Preparation and anti-cancer evaluation of promiximab-MMAE, an anti-CD56 antibody drug conjugate, in small cell lung cancer cell line xenograft models

Antibody-Drug Conjugates Containing Payloads from Marine Origin

Antibody-drug conjugates (ADCs) are an important class of therapeutics for the treatment of cancer. Structurally, an ADC comprises an antibody, which serves as the delivery system, a payload drug that is a potent cytotoxin that kills cancer cells, and a chemical linker that connects the payload with the antibody. Unlike conventional chemotherapy methods, an ADC couples the selective targeting and pharmacokinetic characteristics related to the antibody with the potent cytotoxicity of the payload. This results in high specificity and potency by reducing off-target toxicities in patients by limiting the exposure of healthy tissues to the cytotoxic drug. As a consequence of these outstanding features, significant research efforts have been devoted to the design, synthesis, and development of ADCs, and several ADCs have been approved for clinical use. The ADC field not only relies upon biology and biochemistry (antibody) but also upon organic chemistry (linker and payload). In the latter, total synthesis of natural and designed cytotoxic compounds, together with the development of novel synthetic strategies, have been key aspects of the consecution of clinical ADCs. In the case of payloads from marine origin, impressive structural architectures and biological properties are observed, thus making them prime targets for chemical synthesis and the development of ADCs. In this review, we explore the molecular and biological diversity of ADCs, with particular emphasis on those containing marine cytotoxic drugs as the payload.

Adcitmer® , a new CD56-targeting monomethyl auristatin E-conjugated antibody, is a potential therapeutic approach in Merkel cell carcinoma

BACKGROUND

Merkel cell carcinoma (MCC) is an aggressive skin cancer, whose tumour cells often express CD56. While immune checkpoint inhibitors constitute a major advance for treating patients with MCC with advanced disease, new therapeutic options are still urgently required.

OBJECTIVES

To produce and evaluate the therapeutic performance of a new antibody-drug conjugate (Adcitmer^® ) targeting CD56 in preclinical models of MCC.

METHODS

CD56 expression was evaluated in a MCC cohort (immunohistochemistry on a tissue microarray of 90 tumour samples) and MCC cell lines. Interaction of an unconjugated CD56-targeting antibody with CD56⁺ MCC cell lines was investigated by immunohistochemistry and imaging flow cytometry. Adcitmer^® product was generated by the bioconjugation of CD56-targeting antibody to a cytotoxic drug (monomethyl auristatin E) using the McSAF Inside^® bioconjugation process. The chemical properties and homogeneity of Adcitmer^® were characterized by hydrophobic interaction chromatography. Adcitmer^® cytotoxicity was evaluated in vitro and in an MCC xenograft mice model.

RESULTS

Similar to previous reports, CD56 was expressed by 66% of MCC tumours in our cohort, confirming its relevance as a therapeutic target. Specific binding and internalization of the unconjugated CD56-targeting antibody was validated in MCC cell lines. The high homogeneity of the newly generated Adcitmer^® was confirmed by hydrophobic interaction chromatography. The CD56-mediated cytotoxicity of Adcitmer^® was demonstrated in vitro in MCC cell lines. Moreover, Adcitmer^® significantly reduced tumour growth in a MCC mouse model.

CONCLUSIONS

Our study suggests that Adcitmer^® should be further assessed as a therapeutic option in patients with MCC, as an alternative therapy or combined with immune checkpoint inhibitors.

Duocarmycin-based antibody-drug conjugates as an emerging biotherapeutic entity for targeted cancer therapy: Pharmaceutical strategy and clinical progress

Duocarmycins are a class of DNA minor-groove-binding alkylating molecules. For the past decade, various duocarmycin analogues have been used as payloads in the development of antibody-drug conjugates (ADCs). Currently, more than 15 duocarmycin-based ADCs have been studied preclinically, and some of them such as SYD985 have been granted Fast-Track Designation status. Nevertheless, progress in duocarmycin-based ADCs also faces challenges, with setbacks including the termination of BMS-936561/MDX-1203. In this review, we discuss issues associated with the efficacy, pharmacokinetic profile, and toxicological activity of these biotherapeutics. Furthermore, we summarize the latest advances in duocarmycin-based ADCs that have different target specificities and linker chemistries. Evidence from preclinical and clinical studies has indicated that duocarmycin-based ADCs are promising biotherapeutics for oncological application in the future.

