Discovery, affinity maturation and multimerization of small molecule ligands against human tyrosinase and tyrosinase-related protein 1

Human tyrosinase (hTYR) and tyrosinase-related protein 1 (hTYRP1) are closely-related enzymes involved in the synthesis of melanin, which are selectively expressed in melanocytes and, in a pathological context, in melanoma lesions. We used a previously described tyrosinase inhibitor (Thiamidol™) and DNA-encoded library technology for the discovery of novel hTYR and hTYRP1 ligands, that could be used as vehicles for melanoma targeting. Performing de novo selections with DNA-encoded libraries, we discovered novel ligands capable of binding to both hTYR and hTYRP1. More potent ligands were obtained by multimerizing Thiamidol™ moieties, leading to homotetrameric structures that avidly bound to melanoma cells, as revealed by flow cytometry. These findings suggest that melanoma lesions may, in the future, be targeted not only by monoclonal antibody reagents but also by small organic ligands.

A series of different strategies were oriented toward the discovery of small molecule ligands binding to the human version of tyrosinase (hTYR) and tyrosinase-related protein 1 (hTYRP1), which may represent the basis for novel treatments of melanoma.

IMMU-07. TUMOR STROMA–TARGETING ANTIBODY-CYTOKINE CONJUGATES TO CONVERT THE IMMUNOLOGICALLY COLD GLIOMA MICROENVIRONMENT INTO A HOT ONE

Glioblastoma is an immunological “desert”. The administration of pro-inflammatory cytokines could shift the balance between tumor-associated immune suppression and anti-tumor immunity but the systemic administration of therapeutically active doses of pro-inflammatory cytokines is hampered by toxic side effects. We investigated different antibody-cytokine fusion products that enable a targeted delivery of interleukin (IL-) 2, IL-12 or tumor-necrosis factor (TNF)α to the tumor site upon systemic administration by binding to a tumor-specific epitope of fibronectin. We confirmed the target antigen expression in ex vivo sections of orthotopic syngeneic glioma mouse models and human glioblastoma samples and characterized the distribution of these antibody-conjugates in glioma-bearing mice upon systemic administration using in vivo imaging. Subsequently, we demonstrated potent anti-tumor activity of these antibody-fusion proteins in fully immunocompetent orthotopic mouse glioma models and characterized their mode of action. We also translated this immunotherapeutic strategy to treat patients with recurrent glioblastoma systemically with an antibody-fusion protein that enables the targeted delivery of TNFα to the tumor site. This was well tolerated, led to a treatment-associated tumor necrosis and increased the number of tumor-infiltrating T cells. This work builds a basis for future studies with antibody-cytokine fusion proteins as a promising treatment strategy for central nervous system tumors.

Novel human monoclonal antibodies specific to the alternatively spliced domain D of Tenascin C efficiently target tumors in vivo

Antibody-based delivery of bioactive molecules represents a promising strategy for the improvement of cancer immunotherapy. Here, we describe the generation and characterization of R6N, a novel fully human antibody specific to the alternatively spliced domain D of Tenascin C, which is highly expressed in the stroma of primary tumors and metastasis. The R6N antibody recognized its cognate tumor-associated antigen with identical specificity in mouse and human specimens. Moreover, the antibody was able to selectively localize to solid tumors in vivo as evidenced by immunofluorescence-based biodistribution analysis. Encouraged by these results, we developed a novel fusion protein (termed mIL12-R6N) consisting of the murine interleukin 12 fused to the R6N antibody in homodimeric tandem single-chain variable fragment arrangement. mIL12-R6N exhibited potent antitumor activity in immunodeficient mice bearing SKRC52 renal cell carcinoma, as well as in immunocompetent mice bearing SMA-497 glioma. The experiments presented in this work provide a rationale for possible future applications for the R6N antibody for the treatment of cancer patients.

Targeting an engineered cytokine with interleukin-2 and interleukin-15 activity to the neovasculature of solid tumors

There is a growing interest in the antibody-based delivery of cytokines to the tumor environment as a means to boost the anti-cancer activity of tumor-resident T cells and NK cells. Here, we describe the expression and characterization of fusion proteins, featuring the L19 antibody (specific to the alternatively-spliced EDB domain of fibronectin) and an engineered cytokine with interleukin-2 and interleukin-15 properties. The cytokine moiety was fused either at the N-terminal or at the C-terminal extremity and both fusion proteins showed a selective tumor accumulation in a quantitative biodistribution experiment. The N-terminal fusion inhibited tumor growth in immunocompetent mice bearing F9 carcinomas or WEHI-164 sarcomas when used as single agent. The anticancer activity was compared to the one of the same cytokine payload used as recombinant protein or fused to an anti-hen egg lysozyme antibody, serving as negative control of irrelevant specificity in the mouse. These results indicate that the antibody-based delivery of engineered cytokines to the tumor neovasculature may mediate a potent anticancer activity.

