mAb Conjugates Research Articles

Development of a colloidal gold immunochromatographic strip for rapid detection of avian coronavirus infectious bronchitis virus

Avian infectious bronchitis virus (IBV) still causes serious economic losses in the poultry industry. Currently, there are multiple prevalent genotypes and serotypes of IBVs. It is imperative to develop a new diagnosis method that is fast, sensitive, specific, simple, and broad-spectrum. A monoclonal hybridoma cell, N2D5, against the IBV N protein was obtained after fusion of myeloma SP2/0 cells with spleen cells isolated from the immunized Balb/c mice. The N2D5 monoclonal antibody (mAb) and the previously prepared mouse polyclonal antibody against the IBV N protein were used to target IBV as a colloidal gold–mAb conjugate and a captured antibody, respectively, in order to develop an immunochromatographic strip. The optimal pH and minimum antibody concentration in the reaction system for colloidal gold–mAb N2D5 conjugation were pH 6.5 and 30 μg/mL, respectively. Common avian pathogens were tested to evaluate the specificity of the strip and no cross-reaction was observed. The sensitivity of the strip for detecting IBV was 10−1.4522 EID50/mL. The strip showed a broad-spectrum cross-reactive capacity for detecting IBV antigens, including multiple IBV genotypes in China and all of the seven serotypes of IBV that are currently prevalent in southern China. Additionally, the result can be observed within 2 min without any equipment. The throat and cloacal swab samples of chickens that were artificially infected with three IBV strains were tested using the developed strip and the qPCR method; the strip test demonstrated a high consistency in detecting IBV via qPCR gene detection. In conclusion, the immunochromatographic strip that was established is rapid, sensitive, specific, simple, practical, and broad-spectrum; additionally, it has the potential to serve as an on-site rapid detection method of IBV and can facilitate the surveillance and control of the disease, especially in resource-limited areas.

Abstract 478: Targeted combination nano-drug delivery system to enhance anti-cancer efficacy and reduce side effects

Abstract Background: Colorectal cancer (CRC) is a global health concern, with significant morbidity and mortality. Oxaliplatin (OXL) is a common treatment for CRC but its effectiveness is hampered by side effects, including gastrointestinal and neurotoxic effects. APX3330 exerts anti-angiogenic and neuroprotective effects. It is proposed that the combined use of OXL and APX3330-loaded nanoparticles (NPs) would improve drug delivery to cancer cells with enhanced therapeutic efficacy while reducing side effects of OXL. Methods: We developed dual-loaded NPs containing OXL and APX3330 linked to a cancer targeting monoclonal antibody (NPs+mAb). We characterized the physicochemical properties of the NPs and evaluated their cytotoxicity and drug release using CRC cell lines. In vivo, we assessed their therapeutic efficiency and side effects using an orthotopic CRC mouse model. Results: NPs exhibited an average size of 229±26 nm with a zeta potential of -24.1±2.1 mV. The drug loading and encapsulation efficiency were 3.3±0.2% and 71.9%, respectively. Morphological analysis via scanning electron microscopy confirmed NP structure. In vitro drug release studies showed a slower release profile from NPs compared to free OXL, with a cumulative release of 34% (w/w) after 48 hours. Notably, cytotoxicity evaluation on CT-26 cells revealed a significant reduction in the IC50 for NPs compared to free APX3330 and OXL. In vivo studies demonstrated a remarkable 31% reduction in tumor growth rate in animals treated with NPs+mAb compared to those receiving free forms of OXL and APX3330. Body weight for animals treated with NPs+mAb remained similar to the healthy group, indicating minimal systemic toxicity. Moreover, the length of the colon in healthy organs remained steady compared to animals treated with OXL, which experienced a reduction in colon length. Animals treated with the free form of OXL exhibited diarrhoea, while the stool water content for animals treated with NPs+mAb remained at a similar level as the healthy group, suggesting reduced gastrointestinal side effects. Conclusions: This study demonstrates the potential of NPs with improved retention and encapsulation efficiency for effective drug delivery. Our research validates our novel method for creating NPs with mAb conjugation, enhancing cytotoxicity against CRC cell lines. In conclusion, the designed NPs+mAb formulation improves OXL treatment efficacy, providing targeted delivery of anti-cancer drugs to the tumor site and reducing tumor size while minimizing side effects. Citation Format: Niloufar Rashidi, Majid Davidson, Vasso Apostolopoulos, Mark R. Kelley, Kulmira Nurgali. Targeted combination nano-drug delivery system to enhance anti-cancer efficacy and reduce side effects [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 478.

