ESR1 and cancer: In addition, agents targeting CDK7 have been shown to have favorable activity in several cancer types (8, 9), and early studies have shown promising results in administering the CDK7 inhibitor samuraciclib in combination with fulvestrant in a heavily pretreated cohort of patients with ER+ breast cancer (NCT03363893), with phase I trials also underway with an independent CDK7 inhibitor, SY-5609 (NCT0424716).