An anti-B7-H4 antibody-drug conjugate for the treatment of breast cancer

Aberrant expression of B7-H4 and B7-H5 contributes to the development of cutaneous squamous cell carcinoma

Cutaneous squamous cell carcinoma (CSCC) is the second most common malignant tumor of the skin. B7 homolog 4 (B7-H4) and B7-H5 (B7 homolog 5) are associated with a variety of tumors. Investigate the potential role of B7-H4 and B7-H5 in regulating the tumorigenesis and progression of CSCC. B7-H4 and B7-H5 transcriptome data were collected from GEO and TCGA databases and subjected to bioinformatical analysis by protein-protein interaction (PPI) network, functional enrichment analysis, immune analysis, and drug-gene interaction prediction analysis. We characterized the expression of B7-H4 and B7-H5 in carcinoma tissues of CSCC patients by immunohistochemistry. Meanwhile, the clinical correlation of B7-H4 and B7-H5 in CSCC was explored by statistical analysis. B7-H4 and B7-H5 genes were under-expressed in CSCC and correlated with tumor staging. According to GO and KEGG Pathway enrichment analysis, B7-H4, and B7-H5 can regulate the proliferation and activation of T cells, lymphocytes, and monocytes, and the expression of cytokines, such as IL-6 and IL-10, in CSCC. B7-H4 and B7-H5 are also jointly involved in the occurrence and development of CSCC via the JAK-STAT and Notch signaling pathways. We found that B7-H4 and B7-H5 proteins were abnormally highly expressed in CSCC tissue and correlated with tumor size and stage. Our findings offer new insights into the pathogenesis of CSCC and suggest that B7-H4 and B7-H5 are novel tissue biomarkers and promising therapeutic targets for CSCC.

A B7-H4-Targeting Antibody-Drug Conjugate Shows Antitumor Activity in PARPi and Platinum-Resistant Cancers with B7-H4 Expression

PURPOSE

Platinum and PARP inhibitors (PARPi) demonstrate activity in breast and ovarian cancers, but drug resistance ultimately emerges. Here, we examine B7-H4 expression in primary and recurrent high-grade serous ovarian carcinoma (HGSOC) and the activity of a B7-H4-directed antibody-drug conjugate (B7-H4-ADC), using a pyrrolobenzodiazepine-dimer payload, in PARPi- and platinum-resistant HGSOC patient-derived xenograft (PDX) models.

EXPERIMENTAL DESIGN

B7-H4 expression was quantified by flow cytometry and IHC. B7-H4-ADC efficacy was tested against multiple cell lines in vitro and PDX in vivo. The effect of B7-H4-ADC on cell cycle, DNA damage, and apoptosis was measured using flow cytometry.

RESULTS

B7-H4 is overexpressed in 92% of HGSOC tumors at diagnosis (n = 12), persisted in recurrent matched samples after platinum treatment, and was expressed at similar levels across metastatic sites after acquired multi-drug resistance (n = 4). Treatment with B7-H4-ADC resulted in target-specific growth inhibition of multiple ovarian and breast cancer cell lines. In platinum- or PARPi-resistant ovarian cancer cells, B7-H4-ADC significantly decreased viability and colony formation while increasing cell-cycle arrest and DNA damage, ultimately leading to apoptosis. Single-dose B7-H4-ADC led to tumor regression in 65.5% of breast and ovarian PDX models (n = 29), with reduced activity in B7-H4 low or negative models. In PARPi and platinum-resistant HGSOC PDX models, scheduled B7-H4-ADC dosing led to sustained tumor regression and increased survival.

CONCLUSIONS

These data support B7-H4 as an attractive ADC target for treatment of drug-resistant HGSOC and provide evidence for activity of an ADC with a DNA-damaging payload in this population. See related commentary by Veneziani et al., p. 1434.

Unraveling Biomarker Signatures in Triple-Negative Breast Cancer: A Systematic Review for Targeted Approaches

Triple-negative breast cancer (TNBC) is one of the most aggressive subtypes of breast cancer, marked by poor outcomes and dismal prognosis. Due to the absence of targetable receptors, chemotherapy still represents the main therapeutic option. Therefore, current research is now focusing on understanding the specific molecular pathways implicated in TNBC, in order to identify novel biomarker signatures and develop targeted therapies able to improve its clinical management. With the aim of identifying novel molecular features characterizing TNBC, elucidating the mechanisms by which these molecular biomarkers are implicated in the tumor development and progression, and assessing the impact on cancerous cells following their inhibition or modulation, we conducted a literature search from the earliest works to December 2023 on PubMed, Scopus, and Web Of Science. A total of 146 studies were selected. The results obtained demonstrated that TNBC is characterized by a heterogeneous molecular profile. Several biomarkers have proven not only to be characteristic of TNBC but also to serve as potential effective therapeutic targets, holding the promise of a new era of personalized treatments able to improve its prognosis. The pre-clinical findings that have emerged from our systematic review set the stage for further investigation in forthcoming clinical trials.

Analysis of B7-H4 Expression Across Salivary Gland Carcinomas Reveals Adenoid Cystic Carcinoma-Specific Prognostic Relevance

B7-H4 (VTCN1), a member of the B7 family, is overexpressed in several types of cancer. Here we investigated the pattern of expression of B7-H4 in salivary gland carcinomas (SGC) and assessed its potential as a prognostic marker and therapeutic target. Immunohistochemistry (IHC) analyses were performed in a cohort of 340 patient tumors, composed of 124 adenoid cystic carcinomas (ACC), 107 salivary duct carcinomas (SDC), 64 acinic cell carcinomas, 36 mucoepidermoid carcinomas (MEC), 9 secretory carcinomas (SC), as well as 20 normal salivary glands (controls). B7-H4 expression was scored and categorized into negative (<5% expression of any intensity), low (5%-70% expression of any intensity or >70% with weak intensity), or high (>70% moderate or strong diffuse intensity). The associations between B7-H4 expression and clinicopathologic characteristics, as well as overall survival, were assessed. Among all tumors, B7-H4 expression was more prevalent in ACC (94%) compared with those of SC (67%), MEC (44%), SDC (32%), and acinic cell carcinomas (0%). Normal salivary gland tissue did not express B7-H4. High expression of B7-H4 was found exclusively in ACC (27%), SDC (11%), and MEC (8%). In SDC, B7-H4 expression was associated with female gender (P = .002) and lack of androgen receptor expression (P = .012). In ACC, B7-H4 expression was significantly associated with solid histology (P < .0001) and minor salivary gland primary (P = .02). High B7-H4 expression was associated with a poorer prognosis in ACC, regardless of clinical stage and histologic subtype. B7-H4 expression was not prognostic in the non-ACC SGC evaluated. Our comparative study revealed distinct patterns of B7-H4 expression according to SGC histology, which has potential therapeutic implications. B7-H4 expression was particularly high in solid ACC and was an independent prognostic marker in this disease but not in the other SGC assessed.

