G1 Therapeutics, Inc. (NASDAQ:GTHX), a clinical-stage oncology company, today reported additional data from the Phase 1b/2a clinical trial investigating its oral CDK4/6 inhibitor lerociclib in combination with fulvestrant for the treatment of estrogen receptor-positive, HER2-negative (ER+, HER2-) breast cancer. Updated findings presented during a poster session (P1-19-17) at the 2019 San Antonio Breast Cancer Symposium (SABCS) showed lerociclib, dosed without a drug holiday, has a differentiated safety and tolerability profile than observed in clinical trials with currently marketed CDK4/6 inhibitors. Preliminary efficacy findings were consistent with other CDK4/6 inhibitors used in combination with fulvestrant.
The Phase 1b/2a trial is designed to evaluate the safety, tolerability and efficacy of lerociclib administered continuously in combination with fulvestrant as a treatment for ER+, HER2- breast cancer and identify the dose and schedule for future trials of lerociclib. Further investigation is ongoing, with longer-duration efficacy data required to determine the dose for future study in a Phase 3 clinical trial. The company expects to share an update in 2020.
“We designed lerociclib to improve upon the clinical profiles of currently available CDK4/6 inhibitors,” said Raj Malik, M.D., Chief Medical Officer and Senior Vice President, R&D. “The findings from this trial showed that twice-daily dosing of lerociclib with fulvestrant was well tolerated, with 150 mg demonstrating less neutropenia and gastrointestinal side effects. We look forward to evaluating the mature efficacy data for the 150 mg and 200 mg cohorts as we prepare to advance lerociclib into pivotal development.”