A Single-Stranded DNA-Encoded Chemical Library Based on a Stereoisomeric Scaffold Enables Ligand Discovery by Modular Assembly of Building Blocks

A versatile and Lipinski-compliant DNA-encoded library (DEL), comprising 366 600 glutamic acid derivatives coupled to oligonucleotides serving as amplifiable identification barcodes is designed, constructed, and characterized. The GB-DEL library, constructed in single-stranded DNA format, allows de novo identification of specific binders against several pharmaceutically relevant proteins. Moreover, hybridization of the single-stranded DEL with a set of known protein ligands of low to medium affinity coupled to a complementary DNA strand results in self-assembled selectable chemical structures, leading to the identification of affinity-matured compounds.

Quantitative and Qualitative Analysis of Humoral Immunity Reveals Continued and Personalized Evolution in Chronic Viral Infection

Control of established chronic lymphocytic choriomeningitis virus (LCMV) infection requires the production of neutralizing antibodies, but it remains unknown how the ensemble of antibodies evolves during ongoing infection. Here, we analyze the evolution of antibody responses during acute or chronic LCMV infection, combining quantitative functional assays and time-resolved antibody repertoire sequencing. We establish that antibody responses initially converge in both infection types on a functional and repertoire level, but diverge later during chronic infection, showing increased clonal diversity, the appearance of mouse-specific persistent clones, and distinct phylogenetic signatures. Chronic infection is characterized by a longer-lasting germinal center reaction and a continuous differentiation of plasma cells, resulting in the emergence of higher-affinity plasma cells exhibiting increased antibody secretion rates. Taken together, our findings reveal the emergence of a personalized antibody response in chronic infection and support the concept that maintaining B cell diversity throughout chronic LCMV infection correlates with the development of infection-resolving antibodies.

Sortase-Mediated Site-Specific Modification of Interleukin-2 for the Generation of a Tumor-Targeting Acetazolamide-Cytokine Conjugate

Small ligands specific to tumor-associated antigens can be used as alternatives to antibodies for the delivery of small payloads such as radionuclides, cytotoxic drugs, and fluorophores. Their use as a delivery moiety of bioactive proteins such as cytokines remains largely unexplored. Here, we describe the preparation and in vivo characterization of the first small molecule-cytokine conjugate targeting carbonic anhydrase IX (CAIX), a marker of renal cell carcinoma and hypoxia. Site-specific conjugation between interleukin-2 and acetazolamide was obtained by sortase A-mediated transpeptidation. Binding of the conjugate to the cognate CAIX antigen was confirmed by surface plasmon resonance. The in vivo targeting of structures expressing carbonic anhydrase IX was assessed by biodistribution experiments in tumor-bearing mice. Optimization of manufacturability and tumor-targeting performance of acetazolamide-cytokine products will be required in order to enable industrial applications.

Immunocytokines are a promising immunotherapeutic approach against glioblastoma

Glioblastoma is a poorly immunogenic cancer, and the successes with recent immunotherapies in extracranial malignancies have, so far, not been translated to this devastating disease. Therefore, there is an urgent need for new strategies to convert the immunologically cold glioma microenvironment into a hot one to enable effective antitumor immunity. Using the L19 antibody, which is specific to a tumor-associated epitope of extracellular fibronectin, we developed antibody-cytokine fusions—immunocytokines—with interleukin-2 (IL2), IL12, or tumor necrosis factor (TNF). We showed that L19 accumulated in the tumor microenvironment of two orthotopic immunocompetent mouse glioma models. Furthermore, intravenous administration of L19-mIL12 or L19-mTNF cured a proportion of tumor-bearing mice, whereas L19-IL2 did not. This therapeutic activity was abolished in RAG−/− mice or upon depletion of CD4 or CD8 T cells, suggesting adaptive immunity. Mechanistically, both immunocytokines promoted tumor-infiltrating lymphocytes and increased the amounts of proinflammatory cytokines within the tumor microenvironment. In addition, L19-mTNF induced tumor necrosis. Systemic administration of the fully human L19-TNF fusion protein to patients with glioblastoma (NCT03779230) was safe, decreased regional blood perfusion within the tumor, and was associated with increasing tumor necrosis and an increase in tumor-infiltrating CD4 and CD8 T cells. The extensive preclinical characterization and subsequent clinical translation provide a robust basis for future studies with immunocytokines to treat malignant brain tumors.