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

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). 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. 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. 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.

Liquid Chromatography ICP-MS to Assess the Stability of 175Lu- and natGa-Based Tumor-Targeting Agents towards the Development of 177Lu- and 68Ga-Labeled Radiopharmaceuticals.

In recent years, nuclear medicine has gained great interest, partly due to the success story of [177Lu]Lu-PSMA-617 (PluvictoTM). Still, in-depth preclinical characterization of radiopharmaceuticals mainly happens at centers that allow working with radioactive material. To support the development of novel radiopharmaceuticals, alternative non-radioactive characterization assays are highly desirable. The aim of this study was to demonstrate that inductively coupled plasma mass spectrometry (ICP-MS) associated with a chromatographic system can serve as a surrogate for the classical high-performance liquid chromatography (HPLC)-radiodetector combination for preclinical in vitro characterization of non-radioactive metal-labeled analogs of radiopharmaceuticals. In this proof-of-concept study, we demonstrate the applicability of HPLC-ICP-MS by assessing the stability of 175Lu- and natGa-labeled prostate-specific membrane antigen (PSMA)-targeting peptidomimetics, single domain antibody (sdAb) conjugates, and monoclonal antibody (mAb) conjugates. 175Lu-labeled DOTAGA-conjugated and natGa-labeled NODAGA-conjugated sdAbs and mAbs showed the highest stability with >90% still intact after 24 h. The peptidomime-tics [175Lu]Lu-PSMA-617 and [natGa]Ga-PSMA-11 showed identical in vitro serum stability as it was reported for their corresponding radioligands with >99% intact species after 24 h incubation in mouse serum, demonstrating the reliability of the method. Hence, the established HPLC-ICP-MS methods can support the development of novel radiopharmaceuticals in a classical pharmaceutical setting.

A first-in-class dual-chelator theranostic agent designed for use with imaging-therapy radiometal pairs of different elements.

A covalent adduct of DFOB and DOTA separated by a l-lysine residue (DFOB-l-Lys-N 6-DOTA) exhibited remarkable regioselective metal binding, with {1H}-13C NMR spectral shifts supporting Zr(iv) coordinating to the DFOB unit, and Lu(iii) coordinating to the DOTA unit. This first-in-class, dual-chelator theranostic design could enable the use of imaging-therapy radiometal pairs of different elements, such as 89Zr for positron emission tomography (PET) imaging and 177Lu for low-energy β--particle radiation therapy. DFOB-l-Lys-N 6-DOTA was elaborated with an amine-terminated polyethylene glycol extender unit (PEG4) to give DFOB-N 2-(PEG4)-l-Lys-N 6-DOTA (compound D2) to enable installation of a phenyl-isothiocyanate group (Ph-NCS) for subsequent monoclonal antibody (mAb) conjugation (mAb = HuJ591). D2-mAb was radiolabeled with 89Zr or 177Lu to produce [89Zr]Zr-D2-mAb or [177Lu]Lu-D2-mAb, respectively, and in vivo PET/CT imaging and in vivo/ex vivo biodistribution properties measured with the matched controls [89Zr]Zr-DFOB-mAb or [177Lu]Lu-DOTA-mAb in a murine LNCaP prostate tumour xenograft model. The 89Zr-immuno-PET imaging function of [89Zr]Zr-D2-mAb and [89Zr]Zr-DFOB-mAb showed no significant difference in tumour accumulation at 48 or 120 h post injection. [89Zr]Zr-D2-mAb and [177Lu]Lu-D2-mAb showed similar ex vivo biodistribution properties at 120 h post-injection. Tumour uptake of [177Lu]Lu-D2-mAb shown by SPECT/CT imaging at 48 h and 120 h post-injection supported the therapeutic function of D2, which was corroborated by similar therapeutic efficacy between [177Lu]Lu-D2-mAb and [177Lu]Lu-DOTA-mAb, both showing a sustained reduction in tumour volume (>80% over 65 d) compared to vehicle. The work identifies D2 as a trifunctional chelator that could expand capabilities in mixed-element radiometal theranostics to improve dosimetry and the clinical outcomes of molecularly targeted radiation.

