ChemoCentryx, Inc. announced the presentation of safety results from the ongoing Phase I clinical study of CCX559, the Company's highly potent, orally administered PD-L1 checkpoint inhibitor, in patients with advanced solid tumors during a poster session at the 2022 American Society of Clinical Oncology (ASCO) Annual Meeting. In the ASCO poster titled, Results From an Ongoing Phase 1 Dose-Escalation Study of CCX559, an Orally Administered Small Molecule PD-L1 Inhibitor, in Patients With Advanced Solid Tumors (abstract #2593), ChemoCentryx reported patient baseline characteristics and safety data available from the ongoing study as of April 27, 2022, from the first 13 patients enrolled across four dose cohorts: 30 mg, 60 mg, 120 mg, and 180 mg. The first-in-human Phase I study is assessing CCX559 in patients with a range of advanced solid tumors.

Ten of the 13 patients enrolled have received at least two or more prior lines of systemic therapy. The primary objectives of the study are to evaluate the safety and tolerability, and to inform dose selection for the planned Phase Ib/II clinical trial. To date, there have been no dose limiting toxicities (DLTs) or treatment-related serious or severe (= grade 3) adverse events (AEs) reported.

Two patients receiving 120 mg once daily CCX559 presented with three probable immune-related AEs, which provides supportive evidence of immune activation. There have been no treatment-related AEs reported in more than one patient. The ASCO poster also includes pharmacokinetic (PK) and pharmacodynamic (PD) data that build on the positive findings presented during the 2022 American Association for Cancer Research (AACR) Annual Meeting in April, providing evidence that CCX559 is pharmacologically active and 120 mg once daily is a therapeutically relevant dose.

Results presented during ASCO indicate continued dose-dependent PK exposure at Day 1 for CCX559. The mean exposure at 120 mg (n=10) remains in line with preclinical projections and continues to increase at the 180 mg level (n=1). Consistent with approved antibody inhibitors of PD-L1, CCX559 demonstrates immunomodulatory activity in first cycle of treatment.

ChemoCentryx expects to present additional findings from this ongoing Phase I study at major oncology conferences through 2022. The tumor types being evaluated in the Phase I study are not known to be responsive to treatment with anti-PD-1/PD-L1 therapies, and the Company plans to advance CCX559 into a Phase Ib/II clinical trial to measure anti-tumor effects of CCX559 more directly during the second half of 2022.