Ubiquitin Phosphorylation at Thr12 Modulates the DNA Damage Response

The ubiquitin system regulates the DNA damage response (DDR) by modifying histone H2A at Lys15 (H2AK15ub) and triggering downstream signaling events. Here, we find that phosphorylation of ubiquitin at Thr12 (pUbT12) controls the DDR by inhibiting the function of 53BP1, a key factor for DNA double-strand break repair by non-homologous end joining (NHEJ). Detectable as a chromatin modification on H2AK15ub, pUbT12 accumulates in nuclear foci and is increased upon DNA damage. Mutating Thr12 prevents the removal of ubiquitin from H2AK15ub by USP51 deubiquitinating enzyme, leading to a pronounced accumulation of ubiquitinated chromatin. Chromatin modified by pUbT12 is inaccessible to 53BP1 but permissive to the homologous recombination (HR) proteins RNF169, RAD51, and the BRCA1/BARD1 complex. Phosphorylation of ubiquitin at Thr12 in the chromatin context is a new histone mark, H2AK15pUbT12, that regulates the DDR by hampering the activity of 53BP1 at damaged chromosomes.

An Antibody-Tumor Necrosis Factor Fusion Protein that Synergizes with Oxaliplatin for Treatment of Colorectal Cancer

We have cloned and characterized a novel fusion protein (Sm3E-TNF), consisting of the mAb, S 6m3E, in single-chain Fv fragment format, fused to murine TNF. The protein, which was expressed in mammalian cells and purified as a noncovalent stable homotrimer, bound to the cognate carcinoembryonic antigen (CEA) and retained TNF activity. A quantitative biodistribution experiment, performed in immunocompetent mice with CT26 colon carcinomas transfected with human CEA, revealed that Sm3E-TNF was able to preferentially accumulate in the tumors with excellent selectivity (tumor:blood ratio = 56:1, 24 hours after intravenous administration). The fusion protein mediated a rapid hemorrhagic necrosis of a large portion of the tumor mass, but a rim survived and eventually regrew. Surprisingly, the combination of Sm3E-TNF with 5-fluorouracil led to a reduction of therapeutic activity, while a combination with oxaliplatin led to a prolonged stabilization, with complete tumor eradication in 40% of treated mice. These therapy results were confirmed in a second immunocompetent mouse model of colorectal cancer (CEA-transfected C51 tumors) and provide a rationale for the possible clinical use of oxaliplatin in combination with fully human antibody-TNF fusions.

Selective Fragments for the CREBBP Bromodomain Identified from an Encoded Self-assembly Chemical Library

DNA-encoded chemical libraries (DECLs) are collections of chemical moieties individually coupled to distinctive DNA barcodes. Compounds can be displayed either at the end of a single DNA strand (i. e., single-pharmacophore libraries) or at the extremities of two complementary DNA strands (i. e., dual-pharmacophore libraries). In this work, we describe the use of a dual-pharmacophore encoded self-assembly chemical (ESAC) library for the affinity maturation of a known 4,5-dihydrobenzodiazepinone ring (THBD) acetyl-lysine (KAc) mimic for the cyclic-AMP response element binding protein (CREB) binding protein (CREBBP or CBP) bromodomain. The new pair of fragments discovered from library selection showed a sub-micromolar affinity for the CREBBP bromodomain in fluorescence polarization and ELISA assays, and selectivity against BRD4(1).

The targeted delivery of interleukin-12 to the carcinoembryonic antigen increases the intratumoral density of NK and CD8+ T cell in an immunocompetent mouse model of colorectal cancer

The recent success achieved by immune checkpoint inhibitors in the field of immuno-oncology has been less evident for the treatment of metastatic colorectal cancer (mCRC) patients. To date, cancer immunotherapy has been efficacious only in few patients bearing high mutational burden (less than 25%) mCRCs. In this Communication, we report the generation of a novel antibody cytokine fusion protein (termed Sm3E-mIL12) targeting the CRC-associated carcinoembryonic antigen (CEA). The antibody moiety bound avidly to CEA when immobilized on solid supports, and selectively stained C51 tumor cells transfected with the antigen (C51-CEA). The cytokine payload retained full activity in vitro, as compared to the parental recombinant interleukin-12 (IL12). Ex vivo microscopic analyses revealed a homogenous distribution of Sm3E-mIL12 in the neoplastic mass upon intravenous administration. In vivo, Sm3E-mIL12 was well tolerated up to 180 µg per mouse. The targeted delivery of IL12 to CEA-expressing C51 carcinomas led to durable complete responses in 60% of the treated mice. The intratumoral density of immune effector cells was markedly increased after the third injection of Sm3E-mIL12, in keeping with the progressive regression of the neoplastic mass. The data suggest that a fully human analogue may be considered for the treatment of patients with mCRC.

