GS-3583

P1, N=13, Terminated, Gilead Sciences | Phase classification: P1b --> P1

PD analysis shows that administration of GS-3583 resulted in transient, dose-dependent increases in cDC1 cells that returned to baseline within 3 weeks of drug administration. The pharmacokinetics and pharmacodynamics of GS-3583 following single dosing were characterized in this study which enabled subsequent phase Ib assessments in patients with advanced solid tumors.

GS-3583 was relatively well tolerated and induced dose-dependent expansion of cDCs in the periphery of patients with advanced solid tumors. However, development of a second primary malignancy provides a cautionary tale for the FLT3 agonist mechanism.

GS-3583 was safe and well tolerated and induced dose-dependent expansion of cDCs in the periphery in patients with advanced solid tumors up to doses of 12 mg. These findings support further dose escalation and clinical development of GS-3583 in combination with agents that would stimulate the expanded cDCs to produce anti-tumor responses.

Assessments include safety, PK, pharmacodynamics including cDCs, immunogenicity, and efficacy by RECIST 1.1 in CT/MRI imaging conducted every 8 weeks . Accrual at approximately 3-4 centers in the US is ongoing.