Structure and conformational variability of the HER2-trastuzumab-pertuzumab complex.

Single particle analysis from cryogenic transmission electron microscopy (cryo-EM) is particularly attractive for complexes for which structure prediction remains intractable, such as antibody-antigen complexes. Here we obtain the detailed structure of a particularly difficult complex between human epidermal growth factor receptor 2 (HER2) and the antigen-binding fragments from two distinct therapeutic antibodies binding to distant parts of the flexible HER2, pertuzumab and trastuzumab (HTP). We highlight the strengths and limitations of current data processing software in dealing with various kinds of heterogeneities, particularly continuous conformational heterogeneity, and in describing the motions that can be extracted from our dataset. Our HTP structure provides a more detailed view than the one previously available for this ternary complex. This allowed us to pinpoint a previously overlooked loop in domain IV that may be involved both in binding of trastuzumab and in HER2 dimerization. This finding may contribute to explain the synergistic anticancer effect of the two antibodies. We further propose that the flexibility of the HTP complex, beyond the difficulties it causes for cryo-EM analysis, actually reflects regulation of HER2 signaling and its inhibition by therapeutic antibodies. Notably we obtain our best data with ultra-thin continuous carbon grids, showing that with current cameras their use to alleviate particle misdistribution is compatible with a protein complex of only 162 kDa. Perhaps most importantly, we provide here a dataset for such a smallish protein complex for further development of software accounting for continuous conformational heterogeneity in cryo-EM images.

Comparison of Tumor Non-specific and PD-L1 Specific Imaging by Near-Infrared Fluorescence/Cerenkov Luminescence Dual-Modality In-situ Imaging.

Background: Labeled antibodies are excellent imaging agents in oncology to non-invasively visualize cancer-related antigens expression levels. However, tumor tracer uptake (TTU) of specific antibodies in-vivo may be inferior to non-specific IgG in some cases. Objectives: To explore factors affecting labeled antibody visualization by PD-L1 specific and non-specific imaging of nude mouse tumors. Methods: TTU was observed in RKO model on Cerenkov luminescence (CL) and near-infrared fluorescence (NIRF) imaging of radionuclide 131I or NIRF dyes labeled Atezolizumab and IgG. A mixture of NIRF dyes labeled Atezolizumab and 131I-labeled IgG was injected, and TTU was observed in the RKO and HCT8 model by NIRF/CL dual-modality in-situ imaging. TTU were observed by 131I-labeled Atezolizumab and IgG in-vitro distribution. Results: Labeled IgG concentrated more in tumors than Atezolizumab. NIRF/CL imaging in 24 to 168 h showed that TTU gradually decreased over time, which decreased more slowly on CL imaging compared to NIRF imaging. The distribution data in-vitro showed that TTU of 131I-labeled IgG was higher than that of 131I-labeled Atezolizumab at any time point. Conclusion: Non-specific IgG may not be suitable as a control for Atezolizumab in comparing tumor PD-L1 expression in nude mice via labeled antibody optical imaging under certain circumstances.

Crystal structures of human CD40 in complex with monoclonal antibodies dacetuzumab and bleselumab.

CD40 is a member of the tumor necrosis factor receptor superfamily, and it is widely expressed on immune and non-immune cell types. The interaction between CD40 and the CD40 ligand (CD40L) plays an essential function in signaling, and the CD40/CD40L complex works as an immune checkpoint molecule. CD40 has become a therapeutic target, and a variety of agonistic/antagonistic anti-CD40 monoclonal antibodies (mAbs) have been developed. To better understand the mode of action of anti-CD40 mAbs, we determined the X-ray crystal structures of dacetuzumab (agonist) and bleselumab (antagonist) in complex with the extracellular domain of human CD40, respectively. The structure reveals that dacetuzumab binds to CD40 on the top of cysteine-rich domain 1 (CRD1), which is the domain most distant from the cell surface, and it does not compete with CD40L binding. The binding interface of bleselumab spread between CRD2 and CRD1, overlapping with the binding surface of the ligand. Our results offer important insights for future structural and functional studies of CD40 and provide clues to understanding the mechanism of biological response. These data can be applied to developing new strategies for designing antibodies with more therapeutic efficacy.

Design and synthesis of novel site-specific antibody-drug conjugates that target TROP2.

