Body mass index and nutritional intake following Elexacaftor/Tezacaftor/Ivacaftor modulator therapy in adults with cystic fibrosis.

BACKGROUND: Elexacaftor/Tezacaftor/Ivacaftor (ETI) modulator therapy is often associated with increased body mass index (BMI) in people with cystic fibrosis (CF). This is thought to reflect improved clinical stability and increased appetite and nutritional intake. We explored the change in BMI and nutritional intake following ETI modulator therapy in adults with CF. METHODS: Dietary intake, measured with myfood24®, and BMI were collected from adults with CF at baseline and follow-up as part of an observational study. Changes in BMI and nutritional intake in participants who commenced ETI therapy between time points were assessed. To contextualize findings, we also assessed changes in BMI and nutritional intake between study points in a group on no modulators. RESULTS: In the pre and post ETI threapy group (n = 40), BMI significantly increased from 23.0 kg/m2 (IQR 21.4, 25.3) at baseline to 24.6 kg/m2 (IQR 23.0, 26.7) at follow-up (p<0.001), with a median of 68 weeks between time points (range 20-94 weeks) and median duration of ETI therapy was 23 weeks (range 7-72 weeks). There was a significant decrease in energy intake from 2551 kcal/day (IQR 2107, 3115) to 2153 kcal/day (IQR 1648, 2606), p<0.001. In the no modulator group (n = 10), BMI and energy intake did not significantly change between time points (p>0.05), a median of 28 weeks apart (range 20-76 weeks). CONCLUSIONS: These findings tentatively suggest that the increase in BMI with ETI therapy may not simply be attributable to an increase in oral intake. Further exploration into the underlying aetiology of weight gain with ETI therapy is needed.

Determination of microsome and hepatocyte scaling factors for in vitro/in vivo extrapolation in the rat and dog.

1. In vivo clearance predictions from in vitro assays require scaling factors to relate the concentrations of hepatocytes or microsomal protein to the intact liver. 2. The aims were to measure the variability in scaling factors for Wistar rat and beagle dog for which the literature is particularly scarce and determine any sex differences. 3. Scaling factors were determined by comparing the cytochrome P450 (P450) content in hepatocytes or microsomes against the P450 content of fresh liver homogenate. The use of fresh homogenate is recommended as freezing can increase contamination and affect the P450 assay. 4. Mean(geo) hepatic microsomal concentrations in Wistar rats were 61 mg g(-1) liver (95% confidence interval (CI); 47-75 mg g(-1) liver) and in beagle dogs 55 mg g(-1) liver (95% CI = 48-62 mg g(-1) liver). Mean(geo) hepatocellularity was 163 x 10(6) cells g(-1) liver for Wistar rats (95% CI = 127-199 x 10(6) cells g(-1) liver) and 169 x 10(6) cells g(-1) liver (95% CI = 131-207 x 10(6) cells g(-1) liver) for beagle dogs. The data generated in this study indicate a consistency in scaling factors between rat and dog. No sex differences were observed.