G1 Therapeutics reports Phase 2 results of trilaciclib in breast cancer

G1 Therapeutics provided initial results from a 24 patient Phase 2 mechanism of action – MOA – trial showing favorable alterations in the tumor microenvironment from a single dose of trilaciclib monotherapy as measured by increases in the proportions of CD8+ T cells compared to T regulatory cells in patients with early-stage triple negative breast cancer – TNBC -. CMO Raj Malik said, "These are the first data to show the beneficial effect of a single dose of trilaciclib, one week after administration, on the tumor microenvironment. These results show that trilaciclib monotherapy can improve the ratio of CD8+ T cells to Tregs and thus may enhance the overall antitumor immune response and confirm the trends we observed in preclinical studies and in peripheral blood in our Phase 2 trial in TNBC. We look forward to the pathologic complete response data in 2Q23 which we believe will clarify the ability of trilaciclib to improve anti-tumor efficacy for TNBC patients in this early-stage treatment setting, particularly in combination with a checkpoint inhibitor." Initial safety and tolerability results from the treatment phase are consistent with historical safety data from the standard of care neoadjuvant regimen with potential observed reductions in certain hematologic adverse events. There were no instances of grade 3/4 diarrhea in patients receiving trilaciclib in this trial. The new Phase 2 MOA initial clinical results reinforce those from two nonclinical studies presented at SITC, which showed that trilaciclib upregulates key processes within the cancer immunity cycle. Both the clinical and nonclinical data elucidate the immunologic mechanisms underlying the significant survival benefit shown in the previous Phase 2 trial of metastatic triple negative breast cancer patients who received trilaciclib prior to gemcitabine/carboplatin. Additionally, the combined data sets offer proof of principle data that trilaciclib may confer multidimensional clinical benefits across different tumor types and classes of drug.