BACKGROUND: Cystic fibrosis (CF) is a chronic, progressive genetic disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene resulting in a dysfunctional CFTR protein. Elexacaftor/tezacaftor/ivacaftor (ELX/TEZ/IVA) is a triple combination oral drug therapy with an annual cost greater than $300,000 and available to nearly 90% of the CF population based on age and genotype. Limited real-world direct medical cost offset data are available for ELX/TEZ/IVA among commercially insured individuals. OBJECTIVE: To describe and compare total cost of care and health care resource utilization (HRU) 180 days before and 180 days after first ELX/TEZ/IVA drug claim among CFTR modulator treatment-naive, commercially insured members. METHODS: This study was a retrospective analysis of integrated pharmacy and medical claims data from 17.9 million commercially insured members. A 180-day prestudy and 180-day poststudy design was used to compare outcomes prior to and following ELX/TEZ/IVA initiation. Study inclusion was limited to members with first ELX/TEZ/IVA claim (index date) between October 21, 2019, and December 31, 2021, continuously enrolled 180 days before and 180 days after index date, and no CFTR-modulator drug claim 180 days prior to index date. Total paid amounts from medical and pharmacy claims after network discounts (defined as total cost of care), HRU, and pulmonary exacerbation events were summarized using descriptive statistics and compared using Wilcoxon signed rank test. RESULTS: 494 members newly initiating ELX/TEZ/IVA met inclusion criteria. Prestudy to poststudy mean member total cost of care increased from $58,180 to $198,815 (difference: $140,635; P < 0.001). Mean member medical benefit costs decreased from $28,764 to $12,484 (difference: -$16,280; P < 0.001), whereas mean member pharmacy benefit costs increased from $29,416 to $186,331 (difference: $156,915; P < 0.001). Mean member inpatient hospitalizations (62% absolute reduction; P < 0.001), emergency department visits (43% absolute reduction; P < 0.01), and pulmonary exacerbation events (44% absolute reduction; P < 0.001) were significantly lower in the postperiod compared with the preperiod. CONCLUSIONS: Among members with CF newly initiating CFTR modulator with ELX/TEZ/IVA, mean member total cost of care increased 3-fold despite significant and meaningful reductions in pulmonary exacerbation events, HRU, and medical benefit spend. Pharmacy benefit spend outpaced medical benefit spend at a rate of $9.64 to $1 in the 180 days following ELX/TEZ/IVA initiation. Real-world data should be used to objectively measure the clinical and economic benefits of costly medications, such as CFTR modulators, to align price with value. DISCLOSURES: Drs Marshall, Espinosa, Starner, and Gleason are employees of Prime Therapeutics. The study was funded by Prime Therapeutics.