Cholesteryl-Conjugated Ribonuclease A Exhibits Enzyme Activity in Aqueous Solution and Resistance to Dimethyl Sulfoxide

Using bovine pancreatic ribonuclease A (RNase A) and cholesterol, we synthesized cholesteryl-conjugated ribonuclease A (CHRNase A) to evaluate the influence of a conjugated hydrophobic moiety on protein function. Nuclear magnetic resonance and matrix-assisted laser desorption/ionization time-of-flight spectrometry suggested that one cholesteryl group was conjugated to RNase A. Differential scanning calorimetry indicated that CHRNase A was denatured in the solid state but was folded in phosphate buffer (0.05 mol/L, pH 6.5). CHRNase A resembled RNase A in its secondary structure, but circular dichroism (CD) spectra revealed that the helical content of CHRNase A was decreased and the tertiary structure of CHRNase A differed from that of RNase A. Furthermore, fluorescence measurements, CD spectra, an 8-anilino-1-naphthalenesulfonic acid ammonium salt-based assay, and surface tension measurements suggested that cholesterol was conjugated to a tyrosine residue on the protein surface. The relative activity of CHRNase A to RNase A was 79 ± 7%, and the enzyme activity of CHRNase A by adding β-cyclodextrin (β-CyD) increased to 129 ± 7%. Therefore, we considered that the cholesteryl group interacted with substrate (cytidine 2'3'-cyclic monophosphate monosodium salt) to inhibit the enzyme reaction. Finally, the environment around tyrosine residues in CHRNase A in dimethyl sulfoxide was similar to that of native RNase A in phosphate buffer (0.05 mol/L, pH 6.5). These results suggest that cholesterol conjugation to RNase A altered RNase A functionality, including improvement of RNase A resistance to dimethyl sulfoxide and modulation of the ability of β-CyD to control RNase A enzymatic activity.

Isolation and preliminary characterization of a human 'phage display'-derived antibody against neural adhesion molecule-1 antigen interfering with fibroblast growth factor receptor-1 binding

BACKGROUND

The NCAM or CD56 antigen is a cell surface glycoprotein belonging to the immunoglobulin super-family involved in cell-cell and cell-matrix adhesion. NCAM is also over-expressed in many tumour types and is considered a tumour associated antigen, even if its role and biological mechanisms implicated in tumour progression and metastasis have not yet to be elucidated. In particular, it is quite well documented the role of the interaction between the NCAM protein and the fibroblast growth factor receptor-1 in metastasis and invasion, especially in the ovarian cancer progression.

OBJECTIVE

Here we describe the isolation and preliminary characterization of a novel human anti-NCAM single chain Fragment variable antibody able to specifically bind NCAM-expressing cells, including epithelial ovarian cancer cells.

METHODS

The antibody was isolate by phage display selection and was characterized by ELISA, FACS analysis and SPR experiments. Interference in EOC migration was analyzed by scratch test.

RESULTS

It binds a partially linear epitope lying in the membrane proximal region of two fibronectin-like domains with a dissociation constant of 3.43 × 10-8 M. Interestingly, it was shown to interfere with the NCAM-FGFR1 binding and to partially decrease migration of EOC cells.

CONCLUSIONS

According to our knowledge, this is the first completely human antibody able to interfere with this newly individuated cancer mechanism.