Integrated PK/PD Modeling Relates Smoothened Inhibitor Biomarkers to The Heterogeneous Intratumor Disposition of Cetuximab in Pancreatic Cancer Tumor Models

Therapeutic antibodies have shown little efficacy in the treatment of pancreatic ductal adenocarcinomas (PDAC). Tumor desmoplasia, hypovascularity, and poor perfusion result in insufficient tumor cell exposure, contributing to treatment failure. Smoothened inhibitors of hedgehog signaling (sHHi) increase PDAC tumor permeability, perfusion, and drug delivery, and provide a tool to develop a quantitative, mechanistic understanding as to how the temporal dynamics of tumor priming can impact intratumor distribution of monoclonal antibodies (mAb). A linked pharmacokinetic (PK)/pharmacodynamic (PD) model was developed to integrate the plasma and tumor PK of a sHHi priming agent with its effects upon downstream stromal biomarkers Gli1, hyaluronic acid, and interstitial fluid pressure in PDAC patient-derived xenograft (PDX) tumors. In parallel, in situ tumor concentrations of cetuximab (CTX: anti-epidermal growth factor receptor; EGFR) were quantified as a marker for tumor delivery of mAb or antibody-drug conjugates. A minimal, physiologically-based pharmacokinetic (mPBPK) model was constructed to link sHHi effects upon mechanistic effectors of tumor barrier compromise with the intratumor distribution of CTX, and CTX occupancy of EGFR in tumors. Integration of the mPBPK model of mAb deposition and intratumor distribution with the PK/PD model of tumor responses to priming not only identified physiological parameters that are critical for tumor antibody distribution, but also provides insight into dosing regimens that could achieve maximal tumor disposition of therapeutic antibodies under conditions of transient PDAC tumor permeability barrier compromise that mechanistically-diverse tumor priming strategies may achieve.

Development of a Novel CLDN18.2-directed Monoclonal Antibody and Antibody-Drug Conjugate for Treatment of CLDN18.2-Positive Cancers.

Gastric and pancreatic cancers are malignancies of high unmet clinical need. Expression of CLDN18.2 in these cancers, coupled with it's absence from most normal tissues, provides a potential therapeutic window against this target. We present preclinical development and characterization of a novel therapeutic mAb and antibody-drug conjugate (ADC) targeting CLDN18.2. A humanized CLDN18.2 specific mAb, CLDN18.2-307-mAb, was generated through immunization in mice followed by full humanization of the mouse mAb sequences. Antibody clones were screened by flow cytometry for selective binding to membrane bound CLDN18.2. A CLDN18.2-directed ADC (CLDN18.2-307-ADC) was also generated by conjugating MMAE to CLDN18.2 mAb using a cleavable linker. Tissue expression of CLDN18.2 was determined by IHC assay using a CLDN18.2-specific mAb. CLDN18.2-307-mAb binds with high affinity to CLDN18.2-positive (CLDN18.2+) cells and induces antibody-dependent cell-mediated cytotoxicity (ADCC). Treatment with this CLDN18.2-mAb blocked the growth of CLDN18.2+ gastric and pancreas cancer cell line xenograft (CDX) models. Upon binding to the extracellular domain of this target, the CLDN18.2-ADC/CLDN18.2 protein was internalized and subsequently localized to the lysosomal compartment inducing complete and sustained tumor regressions in CLDN18.2+ CDXs and patient-derived pancreatic cancer xenografts (PDX). A screen of human cancer tissues, by IHC, found 58% of gastric, 60% of gastroesophageal junction, and 20% of pancreatic adenocarcinomas to be positive for membrane expression of CLDN18.2. These data support clinical development of the CLDN18.2-307-mAb and CLDN18.2-307-ADC for treatment of CLDN18.2+ cancers. Both are now being investigated in phase I clinical studies.

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 IC50 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.

