Trilaciclib Increases Pool of Memory T Cells in the Tumor Microenvironment Responsible for Long Term Immune Surveillance and Efficacy

- Phase 2 Mechanism of Action Trial Results Demonstrate the Immunomodulatory Effects of Trilaciclib in the Tumor Microenvironment -

- Trilaciclib Enhances Expression of Genes Associated with Memory T Cells -

- Trilaciclib Increases Multiple Surrogate Immune Markers for Memory CD8+ T Cell Differentiation, Infiltration,
and Function -

RESEARCH TRIANGLE PARK, N.C., June 04, 2023 (GLOBE NEWSWIRE) -- G1 Therapeutics, Inc. (Nasdaq: GTHX), a commercial-stage oncology company, today presented results from 24 patients enrolled in its Phase 2, single arm mechanism of action study of trilaciclib administered as a single agent to patients with early-stage triple-negative breast cancer (TNBC) prior to receiving trilaciclib and neoadjuvant therapy. These results highlight the potential for trilaciclib to enhance long term immune surveillance by increasing T cell function and generation of certain memory T cells and demonstrate gene expression profiles that may be associated with improved clinical outcome. These data support earlier findings from this Phase 2 trial demonstrating an increase in the ratio of CD8+ T cells to regulatory T cells (Tregs); a high ratio of CD8+ T cell to Tregs is predictive of overall survival (OS) and is associated with pathologic complete response (pCR). As expected, high rates of pCR were observed in patients with PD-L1(+) tumors and in patients with inflamed tumor immune microenvironments.

Data generated across multiple preclinical and clinical studies to date show that trilaciclib has the greatest effect on longer term endpoints including OS rather than earlier efficacy measures such as objective response rate (ORR), pCR, and progression free survival (PFS), consistent with other immunotherapies like checkpoint inhibitors. These results suggest that this is likely due to trilaciclib’s immune-mediated mechanism of action that protects the immune system from damage caused by cytotoxic therapy and enhances long-term immune surveillance by increasing the generation of certain memory T cells. This dual benefit may provide important longer-term benefits for patients by improving their ability to generate robust immune responses, particularly when treated with future subsequent therapies.