Antibody-Drug Conjugate Efficacy in Neuroblastoma: Role of Payload, Resistance Mechanisms, Target Density, and Antibody Internalization

Update of antibody-drug conjugates for hematological malignancies

PURPOSE OF REVIEW

Antibody-drug conjugates (ADCs), consisting of monoclonal antibodies (mAbs) covalently linked to cytotoxic drugs via chemical linkers, are a kind of promising tumor immunotherapy. ADCs also face a number of challenges, including unavoidable adverse effects, drug resistance, tumor targeting and payload release. To address these issues, in addition to optimizing the individual components of ADCs, such as new payloads, linkage sites and new targets, and using bispecific antibodies to increase precision, attention should be paid to optimizing the dosage of ADCs.

RECENT FINDINGS

There are currently 7 ADCs approved for marketing by the Food and Drug Administration (FDA) for hematological malignancies, and dozens of other ADCs are either in clinical trials or in the process of applying for marketing. In recent clinical studies targeting ADCs in hematologic malignancies, in addition to validating effectiveness in different indications, researchers have attempted to combine ADCs with other chemotherapeutic agents in anticipation of increased therapeutic efficacy. Furthermore, the availability of bispecific antibodies may increase the safety and efficacy of ADCs.

SUMMARY

This review summarized the progress of research on ADCs in hematological malignancies, the challenges being faced, and possible future directions to improve the efficacy of ADCs, which can provide novel insight into the future exploration of ADCs in the treatment of hematological malignancies.

Research progress on novel antibody drug conjugates in cancer therapy

Traditional antibody drug conjugates (ADC) combine monoclonal antibodies with cytotoxic drugs to accurately strike cancer cells, but there are still many shortcomings in stability, targeting, efficacy, and safety. Novel ADC, such as bi-specific, site-specific, dual-payload, and pro-drug type ADC, can be optimized by simultaneously binding 2 different antigens or epitopes, selecting more stable linkers, coupling with specific amino acid sites of antibodies, carrying different drug payloads, and adopting prodrug strategies, while retaining the characteristics of traditional ADC. Significantly improving the stability, targeting, efficacy and safety of drugs can better meet the needs of clinical treatment. Novel ADC will play a more important role in cancer treatment in the future. Discussing the progress of novel ADC in cancer treatment and analyzing their advantages and challenges can provide theoretical support for the development of anti-cancer strategies and provide directions for drug research and development.

New insights into the anticancer therapeutic potential of maytansine and its derivatives

Maytansine is a pharmacologically active 19-membered ansamacrolide derived from various medicinal plants and microorganisms. Among the most studied pharmacological activities of maytansine over the past few decades are anticancer and anti-bacterial effects. The anticancer mechanism of action is primarily mediated through interaction with the tubulin thereby inhibiting the assembly of microtubules. This ultimately leads to decreased stability of microtubule dynamics and cause cell cycle arrest, resulting in apoptosis. Despite its potent pharmacological effects, the therapeutic applications of maytansine in clinical medicine are quite limited due to its non-selective cytotoxicity. To overcome these limitations, several derivatives have been designed and developed mostly by modifying the parent structural skeleton of maytansine. These structural derivatives exhibit improved pharmacological activities as compared to maytansine. The present review provides a valuable insight into maytansine and its synthetic derivatives as anticancer agents.

Chimeric antigen receptor-T cells are effective against CEACAM5 expressing non-small cell lung cancer cells resistant to antibody-drug conjugates

Chimeric antigen receptor-T (CAR-T) cells and antibody-drug conjugates (ADCs) are promising therapeutic strategies in oncology. The carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5) is overexpressed in tumors including non-small cell lung cancer (NSCLC) and pancreatic ductal adenocarcinoma (PDAC), and is an attractive target for therapies based on CAR-T cell or/and ADCs. We previously developed a highly specific antibody-based CAR-T cells targeting CEACAM5 and the tumoricidal effect of CAR-T cells was proved against neuro-endocrine prostate cancer (NEPC) cells expressing CEACAM5. Here, we compare the anti-tumor efficacy of our CAR-T cells with that of an anti-CEACAM5 ADC being clinically evaluated against NSCLC. Our anti-CEACAM5 CAR-T cells showed cytotoxicity in a CEACAM5 surface concentration dependent manner and reduced tumor growth in both ADC-responsive and -non-responsive CEACAM5-expressing NSCLC cells in vitro and in vivo. In contrast, the ADC exhibited cytotoxicity independent on the CEACAM5 cell surface concentration. Even though clinical translation of CEACAM5 targeting CAR-T cell therapies is still in preclinical stage, our CAR-T cell approach could provide a potential therapeutic strategy for CEACAM5-positive cancer patients with resistance to ADCs.

GPC2 antibody-drug conjugate reprograms the neuroblastoma immune milieu to enhance macrophage-driven therapies

BACKGROUND

Antibody-drug conjugates (ADCs) that deliver cytotoxic drugs to tumor cells have emerged as an effective and safe anticancer therapy. ADCs may induce immunogenic cell death (ICD) to promote additional endogenous antitumor immune responses. Here, we characterized the immunomodulatory properties of D3-GPC2-PBD, a pyrrolobenzodiazepine (PBD) dimer-bearing ADC that targets glypican 2 (GPC2), a cell surface oncoprotein highly differentially expressed in neuroblastoma.

