(P 361) PEXIDARTINIB FOR THE TREATMENT OF TENOSYNOVIAL GIANT CELL TUMORS: CLINICAL EXPERIENCE FROM FIVE CHINESE PATIENTS

Objective: To describe long-term efficacy and safety of pexidartinib (pexi) in patients with diffuse-type tenosynovial giant cell tumors (D-TGCT) in China.

Methods: From 11/2020-5/2025, five Chinese patients with D-TGCT not amenable to surgery received pexi 400 mg BID at the Beijing Jishuitan Hospital, Peking University Cancer Hospital, and Fudan University Shanghai Cancer Center.

Results: Patient A: Female (62 years) with right knee D-TGCT received pexi for ~4.5 years. MRI evaluation showed a 16.7% reduction in tumor diameter (150 mm to 125 mm). Following treatment, the patient achieved disease control lasting >4 years. Patient B: Female (34 years) with right knee D-TGCT received pexi for ~4.5 years. Following treatment, MRI assessment showed a 19.1% reduction in tumor diameter (115 mm to 93 mm). The patient achieved disease control and improvement of joint mobility lasting >4 years. Patient C: Male (18 years) with right knee D-TGCT received pexi for 4 years. Following treatment, MRI evaluation showed a reduction in tumor diameter (141 mm to 80-90 mm); the range of joint motion was improved. Patient D: Female (29 years) with left hip D-TGCT received pexi for 4 years. After 3 months of treatment, a significant improvement in hip joint swelling was observed. Following treatment, MRI assessment showed a 64.1% reduction in tumor diameter (169.1 mm to 60.7 mm). Improvements in range of hip joint motion were observed, especially flexion and internal rotation. Patient E: Female (67 years) with dorsal foot D-TGCT received pexi for 4 years. The patient exhibited improvements in range of joint motion, and MRI assessment showed a reduction in tumor area from 23 × 10 mm to 16 × 11 mm. Overall, most treatment-related AEs (TRAEs) were grade 1-2 in severity. TRAEs reported by >1 patient included facial edema, GGT increased, blood AST increased, blood ALT increased, blood LDH increased, serum creatine kinase increased, and pruritus. Dose reductions occurred in 4 patients.

Conclusion: These real-world observations from five Chinese patients with D-TGCT who were treated with pexi for >4 years showed improvements in TGCT-related symptoms in all patients. Most patients achieved long-term improvements in range of motion and reductions in tumor diameter. Most TRAEs were grade 1-2 in severity and represented the known safety profile of pexi.