The co-inhibitory immune checkpoint proteins B7-H1(PD-L1) and B7-H4 in high grade glioma: From bench to bedside

Co-inhibitory immune checkpoints play a crucial role in tumor progression, and PD-1/PD-L1 inhibitor has been a breakthrough for treating multiple refractory tumors in last decade. Nevertheless, results of several phase III clinical trials of PD-1/PD-L1 inhibitor are unsatisfactory in high grade gliomas recently. This article reviews the promising biomarkers which can predict the efficacy of PD-1/PD-L1 blockade immunotherapy and current status of emerging strategies involving PD-1/PD-L1 inhibitors, especially the combination treatment and neoadjuvant PD-1 therapy in gliomas. In addition, B7-H4, one of the most promising immune checkpoints, is also briefly reviewed here for its clinical significance, regulatory mechanism and developing immunotherapeutic strategies in pre-clinical glioma models.

SGN-B7H4V, an investigational vedotin ADC directed to the immune checkpoint ligand B7-H4, shows promising activity in preclinical models

BACKGROUND

SGN-B7H4V is a novel investigational vedotin antibody-drug conjugate (ADC) comprising a B7-H4-directed human monoclonal antibody conjugated to the cytotoxic payload monomethyl auristatin E (MMAE) via a protease-cleavable maleimidocaproyl valine citrulline (mc-vc) linker. This vedotin linker-payload system has been clinically validated in multiple Food and Drug Administration approved agents including brentuximab vedotin, enfortumab vedotin, and tisotumab vedotin. B7-H4 is an immune checkpoint ligand with elevated expression on a variety of solid tumors, including breast, ovarian, and endometrial tumors, and limited normal tissue expression. SGN-B7H4V is designed to induce direct cytotoxicity against target cells by binding to B7-H4 on the surface of target cells and releasing the cytotoxic payload MMAE upon internalization of the B7-H4/ADC complex.

METHODS

B7-H4 expression was characterized by immunohistochemistry across multiple solid tumor types. The ability of SGN-B7H4V to kill B7-H4-expressing tumor cells in vitro and in vivo in a variety of xenograft tumor models was also evaluated. Finally, the antitumor activity of SGN-B7H4V as monotherapy and in combination with an anti-programmed cell death-1 (PD-1) agent was evaluated using an immunocompetent murine B7-H4-expressing Renca tumor model.

RESULTS

Immunohistochemistry confirmed B7-H4 expression across multiple solid tumors, with the highest prevalence in breast, endometrial, and ovarian tumors. In vitro, SGN-B7H4V killed B7-H4-expressing tumor cells by MMAE-mediated direct cytotoxicity and antibody-mediated effector functions including antibody-dependent cellular cytotoxicity and antibody-dependent cellular phagocytosis. In vivo, SGN-B7H4V demonstrated strong antitumor activity in multiple xenograft models of breast and ovarian cancer, including xenograft tumors with heterogeneous B7-H4 expression, consistent with the ability of vedotin ADCs to elicit a bystander effect. In an immunocompetent murine B7-H4-expressing tumor model, SGN-B7H4V drove robust antitumor activity as a monotherapy that was enhanced when combined with an anti-PD-1 agent.

CONCLUSION

The immune checkpoint ligand B7-H4 is a promising molecular target expressed by multiple solid tumors. SGN-B7H4V demonstrates robust antitumor activity in preclinical models through multiple potential mechanisms. Altogether, these preclinical data support the evaluation of SGN-B7H4V as a monotherapy in the ongoing phase 1 study of SGN-B7H4V in advanced solid tumors (NCT05194072) and potential future clinical combinations with immunotherapies.

Discovery and Preclinical Characterization of XMT-1660, an Optimized B7-H4-Targeted Antibody-Drug Conjugate for the Treatment of Cancer

Antibody-drug conjugates (ADC) achieve targeted drug delivery to a tumor and have demonstrated clinical success in many tumor types. The activity and safety profile of an ADC depends on its construction: antibody, payload, linker, and conjugation method, as well as the number of payload drugs per antibody [drug-to-antibody ratio (DAR)]. To allow for ADC optimization for a given target antigen, we developed Dolasynthen (DS), a novel ADC platform based on the payload auristatin hydroxypropylamide, that enables precise DAR-ranging and site-specific conjugation. We used the new platform to optimize an ADC that targets B7-H4 (VTCN1), an immune-suppressive protein that is overexpressed in breast, ovarian, and endometrial cancers. XMT-1660 is a site-specific DS DAR 6 ADC that induced complete tumor regressions in xenograft models of breast and ovarian cancer as well as in a syngeneic breast cancer model that is refractory to PD-1 immune checkpoint inhibition. In a panel of 28 breast cancer PDXs, XMT-1660 demonstrated activity that correlated with B7-H4 expression. XMT-1660 has recently entered clinical development in a phase I study (NCT05377996) in patients with cancer.

Role of B7 family members in glioma: Promising new targets for tumor immunotherapy

Glioma, is a representative type of intracranial tumor among adults, usually has a weak prognosis and limited treatment options. Traditional therapies, including surgery, chemotherapy, and radiotherapy, have had little impact on patient survival time. Immunotherapies designed to target the programmed cell death protein 1 (PD-1)/programmed death ligand 1 (PD-L1) signaling pathway have successfully treated various human cancers, informing the development of similar therapies for glioma. However, anti-PD-L1 response rates remain limited in glioma patients. Thus, exploring novel checkpoints targeting additional immunomodulatory pathways for activating durable antitumor immune responses and improving glioma outcomes is needed. Researchers have identified other B7 family checkpoint molecules, including PD-L2, B7-H2, B7-H3, B7-H4, and B7-H6. The current review article evaluates the expression of all 10 reported members of the B7 family in human glioma using The Cancer Genome Atlas (TCGA) and the Genotype-Tissue Expression (GTEx) data, as well as summarizes studies evaluating the clinical meanings and functions of B7 family molecules in gliomas. B7 family checkpoints may contribute to different immunotherapeutic management options for glioma patients.

B7 Family Members in Pancreatic Ductal Adenocarcinoma: Attractive Targets for Cancer Immunotherapy

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers, with a five-year survival rate of approximately 5-10%. The immune checkpoint blockade represented by PD-1/PD-L1 inhibitors has been effective in a variety of solid tumors but has had little clinical response in pancreatic cancer patients. The unique suppressive immune microenvironment is the primary reason for this outcome, and it is essential to identify key targets to remodel the immune microenvironment. Some B7 family immune checkpoints, particularly PD-L1, PD-L2, B7-H3, B7-H4, VISTA and HHLA2, have been identified as playing a significant role in the control of tumor immune responses. This paper provides a comprehensive overview of the recent research progress of some members of the B7 family in pancreatic cancer, which revealed that they can be involved in tumor progression through immune-dependent and non-immune-dependent pathways, highlighting the mechanisms of their involvement in tumor immune escape and assessing the prospects of their clinical application. Targeting B7 family immune checkpoints is expected to result in novel immunotherapeutic treatments for patients with pancreatic cancer.