METHODS

ADC-mediated induction of ICD was studied in GPC2-expressing murine neuroblastomas in vitro and in vivo. ADC reprogramming of the neuroblastoma tumor microenvironment was profiled by RNA sequencing, cytokine arrays, cytometry by time of flight and flow cytometry. ADC efficacy was tested in combination with macrophage-driven immunoregulators in neuroblastoma syngeneic allografts and human patient-derived xenografts.

RESULTS

The D3-GPC2-PBD ADC induced biomarkers of ICD, including neuroblastoma cell membrane translocation of calreticulin and heat shock proteins (HSP70/90) and release of high-mobility group box 1 and ATP. Vaccination of immunocompetent mice with ADC-treated murine neuroblastoma cells promoted T cell-mediated immune responses that protected animals against tumor rechallenge. ADC treatment also reprogrammed the tumor immune microenvironment to a proinflammatory state in these syngeneic neuroblastoma models, with increased tumor trafficking of activated macrophages and T cells. In turn, macrophage or T-cell inhibition impaired ADC efficacy in vivo, which was alternatively enhanced by both CD40 agonist and CD47 antagonist antibodies. In human neuroblastomas, the D3-GPC2-PBD ADC also induced ICD and promoted tumor phagocytosis by macrophages, which was further enhanced when blocking CD47 signaling in vitro and in vivo.

CONCLUSIONS

We elucidated the immunoregulatory properties of a GPC2-targeted ADC and showed robust efficacy of combination immunotherapies in diverse neuroblastoma preclinical models.

All-trans retinoic acid works synergistically with the γ-secretase inhibitor crenigacestat to augment BCMA on multiple myeloma and the efficacy of BCMA-CAR T cells

B-cell maturation antigen (BCMA) is the lead antigen for chimeric antigen receptor (CAR) T-cell therapy in multiple myeloma (MM). A challenge is inter- and intra-patient heterogeneity in BCMA expression on MM cells and BCMA downmodulation under therapeutic pressure. Accordingly, there is a desire to augment and sustain BCMA expression on MM cells in patients that receive BCMA-CAR T-cell therapy. We used all-trans retinoic acid (ATRA) to augment BCMA expression on MM cells and to increase the efficacy of BCMA-CAR T cells in pre-clinical models. We show that ATRA treatment leads to an increase in BCMA transcripts by quantitative reverse transcription polymerase chain reaction and an increase in BCMA protein expression by flow cytometry in MM cell lines and primary MM cells. Analyses with super-resolution microscopy confirmed increased BCMA protein expression and revealed an even distribution of non-clustered BCMA molecules on the MM cell membrane after ATRA treatment. The enhanced BCMA expression on MM cells after ATRA treatment led to enhanced cytolysis, cytokine secretion and proliferation of BCMA-CAR T cells in vitro, and increased efficacy of BCMA-CAR T-cell therapy in a murine xenograft model of MM in vivo (NSG/MM.1S). Combination treatment of MM cells with ATRA and the γ- secretase inhibitor crenigacestat further enhanced BCMA expression and the efficacy of BCMA-CAR T-cell therapy in vitro and in vivo. Taken together, the data show that ATRA treatment leads to enhanced BCMA expression on MM cells and consecutively, enhanced reactivity of BCMA-CAR T cells. The data support the clinical evaluation of ATRA in combination with BCMA-CAR T-cell therapy and potentially, other BCMA-directed immunotherapies.

Therapeutic efficacy of antibody-drug conjugates targeting GD2-positive tumors

BACKGROUND

Both ganglioside GD2-targeted immunotherapy and antibody-drug conjugates (ADCs) have demonstrated clinical success as solid tumor therapies in recent years, yet no research has been carried out to develop anti-GD2 ADCs against solid tumors. This is the first study to analyze cytotoxic activity of clinically relevant anti-GD2 ADCs in a wide panel of cell lines with varying GD2 expression and their effects in mouse models of GD2-positive solid cancer.

METHODS

Anti-GD2 ADCs were generated based on the GD2-specific antibody ch14.18 approved for the treatment of neuroblastoma and commonly used drugs monomethyl auristatin E (MMAE) or F (MMAF), conjugated via a cleavable linker by thiol-maleimide chemistry. The antibody was produced in a mammalian expression system, and its specific binding to GD2 was analyzed. Antigen-binding properties and biodistribution of the ADCs in mice were studied in comparison with the parent antibody. Cytotoxic effects of the ADCs were evaluated in a wide panel of GD2-positive and GD2-negative tumor cell lines of neuroblastoma, glioma, sarcoma, melanoma, and breast cancer. Their antitumor effects were studied in the B78-D14 melanoma and EL-4 lymphoma syngeneic mouse models.

