Discovery and Characterization of a First-in-Class LIV1-TLR7/8 Immunomodulatory Conjugate with Robust Myeloid Activation and Antitumor Activity.

Herein, we describe the discovery of a novel immunostimulatory drug conjugate (IMC) that employs TLR7/8 agonists conjugated to a tumor-targeting LIV1 antibody. Targeting TLR7/8 agonists to LIV1-expressing tumors enables localized delivery, thereby minimizing systemic toxicity while promoting inflammation and T cell recruitment within the tumor microenvironment (TME) for enhanced antitumor efficacy. Dual activation of TLR7 and TLR8 within the TME facilitates the recruitment of diverse immune cells and induces a broad spectrum of pro-inflammatory cytokines, effectively reshaping the immunosuppressive TME by upregulating costimulatory molecules.

Antibody-Drug Conjugates of NLRP3 Agonists: How Overcoming Lysosomal Accumulation Necessitated Noncanonical Linker Attachments.

An initial series of NLRP3 agonist antibody-drug conjugates (ADCs) failed to induce IL-1β in vitro due to lysosomal trapping of the payload. To address this, we developed assays and computational tools to identify a new payload that could diffuse out of the lysosomes. ADCs derived from this payload were active, emphasizing the need to avoid payload lysosomal accumulation for nonlysosomal targets.

Targeted Delivery of TLR7 Agonists to the Tumor Microenvironment Enhances Tumor Immunity via Activation of Tumor-Resident Myeloid Cells.

Toll-like receptors (TLR) are phylogenetically conserved mediators of innate immunity that are essential for establishing adaptive immune responses against invading pathogens. TLR7 is an endosomal receptor expressed predominantly in myeloid and B cells. Activation of TLR7 induces Type I interferon and proinflammatory responses; therefore, targeting TLR7 is a promising strategy for antitumor therapy.

Structure-Based Design of Novel TLR7/8 Agonist Payloads Enabling an Immunomodulatory Conjugate Approach.

Dual activation of the TLR7 and TLR8 pathways leads to the production of type I interferon and proinflammatory cytokines, resulting in efficient antigen presentation by dendritic cells to promote T-cell priming and antitumor immunity. We developed a novel series of TLR7/8 dual agonists with varying ratios of TLR7 and TLR8 activity for use as payloads for an antibody-drug conjugate approach. The agonist-induced production of several cytokines in human whole blood confirmed their functional activity.

The New Frontier: Merging Molecular Glue Degrader and Antibody-Drug Conjugate Modalities To Overcome Strategic Challenges.

Herein, we discuss advancements in the field of a unique class of antibody-drug conjugates (ADCs) named molecular glue-antibody conjugate (MAC). ADCs traditionally employ cytotoxic agents as payloads, and this approach has been used in all approved ADCs to treat cancer. Complementary to this approach, proteolysis targeting chimera (PROTAC) degrader antibody conjugates (DACs) provide a unique opportunity to deliver these bifunctional agents to tumors by using antibodies as a delivery mechanism to overcome the bioavailability issues encountered by PROTAC payloads.