Tumor immune checkpoints and their associated inhibitors

Immunological evasion is one of the defining characteristics of cancers, as the immune modification of an immune checkpoint (IC) confers immune evasion capabilities to tumor cells. Multiple ICs, such as programmed cell death protein-1 (PD-1) and cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4), can bind to their respective receptors and reduce tumor immunity in a variety of ways, including blocking immune cell activation signals. IC blockade (ICB) therapies targeting these checkpoint molecules have demonstrated significant clinical benefits. This is because antibody-based IC inhibitors and a variety of specific small molecule inhibitors can inhibit key oncogenic signaling pathways and induce durable tumor remission in patients with a variety of cancers. Deciphering the roles and regulatory mechanisms of these IC molecules will provide crucial theoretical guidance for clinical treatment. In this review, we summarize the current knowledge on the functional and regulatory mechanisms of these IC molecules at multiple levels, including epigenetic regulation, transcriptional regulation, and post-translational modifications. In addition, we provide a summary of the medications targeting various nodes in the regulatory pathway, and highlight the potential of newly identified IC molecules, focusing on their potential implications for cancer diagnostics and immunotherapy.

Novel immune scoring dynamic nomograms based on B7-H3, B7-H4, and HHLA2: Potential prediction in survival and immunotherapeutic efficacy for gallbladder cancer

Background

Gallbladder cancer (GBC) is a mortal malignancy with limited therapeutic strategies. We aimed to develop novel immune scoring systems focusing on B7-H3, B7-H4, and HHLA2. We further investigated their potential clinical effects in predicting survival and immunotherapeutic efficacy for GBC.

Methods

This was a retrospective cohort study in a single center that explored the expression characteristics of B7-H3, B7-H4, and HHLA2. The immune scoring nomograms for prognostic were developed via logistic regression analyses. Their performance was evaluated using the Harrell concordance index (C-index) and decision curves analysis (DCA), and validated with calibration curves.

Results

B7-H3, B7-H4, and HHLA2 manifested with a relatively high rate of co-expression patterns in GBC tissues. They were associated with worse clinicopathological stage, suppression of immune microenvironment, and unfavorable prognosis in postoperative survival. B7 stratification established based on B7-H3, B7-H4, and HHLA2 was an independent prognostic predictor (p&lt;0.05 in both groups). Moreover, immune stratification was also successfully constructed based on B7 stratification and the density of CD8+ TILs (all p&lt;0.001). The prediction models were developed based on B7-/or immune stratification combined with the TNM/or Nevin staging system. These novel models have excellent discrimination ability in predicting survival and immunotherapeutic efficacy for GBC patients by DCA and clinical impact plots. Finally, dynamic nomograms were developed for the most promising clinical prediction models (B7-TNM model and Immune-TNM model) to facilitate prediction.

Conclusions

Immune scoring systems focusing on B7-H3, B7-H4, and HHLA2 may effectively stratify the prognosis of GBC. Prognostic nomograms based on novel immune scoring systems may potentially predict survival and immunotherapeutic efficacy in GBC. Further valid verification is necessary.

Comparison of the Clinicopathologic Features and T-Cell Infiltration of B7-H3 and B7-H4 Expression in Triple-negative Breast Cancer Subtypes

Previously we revealed an upregulated expression of B7-H3 and B7-H4 mRNA and protein in breast cancer, including triple-negative breast cancer (TNBC). However, little is known regarding the clinical impact and value of B7-H3 and B7-H4 in TNBC subtypes. Thus, this study evaluated the clinicopathologic effects of B7-H3 and B7-H4 mRNA and protein expression according to the TNBC subtypes. RNAscope in situ hybridization and immunohistochemistry of B7-H3 and B7-H4 was done for 186 TNBC samples using tissue microarray. Immunohistochemistry was also performed for TNBC molecular subtype-surrogate markers, CD3, and CD8. TNBCs were classified into basal-like (BL) (64.5%), luminal androgen receptor (10.8%), and unclassifiable (24.7%) subtypes. Tumor B7-H4 mRNA expression was associated with younger age at the initial diagnosis and with molecular TNBC subtypes. Expression of B7-H3 mRNA and protein in the tumor cells was negatively correlated with CD3+ and CD8+ T-cell infiltration density in the tumor and/or stromal region of TNBCs and their subtypes. High stromal B7-H3 mRNA expression was associated with poor disease-free and overall survival in the TNBCs and with overall survival in the unclassifiable subtype. Stromal B7-H3 mRNA expression was independently associated with overall survival and disease-free survival in the TNBCs and BL subtype, respectively. Our results indicate the importance of the stromal expression of B7-H3 mRNA as a prognostic factor in the TNBCs and BL subtype. The inverse relationship between B7-H3 expression and CD3+ and CD8+ T-lymphocyte infiltration represents a promising target for immunotherapy for the TNBCs, especially the BL subtype.

Antibody-Drug Conjugate Targets, Drugs and Linkers

Antibody-drug conjugates offer the possibility of directing powerful cytotoxic agents to a malignant tumor while sparing normal tissue. The challenge is to select an antibody target expressed exclusively or at highly elevated levels on the surface of tumor cells and either not all or at low levels on normal cells. The current review explores 78 targets that have been explored as antibody-drug conjugate targets. Some of these targets have been abandoned, 9 or more are the targets of FDA-approved drugs, and most remain active clinical interest. Antibody-drug conjugates require potent cytotoxic drug payloads, several of these small molecules are discussed, as are the linkers between the protein component and small molecule components of the conjugates. Finally, conclusions regarding the elements for the successful antibody-drug conjugate are discussed.

Development of T-cell engagers selective for cells co-expressing two antigens

T cell-engaging bispecific antibodies (TCEs) are clinically effective treatments for hematological cancers. While the utility of TCEs in solid malignancies is being explored, toxicities arising from antigen expression on normal tissues have slowed or halted several clinical trials. Here, we describe the development of TCEs that preferentially drive T cell-mediated death against target cells co-expressing two tumor-associated antigens. We show that Ly6E and B7-H4 are simultaneously expressed on approximately 50% of breast cancers, whereas normal tissue expression is limited and mostly orthogonal. Traditional bispecific TCEs targeting a singular antigen, either Ly6E or B7-H4, are active when paired with high-affinity CD3-engagers, but normal tissue expression presents a toxicity risk. Treatment with a murine cross-reactive B7-H4-TCE results in rapid and severe weight loss in mice along with damage to B7-H4-expressing tissues. To overcome on-target toxicity, we designed trispecific antibodies co-targeting Ly6E, B7-H4, and CD3 and characterized the impact of dual-antigen binding and the relative placement of each binding domain on tumor killing in vitro and in vivo. In vitro killing of tumor cells co-expressing both antigens correlates to the placement of the higher affinity B7-H4 binding domain, with only modest enhancements seen upon addition of Ly6E binding. In xenograft models, avid binding of appropriately designed trispecific TCEs enables tumor growth inhibition while evading the poor tolerability seen with active bispecific TCEs. Collectively these data highlight the potential for dual-antigen targeting to improve safety and efficacy, and expand the scope of tumors that may effectively be treated by TCEs.

