(673) Trikafta^TM corrects function of H1085R-, N1303K- and R334W-CFTR and improves clinical status of patients.

Background: The next generation CFTR modulator Trikafta™ is the combination of correctors (elexacaftor and tezacaftor) with potentiator (ivacaftor). So far Trikafta^TM has been approved in Europe for patients carrying at least one F508del-CFTR allele (p.Phe508del). In France, patients with severe respiratory impairment can receive Trikafta^TM treatment as part of the Temporary Authorization for Use -ATU. We aimed to study the efficacy of Trikafta^TM to correct activity of non-F508del-CFTR variants with processing defects in the human nasal epithelial (HNE) primary cell model.

Methods: CF patients with severe respiratory insufficiency were recruited for HNE sampling with following genotypes (N1303K/N1303K, M1T/R334W N1303K/H1085R (n=2)). HNE were amplified with conditional reprogramming and differentiated in air-liquid interface (ALI) conditions. To asses CFTR function, the short-circuit current measures were performed on ALI HNE cultures treated with DMSO or Trikafta (elexacaftor and tezacaftor at 3 µM and ivacaftor at 100 nM) for 48h.

Results: Trikafta^TM significantly corrected N1303K-CFTR and R334W-CFTR chloride secretion activity up to 5.2% (range 4.7% – 5.5%) and up to 10% (range 8.5% – 11.8%) of the WT-CFTR function. The most spectacular, significant increase of CFTR-dependent chloride secretion was measured in N1303K/H1085R cells, which reached the level over 63% (range 57% - 69%) of WT-CFTR activity. Bicarbonate transport in the M1T/R334W patient’s HNE cells was improved up to 13% and in N1303K/H1085R cells up to 60% (range 40% - 70%) of WT-CFTR level.

All these patients improved at short time FEV1 by a mean of 40% (range 20% - 67%), and body weight by a mean of 4.3 kg (range 1.5 kg – 7.4 kg). Sweat chloride was significantly decreased by a mean of 65 mmol/l (range 56 – 74 mmol/l) apart the N1303K homozygous patient.

Conclusions: Trikafta^TM significantly improves CFTR activity of N1303K, H1085R and R334W variants. Clinical data supported by in vitro results strongly suggested that the use of Trikafta^TM could be therapeutically beneficial for patients with N1303K, H1085R and R334W mutations. Compassionate therapy program could confirm the predictive character of the HNE model and will allow to test new therapeutic molecules.

Acknowledgements: This work was supported by Vaincre la Mucoviscidose.

References: Veit G, Roldan A, Hancock MA, Da Fonte DF, Xu H, Hussein M, Frenkiel S, Matouk E, Velkov T, Lukacs GL. Allosteric folding correction of F508del and rare CFTR mutants by elexacaftor-tezacaftor-ivacaftor (Trikafta) combination. JCI Insight. 2020 Sep 17;5(18):e139983. doi: 10.1172/jci.insight.139983.

Laselva O, Bartlett C, Gunawardena TNA, Ouyang H, Eckford PDW, Moraes TJ, Bear CE, Gonska T. Rescue of multiple class II CFTR mutations by elexacaftor+tezacaftor+ivacaftor mediated in part by the dual activities of elexacaftor as both corrector and potentiator. Eur Respir J. 2021 Jun 17;57(6):2002774.