3H-3000, AN FGFR2B-SPECIFIC MONOCLONAL ANTIBODY, SHOWS SUPERIOR TUMOR KILLING IN VIVO

Abstract Background and significance Fibroblast growth factor receptor 2b (FGFR2b), a splice isoform of FGFR2, is found to overexpress across multiple cancers types and promotes dysregulated tyrosine kinase activation, resulting in tumor cell proliferation and unchecked malignancy. Cohort studies reveal FGFR2b overexpression and/or amplification in Gastric cancer (~30.2%), squamous non-small cell lung cancer (~20.8%), and endometrial carcinoma (~40%). About 80–85% patients who have advanced HER2-negative gastro-esophageal cancer undergoes approximately 12-14 months of median overall survival (mOS). Thus, there is an urgent need for novel and effective molecular targeted agents. With the recent advancement of mechanistic studies, however, FGFR2b is becoming the optimal target of multiple modalities such as mAb, bispecifics, or antibody-drug conjugate. Bemarituzumab, a FGFR2b blocking antibody, developed by Five Prime clinically demonstrates the safety of FGFR2b target and exhibits preliminary efficacy in advanced GE/GEJ adenocarcinoma patients with overexpression of FGFR2 in at least 5% or 10% of tumor cells. 3H Pharmaceuticals developed a FGFR2b-specific mAb, 3H-3000, of high-affinity, differentiated epitope and enhanced ADCC effect for FGFR2b-overexpressing gastric cancer or other FGFR2b-associated cancer types. In the meantime, we will also explore the versatility of this mAb in other format and in the combination with small molecules that will bring about a wider therapeutic spectrum. Method and Result 3H-3000 is a humanized IgG1kappa antibody with a single digit nM affinity for FGFR2b and no binding to other FGFR2 isoforms. 3H-3000 shows potent proliferation-inhibitive effects on FGFR2b-overexpressing human tumor cells. In gastric cancer cell line SNU16, 3H-3000 can fully inhibit FGF7-induced phosphorylation of FGFR2b and SNU16 proliferation in vitro. On top of signaling blocking, we strongly believe efficacy of antibody-dependent cell cytotoxicity (ADCC) is another viable mechanism for growth factor-targeting therapy. Therefore, 3H-3000 was further engineered with a 20-fold ADCC enhancement which is validated through a CD16-F158 variant-based reporter system. In FGFR2b-overexpressing human gastric cancer SNU16 or OCUM-2M xenograft model, 3H-3000 was shown to inhibit tumor growth and even induce regression, which is rather unexpected given the relative low expression of FGFR2b on SNU16 and none of the competitors exhibit similar phenomenon. With potent efficacy of tumor inhibition and killing, and excellent biophysical characteristics and developability of 3H-3000, we expect to push the molecule to clinical development in the middle of 2024. Conclusion 3H-3000 is a potent FGFR2b blocker with well-defined ADCC efficacy enhancement. It demonstrates strong blocking activity of FGFR2 signaling, strikingly enhanced ADCC activity in vitro and potent efficacy of tumor inhibition in vivo. These data strongly support its clinical development in FGFR2b-overexpressing cancers. In parallel, 3H Pharmaceuticals are also developing FGFR2- selectively tyrosine kinase inhibitors targeting FGFR2 mutations or fusion. We propose a combination of small molecule FGFR2 inhibitors and mAb of FGFR2b specificity will significantly broaden the therapeutic spectrum of heterogenous tumors where mechanism is centered around FGFR2b alteration including mutation, fusion, and overexpression.

Abstract 1863: Evaluation of BDB101, a first-in-class TLR7/8 dual agonist conjugated to an anti-PD-L1 mAb, in cancer treatment

Abstract Background Responses to antiPDL1 checkpoint inhibitors (CPIs) in many tumors are governed by the PDL1 expression on tumor and immune cells in the tumor microenvironment (TME). Increasing PDL1 expression on cells may enhance the response to CPIs. Tolllike receptor (TLR) agonists have shown to induce PDL1 expression in the TME and may enhance the antitumor effects of CPIs. The effective dose of TLR agonist administered to patients is limited by systemic toxicities. To overcome this limitation, one approach is to conjugate the TLR agonist to an antibody. This allows for delivery and release of higher doses of the TLR agonist in the TME while limiting systemic exposure.BDB001 is an intravenously (IV) delivered TLR7/8 dual agonist that activates both the innate and adaptive immune system. In clinical trials, BDB001 has been well tolerated and shown promising antitumor responses in monotherapy and in combination with antiPDL1 therapy (Patel M. et al, SITC 2020 and SITC 2021). To further enhance the antitumor effect and allow for increased concentration of the TLR7/8 dual agonist in the TME, we developed BDB101, a proprietary firstinclass TLR7/8 dual agonist - antiPDL1 monoclonal antibody (mAb) conjugate using our TollLike receptor Agonist Conjugate (TLAC) platform. Here we report on the preclinical and nonhuman primate (NHP) evaluation of BDB101. Methods BDB101 utilizes a cleavable linker, allowing for the TLR7/8 dual agonist payload to be released in the TME and enabling a bystander effect. BDB101 was assessed for in vitro TLR7/8 dual agonist activity and PDL1 binding, and in vivo antitumor efficacy in immune competent mouse models. The pharmacokinetic and pharmacodynamic effects of BDB101 was evaluated in NHP. Results The conjugated TLR7/8 dual agonist did not change the PDL1 binding specificity of the antibody, and the uncleaved conjugate did not activate TLR7 or TLR8. In the C26 mouse model, a BDB101 mouse surrogate showed a significantly more robust antitumor effect compared to the TLR7/8 dual agonist or the antiPDL1 mAb alone. In NHP, a single IV infusion of BDB101 showed no significant differences in PK parameters between BDB101 and the total antiPDL1 mAb. BDB101 demonstrated remarkable in vitro stability in human plasma for up to 21 days. In NHP, BDB101 was also very stable with minimal release of free TLR7/8 dual agonist payload. Pharmacodynamic studies in NHP were consistent with PK behavior. Conclusions BDB101 exhibits robust preclinical efficacy and prolonged stability in NHP. The low rate of free TLR7/8 dual agonist payload released into the systemic circulation from the conjugated form of BDB101, should minimize the risk of systemic TLR7/8 dual agonist exposure, while maintaining the ability to deliver the payload to the TME. These results indicate that BDB101 will likely have a good in vivo therapeutic window and strongly support the clinical development of BDB101. Citation Format: Jing Yang, Robert H. Andtbacka, Walter Lau, Lixin Li. Evaluation of BDB101, a first-in-class TLR7/8 dual agonist conjugated to an anti-PD-L1 mAb, in cancer treatment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1863.

