Despite achieving co-primary endpoints, G1 Therapeutics scraps PRESERVE 1 trial

G1 Therapeutics’ (Nasdaq: GTHX) shares fell 51.8% to $3.43 pre-market today, as the US oncology drug developer said it would terminate a study of its lead drug, trilaciclib, as it was unlikely to be effective in extending survival in patients with a type of colorectal cancer.

The company announced top-line results from its pivotal Phase III PRESERVE 1 trial showing that the trial achieved its co-primary endpoints related to severe neutropenia with statistical significance; however, early anti-tumor efficacy data, including overall response rate (ORR) and preliminary measures of survival, favored the placebo arm.

PRESERVE 1 achieved its co-primary endpoints showing clinically-meaningful and statistically-significant reductions in both occurrence of severe neutropenia during induction (placebo=20% versus trilaciclib=1%; p<0.001) and mean duration of severe neutropenia in Cycles 1 through 4 (placebo=1.3 days vs trilaciclib=0.1 days; p<0.001). In addition, patients receiving trilaciclib had a clinically-meaningful reduction in the rate of chemotherapy-induced diarrhea, including a 50% reduction in the rate of Grade 3/4 diarrhea and a 30% reduction in the rate of any grade diarrhea, compared to placebo.