Antibody homotypic interactions are encoded by germline light chain complementarity determining region 2

A Phase I Clinical Trial Adding OX40 Agonism to In Situ Therapeutic Cancer Vaccination in Patients with Low-Grade B-cell Lymphoma Highlights Challenges in Translation from Mouse to Human Studies

PURPOSE

Activating T-cell costimulatory receptors is a promising approach for cancer immunotherapy. In preclinical work, adding an OX40 agonist to in situ vaccination with SD101, a TLR9 agonist, was curative in a mouse model of lymphoma. We sought to test this combination in a phase I clinical trial for patients with low-grade B-cell lymphoma.

PATIENTS AND METHODS

We treated 14 patients with low-dose radiation, intratumoral SD101, and intratumoral and intravenous BMS986178, an agonistic anti-OX40 antibody. The primary outcome was safety. Secondary outcomes included overall response rate and progression-free survival.

RESULTS

Adverse events were consistent with prior experience with low-dose radiation and SD101. No synergistic or dose-limiting toxicities were observed. One patient had a partial response, and nine patients had stable disease, a result inferior to our experience with TLR9 agonism and low-dose radiation alone. Flow cytometry and single-cell RNA sequencing of serial tumor biopsies revealed that T and NK cells were activated after treatment. However, high baseline OX40 expression in T follicular helper and T regulatory type 1 cells, as well as high posttreatment soluble OX40, shed from these T cells upon activation, associated with progression-free survival of less than 6 months.

CONCLUSIONS

Clinical results of T-cell costimulatory receptor agonism have now repeatedly been inferior to the motivating preclinical results. Our study highlights potential barriers to clinical translation, particularly differences in preclinical and clinical reagents and the complex biology of these coreceptors in heterogeneous T cell subpopulations, some of which may antagonize immunotherapy.

Strategies to boost antibody selectivity in oncology

Antibodies in oncology are being equipped with toxic cargoes and effector functions that can kill cells at very low concentrations. A key challenge is that most targets on cancer cells are also present on at least some healthy cells. Shared targets can result in off-tumor binding and compromise the safety and potential of therapeutic candidates. In this review, we survey strategies that can help direct biologics to cancer sites more selectively. These strategies are becoming increasingly feasible thanks to advances in molecular design and engineering. The objective is to create therapeutics that exploit changes in cancer and leverage the human body infrastructure, enabling therapeutics that discriminate not just self from non-self but diseased from healthy tissue.

i-shaped antibody engineering enables conformational tuning of biotherapeutic receptor agonists

The ability to leverage antibodies to agonize disease relevant biological pathways has tremendous potential for clinical investigation. Yet while antibodies have been successful as antagonists, immune mediators, and targeting agents, they are not readily effective at recapitulating the biology of natural ligands. Among the important determinants of antibody agonist activity is the geometry of target receptor engagement. Here, we describe an engineering approach inspired by a naturally occurring Fab-Fab homotypic interaction that constrains IgG in a unique i-shaped conformation. i-shaped antibody (iAb) engineering enables potent intrinsic agonism of five tumor necrosis factor receptor superfamily (TNFRSF) targets. When applied to bispecific antibodies against the heterodimeric IL-2 receptor pair, constrained bispecific IgG formats recapitulate IL-2 agonist activity. iAb engineering provides a tool to tune agonist antibody function and this work provides a framework for the development of intrinsic antibody agonists with the potential for generalization across broad receptor classes.

Antibody Interfaces Revealed Through Structural Mining

Antibodies are fundamental effectors of humoral immunity, and have become a highly successful class of therapeutics. There is increasing evidence that antibodies utilize transient homotypic interactions to enhance function, and elucidation of such interactions can provide insights into their biology and new opportunities for their optimization as drugs. Yet the transitory nature of weak interactions makes them difficult to investigate. Capitalizing on their rich structural data and high conservation, we have characterized all the ways that antibody fragment antigen-binding (Fab) regions interact crystallographically. This approach led to the discovery of previously unrealized interfaces between antibodies. While diverse interactions exist, β-sheet dimers and variable-constant elbow dimers are recurrent motifs. Disulfide engineering enabled interactions to be trapped and investigated structurally and functionally, providing experimental validation of the interfaces and illustrating their potential for optimization. This work provides first insight into previously undiscovered oligomeric interactions between antibodies, and enables new opportunities for their biotherapeutic optimization.