Ripretinib Shows Promise In Patients with Refractory Advanced GIST

According to a phase 1 trial, switch-control kinase inhibitor ripretinib shows promise as a treatment option for patients with refractory advanced gastrointestinal stromal tumors (GIST; J Clin Oncol. 2020 Oct 1;38(28):3294-3303.).

“In advanced gastrointestinal stromal tumor (GIST), there is an unmet need for therapies that target both primary and secondary mutations of pathogenic KIT/PDGFRA oncoproteins. Ripretinib is a novel switch-control kinase inhibitor designed to inhibit a wide range of KIT and PDGFRA mutations,” explained Filip Janku, MD, PhD, Department of Investigational Cancer Therapeutics, The University of Texas MD Anderson Cancer Center, Houston, and colleagues.

Researchers claim that, to their knowledge, this is the first-in-human phase I study of ripretinib. The trial also included a dose-escalation phase and subsequent expansion phase at the recommended phase II dose (RP2D). Eligible patients were those with advanced GIST who were intolerant to or experienced progression on ≥ 1 line of systemic therapy and other advanced malignancies. 

At the time of data cutoff in August 2019, 258 patients (n = 184 GIST) were enrolled, 68 of whom were in the dose-escalation phase. A total of 3 dose-limiting toxicities (DLTs) were reported: grade 3 lipase increase (n = 2; 100 mg and 200 mg twice a day) and grade 4 increased creatine phosphokinase (n = 1; 150 mg once daily). Furthermore, the maximum-tolerated dose (MTD) was not reached; the maximum dose evaluated was 200mg a day, with the RP2D established as 150mg once daily. 

The objective response rate (ORR) was 11.3% (n=16) ranging from 7.2 (n=6/82; fourth line or greater) to 19.4% (n=6/31;second line) and median progression-free survival (PFS) ranged from 5.5 months (fourth line or greater) to 10.7 months (second line), according to investigator assessment. 

The most common treatment-emergent adverse events (AEs) in GIST patients receiving ripretinib 150mg once daily (n=142) were alopecia, fatigue, myalgia, nausea, palmar-plantar erythrodysesthesia, constipation, decreased appetite, and diarrhea.

“Ripretinib is a well-tolerated, novel inhibitor of KIT and PDGFRA mutant kinases with promising activity in patients with refractory advanced GIST,” concluded Janku et al.—Alexandra Graziano