Abstract Disclosure: N. Mon: None. S.S. Krishnasamy: None. G. Bakeerathan: None. L. Healy: None. E. Favier: None. S. Foushee: None. Background: Cystic fibrosis related bone disease (CFBD) is a common complication of adult Cystic fibrosis (CF) patients due to calcium, vitamin D and K malabsorption from exocrine pancreatic insufficiency, increased inflammatory cytokines, glucocorticoid therapy, delayed puberty, physical inactivity, and hypogonadism. Newer CF transmembrane conductance regulator (CFTR) modulator therapy elexacaftor/tezacaftor/ivacaftor (Trikafta) has proven benefit in pulmonary and nutritional outcomes. There is limited data on effects of Trikafta on bone health and body composition. The aim is to examine the effects of Trikafta on bone mineral density (BMD) at the lumbar spine (LS) and femoral neck (FN), and body composition in terms of fat free mass index (FFMI) and fat mass index (FMI) in our CF patients. Method: We conducted a cross sectional and retrospective review of 38 adults with CF (Ages 20-59, 28 males and 10 females) in our CF clinic. Body Mass Index (BMI), Body composition measured by bioelectric impedance analysis, BMD of LS and FN by Dual-energy X-ray absorptiometry, Vitamin D level, and forced expiratory volume in one second (FEV1 % predicted) in patients taking Trikafta were analyzed and compared with control CF group who were not on Trikafta. Results: 38 subjects on Trikafta, aged 33.29 ± 10.36 years with FEV1 % predicted 65.11± 28.14% were studied. Serum 25-hydroxyvitamin D level was 35.92 ± 18.52 ng/dL. Of the 38 study patients, 23 (60.53%) had a diagnosis of CF related diabetes (CFRD). Among the Trikafta cohort, 18 (50%) had low BMD with Z-scores ≤ -2.0 and 7 (19.44%) of them had Z score ≤ -1.0 and > -2.0. Compared with the control group, LS BMD 0.93 ± 0.16 g/cm2 and FN BMD 0.73± 0.13g/cm2 (p >0.05) were not improved significantly. BMI of study population 23.09 ± 4.21 kg/m2 (p <0.05) and FMI 6.11 ± 4.25 kg/m2 (p <0.05) increased significantly; however, there was a decrease in FFMI 9.60 ± 1.44 kg/m2 (p <0.05). Conclusion: Treatment with Trikafta in CF patients was associated with increases in BMI and fat mass index but decrease in fat free mass index. There was no statistically significant difference in BMD at LS and FN in our study cohort. This study has limitations in terms of gender differences within the study cohort, duration of Trikafta use in relation to bone mass, and also extent of glucocorticoid use among the study subjects. Larger prospective clinical trials are needed to study efficacy of Trikafta on CFBD. Presentation: 6/3/2024