Abbreviations: Chimeric antigen receptor T cells (CAR-Ts), dual-antigen targeted T cell engagers (DAT-TCE), Fragment antigen-binding (Fab), Hematoxylin and eosin (H&E), Institutional Animal Care and Use Committee (IACUC), Immunoglobulin G (IgG), immunohistochemistry (IHC), NOD SCID gamma (NSG), peripheral blood mononuclear cells (PBMCs), surface plasmon resonance (SPR), T cell-engagers (TCEs)

Associations of B7-H3 and B7-H4 Expression in Ductal Carcinoma In Situ of the Breast With Clinicopathologic Features and T-Cell Infiltration

B7-H3 and B7-H4 play an inhibitory role in T-cell function by limiting proliferation and cytokine production. Information about B7-H3 and B7-H4 expression in ductal carcinoma in situ (DCIS) remains uncertain. The objective of this study was to evaluate the expression levels of B7-H3 and B7-H4 in DCIS and their associations with clinicopathologic features and T-cell infiltration. B7-H3 and B7-H4 mRNA and protein expression levels in 8 pairs of DCIS tissues and matched normal adjacent tissues were examined by RNAscope in situ hybridization and immunohistochemistry analysis. Immunohistochemical staining of B7-H3, B7-H4, CD3, and CD8 was performed for 79 DCIS samples using tissue microarray. RNAscope in situ hybridization and immunohistochemistry analysis revealed that expression levels of B7-H3 and B7-H4 in DCIS tissues were higher than those in corresponding normal tissues. B7-H3 and B7-H4 mRNA and protein appeared to be mainly expressed in DCIS carcinoma cells. High B7-H3 and B7-H4 expression was observed in 58 (73.4%) and 62 (78.5%) cases with DCIS, respectively. High B7-H3 expression was significantly associated with high-nuclear grade and presence of comedo-type necrosis (both P<0.05). B7-H3 expression in HR/HER2 subtype was higher than that in HR/HER2 subtype (P<0.05). B7-H3 and B7-H4 expression levels were negatively related to the density of CD3 and CD8 T-cell infiltrates. B7-H3 and B7-H4 may play an important role in immune surveillance mechanisms of DCIS. They might be useful targets to develop immune-based therapy to alter or prevent DCIS progression.

The Expression of Three Negative Co-Stimulatory B7 Family Molecules in Small Cell Lung Cancer and Their Effect on Prognosis

Background

In recent years, immune checkpoint inhibitors have shown significant effects in a variety of solid tumors. However, due to the low incidence of small cell lung cancer (SCLC) and its unclear mechanism, immune checkpoints in SCLC have not been fully studied.

Methods

We evaluated the expression of PD-L1, B7-H3, and B7-H4 in 115 SCLC tissue specimens using immunohistochemistry. The clinical data of patients with SCLC were retrospectively reviewed to investigate three negative co-stimulatory B7 family molecules’ ability to affect the prognosis of SCLC.

Results

Among the SCLC patients with complete follow-up data (n = 107), sixty-nine (64.49%) expressed moderate to high B7-H3 levels, which correlated positively with tumor sizes (P < 0.001). Eighty (74.77%) patients expressed moderate to high B7-H4 levels, which correlated positively with metastases (P = 0.049). The positive expression of B7-H3 and B7-H4 correlated significantly with shortened overall survival (OS) (B7-H3, P = 0.006; B7-H4, P = 0.019). PD-L1 was positively expressed only in 13.08% of cancer tissues, and there was no significant correlation with prognosis. The Cox proportional hazards regression showed that B7-H3 was an independent prognostic indicator of OS (P = 0.028; HR = 2.125 [95% CI = 0.985-4.462]).

Conclusions

Our results suggest that B7-H3 has a negative predictive effect on SCLC. This outcome provides a theoretical basis for the subsequent research on immune checkpoint inhibitors targeting B7-H3.

Depleting Tumor Cells Expressing Immune Checkpoint Ligands-A New Approach to Combat Cancer

Antibodies against inhibitory immune checkpoint molecules (ICPMs), referred to as immune checkpoint inhibitors (ICIs), have gained a prominent place in cancer therapy. Several ICIs in clinical use have been engineered to be devoid of effector functions because of the fear that ICIs with preserved effector functions could deplete immune cells, thereby curtailing antitumor immune responses. ICPM ligands (ICPMLs), however, are often overexpressed on a sizeable fraction of tumor cells of many tumor types and these tumor cells display an aggressive phenotype with changes typical of tumor cells undergoing an epithelial-mesenchymal transition. Moreover, immune cells expressing ICPMLs are often endowed with immunosuppressive or immune-deviated functionalities. Taken together, these observations suggest that compounds with the potential of depleting cells expressing ICPMLs may become useful tools for tumor therapy. In this article, we summarize the current state of the art of these compounds, including avelumab, which is the only ICI targeting an ICPML with preserved effector functions that has gained approval so far. We also discuss approaches allowing to obtain compounds with enhanced tumor cell-depleting potential compared to native antibodies. Eventually, we propose treatment protocols that may be applied in order to optimize the therapeutic efficacy of compounds that deplete cells expressing ICPMLs.

Severing Ties: Quantifying the Payload Release from Antibody Drug Conjugates

As a key mediator of efficacy and toxicity, the linker connecting the payload in antibody drug conjugates determines cellular distribution and payload release. Sorkin et al. (2019) have created novel fluorescence-based linkers to quantify the rate of intracellular bond cleavage and track live-cell kinetics for designing more effective agents.

B7-H3 and B7-H4 Expression in Breast Cancer and Their Association with Clinicopathological Variables and T Cell Infiltration

OBJECTIVES

B7-H3 and B7-H4 proteins are expressed in breast cancer tissues, but their relationships with respect to tumor immune surveillance and outcomes in breast cancer are not conclusive.

METHODS

We first examined B7-H3 and B7-H4 mRNA expression in the Genotype-Tissue Expression (GTEx) and The Cancer Genome Atlas (TCGA) datasets. Next, mRNA and protein expression were assessed by RNAscope in situ hybridization (ISH) and immunohistochemistry in 10 pairs of breast cancer and matched normal tissues. Immunohistochemical staining of B7-H3, B7-H4, CD3, and CD8 was performed in tissue microarray slides containing 198 breast cancer samples. Association of B7-H3 and B7-H4 expression with survival was verified using the publicly accessible BreastMark tool.

RESULTS

B7-H3 and B7-H4 mRNA expression were significantly higher in breast cancer samples in the TCGA dataset than in normal breast tissues in the GTEx dataset. RNAscope ISH and immunohistochemistry showed that B7-H3 and B7-H4 mRNA and protein appeared to be mainly expressed in cancer cells. Expression of B7-H3 and B7-H4 tended to be associated with low-density scores of stromal tumor-infiltrating lymphocytes (TILs) as well as molecular subtypes. Expressions of B7-H3 and B7-H4 were negatively correlated with stromal CD3+ and CD8+ T cell infiltration density. B7-H3 and B7-H4 expression was not associated with survival, which was verified by BreastMark analysis.