Sampling algorithm for geno- and subtyping of hepatitis B virus using panel of monoclonal antibodies in enzyme immunoassay

Introduction. Previously, a domestic method for determining hepatitis B virus (HBV) genotypes and HBV surface antigen (HBsAg) subtypes in HBsAgpositive blood serum samples with a Monoclonal Antibody Panel (MAB) by enzyme immunoassay (ELISA) was described. In routine laboratory practice, HBsAg detection results are obtained in units of optical density (OD).Purpose. To describe the sampling algorithm for ELISA geno- and subtyping of HBV with the MAB Panel.Materials and methods. We studied 40 blood serum samples with positive results of HBsAg determination. HBV genotypes and HBsAg subtypes were determined using four different MAB conjugates with horseradish peroxidase using the ELISA method described previously.Results. In samples with OD less than 2.0 o. u. and confirmation of HBsAg after a single confirmatory study (n = 19) HBV genotypes/ HBsAg subtypes not established. In samples with an OD above 2.0 o. u. and verification of the presence of the antigen in the standard mode of registration (n = 15), immunoenzymatic geno- and subtyping of HBV was effective in 27 % of cases (4/15); for samples with HBsAg verification carried out in an auxiliary measurement (n = 6) the effectiveness of the technique was 100 %. Using the MAB panel in ELISA, the characteristics of HBV in 10 samples with the presence of HBsAg were studied: HBV genotype D (n = 10), subtypes ayw2 (n = 7), ayw3 (n = 3).Conclusions. For the most effective application of the HBV geno- and subtyping technique using the MAB Panel in ELISA, HBsAg+ samples with OD signals of more than 2.0 o. u. in screening and verification of the presence of an antigen in the auxiliary mode of registration of results should be used.

Enabling the formation of native mAb, Fab' and Fc-conjugates using a bis-disulfide bridging reagent to achieve tunable payload-to-antibody ratios (PARs).

Either as full IgGs or as fragments (Fabs, Fc, etc.), antibodies have received tremendous attention in the development of new therapeutics such as antibody-drug conjugates (ADCs). The production of ADCs involves the grafting of active payloads onto an antibody, which is generally enabled by the site-selective modification of native or engineered antibodies via chemical or enzymatic methods. Whatever method is employed, controlling the payload-antibody ratio (PAR) is a challenge in terms of multiple aspects including: (i) obtaining homogeneous protein conjugates; (ii) obtaining unusual PARs (PAR is rarely other than 2, 4 or 8); (iii) using a single method to access a range of different PARs; (iv) applicability to various antibody formats; and (v) flexibility for the production of heterofunctional antibody-conjugates (e.g. attachment of multiple types of payloads). In this article, we report a single pyridazinedione-based trifunctional dual bridging linker that enables, in a two-step procedure (re-bridging/click), the generation of either mAb-, Fab'-, or Fc-conjugates from native mAb, (Fab')2 or Fc formats, respectively. Fc and (Fab')2 formats were generated via enzymatic digestion of native mAbs. Whilst the same reduction and re-bridging protocols were applied to all three of the protein formats, the subsequent click reaction(s) employed to graft payload(s) drove the generation of a range of PARs, including heterofunctional PARs. As such, exploiting click reactivity and/or orthogonality afforded mAb-conjugates with PARs of 6, 4, 2 or 4 + 2, and Fab'- and Fc-conjugates with a PAR of 3, 2, 1 or 2 + 1 on-demand. We believe that the homogeneity, novelty and variety in accessible PARs, as well as the applicability to various antibody-conjugate formats enabled by our non-recombinant method could be a suitable tool for antibody-drug conjugates optimisation (optimal PAR value, optimal payloads combination) and boost the development of new antibody therapeutics (Fab'- and Fc-conjugates).

