Molecular Imaging of Innate Immunity and Immunotherapy

The innate immune system plays a key role as the first line of defense in various human diseases including cancer, cardiovascular and inflammatory diseases. In contrast to tissue biopsies and blood biopsies, in vivo imaging of the innate immune system can provide whole body measurements of immune cell location and function and changes in response to disease progression and therapy. Rationally developed molecular imaging strategies can be used in evaluating the status and spatio-temporal distributions of the innate immune cells in near real-time, mapping the biodistribution of novel innate immunotherapies, monitoring their efficacy and potential toxicities, and eventually for stratifying patients that are likely to benefit from these immunotherapies. In this review, we will highlight the current state-of-the-art in noninvasive imaging techniques for preclinical imaging of the innate immune system particularly focusing on cell trafficking, biodistribution, as well as pharmacokinetics and dynamics of promising immunotherapies in cancer and other diseases; discuss the unmet needs and current challenges in integrating imaging modalities and immunology and suggest potential solutions to overcome these barriers.

CD47-SIRPα-targeted therapeutics: status and prospects

CD47 is a "don't eat me" signal to phagocytes that is overexpressed on many tumor cells as a potential mechanism for immune surveillance evasion. CD47 and its interaction with signal-regulating protein alpha (SIRPα) on phagocytes is therefore a promising cancer target. Therapeutic antibodies and fusion proteins that block CD47 or SIRPα have been developed and have shown activity in preclinical models of hematologic and solid tumors. Anemia is a common adverse event associated with anti-CD47 treatment, but mitigation strategies-including use of a low 'priming' dose-have substantially reduced this risk in clinical studies. While efficacy in single-agent clinical studies is lacking, findings from studies of CD47-SIRPα blockade in combination with agents that increase 'eat me' signals or with antitumor antibodies are promising. Magrolimab, an anti-CD47 antibody, is the furthest along in clinical development among agents in this class. Magrolimab combination therapy in phase Ib/II studies has been well tolerated with encouraging response rates in hematologic and solid malignancies. Similar combination therapy studies with other anti-CD47-SIRPα agents are beginning to report. Based on these early clinical successes, many trials have been initiated in hematologic and solid tumors testing combinations of CD47-SIRPα blockade with standard therapies. The results of these studies will help determine the role of this novel approach in clinical practice and are eagerly awaited.

Embracing nanomaterials' interactions with the innate immune system

Immunotherapy has firmly established itself as a compelling avenue for treating disease. Although many clinically approved immunotherapeutics engage the adaptive immune system, therapeutically targeting the innate immune system remains much less explored. Nanomedicine offers a compelling opportunity for innate immune system engagement, as many nanomaterials inherently interact with myeloid cells (e.g., monocytes, macrophages, neutrophils, and dendritic cells) or can be functionalized to target their cell-surface receptors. Here, we provide a perspective on exploiting nanomaterials for innate immune system regulation. We focus on specific nanomaterial design parameters, including size, form, rigidity, charge, and surface decoration. Furthermore, we examine the potential of high-throughput screening and machine learning, while also providing recommendations for advancing the field. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

A HER2 Tri-Specific NK Cell Engager Mediates Efficient Targeting of Human Ovarian Cancer

Simple Summary

HER2 is a marker known to be over-expressed on breast cancer, rendering it one of the most useful solid tumor targets for antibody-based therapies. Despite expression on ovarian cancer, results targeting HER2 in this setting have been disappointing, thus requiring more aggressive approaches. Natural killer (NK) cells are known as principal mediators of cancer cell killing, but cancer cells find ways to deter them. We devised a tri-specific biological drug containing antibody fragments that simultaneously binds NK cells and cancer cells and at the same time delivers a natural cytokine signal that triggers robust NK cell expansion. In vitro studies show the drug augments NK cell killing of a number of HER2-positive human cell lines, while enhancing NK cell activation and proliferation. Studies in mice engrafted with human ovarian cancer showed the drug has anti-tumor efficacy, clearly demonstrating its ability to bolster NK cells in their ability to contain tumor cell growth.

Abstract

Clinical studies validated antibodies directed against HER2, trastuzumab, and pertuzumab, as useful methodology to target breast cancer cases where HER2 is expressed. The hope was that HER2 targeting using these antibodies in ovarian cancer patients would prove useful as well, but clinical studies have shown lackluster results in this setting, indicating a need for a more comprehensive approach. Immunotherapy approaches stimulating the innate immune system show great promise, although enhancing natural killer (NK) function is not an established mainstream immunotherapy. This study focused on a new nanobody platform technology in which the bispecific antibody was altered to incorporate a cytokine. Herein we describe bioengineered CAM1615HER2 consisting of a camelid VHH antibody fragment recognizing CD16 and a single chain variable fragment (scFv) recognizing HER2 cross-linked by the human interleukin-15 (IL-15) cytokine. This tri-specific killer engager (TriKE^TM) showed in vitro prowess in its ability to kill ovarian cancer human cell lines. In addition, we demonstrated its efficacy in inducing potent anti-cancer effects in an in vivo xenograft model of human ovarian cancer engrafting both cancer cells and human NK cells. While previous approaches with trastuzumab and pertuzumab faltered in ovarian cancer, the hope is incorporating targeting and cytokine priming within the same molecule will enhance efficacy in this setting.

NK-Cell-Mediated Targeting of Various Solid Tumors Using a B7-H3 Tri-Specific Killer Engager In Vitro and In Vivo

We improved the bispecific antibody platform that primarily engages natural killer (NK) cells to kill cancer cells through antibody-dependent cellular cytotoxicity (ADCC) by adding IL-15 as a crosslinker that expands and self-sustains the effector NK cell population. The overall goal was to target B7-H3, an established marker predominantly expressed on cancer cells and minimally expressed on normal cells, and prove that it could target cancer cells in vitro and inhibit tumor growth in vivo. The tri-specific killer engager (TriKE^TM) was assembled by DNA shuffling and ligation using DNA encoding a camelid anti-CD16 antibody fragment, a wild-type IL-15 moiety, and an anti-B7-H3 scFv (clone 376.96). The expressed and purified cam1615B7H3 protein was tested for in vitro NK cell activity against a variety of tumors and in vivo against a tagged human MA-148 ovarian cancer cell line grafted in NSG mice. cam1615B7H3 showed specific NK cell expansion, high killing activity across a range of B7-H3+ carcinomas, and the ability to mediate growth inhibition of aggressive ovarian cancer in vivo. cam1615B7H3 TriKE improves NK cell function, expansion, targeted cytotoxicity against various types of B7-H3-positive human cancer cell lines, and delivers an anti-cancer effect in vivo in a solid tumor setting.