Efficacy and safety of pimitespib in gastrointestinal tumors.

[BACKGROUND] The aim of this study was to assess the efficacy and safety of pimitespib in real-world clinical settings for tyrosine kinase inhibitor-resistant GISTs.

[METHODS] We retrospectively analyzed 15 patients at Osaka University Hospital. Patients treated with pimitespib as a fourth- or later-line treatment for unresectable or recurrent GISTs were included. Patient background, pimitespib dose, number of courses, adverse events, best response, progression-free survival, and overall survival were analyzed.

[RESULTS] The median overall survival of patients treated with pimitespib was 24.4 months（95% confidence interval [CI] 7.2-not reached) and the one-year overall survival rate was 70.9%. The median progression-free survival was 4.6 months (95%CI 1.8-7.4), and the one-year progression-free survival rate was 15.2%. A partial response was observed in 0 patients, stable disease lasting for ≥ 12 weeks in 7 (46.7%), progressive disease in 7 (40.0%), and a non-evaluable state in 2 (13.3%). The disease control rate was 40%. Treatment-related adverse events were reported in all patients, with the most common being diarrhea (87%), followed by anorexia (27%), nausea (27%), and increased blood creatinine levels (27%). None of the patients discontinued the treatment because of adverse events.

[CONCLUSION] Pimitespib may offer a tolerable and effective treatment option for patients with unresectable or recurrent GISTs in clinical practice.