The approval of Trodelvy® validates TROP2 as a druggable but challenging target for antibody-drug conjugates (ADCs) to treat metastatic triple-negative breast cancer (mTNBC). Here, based on the TROP2-targeted antibody sacituzumab, we designed and developed several site-specific ADC candidates, which employ MMAE (monomethyl auristatin E) as the toxin, via IgG glycoengineering or affinity-directed traceless conjugation. Systematic evaluation of these site-specific ADCs in homogeneity, hydrophilicity, stability, and antitumor efficiency was conducted. The results indicate that the site-specific ADCs gsADC 3b made from one-step glycoengineering exhibit good aggregation stability and in vivo efficacy, providing a new format of ADCs that target TROP2.

Synthesis of chitosan polyethylene glycol antibody complex for delivery of Imatinib in lung cancer cell lines.

Lung cancer is known as the most common cancer. Although the Ramucirumab antibody is a second-line treatment for lung cancer, the high interstitial fluid pressure limits the antibody's performance. In this way, Imatinib is a chemotherapeutic drug to reduce the interstitial fluid pressure. Up to now, unfortunately, both Ramucirumab and imatinib have not been reported in one nanosystem for cancer therapy. To fulfill this shortcoming, this paper aims to design a chitosan nanocarrier that loads imatinib and attaches to Ramucirumab for selective bonding to A549. Therefore, this paper aims to develop a polymeric nanosystem for non-small cell lung cancer (NSCLC) treatment. In first, the chitosan polyethylene glycol nanoparticle is synthesized, loaded with imatinib, and then targeted using Ramucirumab. Afterwards, the CS-PEG-Ab-Im by FTIR, TEM, DLS, zeta potential, and TGA techniques are characterized. The size of CS-PEG-Ab-Im was 25-30 nm, its surface charge was 13.1 mV, and the shape of CS-PEG-Ab-Im was nearly spherical and cylindrical. The therapeutic potential of CS-PEG-Ab-Im was assessed using the A549 cell line. According to the obtained results, the cell viability was 48% after 48 h of treatment of A549 cells using the IC50 concentration of CS-PEG-Ab-Im (100 nanomolar). Moreover, the apoptosis and cell cycle arrest percentages were increased by 3 and 6 times, respectively, as compared to free imatinib. Furthermore, the release rate of imatinib from CS-PEG-Ab-Im in an acidic medium was 17% during 1 h, indicating five times the imatinib release in the natural medium. Eventually, the result of flow cytometry indicates the more apoptotic effect of nanosystem to free imatinib and CS-PEG-Ab. Besides, cell arresting result exhibits the CS-PEG-Ab-Im and causes cell arrested at G1 by %8.17. Thus, it can be concluded that CS-PEG-Ab-Im can be an ideal nanosystem in NSCLC treatment.

Development of time-resolved fluoroimmunoassay with enhanced fluorescence reaction for the quantitation of atezolizumab in plasma.

Atezolizumab (ATZ) is a human monoclonal antibody, which has been granted multiple approvals from the US Food and Drug Administration (FDA) for the immunotherapy of different types of cancer. This study describes the prototype of a time-resolved fluoroimmunoassay (TRFIA) for the quantitation of ATZ in plasma. The assay involved the non-competitive binding of ATZ to its specific antigen [programmed death-ligand 1 (PD-L1) protein]. The immune complex formed on the inner surface of the assay plate wells was quantified by anti-human secondary antibody labeled with a chelate of europium-ethylenediaminetetraacetic acid. The enhanced fluorescence signal was generated by an enhanced fluorescence solution composed of thenoyltrifluoroacetone, trioctylphosphine oxide, and Triton X-100. The conditions of the TRFIA were refined, and its optimum procedures were established. The assay was validated in accordance with the immunoassay validation guidelines, and all the validation parameters were acceptable. The working range of the assay was 20-1000 pg mL-1, and its limit of quantitation was 20 pg mL-1. The assay was applied to the quantitation of ATZ in plasma samples with satisfactory accuracy and precision. The proposed TRFIA has significant benefits over the existing methodologies for the quantitation of ATZ in clinical settings.

Application of newly developed and validated LC-MS/MS method for pharmacokinetic study of adagrasib and pembrolizumab simultaneously in rat plasma.