Current Protein Conjugation Strategies and Pioneering Anti-Cancer Applications.

The escalating global impact of cancer demands targeted and efficient therapies. Many targeted cancer therapeutics have been fostered into the market in recent years. The leading class of targeted therapeutics is monoclonal antibodies (mAbs). The success of mAbs sparked significant interest and subsequently paved the way for the development of various recombinant protein-based products that were conjugated to other compounds to form antibody-drug conjugates (ADCs) for the treatment of cancer. This review explores diverse mAb conjugation strategies and pioneering approaches for cancer applications, to optimize drug delivery through site-directed conjugation, prodrug conjugates and antibody conjugated nanoparticles. It also highlights promising innovations and addresses challenges including stability issues of ADCs, drug resistance, payload retention and some of the shortcomings of ADCs such as limited bioavailability, short serum half-life, and reduced drug buildup caused by obstacles in the tumor environment primarily associated with heightened interstitial fluid pressure (IFP).

Optimizing and determining the click chemistry mediated Cu-64 radiolabeling and physiochemical characteristics of trastuzumab conjugates

Over the last decade, 64Cu-labeling of monoclonal antibody (mAb) via inverse electron demand Diels-Alder click chemistry (IEDDA) have received much attention. Despite the tetrazine-transcyclooctene (Tz-TCO) click chemistry's convenience and efficiency in mAb labeling, there is limited information about the ideal parameters in the development of click chemistry mediated (radio)immunoconjugates. This encourages us to conduct a systematic optimization while concurrently determining the physiochemical characteristics of the model mAb, trastuzumab, and TCO conjugates. To accomplish this, we investigated a few critical parameters, first, we determined the degree of conjugations with varying molar equivalents (eq.) of TCO (3, 5, 10, and 15 eq.). Through analytical techniques like size exclusion chromatography, dynamic light scattering, and zeta potential, qualitative analysis were performed to determine the purity, degree of aggregation and net charge of the conjugates. We found that as the degree of conjugation increased the purity of intact mAb fraction is compromised and net charge of conjugates became less positive. Next, all trastuzumab-PEG4-TCO conjugates with varying molar ratio and quantity (30, 50, 100, 200, 250 μg) were radiolabeled with 64Cu-NOTA-PEG4-Tz via IEDDA click chemistry and radiochemical yields were determined by radio-thin layer chromatography. The radiochemical yields of trastuzumab conjugates improved with increased amount and molar ratio. Next, we investigated the effect of the radioprotectant ascorbic acid (AA) of varied concentrations (0.25, 0.5, 0.75, 1 mM) on radiochemical yields and subsequent pharmacokinetics. A concentration of 0.25 mM of AA was found to be optimal for click reaction and in vivo biodistribution. Finally, we investigated the indirect influence of bioconjugation buffers on radiochemical yields and biodistribution in NIH3T6.7 tumor models that resulted approximately ∼11 %ID/g tumor uptake.

Conjugation of Listeriolysin O to Anti-CD47 mAb: Harnessing Listeria Toxin to Weaponize Macrophages against Tumor Cells