CONCLUSION

Expression levels of B7-H3 and B7-H4 were independent of clinical outcomes of breast cancer. There was an inverse relationship between the expression of B7-H3 and B7-H4 in breast cancer and the density of stromal TILs and CD8+ T lymphocytes. This inverse relationship may represent a promising target in the field of breast cancer immunotherapy.

Chimeric Antigen Receptor T Cell Immunotherapy for Tumor: A Review of Patent Literatures

BACKGROUND

Chimeric Antigen Receptor (CAR) T cell immunotherapy, as an innovative method for tumor immunotherapy, acquires unprecedented clinical outcomes. Genetic modification not only provides T cells with the antigen-binding function but also endows T cells with better immunological functions both in solid and hematological cancer. However, the CAR T cell therapy is not perfect because of several reasons, such as tumor immune microenvironment, and autologous limiting factors of CAR T cells. Moreover, the safety of CAR T cells should be improved.

OBJECTIVE

Recently many patents and publications have reported the importance of CAR T cell immunotherapy. Based on the patents about CAR T cell immunotherapy, we conclude some methods for designing the CAR which can provide useful information to readers.

METHODS

This review presents recent patents and publications, summarizes some specific antigens for oncotherapy from patents and enumerate some approaches to treatment of immunosuppression and reinforcing the immune response of CAR T cells. We also sum up some strategies for improving the safety of CAR T cell immunotherapy.

RESULTS

CAR T cell immunotherapy as a neotype cellular immunotherapy has been proved effective in oncotherapy and authorized by the FDA. Improvements in CAR designing have enhanced the functions of CAR T cells.

CONCLUSION

This review, summarizing antigens and approaches to overcome defects of CAR T cell immunotherapy from patents and publications, might contribute to a broad readership.

B7-H4, a promising target for immunotherapy

The coinhibitory molecule B7-H4, an important member of the B7 family, is abnormally expressed in tumors, inflammation and autoimmune diseases. B7-H4 negatively regulates T cell immune response and promotes immune escape by inhibiting the proliferation, cytokine secretion, and cell cycle of T cells. Moreover, B7-H4 plays an extremely important role in tumorigenesis and tumor development including cell proliferation, invasion, metastasis, anti-apoptosis, etc. In addition, B7-H4 has the other biological functions, such as protection against type 1 diabetes (T1D) and islet cell transplantation. Therefore, B7-H4 has been identified as a novel marker or a therapeutic target for the treatment of tumors, inflammation, autoimmune diseases, and organ transplantation. Here, we summarized the expression profiles, physiological and pathological functions, and regulatory mechanisms of B7-H4, the signaling pathways involved, as well as B7-H4-based immunotherapy.

The B7x Immune Checkpoint Pathway: From Discovery to Clinical Trial

B7x (B7 homolog x, also known as B7-H4, B7S1, and VTCN1) was discovered by ourselves and others in 2003 as the seventh member of the B7 family. It is an inhibitory immune checkpoint of great significance to human disease. Tissue-expressed B7x minimizes autoimmune and inflammatory responses. It is overexpressed in a broad spectrum of human cancers, where it suppresses antitumor immunity. Further, B7x and PD-L1 tend to have mutually exclusive expression in cancer cells. Therapeutics targeting B7x are effective in animal models of cancers and autoimmune disorders, and early-phase clinical trials are underway to determine the efficacy and safety of targeting B7x in human diseases. It took 15 years moving from the discovery of B7x to clinical trials. Further studies will be necessary to identify its receptors, reveal its physiological functions in organs, and combine therapies targeting B7x with other treatments.

B7x-from bench to bedside

B7x is an immune checkpoint molecule which belongs to the B7 family of ligands which includes PD-L1, PD-L2, B7-H3 and HHLA2. B7x belongs to the Immunoglobulin superfamily and its protein structure is similar to other members with a N terminus peptide, IgV and IgC like extracellular domain with four cysteine residues. Its receptor is yet to be identified. B7x inhibits T cell proliferation and expansion by IL-2 dependent and non-IL-2 dependent pathways. Even though high levels of B7x mRNA can be detected in most tissues its protein expression is highly limited suggesting significant post translational control. In vivo data, show that B7x plays an important role in limiting autoimmunity in the peripheral tissues and fine-tuning autoimmune responses. B7x is highly expressed in various cancers and in prostate cancer its expression is corelated with poorer outcomes. Local production of IL-6 and IL-10 in various cancers promotes B7x expression and tumor immune evasion. B7x is especially expressed in PD-L1 negative tumors suggesting that this may be an important method of immune evasion in these tumors. Currently drug development, targeting B7x through various mechanisms including monoclonal antibodies and antibody drug conjugates are in development in cancers and increasing B7x expression with fusion proteins in autoimmune diseases is underway.

A T-cell-engaging B7-H4/CD3-bispecific Fab-scFv Antibody Targets Human Breast Cancer

PURPOSE

The B7 homolog 4 (B7-H4, VTCN1) is an immune checkpoint molecule that negatively regulates immune responses and is known to be overexpressed in many human cancers. Previously, we generated a mouse anti-human B7-H4 mAb that did not have a significant antitumor effect in vivo probably because of molecule instability. In this study, we designed a B7-H4/CD3-bispecific antibody (BsAb) and investigated its antitumor activity in vitro and in vivo using a humanized mouse model.

EXPERIMENTAL DESIGN

cDNAs of the antibody-binding fragment (Fab)-single-chain variable fragment (scFv) and scFv-scFv of the anti-B7-H4/CD3 BsAb were synthesized, and the BsAb antibodies were produced in HEK293 cells. The antitumor activity against human breast cancer cells by human peripheral blood mononuclear cells (hPBMC) with BsAb was measured by lactate dehydrogenase release in vitro, and in vivo using hPBMC-transplanted MHC class I- and class II-deficient NOG mice.

RESULTS

hPBMCs with anti-B7-H4/CD3 BsAbs successfully lysed the human breast cancer cell line MDA-MB-468 (EC₅₀: 0.2 ng/mL) and other B7-H4⁺ cell lines in vitro. When BsAb was injected in a humanized mouse model, there was an immediate and strong antitumor activity against MDA-MB-468, HCC-1954, and HCC-1569 tumors and CD8⁺ and granzyme B⁺ CTL infiltration into the tumor, and there were no adverse effects after long-term observation. CD8⁺ T-cell depletion by an anti-CD8 antibody mostly reduced the antitumor effect of BsAb in vivo.

CONCLUSIONS

An anti-B7-H4/CD3 BsAb may be a good therapeutic tool for patients with B7-H4⁺ breast cancers.

