibrosis

Abstract

CFTR modulator therapy with elexacaftor/tezacaftor/ivacaftor (ETI) has been approved for people with CF and at least one F508del allele in Europe. In the US, the ETI label has been expanded to 177 rare <i>CFTR</i> mutations responsive in Fischer rat thyroid cells, including <i>G85E</i>, but not <i>N1303K</i>. However, knowledge on the effect of ETI on G85E or N1303K CFTR function remains limited. In vitro effects of ETI were measured in primary human nasal epithelial cultures (pHNECs) of a <i>G85E</i> homozygous patient and an <i>N1303K</i> homozygous patient. Effects of ETI therapy in vivo in these patients were assessed using clinical outcomes, including multiple breath washout and lung MRI, and the CFTR biomarkers sweat chloride concentration (SCC), nasal potential difference (NPD) and intestinal current measurement (ICM), before and after initiation of ETI. ETI increased CFTR-mediated chloride transport in <i>G85E</i>/<i>G85E</i> and <i>N1303K</i>/<i>N1303K</i> pHNECs. In the <i>G85E</i>/<i>G85E</i> and the <i>N1303K</i>/<i>N1303K</i> patient, we observed an improvement in lung function, SCC, and CFTR function in the respiratory and rectal epithelium after initiation of ETI. The approach of combining preclinical in vitro testing with subsequent in vivo verification can facilitate access to CFTR modulator therapy and enhance precision medicine for patients carrying rare <i>CFTR</i> mutations.