Non-small cell lung cancer (NSCLC) is a significant subtype of lung cancer, and poses a dangerous global threat. One of the current approaches of NSCLC treatment is a combination therapy of adagrasib and pembrolizumab. Accurate monitoring of these drug concentrations in biological fluids is critical for treatment efficacy. Since no method was reported for simultaneous estimation of these drugs, this study focuses on the development of a validated LC-MS/MS bioanalytical method for simultaneous quantification of Adagrasib and Pembrolizumab in rat plasma. The analytes were extracted from the biological matrix through liquid-liquid extraction techniques using acetonitrile as extraction solvent. The analytes were separated on a Waters X-bridge phenyl C18 column, with a mixture of acetonitrile: 0.1 % TFA in water (50: 50 v/v) as mobile phase at an isocratic flow rate of 1.0 mL/min with a runtime of about 5 min. Adagrasib (m/z 605.12 → 201.62), Pembrolizumab (m/z 146.32 → 85.15), and Sotorasib (m/z 561.59 → 218.92) were determined by recording the mass spectra through multiple reaction monitoring in positive mode. The method was validated according to USFDA guidelines. The results demonstrate satisfactory linearity with an r2 value of 0.9998 in the ranges of 40-800 and 10-200 ng/mL, accuracy with mean percentage recovery of 95.22-98.59 % and 96.98-98.57 %, precision indicated with %RSD ranged between 0.39-1.91 % and 0.85-9.03 % for Adagrasib and Pembrolizumab respectively, and other key parameters. The developed method can determine the pharmacokinetic parameters to indicate the efficacy and safety of the drugs, and also can quantify selected drugs simultaneously in biological samples.

Structural insights into the unique pH-responsive characteristics of the anti-TIGIT therapeutic antibody Ociperlimab.

TIGIT is mainly expressed on T cells and is an inhibitory checkpoint receptor that binds to its ligand PVR in the tumor microenvironment. Anti-TIGIT monoclonal antibodies (mAbs) such as Ociperlimab and Tiragolumab block the TIGIT-PVR interaction and are in clinical development. However, the molecular blockade mechanism of these mAbs remains elusive. Here, we report the crystal structures of TIGIT in complex with Ociperlimab_Fab and Tiragolumab_Fab revealing that both mAbs bind TIGIT with a large steric clash with PVR. Furthermore, several critical epitopic residues are identified. Interestingly, the binding affinity of Ociperlimab toward TIGIT increases approximately 17-fold when lowering the pH from 7.4 to 6.0. Our structure shows a strong electrostatic interaction between ASP103HCDR3 and HIS76TIGIT explaining the pH-responsive mechanism of Ociperlimab. In contrast, Tiragolumab does not show an acidic pH-dependent binding enhancement. Our results provide valuable information that could help to improve the efficacy of therapeutic antibodies for cancer treatment.

Demonstration of Physicochemical and Functional Similarity of the Biosimilar BAT1806/BIIB800 to Reference Tocilizumab.

BACKGROUND AND OBJECTIVE: Tocilizumab is an immunoglobulin G1 monoclonal antibody targeting the interleukin-6 receptor (IL-6R). BAT1806/BIIB800 (tocilizumab-bavi) has been developed as a biosimilar to the reference product tocilizumab (TCZ). The objective of this study was to demonstrate physicochemical and functional similarity between BAT1806/BIIB800 and TCZ in a comprehensive comparability exercise. METHODS: A comprehensive panel of over 20 methods was used to generate datasets comparing critical and non-critical product quality attributes for 10 BAT1806/BIIB800 lots and 44 TCZ lots (16 sourced from China, 16 from the EU, and 12 from the US). Primary structure, higher-order structure, and physicochemical properties were assessed using liquid chromatography, mass spectrometry, various spectroscopy techniques/methods, capillary electrophoresis, and thermoanalytical techniques. Fragment antigen-binding (Fab)- and fragment crystallizable (Fc)-mediated biological properties were assessed using cell-based assays, immunoassays, flow cytometry, and kinetic binding assays. RESULTS: BAT1806/BIIB800 and TCZ (irrespective of source) were shown to be similar in terms of structural and functional properties. No differences were observed in terms of the most critical quality attributes, that is, soluble-IL-6R binding and inhibition of IL-6-mediated cell proliferation. BAT1806/BIIB800 and TCZ demonstrated similarity in terms of Fab- and Fc-mediated binding and biological activity. Minor differences were observed in glycosylation (afucosylation and sialylation), glycation, aggregation, and charge variants, which were demonstrated to be not clinically relevant. CONCLUSION: BAT1806/BIIB800 and TCZ were highly similar for all critical quality attributes. Where differences were observed in less critical quality attributes, additional analytical assessments and clinical study results determined these to be not clinically meaningful.