Association of B7-H4, PD-L1, and tumor infiltrating lymphocytes with outcomes in breast cancer

B7-H4 (VTCN1) is a member of the CD28/B7 family of immune co-inhibitory molecules. The relationship of tumor and stromal B7-H4 protein expression with PD-L1, tumor infiltrating lymphocytes (TILs) and its association with clinico-pathological variables are not well defined. Herein, we explore the expression level of B7-H4 protein in breast cancer and evaluate its association with TILs, levels of PD-L1 expression, and clinico-pathological characteristics in two independent populations. In this study, we used multiplexed automated quantitative immunofluorescence (QIF) to measure the levels of B7-H4 and PD-L1 protein and determined TILs through pathologist assessment of H&E-stained preparations in over a thousand breast cancer cases from two institutions represented in tissue microarray format. Associations between the marker levels, major clinico-pathological variables, and survival were analyzed. We detected B7-H4 protein was highly expressed in both breast cancer and stromal cells. Its expression was independent of breast cancer intrinsic subtypes. PD-L1 expression was higher in triple negative breast cancers. Neither B7-H4 nor PD-L1 were associated with survival in breast cancer. Our study shows there is a mutually exclusive pattern of B7-H4 with both tumor PD-L1 expression and TILs in all breast cancers, independent of breast cancer intrinsic subtype. This exclusive pattern suggests that some breast tumors may preferentially use one B7-related immune evasion mechanism/pathway. This could explain the clinical benefit that is seen only in a fraction of patients with immune checkpoint inhibitors directed exclusively towards PD-L1 in breast cancer.

B7-H4 overexpression contributes to poor prognosis and drug-resistance in triple-negative breast cancer

Background

The expression of the immunoregulatory protein B7-H4 has been reported in many types of cancer, including breast cancer. However, its role in triple-negative breast cancer (TNBC), especially its correlation with patients’ prognosis and chemoresistance remains unclear.

Methods

The expression of B7-H4 in TNBC tissues and cell lines were measured with Real-Time PCR and western blotting. 65 cases of TNBC tissue samples and adjacent non-tumor tissue samples were analyzed by immunochemistry to demonstrate the correlation between the B7-H4 expression and clinicopathological characteristics. In vitro studies assessed mAb MIH43 alone and in combination with transfecting B7-H4 siRNA on the growth of chemosensitive and chemoresistant TNBC cell lines by CCK-8 and apoptotic enzyme-linked immunosorbent assay (ELISA).

Results

B7-H4 expression was detected positive in 59 of 65 (90.8%) different stage TNBC patients, especially in the samples of recurrence TNBC patients after receiving neoadjuvant chemotherapy treatment. Survival curves showed that patients with B7-H4 overexpression had significantly shorter survival and recurrence time than those with low B7-H4 expression (p < 0.005). Univariate and multivariate COX regression analysis demonstrated that B7-H4 was an independent predictor for advanced tumor stage. The monoclonal antibody of B7-H4 has the potential anti-proliferative effects on inhibiting the chemoresistant TNBC cell lines and increasing the sensitivity of TNBC cell lines to doxorubicin, paclitaxel or carboplatin. RNAi-mediated silencing of B7-H4 in TNBC cells enhanced drug-induced apoptosis via inhibiting PTEN/PI3K/AKT pathway, whereas reexpression of B7-H4 in B7-H4 knockdown and low B7-H4 expressing cells increased the phosphorylation of PI3K and AKT along with restoration of PETN expression.

Conclusions

Our data show that B7-H4 is a biomarker indicative of a poor prognosis in TNBC patients and at least partially downregulated in chemoresistance via PTEN/PI3K/AKT pathway. Targeting B7-H4 might provide an attractive therapeutic approach specifically for TNBC patients.

Electronic supplementary material

The online version of this article (10.1186/s12935-018-0597-9) contains supplementary material, which is available to authorized users.

An Anti-GDNF Family Receptor Alpha 1 (GFRA1) Antibody-Drug Conjugate for the Treatment of Hormone Receptor-Positive Breast Cancer

Luminal A (hormone receptor-positive) breast cancer constitutes 70% of total breast cancer patients. In an attempt to develop a targeted therapeutic for this cancer indication, we have identified and characterized Glial cell line-Derived Neurotrophic Factor (GDNF) Family Receptor Alpha 1 (GFRA1) antibody-drug conjugates (ADC) using a cleavable valine-citrulline-MMAE (vcMMAE) linker-payload. RNAseq and IHC analysis confirmed the abundant expression of GFRA1 in luminal A breast cancer tissues, whereas minimal or no expression was observed in most normal tissues. Anti-GFRA-vcMMAE ADC internalized to the lysosomes and exhibited target-dependent killing of GFRA1-expressing cells both in vitro and in vivo The ADCs using humanized anti-GFRA1 antibodies displayed robust therapeutic activity in clinically relevant cell line-derived (MCF7 and KPL-1) tumor xenograft models. The lead anti-GFRA1 ADC cross-reacts with rodent and cynomolgus monkey GFRA1 antigen and showed optimal pharmacokinetic properties in both species. These properties subsequently enabled a target-dependent toxicity study in rats. Anti-GFRA1 ADC is well tolerated in rats, as seen with other vcMMAE linker-payload based ADCs. Overall, these data suggest that anti-GFRA1-vcMMAE ADC may provide a targeted therapeutic opportunity for luminal A breast cancer patients. Mol Cancer Ther; 17(3); 638-49. ©2017 AACR.

Harnessing a catalytic lysine residue for the one-step preparation of homogeneous antibody-drug conjugates

Current strategies to produce homogeneous antibody-drug conjugates (ADCs) rely on mutations or inefficient conjugation chemistries. Here we present a strategy to produce site-specific ADCs using a highly reactive natural buried lysine embedded in a dual variable domain (DVD) format. This approach is mutation free and drug conjugation proceeds rapidly at neutral pH in a single step without removing any charges. The conjugation chemistry is highly robust, enabling the use of crude DVD for ADC preparation. In addition, this strategy affords the ability to precisely monitor the efficiency of drug conjugation with a catalytic assay. ADCs targeting HER2 were prepared and demonstrated to be highly potent and specific in vitro and in vivo. Furthermore, the modular DVD platform was used to prepare potent and specific ADCs targeting CD138 and CD79B, two clinically established targets overexpressed in multiple myeloma and non-Hodgkin lymphoma, respectively.

Current strategies for producing antibody-drug conjugates often rely on inefficient conjugation chemistry or on generating mutations in the antibody sequence. Here the authors demonstrate a mutation-free, single-step conjugation platform utilizing a buried lysine residue.

Gene signature driving invasive mucinous adenocarcinoma of the lung

Though invasive mucinous adenocarcinoma of the lung (IMA) is pathologically distinctive, the molecular mechanism driving IMA is not well understood, which hampers efforts to identify therapeutic targets. Here, by analyzing gene expression profiles of human and mouse IMA, we identified a Mucinous Lung Tumor Signature of 143 genes, which was unexpectedly enriched in mucin-producing gastrointestinal, pancreatic, and breast cancers. The signature genes included transcription factors FOXA3, SPDEF, HNF4A, mucins MUC5AC, MUC5B, MUC3, and an inhibitory immune checkpoint VTCN1/B7-H4 (but not PD-L1/B7-H1). Importantly, induction of FOXA3 or SPDEF along with mutant KRAS in lung epithelium was sufficient to develop benign or malignant mucinous lung tumors, respectively, in transgenic mice. FOXA3 and SPDEF induced MUC5AC and MUC5B, while HNF4A induced MUC3 in human mucinous lung cancer cells harboring a KRAS mutation. ChIP-seq combined with CRISPR/Cas9 determined that upstream enhancer regions of the mucin genes MUC5AC and MUC5B, which were bound by SPDEF, were required for the expression of the mucin genes. Here, we report the molecular signature and gene regulatory network driving mucinous lung tumors.