<h3>Purpose/Objective(s)</h3> CD47 is expressed on various tumor types including breast, prostate, glioblastoma, non-Hodgkin lymphoma, and hepatocellular carcinoma. Interrupting the CD47-SIRP alpha axis by monoclonal antibodies fosters macrophage-mediated phagocytosis of solid and hematopoietic tumor cells. The pore-forming toxin listeriolysin O (LLO) is activated in the acidic vacuoles of bone marrow-derived macrophages. We hypothesize that LLO conjugation to the anti-CD47 mAb enhances the release of autophagic cargo within macrophages thereby augmenting cGAS-STING activation, antigen presentation, and tumor phagocytosis. <h3>Materials/Methods</h3> The anti-CD47 mAb was conjugated to the LLO toxin using a water-soluble SPDP crosslinker and purified by affinity chromatography. The cytotoxicity of anti-CD47-LLO mAb relative to anti-CD47 mAb was tested in the mouse breast cancer cell line E0771, the human breast cancer cell line MDA-MB-468, the mouse lung cancer cell line LLC, and the human leukemia monocytic cell line THP-1. C57B6 mouse bone marrow-derived macrophages (BMDM) co-cultured with tumor cell lines were analyzed in the presence of anti-CD47-LLO mAb and anti-CD47 mAb to determine the efficiency of BMDM tumor cell phagocytosis, STING activation, and antigen presentation. Tumor growth of E0771-bearing wildtype mice was measured following intratumoral injection of anti-CD47 mAb and anti-CD47-LLO mAB. <h3>Results</h3> The anti-CD47-LLO mAb conjugate enhanced BMDM phagocytosis of LLC and E0771 tumor cells in a dose dependent manner that was significantly higher than cells treated with the anti-CD47 mAb alone. The anti-CD47-LLO mAb significantly increased BMDM levels of phosphorylated STING, interferon-stimulated genes, and antigen presentation relative to anti-CD47 mAb treatment. At doses compatible with preserved animal total body weight, red blood cell counts, and lymphocyte counts, intratumoral injection of anti-CD47-LLO mAb significantly suppressed tumor growth of E0771-bearing wildtype mice relative to the anti-CD47 mAb. <h3>Conclusion</h3> Conjugation of the LLO toxin to anti-CD47 mAb enhances macrophage cGAS-STING activation, antigen presentation, and tumor cell phagocytosis. This novel CD47 antibody builds on clinical interest in targeting macrophages for the treatment of malignancy and may be studied as a supplemental therapy for patients with tumors resistant or refractory to checkpoint therapy.

Reflective FT-NIR and SERS studies of HER-II breast cancer biomarker using plasmonic-active nanostructured thin film immobilized oriented antibody.

We describe the fabrication of plasmonic-active nanostructured thin film substrate as a label-free surface-enhanced Raman scattering (SERS)-based biosensor immobilized covalently with monoclonal HER-II antibody (mAb) to detect overexpressed HER-II as a biomarker in breast cancer serum (BCS). Oriented conjugation of mAb via hydrazone linkage to provide higher mAb accessibility was characterized by UV-vis and reflective Fourier transform near-infrared (FT-NIR) spectroscopic techniques. The interaction of BCS with mAb was studied by FT-NIR and nonresonant SERS at 637 nm. The results showed detection of glycoprotein content at different laser powers including a rise in amino acid and glycan content with varying results at higher power. With nonresonant SERS we observed nonlinear behavior of peak intensity. Analysis of variance was implemented to determine the effect of laser power which was found not to be a contributing factor. However, at the nanoscale, factors including the heating effect and aggregation of molecules can contribute to the nonlinearity of peak intensity.

Stability-indicative and conformation-specific enzyme linked immunosorbent assay for analysis of recombinant human gamma interferon

Recombinant human interferon gamma (rhIFN-γ) is a promising molecule for the treatment of several diseases. A pair of conformation-specific monoclonal antibodies (mAbs) against rhIFN-γ was selected from generated hybridoma cell lines to design a sensitive, stability-indicative, sandwich-type ELISA. The main assay parameters were optimized by the checkerboard method for the highest signal-to-noise ratio: assay buffer composition, coating buffer pH and composition, coating temperature-incubation time parameters, and coating mAb concentration and conjugate dilution. Detection and quantification limits were estimated between 0.019 and 0.078 ng/mL, respectively, and recovery values were from 92.03% to 98.40%. The coefficient of variation of intra-assay precision parameters ranged from 2.32% to 9.21% while the inter-analyst variation was between 4.70% and 10.63%, supporting the method’s repeatability. The ELISA was specific for correctly folded and non-aggregated molecular species, as compared to intrinsic Trp fluorescence (chemical denaturation) and optical density at 340 nm (thermal aggregation), respectively. However, the method was not sensitive to the small C-terminal degradation of full-length rhIFN-γ1–144 (losses of 6–12 amino acid residues) as compared to results with mass spectrometry and gel electrophoresis. ELISA showed good correlation with rhIFN-γ antiviral biological activity. This method was applied to the stability evaluation of rhIFN-γ in physiological buffer at low concentrations using polypropylene and glass vials also in the presence of adsorption protectant excipients. Furthermore, ELISA could be adapted to other applications such as quantification of IFN-γ in serum samples, Mycobacterium tuberculosis diagnosis, etc.