Native ion mobility-mass spectrometry reveals the binding mechanisms of anti-amyloid therapeutic antibodies.

One of the most important attributes of anti-amyloid antibodies is their selective binding to oligomeric and amyloid aggregates. However, current methods of examining the binding specificities of anti-amyloid ß (Aß) antibodies have limited ability to differentiate between complexes that form between antibodies and monomeric or oligomeric Aß species during the dynamic Aß aggregation process. Here, we present a high-resolution native ion-mobility mass spectrometry (nIM-MS) method to investigate complexes formed between a variety of Aß oligomers and three Aß-specific IgGs, namely two antibodies with relatively high conformational specificity (aducanumab and A34) and one antibody with low conformational specificity (crenezumab). We found that crenezumab primarily binds Aß monomers, while aducanumab preferentially binds Aß monomers and dimers and A34 preferentially binds Aß dimers, trimers, and tetrameters. Through collision induced unfolding (CIU) analysis, our data indicate that antibody stability is increased upon Aß binding and, surprisingly, this stabilization involves the Fc region. Together, we conclude that nIM-MS and CIU enable the identification of Aß antibody binding stoichiometries and provide important details regarding antibody binding mechanisms.

Potent antitumor activity of anti-HER2 antibody-topoisomerase I inhibitor conjugate based on self-immolative dendritic dimeric-linker.

Antibody-drug conjugates (ADCs) are a rapidly expanding class of anticancer therapeutics, with 14 ADCs already approved worldwide. We developed unique linker technologies for the bioconjugation of drug molecules with controlled-release applications. We synthesized cathepsin-cleavable ADCs using a dimeric prodrug system based on a self-immolative dendritic scaffold, resulting in a high drug-antibody ratio (DAR) with the potential to reach 16 payloads due to its dendritic structure, increased stability in the circulation and efficient release profile of a highly cytotoxic payload at the targeted site. Using our novel cleavable linker technologies, we conjugated the anti-human epidermal growth factor receptor 2 (anti-HER2) antibody, trastuzumab, with topoisomerase I inhibitors, exatecan or belotecan. The newly synthesized ADCs were tested in vitro on mammary carcinoma cells overexpressing human HER2, demonstrating a substantial inhibitory effect on the proliferation of HER2-positive cells. Importantly, a single dose of our trastuzumab-based ADCs administered in vivo to mice bearing HER2-positive tumors, showed a dose-dependent inhibition of tumor growth and survival benefit, with the most potent antitumor effects observed at 10 mg/kg, which resulted in complete tumor regression and survival of 100% of the mice. Overall, our novel dendritic technologies using the protease-cleavable Val-Cit linker present an opportunity for the development of highly selective and potent controlled-released therapeutic payloads. This strategy could potentially lead to the development of novel and effective ADC technologies for patients diagnosed with HER2-positive cancers. Moreover, our proposed ADC linker technology can be implemented in additional medical conditions such as other malignancies as well as autoimmune diseases that overexpress targets, other than HER2.

Dissecting the stability of Atezolizumab with renewable amino acid-based ionic liquids: Colloidal stability and anticancer activity under thermal stress.

