Study of TTC-352 in Patients With Metastatic Breast Cancer Progressing on Endocrine Therapy

This is open-label, accelerated dose escalation study of TTC 352, a selective human ER partial agonist for treatment of metastatic ER+ breast cancer in patients who received and progressed on at least two lines of endocrine therapy with one that included a CDK4/CDK6 inhibitor. The primary objective of this study is to determine the maximum tolerated dose (MTD) of TTC-352 for the treatment of metastatic ER+ breast cancer progressing after endocrine therapy. The maximum tolerated dose (MTD) of TTC-352 will be determined using initial single-patient cohort escalations until grade 2 toxicity, then expansion to a modified-Fibonacci dose-escalation 3+3 design. Patients enrolled at each dose escalation step must complete the first 28-day cycle of treatment without a dose-limiting toxicity (DLT), or be withdrawn because of a DLT, before additional patients may be enrolled for the next dose escalation step. The MTD dose level cohort will be expanded to a total of 9 patients, to further evaluate safety. In each cohort pharmacokinetics of TTC-352 will be evaluated.