Antineoplastic Agents. 604. The Path of Quinstatin Derivatives to Antibody Drug Conjugates

To further evaluate the exceptional cancer cell growth inhibition by the quinstatins, of which one of the series, quinstatin 8, approaches the exceptional cytotoxic activity of the parent dolastatin 10 (1), four of the quinstatins have been converted to desmethyl derivatives. Three of the four (4, 5, and 8 [7b-d]) were next bonded to the linker (8) employed in the synthesis of the very successful and structurally related anticancer drug Adcetris (3). Owing to these structural modifications, a next step could be taken by bonding to a monoclonal antibody, thereby producing an antibody drug conjugate (ADC) related to Adcetris structurally but with the possibility of a wider spectrum of activity and utility.

Analysis of B7-H4 expression in metastatic pleural adenocarcinoma and therapeutic potential of its antagonists

Background

The increasing incidence and poor outcome associated with malignant pleural effusion (MPE) requires finding an effective treatment for this disease. Inhibitory B7-H4 is expressed in many different human cancers but its role in malignant pleural tissue has yet to be established.

Methods

Here, patients with metastatic pleural adenocarcinoma (MPA) or with early-stage lung adenocarcinoma were clinically and statistically analyzed. Immunohistochemistry and confocal microscopy were used to determinate the expression of B7-H4 in the cancer cells. By using MPE model, we sought to a potential immunotherapy for MPE with anti-B7-H4 mAb.

Results

When compared to early-stage lung adenocarcinoma, MPA possessed higher level of nuclei membranous B7-H4 and lower cytoplasmic B7-H4 expression. Also, nuclei membranous B7-H4 expression was found to be positively correlated to Ki-67 expression, and indicated a possible poor prognosis of MPA. In mouse MPE model, intra-pleurally injection of anti-B7-H4 mAb effectively suppressed MPE formation.

Conclusions

Taken together, our data was in support of the significance of B7-H4 expression in MPA, which also suggest it warrants further exploration for potential immunotherapy of MPE.

B7-H4 overexpression is essential for early hepatocellular carcinoma progression and recurrence

B7-H4, another member of costimulatory molecule, has been shown to be overexpressed in multiple types of tumors, including hepatocellular carcinoma (HCC). However, the specific biological role of B7-H4 in HCC still needs to be further explored. In this study, we observed that B7-H4 was highly overexpressed in HCC tissues and cells, and its overexpression strongly correlated with patient's TNM stage, overall survival and early recurrence. Downregulation of B7-H4 significantly suppressed cell growth, invasion, and stemness of HCC by inducing apoptosis in the in vitro experiment. In addition, depletion of B7-H4 could help restore CD8⁺ T anti-tumor immunity by elevating the expression and secretion levels of CD107a, granzyme A, granzyme B, perforin and IFN-γ. In a xenografted mouse model of HCC, stable depletion of B7-H4 resulted in significantly smaller mean tumor volume and less mean tumor weight after 30 days of growth, compared to the control group. Together, our results provide insights into the diverse functions of B7-H4 involved in the pathogenesis, recurrence and anti-tumor immunity of HCC, indicating B7-H4 as a novel and effective approach for future treatment strategies that benefits anticancer therapy.

Potential targeting of B7-H4 for the treatment of cancer

Observations noting the presence of white blood cell infiltrates within tumors date back more than a century, however the cellular and molecular mechanisms regulating tumor immunity continue to be elucidated. The recent successful use of monoclonal antibodies to block immune regulatory pathways to enhance tumor-specific immune responses for the treatment of cancer has encouraged the identification of additional immune regulatory receptor/ligand pathways. Over the past several years, a growing body of data has identified B7-H4 (VTCN1/B7x/B7S1) as a potential therapeutic target for the treatment of cancer. The potential clinical significance of B7-H4 is supported by the high levels of B7-H4 expression found in numerous tumor tissues and correlation of the level of expression on tumor cells with adverse clinical and pathologic features, including tumor aggressiveness. The biological activity of B7-H4 has been associated with decreased inflammatory CD4⁺ T-cell responses and a correlation between B7-H4-expressing tumor-associated macrophages and FoxP3⁺ regulatory T cells (Tregs) within the tumor microenvironment. Since B7-H4 is expressed on tumor cells and tumor-associated macrophages in various cancer types, therapeutic blockade of B7-H4 could favorably alter the tumor microenvironment allowing for antigen-specific clearance tumor cells. The present review highlights the therapeutic potential of targeting B7-H4.

B7-H3 Expression in NSCLC and Its Association with B7-H4, PD-L1 and Tumor-Infiltrating Lymphocytes

Purpose: The immune checkpoint PD-1 and its receptor B7-H1 (PD-L1) are successful therapeutic targets in cancer but less is known about other B7 family members. Here, we determined the expression level of B7-H3 protein in non-small cell lung cancer (NSCLC) and evaluated its association with tumor-infiltrating lymphocytes (TIL), PD-L1, B7-H4, and major clinicopathologic characteristics is in 3 NSCLC cohorts.Experimental design: We used multiplexed automated quantitative immunofluorescence (QIF) to assess the levels of B7-H3, PD-L1, B7-H4, and TILs in 634 NSCLC cases with validated antibodies. Associations between the marker levels, major clinicopathologic variables and survival were analyzed.Results: Expression of B7-H3 protein was found in 80.4% (510/634) of the cases. High B7-H3 protein level (top 10 percentile) was associated with poor overall survival (P < 0.05). Elevated B7-H3 was consistently associated with smoking history across the 3 cohorts, but not with sex, age, clinical stage, and histology. Coexpression of B7-H3 and PD-L1 was found in 17.6% of the cases (112/634) and with B7-H4 in 10% (63/634). B7-H4 and PD-L1 were simultaneously detected only in 1.8% of NSCLCs (12/634). The expression of B7-H3 was not associated with the levels of CD3-, CD8-, and CD20-positive TILs.Conclusions: B7-H3 protein is expressed in the majority of NSCLCs and is associated with smoking history. High levels of B7-H3 protein have a negative prognostic impact in lung carcinomas. Coexpression of B7-H3 with PD-L1 and B7-H4 is relatively low, suggesting a nonredundant biological role of these targets. Clin Cancer Res; 23(17); 5202-9. ©2017 AACR.