Cell Adhesion Molecules in Plasticity and Metastasis

Prior to metastasis, modern therapeutics and surgical intervention can provide a favorable long-term survival for patients diagnosed with many types of cancers. However, prognosis is poor for patients with metastasized disease. Melanoma is the deadliest form of skin cancer, yet in situ and localized, thin melanomas can be biopsied with little to no postsurgical follow-up. However, patients with metastatic melanoma require significant clinical involvement and have a 5-year survival of only 34% to 52%, largely dependent on the site of colonization. Melanoma metastasis is a multi-step process requiring dynamic changes in cell surface proteins regulating adhesiveness to the extracellular matrix (ECM), stroma, and other cancer cells in varied tumor microenvironments. Here we will highlight recent literature to underscore how cell adhesion molecules (CAM) contribute to melanoma disease progression and metastasis.

Opportunities and obstacles of targeted therapy and immunotherapy in small cell lung cancer

Small cell lung cancer (SCLC) is an aggressive malignant tumour which accounts for approximately 13-15% of all newly diagnosed lung cancer cases. To date, platinum-based chemotherapy are still the first-line treatments for SCLC. However, chemotherapy resistance and systemic toxicity limit the long-term clinical outcome of first-line treatment in SCLC. Recent years, targeted therapy and immunotherapy have made great breakthrough in cancer therapy, and researchers aim to exploit both as a single agent or in combination with chemotherapy to improve the survival of SCLC patients, but limited effectiveness and the adverse events remain the major obstacles in the treatment of SCLC. To overcome these challenges for SCLC therapies, prevention and early diagnosis for this refractory disease is very important. At the same time, we should reveal more information about the pathogenesis of SCLC and the mechanism of drug resistance. Finally, new treatment strategies should also be taken into considerations, such as repurposing drug, optimising of targets, combination therapy strategies or prognostic biomarkers to enhance therapeutic effects and decrease the adverse events rates in SCLC patients. This article will review the molecular biology characteristics of SCLC and discuss the opportunities and obstacles of the current therapy for SCLC patients.

Pre-clinical models of small cell lung cancer and the validation of therapeutic targets

Introduction: Small-cell lung cancer (SCLC) is an aggressive form of lung cancer that has a dismal prognosis. One of the factors hindering therapeutic developments for SCLC is that most SCLC is not surgically resected resulting in a paucity of material for analysis. To address this, significant efforts have been made by investigators to develop pre-clinical models of SCLC allowing for downstream target identification in this difficult to treat cancer.Areas covered: In this review, we describe the current pre-clinical models that have been developed to interrogate SCLC, and outline the benefits and limitations associated with each. Using examples we show how each has been used to (i) improve our knowledge of this intractable cancer, and (ii) identify and validate potential therapeutic targets that (iii) are currently under development and testing within the clinic.Expert opinion: The large numbers of preclinical models that have been developed have dramatically improved the ways in which we can examine SCLC and test therapeutic targets/interventions. The newer models are rapidly providing novel avenues for the design and testing of new therapeutics. Despite this many of these models have inherent flaws that limit the possibility of their use for individualized therapy decision-making for SCLC.

A growth model of neuroendocrine tumor surrogates and the efficacy of a novel somatostatin-receptor-guided antibody-drug conjugate: Perspectives on clinical response?

BACKGROUND

As patient-derived xenografts and other preclinical models of neuroendocrine tumors for testing personalized therapeutics are lacking, we have developed a perfused, 3D bioreactor model to culture tumor surrogates from patient-derived neuroendocrine tumors. This work evaluates the duration of surrogate culture and surrogate response to a novel antibody-drug conjugate.

METHODS

Twenty-seven patient-derived neuroendocrine tumors were cultured. Histologic sections of a pancreatic neuroendocrine tumor xenograft (BON-1) tumor were assessed for SSTR2 expression before tumor implantation into 2 bioreactors. One surrogate was treated with an antibody-drug conjugate composed of an anti-mitotic Monomethyl auristatin-E linked to a somatostatin receptor 2 antibody. Viability and therapeutic response were assessed by pre-imaging incubation with IR-783 and the RealTime-Glo AnnexinV Apoptosis and Necrosis Assay (Promega Corporation, Madison, WI) over 6 days. A primary human pancreatic neuroendocrine tumor was evaluated similarly.

