P114 Predicting poor responses to elexacaftor/tezacaftor/ivacaftor: are all responses created equal?

Although elexacaftor/tezacaftor/ivacaftor (ETI) improves clinical outcomes in the population with cystic fibrosis (CF), little is known about factors influencing response at an individual level. To look this, we investigated to ETI our large adult CF clinic. We looked lung function (ppFEV1), body mass index (BMI) and annualised IV antibiotic days 12 months before after commencing 293 pwCF (mean age 33 years, 44% female). Mean medicines possession ratio was 85%. Using multiple linear regression modelling explore which baseline characteristics (sex, age, genotype, ppFEV1, BMI, days, CF-related diabetes, liver disease, ABPA, colonisation Pseudomonas aeruginosa or Staphylococcus aureus) might predict response. Lowest quartile subset for each outcome were classed as “poor responders.” relative improvement ppFEV1 +13.5% (71.1% [22.6] 79.3% [23.2]), greatest independently predicted by lower y (β = –0.002, p < 0.001), DF508 homozygosity 0.18, 0.001) initiation 0.02). [SD] BMI 24.3 [4.6] kg/m2 mean increase +3.9% [7.4]. Only poorer values greater higher –0.004, 0.0003 β –0.84, 0.001 respectively). ‘Poor responders’ one not risk of being poor responders other (relative [95%CI] 0.73 [0.5 1.1], 0.18). responses are heterogenous but those more severe impairment FEV1, had respective Homozygosity predicts days. Importantly, domain does overall. More work needed characterise long-term trajectories ETI.