Treadwell Announces Initiation of Patient Dosing in TWT-203, a Phase 1b/2 study of TTK Inhibitor, CFI-402257, in Patients with ER+/Her2- Breast cancer

NEW YORK and HONG KONG, June 13, 2022 /PRNewswire/ — Treadwell Therapeutics, a clinical-stage biotechnology company developing novel medicines for unmet needs in cancer, today announced the initiation of patient dosing in TWT-203, its Phase 1b/2 study to evaluate CFI-402257, an oral, best-in-class inhibitor of Threonine Tyrosine Kinase (TTK, also known as MPS1) in patients with advanced solid tumors and ER+/Her2- breast cancer. Dosing of the first patient in the trial commenced June 8th at START Mountain Region in Salt Lake City, Utah.

“Inhibition of TTK, a key mitotic checkpoint, with CFI-402257 represents a novel treatment approach for ER+/Her2-breast cancer, particularly in the context of CDK4/6 inhibitor failure” said Principal Investigator, Dr. Justin A. Call, MD, Director of Clinical Research at START Mountain Region in Salt Lake City, Utah.

“We are excited about the initiation of TWT-203 with our potent and selective TTK inhibitor,” said Dr. Michael Tusche, Treadwell co-CEO. “Previous clinical studies have demonstrated that CFI-402257 has a tolerable safety profile and confirmed responses in ER+/Her2- breast cancer after progression on CDK4/6 inhibitors. We look forward to the continued development of this molecule in breast cancer.”

The Phase 1b/2 clinical trial of CFI-402257 is an open-label, multi-center, dose optimization study designed to assess the safety, tolerability, pharmacokinetic and pharmacodynamic profiles of CFI-402257 as a single agent in advanced solid tumors or in combination with fulvestrant in ER+/Her2- Breast Cancer patients after disease progression on prior CDK4/6 inhibitor and endocrine therapy. The trial will enroll approximately 40 patients at up to 10 sites in the United States. It will include a dose confirming portion in advanced solid tumors and expansions at the Recommended Phase 2 dose as a monotherapy in solid tumors and in combination with fulvestrant in breast cancer patients.

About Treadwell Therapeutics

Treadwell Therapeutics is a clinical-stage multi-modality oncology company developing novel medicines to address unmet needs in patients with cancer. The Company’s internally developed clinical pipeline includes CFI-400945 (PLK4 inhibitor), CFI-402257 and CFI-402411 (HPK1 inhibitor). Treadwell also has a robust pre-clinical pipeline with multiple biologic and next generation TCR based autologous cell therapy programs. For more information, please visit



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