Molecular Pathways: Evaluating the Potential for B7-H4 as an Immunoregulatory Target

With the clinical success of CTLA-4 and PD-1 blockade in treating malignancies, there is tremendous interest in finding new ways to augment antitumor responses by targeting other inhibitory molecules. In this review, we describe one such molecule. B7-H4, a member of the B7 family of immunoregulatory proteins, inhibits T cell proliferation and cytokine production through ligation of an unknown receptor expressed by activated T cells. Notably, B7-H4 protein expression is observed in a high proportion of patients' tumors across a wide variety of malignancies. This high expression by tumors in combination with its low or absent protein expression in normal tissues makes B7-H4 an attractive immunotherapeutic target. Preclinical investigation into B7-H4-specific chimeric antigen receptor (CAR) T cells, antibody-mediated blockade of B7-H4, and anti-B7-H4 drug conjugates has shown antitumor efficacy in mouse models. The first clinical trials have been completed to assess the safety and efficacy of a B7-H4 fusion protein in ameliorating rheumatoid arthritis. Clin Cancer Res; 23(12); 2934-41. ©2017 AACR.

An anti-CD3/anti-CLL-1 bispecific antibody for the treatment of acute myeloid leukemia

Acute myeloid leukemia (AML) is a major unmet medical need. Most patients have poor long-term survival, and treatment has not significantly changed in 40 years. Recently, bispecific antibodies that redirect the cytotoxic activity of effector T cells by binding to CD3, the signaling component of the T-cell receptor, and a tumor target have shown clinical activity. Notably, blinatumomab is approved to treat relapsed/refractory acute lymphoid leukemia. Here we describe the design, discovery, pharmacologic activity, pharmacokinetics, and safety of a CD3 T cell-dependent bispecific (TDB) full-length human IgG1 therapeutic antibody targeting CLL-1 that could potentially be used in humans to treat AML. CLL-1 is prevalent in AML and, unlike other targets such as CD33 and CD123, is not expressed on hematopoietic stem cells providing potential hematopoietic recovery. We selected a high-affinity monkey cross-reactive anti-CLL-1 arm and tested several anti-CD3 arms that varied in affinity, and determined that the high-affinity CD3 arms were up to 100-fold more potent in vitro. However, in mouse models, the efficacy differences were less pronounced, probably because of prolonged exposure to TDB found with lower-affinity CD3 TDBs. In monkeys, assessment of safety and target cell depletion by the high- and low-affinity TDBs revealed that only the low-affinity CD3/CLL1 TDB was well tolerated and able to deplete target cells. Our data suggest that an appropriately engineered CLL-1 TDB could be effective in the treatment of AML.

Tumor Regression and Delayed Onset Toxicity Following B7-H4 CAR T Cell Therapy

B7-H4 protein is frequently overexpressed in ovarian cancer. Here, we engineered T cells with novel B7-H4-specific chimeric antigen receptors (CARs) that recognized both human and murine B7-H4 to test the hypothesis that B7-H4 CAR T cell therapy can be applied safely in preclinical models. B7-H4 CAR T cells specifically secreted IFN-γ and lysed B7-H4(+) targets. In vivo, B7-H4 CAR T cells displayed antitumor reactivity against B7-H4(+) human ovarian tumor xenografts. Unexpectedly, B7-H4 CAR T cell treatment reproducibly showed delayed, lethal toxicity 6-8 weeks after therapy. Comprehensive assessment of murine B7-H4 protein distribution uncovered expression in ductal and mucosal epithelial cells in normal tissues. Postmortem analysis revealed the presence of widespread histologic lesions that correlated with B7-H4(+) expression, and were inconsistent with graft versus host disease. Lastly, expression patterns of B7-H4 protein in normal human tissue were comparable to distribution in mice, advancing our understanding of B7-H4. We conclude that B7-H4 CAR therapy mediates control of cancer outgrowth. However, long-term engraftment of B7-H4 CAR T cells mediates lethal, off-tumor toxicity that is likely due to wide expression of B7-H4 in healthy mouse organs. This model system provides a unique opportunity for preclinical evaluation of safety approaches that limit CAR-mediated toxicity after tumor destruction in vivo.

Differential Expression and Significance of PD-L1, IDO-1, and B7-H4 in Human Lung Cancer

PURPOSE

To determine the expression level, associations, and biological role of PD-L1, IDO-1, and B7-H4 in non-small cell lung cancer (NSCLC).

EXPERIMENTAL DESIGN

Using multiplexed quantitative immunofluorescence (QIF), we measured the levels of PD-L1, IDO-1, B7-H4, and different tumor-infiltrating lymphoycte (TIL) subsets in 552 stages I-IV lung carcinomas from two independent populations. Associations between the marker levels, TILs, and major clinicopathologic variables were determined. Validation of findings was performed using mRNA expression data from The Cancer Genome Atlas (TCGA) and in vitro stimulation of lung adenocarcinoma A549 cells with IFNγ and IL10.

RESULTS

PD-L1 was detected in 16.9% and 21.8% of cases in each population. IDO-1 was expressed in 42.6% and 49.8%; and B7-H4 in 12.8% and 22.6% of cases, respectively. Elevated PD-L1 and IDO-1 were consistently associated with prominent B- and T-cell infiltrates, but B7-H4 was not. Coexpression of the three protein markers was infrequent, and comparable results were seen in the lung cancer TCGA dataset. Levels of PD-L1 and IDO-1 (but not B7-H4) were increased by IFNγ stimulation in A549 cells. Treatment with IL10 upregulated B7-H4 but did not affect PD-L1 and IDO-1 levels.

CONCLUSIONS

PD-L1, IDO-1, and B7-H4 are differentially expressed in human lung carcinomas and show limited co-expression. While PD-L1 and IDO-1 are associated with increased TILs and IFNγ stimulation, B7-H4 is not. The preferential expression of discrete immune evasion pathways in lung cancer could participate in therapeutic resistance and support design of optimal clinical trials. Clin Cancer Res; 23(2); 370-8. ©2016 AACR.

Emerging therapeutic targets in metastatic progression: A focus on breast cancer

Metastasis is the underlying cause of death for the majority of breast cancer patients. Despite significant advances in recent years in basic research and clinical development, therapies that specifically target metastatic breast cancer remain inadequate, and represents the single greatest obstacle to reducing mortality of late-stage breast cancer. Recent efforts have leveraged genomic analysis of breast cancer and molecular dissection of tumor-stromal cross-talk to uncover a number of promising candidates for targeted treatment of metastatic breast cancer. Rational combinations of therapeutic agents targeting tumor-intrinsic properties and microenvironmental components provide a promising strategy to develop precision treatments with higher specificity and less toxicity. In this review, we discuss the emerging therapeutic targets in breast cancer metastasis, from tumor-intrinsic pathways to those that involve the host tissue components, including the immune system.

Immunotherapy for advanced melanoma: future directions

As calculated by the meta-analysis of Korn et al., the prognosis of metastatic melanoma in the pretarget and immunological therapy era was poor, with a median survival of 6.2 and a 1-year life expectancy of 25.5%. Nowadays, significant advances in melanoma treatment have been gained, and immunotherapy is one of the promising approaches to get to durable responses and survival improvement. The aim of the present review is to highlight the recent innovations in melanoma immunotherapy and to propose a critical perspective of the future directions of this enthralling oncology subspecialty.