RESULTS

The ch14.18-MMAE and ch14.18-MMAF ADCs retained antigen-binding properties of the parent antibody. Direct dependence of the cytotoxic effect on the level of GD2 expression was observed in cell lines of different origin for both ADCs, with IC50 below 1 nM for the cells with high GD2 expression and no cytotoxic effect for GD2-negative cells. Within the analyzed cell lines, ch14.18-MMAF was more effective in the cells overexpressing GD2, while ch14.18-MMAE had more prominent activity in the cells expressing low GD2 levels. The ADCs had a similar biodistribution profile in the B78-D14 melanoma model compared with the parent antibody, reaching 7.7% ID/g in the tumor at 48 hours postinjection. The average tumor size in groups treated with ch14.18-MMAE or ch14.18-MMAF was 2.6 times and 3.8 times smaller, respectively, compared with the control group. Antitumor effects of the anti-GD2 ADCs were also confirmed in the EL-4 lymphoma model.

CONCLUSION

These findings validate the potential of ADCs targeting ganglioside GD2 in treating multiple GD2-expressing solid tumors.

Antibody drug conjugate: the "biological missile" for targeted cancer therapy

Antibody-drug conjugate (ADC) is typically composed of a monoclonal antibody (mAbs) covalently attached to a cytotoxic drug via a chemical linker. It combines both the advantages of highly specific targeting ability and highly potent killing effect to achieve accurate and efficient elimination of cancer cells, which has become one of the hotspots for the research and development of anticancer drugs. Since the first ADC, Mylotarg® (gemtuzumab ozogamicin), was approved in 2000 by the US Food and Drug Administration (FDA), there have been 14 ADCs received market approval so far worldwide. Moreover, over 100 ADC candidates have been investigated in clinical stages at present. This kind of new anti-cancer drugs, known as "biological missiles", is leading a new era of targeted cancer therapy. Herein, we conducted a review of the history and general mechanism of action of ADCs, and then briefly discussed the molecular aspects of key components of ADCs and the mechanisms by which these key factors influence the activities of ADCs. Moreover, we also reviewed the approved ADCs and other promising candidates in phase-3 clinical trials and discuss the current challenges and future perspectives for the development of next generations, which provide insights for the research and development of novel cancer therapeutics using ADCs.

A NanoBiT assay to monitor membrane proteins trafficking for drug discovery and drug development

Internalization of membrane proteins plays a key role in many physiological functions; however, highly sensitive and versatile technologies are lacking to study such processes in real-time living systems. Here we describe an assay based on bioluminescence able to quantify membrane receptor trafficking for a wide variety of internalization mechanisms such as GPCR internalization/recycling, antibody-mediated internalization, and SARS-CoV2 viral infection. This study represents an alternative drug discovery tool to accelerate the drug development for a wide range of physiological processes, such as cancer, neurological, cardiopulmonary, metabolic, and infectious diseases including COVID-19.

Membrane protein trafficking is monitored using split nanoluciferase. Receptor internalization leads to complementation on the early endosome and a bioluminescent response, and is applied to receptor internalization/recycling, antibody-mediated internalization and SARS-CoV2 entry.

GPC2 Is a Potential Diagnostic, Immunological, and Prognostic Biomarker in Pan-Cancer

Background

Glypican 2 (GPC2), a member of glypican (GPC) family genes, produces proteoglycan with a glycosylphosphatidylinositol anchor. It has shown its ascending significance in multiple cancers such as neuroblastoma, malignant brain tumor, and small-cell lung cancer. However, no systematic pan-cancer analysis has been conducted to explore its function in diagnosis, prognosis, and immunological prediction.

Methods

By comprehensive use of datasets from The Cancer Genome Atlas (TCGA), Cancer Cell Line Encyclopedia (CCLE), Genotype-Tissue Expression Project (GTEx), cBioPortal, Human Protein Atlas (HPA), UALCAN, StarBase, and Comparative Toxicogenomics Database (CTD), we adopted bioinformatics methods to excavate the potential carcinogenesis of GPC2, including dissecting the correlation between GPC2 and prognosis, gene mutation, immune cell infiltration, and DNA methylation of different tumors, and constructed the competing endogenous RNA (ceRNA) networks of GPC2 as well as explored the interaction of GPC2 with chemicals and genes.

Results

The results indicated that GPC2 was highly expressed in most cancers, except in pancreatic adenocarcinoma, which presented at a quite low level. Furthermore, GPC2 showed the early diagnostic value in 16 kinds of tumors and was positively or negatively associated with the prognosis of different tumors. It also verified that GPC2 was a gene associated with most immune-infiltrating cells in pan-cancer, especially in thymoma. Moreover, the correlation with GPC2 expression varied depending on the type of immune-related genes. Additionally, GPC2 gene expression has a correlation with DNA methylation in 20 types of cancers.

Conclusion

Through pan-cancer analysis, we discovered and verified that GPC2 might be useful in cancer detection for the first time. The expression level of GPC2 in a variety of tumors is significantly different from that of normal tissues. In addition, the performance of GPC2 in tumorigenesis and tumor immunity also confirms our conjecture. At the same time, it has high specificity and sensitivity in the detection of cancers. Therefore, GPC2 can be used as an auxiliary indicator for early tumor diagnosis and a prognostic marker for many types of tumors.