Trained immunity-promoting nanobiologics suppress tumor growth and potentiate checkpoint blockade immunotherapy

We developed a nanobiologic platform that is designed to induce trained immunity. Through extensive in vitro screening, involving stability measurements and training assays on human and murine monocytes, as well as in vivo mouse biodistribution experiments, a bone marrow-avid nanobiologic lead candidate, named MTP10-HDL, was identified. MTP10-HDL's potent anti-tumor capabilities were established in a dose response study. We found that these anti-tumor effects are the result of trained immunity-induced myelopoiesis, caused by the activation of hematopoietic stem cells and multipotent progenitors in the bone marrow. Moreover, we established that MTP10-HDL treatment overcomes the immunosuppressive tumor microenvironment (TME) by reducing the number of myeloid-derived suppressor cells and tumor associated macrophages. The immunologically rebalanced TME potentiated concurrent checkpoint blockade therapy, resulting in augmented anti-tumor efficacy. In conclusion, we show that rationally designed nanobiologics can promote trained immunity and elicit a durable anti-tumor response, as a monotherapy or in combination with checkpoint blockade. We examined MTP10-HDL's effect on hematopoiesis to elucidate the mechanism underlying its anti-tumor effect in C57BL/6 mice without tumors. We performed RNA sequencing (RNA-seq) to investigate HSC activation. Bone marrow from treated and untreated mice was harvested and the HSCs were isolated by flow sorting. Overall design: RNA-Seq: HSCs and MPPs of 4 mice were pooled to 1 sample for RNA isolation. 7 PBS samples were compared with 6 MTP10-HDL samples for HSC, 2 PBS samples were compared with 3 MTP10-HDL samples for MPP. ATAC-Seq: HSCs and MPPs of 6 mice were pooled to 1 sample for ATAC-Seq library creation. 3 PBS samples were compared with 3 MTP10-HDL samples for both HSC and MPP.