On October 30, 2017 Syros Pharmaceuticals (NASDAQ:SYRS), a biopharmaceutical company pioneering the development of medicines to control the expression of disease-driving genes, reported that new preclinical pharmacodynamic (PD) and pharmacokinetic (PK) data providing a rationale for the twice weekly dosing regimen currently being used in the ongoing Phase 1 clinical trial of SY-1365, its first-in-class selective cyclin-dependent kinase 7 (CDK7) inhibitor, in advanced solid tumors were presented at the 2017 AACR (Free AACR Whitepaper)-NCI-EORTC Molecular Targets and Cancer Therapeutics Conference in Philadelphia (Press release, Syros Pharmaceuticals, OCT 30, 2017, View Source [SID1234521306]).

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“We are encouraged by the preclinical PK and PD data for SY-1365,” said David A. Roth, M.D., Chief Medical Officer of Syros. “The prolonged PD effect, coupled with the sustained tumor regressions seen in multiple preclinical models of difficult-to-treat cancers using intermittent dosing, support investigation of a twice-a-week dosing regimen for patients. Additionally, based on the correlation between CDK7 target occupancy and the anti-tumor activity of SY-1365, we developed a PD marker for use in our ongoing Phase 1 trial that we believe will help us efficiently identify the optimal dose and regimen for SY-1365.”

Syros scientists evaluated the relationship between SY-1365’s PK, PD and anti-tumor activity in multiple in vivo models, including preclinical models of triple negative breast cancer (TNBC) and acute myeloid leukemia (AML), across a range of doses and regimens from daily to weekly dosing. SY-1365 is a covalent inhibitor that binds irreversibly to CDK7. The data showed:

A prolonged PD effect, as measured by CDK7 target occupancy, with a half-life of about three days, supporting intermittent dosing.
A dose-dependent relationship between CDK7 target occupancy and anti-tumor activity in a preclinical model of AML.
Sustained tumor regressions in multiple in vivo models using a twice weekly dosing regimen consistent with the initial regimen in the ongoing Phase 1 clinical trial.
CDK7 target occupancy in blood cells in preclinical models similar to that seen in tumor cells, supporting the use of an assay measuring target occupancy in patients’ blood samples as a PD marker in the ongoing Phase 1 trial to help guide optimization of the dose and regimen to establish a recommended Phase 2 dose.
The Phase 1 trial of SY-1365 is a multi-center, open-label trial that is expected to enroll approximately 70 patients with advanced solid tumors. The primary objective of the trial is to assess the safety and tolerability of escalating doses of SY-1365, with the goal of establishing a maximum tolerated dose and a recommended Phase 2 dose and regimen. The dose-escalation phase is open to solid tumor patients for whom standard curative or palliative measures do not exist or are no longer effective. Following the dose-escalation phase, expansion cohorts are planned to further evaluate the safety and anti-tumor activity of SY-1365 in patients with triple negative breast, small cell lung and ovarian cancers, to confirm a recommended Phase 2 dose and regimen, and to enroll patients with tumors of any histology in a cohort focused on analyzing biopsied tumor tissue. Additional details about the trial can be found using the identifier NCT03134638 at www.clinicaltrials.gov.

Syros also announced that a publication co-authored by two of its scientific founders Nathanael S. Gray, Ph.D., and Richard A. Young, Ph.D., in the peer-reviewed scientific journal Cancer Discovery (Rusan M., et al., “Suppression of adaptive responses to targeted cancer therapy by transcriptional repression”) highlighted CDK7 inhibition in combination with targeted therapies as a promising new approach for combatting drug resistance. In multiple in vitro and in vivo models of treatment-resistant cancers, a research tool compound, known as THZ1, which inhibits CDK7, enhanced tumor cell killing and impeded the emergence of drug-resistant cell populations when combined with targeted therapies, including MEK, BRAF, EGFR and ALK inhibitors, compared to either THZ1 or the targeted therapy alone. These findings suggest that CDK7 inhibition prevents the formation of active enhancers that drive the increased expression of genes promoting the emergence of drug resistance in response to targeted therapy and blocks transcriptional programs required for the growth and survival of cancer.

Syros has an exclusive, worldwide license from the Dana-Farber Cancer Institute under certain patents relating to CDK7 inhibitors, including THZ1. Using its internal drug discovery capabilities, Syros generated SY-1365 to have better drug-like properties than THZ1, making it suitable for clinical development.