Cyteir Therapeutics, Inc. presented results from a Phase 1 dose escalation monotherapy trial with CYT-0851 in a poster titled “Phase 1 Results of CYT-0851 in Patients with Advanced Solid and Hematologic Cancers” (Abstract: 3084, Poster: 76) at the 2022 American Society of Clinical Oncology (ASCO) annual meeting in Chicago, Illinois. The primary objectives of the Phase 1 dose escalation trial with CYT-0851 were to determine the recommended Phase 2 dose, determine the maximum tolerated dose (MTD) and to evaluate safety and tolerability. Key secondary objectives include determination of the pharmacokinetic parameters, optimal dosing regimen and preliminary anti-tumor activity.

As of the April 13, 2022 data cutoff, 80 patients were enrolled across twelve dose-escalation cohorts from 30 mg to 1,200 mg total daily dose. Eighty patients were evaluable for safety and 65 patients were evaluable for efficacy. In solid tumors: Forty-five patients were response evaluable and one unconfirmed partial response (PR) was achieved in a patient with soft-tissue sarcoma who was treated for almost 11 months.

Nineteen patients (42%) had stable disease and twelve patients (27%) had a decrease in target lesion size for an overall disease control rate of 44%. Stable disease (42%) was seen in patients with soft-tissue sarcoma, head and neck squamous cell, pancreatic, ovarian, and breast cancers. In hematologic cancers: Eighteen patients with non-Hodgkin lymphoma were response evaluable.

Responses were seen in patients with follicular lymphoma (1 complete response (CR) and 1 PR) and diffuse large B-cell lymphoma (1 PR). Three patients with follicular lymphoma, one patient with diffuse large B-cell lymphoma and one patient with hairy-cell leukemia achieved stable disease. Patients responding to CYT-0851 exhibited a durable clinical benefit as evidenced by the more than 18 months of treatment in the patient with follicular lymphoma who achieved a CR.