Flt3 ligand augments immune responses to anti-DEC-205-NY-ESO-1 vaccine through expansion of dendritic cell subsets.

Generating responses to tumor antigens poses a challenge for immunotherapy. This phase II trial (NCT02129075) tested fms-like tyrosine kinase 3 (Flt3) ligand pre-treatment enhancement of responses to dendritic cell (DC)-targeting vaccines. We evaluated a regimen of Flt3L (CDX-301) to increase DCs and other antigen-presenting cells, poly-ICLC (TLR3 agonist that activates DCs) and a vaccine comprising anti-DEC-205-NY-ESO-1, a fusion antibody targeting CD205, linked to NY-ESO-1.