Syros Presents Initial Data from Phase 1 Clinical Trial of SY-5609, Its Selective Oral CDK7 Inhibitor, at EORTC-NCI-AACR Meeting

Syros Pharmaceuticals (NASDAQ:SYRS), a leader in the development of medicines that control the expression of genes, today announced initial safety, pharmacokinetics (PK) and pharmacodynamics (PD) data from the ongoing dose-escalation portion of its Phase 1 clinical trial of SY-5609 in patients with select solid tumors. SY-5609 is a highly selective and potent oral cyclin-dependent kinase 7 (CDK7) inhibitor. These early data demonstrate proof of mechanism in patients with advanced solid tumors and establish a maximum tolerated dose (MTD) for continuous daily dosing. The data are being presented in a poster session at the 32^nd EORTC-NCI-AACR Symposium.

“These early findings from our Phase 1 trial of SY-5609 reinforce our conviction in CDK7 inhibition as a potentially transformative targeted approach for difficult-to-treat cancers,” said David A. Roth, M.D., Chief Medical Officer of Syros. “As we move forward in this trial, we are committed to fully exploring the potential of SY-5609. To that end, we opened the trial to pancreatic cancer patients, expanded a cohort to focus on lung cancer patients, and also expanded the combination cohort in treatment-resistant breast cancer patients. Additionally, we opened cohorts evaluating alternate dosing regimens, all with the goal of identifying optimal next steps for pursuing single-agent and combination development opportunities and ultimately delivering the greatest benefit to patients.”

Early Data Demonstrate Proof-of-Mechanism at Tolerable Doses

Syros presented initial data from its ongoing Phase 1 multi-center, open-label, dose-escalation study of SY-5609 in patients with advanced breast, colorectal, lung, ovarian or pancreatic cancer, or other solid tumors with Rb pathway alterations. The study also includes a cohort evaluating SY-5609 in combination with fulvestrant in CDK4/6 inhibitor-resistant HR-positive breast cancer patients.

As of August 21, 17 patients had been enrolled in the trial and were eligible for safety, PK and PD analysis. Patients were either treated with continuous daily dosing of single-agent SY-5609 at 1, 3, 4 or 5 mg, or for three weeks on and one week off at 3 mg in combination with fulvestrant. The median age of the patients enrolled in the study was 64. Patients were heavily pretreated with a median of four prior therapies. The MTD for continuous daily dosing was achieved at 3 mg. The data showed that: