INTRIGUE Trial Insights and ctDNA Applications

Dr. Agulnik analyzes the INTRIGUE trial's landmark contributions to GIST management, representing the first head-to-head Phase 3 comparison rather than placebo-controlled study. The trial compared ripretinib 150mg daily against sunitinib 50mg (4-weeks-on/2-weeks-off) and, while not meeting its primary endpoint, provided crucial insights into patient selection.

Both arms achieved progression-free survival exceeding 8 months, substantially better than historical placebo comparisons of approximately 6 months, suggesting improved patient selection and management strategies. The true breakthrough emerged from ctDNA analysis revealing distinct patient populations with differential responses based on secondary resistance mutations.

Patients with KIT exon 11 primary mutations plus secondary exon 13/14 mutations demonstrated exceptional outcomes with sunitinib (greater than 14 months progression-free survival), while those with exon 11 plus exon 17/18 secondary mutations benefited dramatically from ripretinib. These differences exceeded statistical noise, representing clinically meaningful treatment selection opportunities.

The trial's ctDNA work established the foundation for mutation-guided therapy selection and informed the subsequent INSIGHT trial design. However, practical limitations remain: approximately 20% of patients lack detectable ctDNA despite progressive disease, likely reflecting shedding heterogeneity rather than absent mutations.

Dr. Agulnik emphasizes incorporating ctDNA testing at progression when feasible, though rapid progression may necessitate empiric treatment selection with subsequent pivoting based on results. The technology's sensitivity continues improving, though tumor burden correlation remains important for detection reliability.