Real-world utilization pattern of pexidartinib in patients with tenosynovial giant cell tumor (TGCT)

e18792 Background: In August 2019, pexidartinib became the first and only systemic therapy approved in the US for the treatment of symptomatic TGCT associated with severe morbidity or functional limitations and not amenable to improvement with surgery. As TGCT is a rare condition, real-world pexidartinib utilization data are limited and greatly needed to inform clinical use. Methods: Adults (≥18 years) with ≥1 pexidartinib claim from 8/2/2019 - 1/1/2022 identified in the IQVIA Longitudinal Prescription Claims (LRx) linked with Medical Claims (Dx) databases were analyzed. Patient characteristics 6 months before first (index) pexidartinib claim were summarized. Pexidartinib dosing, interruption, and treatment duration were assessed post-index. Discontinuation was defined as treatment gap of ≥90 days. Results: Of 167 patients treated with pexidartinib (median age, 45 years; 59.9% female), the most common comorbidities were osteoarthritis (10.8%), hypertension (8.4%), and obesity (7.8%); 3 patients (1.8%) had mild liver disease and none had moderate-to-severe liver disease pre-index. Median starting dose was 800 mg/day (Table). Over median follow-up of 17.9 months, median (IQR) dose was 622 (442-750) mg/day. Dose reduction was observed in 57 (34.1%) patients and dose increase in 14 (8.4%) patients. Probability of discontinuation was 24.0%, 38.3% and 53.7% at 3-, 6- and 12-month follow-up, respectively. Median (95% confidence interval [CI]) time to pexidartinib discontinuation was 10.1 (7.1, 13.0) months. Fourteen (8.4%) patients restarted pexidartinib after discontinuation. Overall, median (95% CI) time on treatment was 14.2 (10.1, 18.4) months when treatment duration after restart of therapy was considered. Rate of joint surgery after pexidartinib treatment was low (7.2%, n = 12) with median (IQR) time from index to surgery of 5.4 (4.2-12.5) months and median time from last pexidartinib claim to surgery of 2.7 (1.0-8.2) months. Three patients restarted pexidartinib after surgery. Conclusions: Compared to patients in ENLIVEN, real-world pexidartinib patients had similar demographic characteristics. Real-world average daily dose was lower than the full dose recommended in the prescribing information. Compared to ENLIVEN, rate of discontinuation was higher in first 6 months but similar at 12 months. Findings could inform treatment strategy in clinical practice and future research in TGCT. [Table: see text]