Monoclonal antibodies (mAbs) have revolutionised the biopharmaceutical market. Being proteinaceous, mAbs are prone to chemical and physical instabilities. Various approaches were attempted to stabilise proteins against degradation factors. Ionic liquids (ILs) and deep eutectic solvents (DESs) have been established as green solvents for ever-increasing pharmaceutical and biopharmaceutical applications. Hence, amino acid (AA)-based ILs, were used for the first time, for mAb stabilisation. Choline (Ch)-based DESs were also utilised for comparison purposes. The prepared ILs and DESs were utilised to stabilise Atezolizumab (Amab, anti-PDL-1 mAb). The formulations of Amab in ILs and DESs were incubated at room temperature, 45 or 55 °C. Following this, the structural stability of Amab was appraised. Interestingly, Ch-Valine retained favourable structural stability of Amab with minimal detected aggregation or degradation as confirmed by UV-visible spectroscopy and protein Mass Spectroscopy. The measured hydrodynamic diameter of Amab in Ch-Valine ranged from 10.40 to 11.65 nm. More interestingly, the anticancer activity of Amab was evaluated, and Ch-Valine was found to be optimum in retaining the activity of Amab when compared to other formulations, including the control Amab sample. Collectively, this study has spotlighted the advantages of adopting the Ch-AA ILs for the structural and functional stabilising of mAbs.

Structural basis for the recognition of IFNAR1 by the humanized therapeutic monoclonal antibody QX006N for the treatment of systemic lupus erythematosus.

Interferon (IFN) alpha/beta receptor 1 (IFNAR1) is indispensable for antiviral responses and the immune regulation. Dysregulation of the IFNAR1-mediaetd signaling pathways leads to deleterious autoimmune diseases such as systemic lupus erythematosus (SLE). QX006N, a humanized therapeutic monoclonal antibody, specifically targets human IFNAR1 and is in the clinical trial phase for treating SLE, but the molecular mechanism underlying the QX006N-mediated recognition of IFNAR1 remains unclear. Here, we report the high neutralization activities of QX006N against IFNAR1-mediated signal transduction. Meanwhile, we determine the structures of the fragment antigen-binding domain (Fab) of QX006N (QX006N-Fab) and QX006N-Fab in complex with the subdomains 1-3 of IFNAR1 (IFNAR1-SD123) at 2.87 Å and 2.68 Å resolutions, respectively. In the structure of the QX006N-Fab/IFNAR1-SD123 complex, QX006N-Fab only recognizes the SD3 subdomain of IFNAR1 by the hydrophobic, hydrogen-bonding and electrostatic interactions. Compared with the structure of the IFN/IFNAR1/IFNAR2 complex, the binding of QX006N-Fab to IFNAR1-SD3 blocks its association with IFN due to steric hindrance, which inhibits the IFN/IFNAR1/IFNAR2 complex formation for signal transduction. The results of this study provide the structural evidence for the specific targeting of IFNAR1 by the therapeutic antibody QX006N and pave the way for the rational design of antibody drugs to combat IFNAR1-related autoimmune diseases.

Prospective effect of linkers type on the anticancer activity of pemetrexed-monoclonal antibody (atezolizumab) conjugates.

Background: Conventional chemotherapy results in severe toxic side effects due to affecting normal and cancer cells. The conjugation of chemotherapy with mAb will improve the chemotherapy selectivity towards cancer cells and at the same time will potentiate immune system to detect and kill cancer cells. The aim of the study was to prepare atezolizumab-pemetrexed conjugate using two types of linkers (linker conjugated with -NH2 of lysine amino acid in the mAb). Methods: This study utilizes (for the first time) the mAb atezolizumab (AtZ) to prepare a new, selective conjugate carrier for pemetrexed (PMX) by using gamma amino butyric acid (GABA) as linker for the first time in comparison to the commonly used linker polyethylene glycol (PEG) using carbodiimide (EDC) / N-hydroxysulfosuccinimide (Sulfo-NHS) zero length cross linker. Stepwise evaluation for PMX-linkers linkage as well as mAb conjugates was evaluated by FTIR, 1HNMR, DSC, LC-MS, gel-electrophoresis as well as the anticancer activity against lung cells A549. Results: The work revealed that two molecules of GABA combined with PMX, which in turn conjugated with an average ratio of 4:1 with mAb, while one molecule of PEG combined with PMX, which in turn conjugated with mAb in the same average ratio. The IC 50 for the prepared PMX-GABA-AtZ conjugate was 0.048 µM, which was much lower than PMX alone, antibody AtZ alone as well as PMX-PEG-AtZ conjugate in a dose and time dependent manner. Conclusions: The potential use of such conjugate that selectively directed to the overexpressed lung cells antigen in a low dose leading to reduction of serious side effects of PMX and the cost of therapeutically AtZ mAb used.