G1 Therapeutics' Cosela ineffective in key TNBC survival study

G1 Therapeutics announced on Monday that the Phase III PRESERVE 2 trial examining Cosela (trilaciclib) in patients with triple-negative breast cancer (TNBC) did not meet its primary goal of improving overall survival (OS). CEO Jack Bailey described the results as "unexpected" and expressed the company's disappointment, noting that the trial did not yield the anticipated benefits.

The PRESERVE 2 study's outcome had already raised concerns earlier this year when G1 Therapeutics revealed in February that it would proceed to the final survival analysis, dampening expectations for an early data readout. Additionally, the company had delayed an interim OS analysis from the second half of 2023 to the first half of 2024, citing a slower-than-expected occurrence of actual events.

On Monday, G1 Therapeutics provided detailed results, showing that the median OS in the group receiving trilaciclib plus chemotherapy was 17.4 months, compared to 17.8 months in the control group, resulting in a hazard ratio (HR) of 0.91. Despite a numerical favorability in OS for the trilaciclib arm within both PD-L1 subgroups, neither achieved statistical significance.

The study involved 187 patients with locally advanced unresectable or metastatic TNBC who received either Cosela or a placebo before undergoing chemotherapy with gemcitabine and carboplatin. G1 Therapeutics plans to present the detailed findings from this study at an upcoming medical conference.

Cosela was initially approved by the FDA in 2021 to decrease the incidence of chemotherapy-induced myelosuppression in adults receiving certain types of chemotherapy for extensive-stage small-cell lung cancer. The drug, a transient CDK4/6 inhibitor, also received approval in China for the same indication, through a partnership with Simcere Pharmaceuticals.