Impact of Bioconjugation on Structure and Function of Antibodies for Use in Immunoassay by Hydrogen-Deuterium Exchange Mass Spectrometry

Monoclonal antibodies (mAbs) are widely used as analytical components in immunoassays to detect target molecules in applications such as clinical diagnostics, food analysis and drug discovery. Functional groups are often conjugated to lysine or cysteine residues to aid immobilization of mAbs or to enable their detection in an antibody antigen complex. Good assay performance depends on the affinity and specificity of the mAbs for the antigen. The conjugation reaction however can cause higher order structural (HOS) changes and ultimately affect the assay performance. In this study, four differently conjugated mAbs were selected as model systems and characterized by mass spectrometry. Particularly, intact protein analysis by liquid-chromatography mass-spectrometry (LC-MS) was performed to determine the amount and distribution of conjugation. Hydrogen deuterium exchange mass spectrometry (HDX-MS) experiments were carried out for the structural characterization of the conjugated mAbs. Immunoassay experiments were performed to monitor the effects of conjugation on the binding properties of the antibodies selected. Good agreement between the mass spectrometry and binding experiment results was found. Particularly, it was noted that the overall structural flexibility of the antibodies increases upon cysteine conjugation and decreases for lysine conjugation. The conjugation of mAbs with bulky functional groups tends to decrease the deuterium uptake kinetics due to induced steric effects. Overall, this study shows correlations between conjugation, structure and function of immunoassay antibodies and the benefits of mass spectrometry to improve understanding of the conjugation reaction and provide insights that can predict immunoassay performance.

In Vitro Characterization of 177Lu-DOTA-M5A Anti-Carcinoembryonic Antigen Humanized Antibody and HSP90 Inhibition for Potentiated Radioimmunotherapy of Colorectal Cancer.

Carcinoembryonic antigen (CEA) is an antigen that is highly expressed in colorectal cancers and widely used as a tumor marker. 131I and 90Y-radiolabeled anti-CEA monoclonal antibodies (mAbs) have previously been assessed for radioimmunotherapy in early clinical trials with promising results. Moreover, the heat shock protein 90 inhibitor onalespib has previously demonstrated radiotherapy potentiation effects in vivo. In the present study, a 177Lu-radiolabeled anti-CEA hT84.66-M5A mAb (M5A) conjugate was developed and the potential therapeutic effects of 177Lu-DOTA-M5A and/or onalespib were investigated. The 177Lu radiolabeling of M5A was first optimized and characterized. Binding specificity and affinity of the conjugate were then evaluated in a panel of gastrointestinal cancer cell lines. The effects on spheroid growth and cell viability, as well as molecular effects from treatments, were then assessed in several three-dimensional (3D) multicellular colorectal cancer spheroid models. Stable and reproducible radiolabeling was obtained, with labeling yields above 92%, and stability was retained at least 48 h post-radiolabeling. Antigen-specific binding of the radiolabeled conjugate was demonstrated on all CEA-positive cell lines. Dose-dependent therapeutic effects of both 177Lu-DOTA-M5A and onalespib were demonstrated in the spheroid models. Moreover, effects were potentiated in several dose combinations, where spheroid sizes and viabilities were significantly decreased compared to the corresponding monotherapies. For example, the combination treatment with 350 nM onalespib and 20 kBq 177Lu-DOTA-M5A resulted in 2.5 and 2.3 times smaller spheroids at the experimental endpoint than the corresponding monotreatments in the SNU1544 spheroid model. Synergistic effects were demonstrated in several of the more effective combinations. Molecular assessments validated the therapy results and displayed increased apoptosis in several combination treatments. In conclusion, the combination therapy of anti-CEA 177Lu-DOTA-M5A and onalespib showed enhanced therapeutic effects over the individual monotherapies for the potential treatment of colorectal cancer. Further in vitro and in vivo studies are warranted to confirm the current study findings.

Coumarins to Cyanines: Synthesis of Hemicyanines.

Near-infrared (NIR) emitting fluorophores are powerful tools for optical imaging. However, there are only a handful of broadly employed NIR-emitting scaffolds, and the synthetic methods to prepare these molecules are often problematic. Here, we describe a novel, three-step synthesis of chromene-containing hemicyanine probes exhibiting large Stokes shifts and NIR emissions. We develop a pH-activatable probe for visualizing lysosomal trafficking of mAb conjugates. These studies provide a concise approach to hemicyanines with promising properties.