RESULTS

Mean surrogate growth duration was 34.8 days. Treated BON-1 surrogates exhibited less proliferation (1.2 vs 1.9-fold) and greater apoptosis (1.5 vs 1.1-fold) than controls, whereas treated patient-derived neuroendocrine tumor bioreactors exhibited greater degrees of apoptosis (13- vs 9-fold) and necrosis (2.5- vs 1.6-fold).

CONCLUSION

Patient-derived neuroendocrine tumor surrogates can be cultured reliably within the bioreactor. This model can be used to evaluate the efficacy of antibody-guided chemotherapy ex vivo and may be useful for predicting clinical responses.

Expression of SUMO1P3 Compared with SUMO1 is an Independent Predictor of Patient Outcome in Lung Adenocarcinoma

Background

The small ubiquitin-like modifier 1 (SUMO1) and small ubiquitin-like modifier 1 pseudogene 3 (SUMO1P3) are long noncoding RNAs (lncRNAs). The prognostic significance of SUMO1 and SUMO1P3 expression in non-small cell lung cancer (NSCLC) remains unclear. This study aimed to use clinical, genetic, and survival data from the Cancer Genome Atlas (TCGA), to analyze the prognostic significance of SUMO1 and SUMO1P3 expression in the two main subtypes of NSCLC, lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC).

Material/Methods

Data were acquired from TCGA and in silico survival analysis was performed. SUMO1 and SUMO1P3 expression were compared between patients with LUAD and LUSC. Patient outcome was assessed as complete remission (CR), partial remission (PR), stable disease (SD), and progressive disease (PD). Recurrence-free survival (RFS) was defined as the survival time from primary surgery to the time of locoregional or distant recurrence of lung cancer.

Results

SUMO1P3 was significantly increased in LUSC and LUAD tissues compared with adjacent normal lung tissue and was significantly co-expressed with SUMO1. SUMO1P3 expression was significantly increased in patients with LUAD but not LUSC with reduced RFS after primary or follow-up treatment. Although patients with LUAD who had high SUMO1 or SUMO1P3 expression had reduced RFS compared with low expression groups, univariate and multivariate analysis showed that only SUMO1P3 expression was independently associated reduced RFS (HR, 1.418; 95% CI, 1.041–1.930; p=0.027).

Conclusions

SUMO1P3 expression was an independent indicator of reduced RFS in patients with LUAD.

Future Options of Molecular-Targeted Therapy in Small Cell Lung Cancer

Lung cancer is the leading cause of cancer-related deaths worldwide. With a focus on histology, there are two major subtypes: Non-small cell lung cancer (NSCLC) (the more frequent subtype), and small cell lung cancer (SCLC) (the more aggressive one). Even though SCLC, in general, is a chemosensitive malignancy, relapses following induction therapy are frequent. The standard of care treatment of SCLC consists of platinum-based chemotherapy in combination with etoposide that is subsequently enhanced by PD-L1-inhibiting atezolizumab in the extensive-stage disease, as the addition of immune-checkpoint inhibition yielded improved overall survival. Although there are promising molecular pathways with potential therapeutic impacts, targeted therapies are still not an integral part of routine treatment. Against this background, we evaluated current literature for potential new molecular candidates such as surface markers (e.g., DLL3, TROP-2 or CD56), apoptotic factors (e.g., BCL-2, BET), genetic alterations (e.g., CREBBP, NOTCH or PTEN) or vascular markers (e.g., VEGF, FGFR1 or CD13). Apart from these factors, the application of so-called 'poly-(ADP)-ribose polymerases' (PARP) inhibitors can influence tumor repair mechanisms and thus offer new perspectives for future treatment. Another promising therapeutic concept is the inhibition of 'enhancer of zeste homolog 2' (EZH2) in the loss of function of tumor suppressors or amplification of (proto-) oncogenes. Considering the poor prognosis of SCLC patients, new molecular pathways require further investigation to augment our therapeutic armamentarium in the future.