A Microdosing Study with 99mTc-PHC-102 for the SPECT/CT Imaging of Primary and Metastatic Lesions in Renal Cell Carcinoma Patients

^99mTc-PHC-102 is a ^99mTc-labeled derivative of acetazolamide, a high-affinity small organic ligand of carbonic anhydrase IX (CAIX). ^99mTc-PHC-102 has previously shown favorable in vivo biodistribution properties in mouse models of CAIX-positive clear cell renal cell carcinoma (ccRCC) and colorectal cancer. In this study, we aimed to explore the targeting performance of ^99mTc-PHC-102 in SPECT in patients with renal cell carcinoma while also assessing the safety and tolerability of the radiotracer. Methods: We studied 5 patients with localized or metastatic ccRCC in a microdosing regimen, after the administration of a 50-μg total of CAIX ligand and 600-800 MBq of ^99mTc-PHC-102. Tissue distribution and residence time in normal organs and tumors were analyzed by serial SPECT/CT scans at 3 time points (30 min, 2 h, and 6 h) after intravenous administration. Results: In the 5 patients studied, ^99mTc-PHC-102 was well tolerated and no study drug-related adverse events were recorded. In the stomach, kidneys, and gallbladder, the radiotracer showed a rapid initial uptake, which cleared over time. Localization of the study drug in primary tumors of 5 patients was observed, with favorable tumor-to-background ratios. ^99mTc-PHC-102 SPECT/CT allowed the identification of 4 previously unknown lung and lymph node metastases in 2 patients. Conclusion: ^99mTc-PHC-102 is a promising SPECT tracer for the imaging of patients with ccRCC. This tracer has the potential to identify primary and metastatic lesions in different anatomic locations. ^99mTc-PHC-102 might also serve as a companion diagnostic agent for future CAIX-targeting therapeutics.

Stereotactic ablative body radiotherapy (SABR) combined with immunotherapy (L19-IL2) versus standard of care in stage IV NSCLC patients, ImmunoSABR: a multicentre, randomised controlled open-label phase II trial

BACKGROUND

About 50% of non-small cell lung cancer (NSCLC) patients have metastatic disease at initial diagnosis, which limits their treatment options and, consequently, the 5-year survival rate (15%). Immune checkpoint inhibitors (ICI), either alone or in combination with chemotherapy, have become standard of care (SOC) for most good performance status patients. However, most patients will not obtain long-term benefit and new treatment strategies are therefore needed. We previously demonstrated clinical safety of the tumour-selective immunocytokine L19-IL2, consisting of the anti-ED-B scFv L19 antibody coupled to IL2, combined with stereotactic ablative radiotherapy (SABR).

METHODS

This investigator-initiated, multicentric, randomised controlled open-label phase II clinical trial will test the hypothesis that the combination of SABR and L19-IL2 increases progression free survival (PFS) in patients with limited metastatic NSCLC. One hundred twenty-six patients will be stratified according to their metastatic load (oligo-metastatic: ≤5 or poly-metastatic: 6 to 10) and randomised to the experimental-arm (E-arm) or the control-arm (C-arm). The C-arm will receive SOC, according to the local protocol. E-arm oligo-metastatic patients will receive SABR to all lesions followed by L19-IL2 therapy; radiotherapy for poly-metastatic patients consists of irradiation of one (symptomatic) to a maximum of 5 lesions (including ICI in both arms if this is the SOC). The accrual period will be 2.5-years, starting after the first centre is initiated and active. Primary endpoint is PFS at 1.5-years based on blinded radiological review, and secondary endpoints are overall survival, toxicity, quality of life and abscopal response. Associative biomarker studies, immune monitoring, CT-based radiomics, stool collection, iRECIST and tumour growth rate will be performed.

DISCUSSION

The combination of SABR with or without ICI and the immunocytokine L19-IL2 will be tested as 1st, 2nd or 3rd line treatment in stage IV NSCLC patients in 14 centres located in 6 countries. This bimodal and trimodal treatment approach is based on the direct cytotoxic effect of radiotherapy, the tumour selective immunocytokine L19-IL2, the abscopal effect observed distant from the irradiated metastatic site(s) and the memory effect. The first results are expected end 2023.

TRIAL REGISTRATION

ImmunoSABR Protocol Code: NL67629.068.18; EudraCT: 2018-002583-11; Clinicaltrials.gov: NCT03705403; ISRCTN ID: ISRCTN49817477; Date of registration: 03-April-2019.

Immunotherapy of CT26 murine tumors is characterized by an oligoclonal response of tissue-resident memory T cells against the AH1 rejection antigen

Mice bearing CT26 tumors can be cured by administration of L19-mIL12 or F8-mTNF, two antibody fusion proteins which selectively deliver their cytokine payload to the tumor. In both settings, cancer cures crucially depended on CD8⁺ T cells and the AH1 peptide (derived from the gp70 protein of the murine leukemia virus) acted as the main tumor-rejection antigen, with ∼50% of CD8⁺ T cells in the neoplastic mass being AH1-specific after therapy. In order to characterize the clonality of the T cell response, its phenotype, and activation status, we isolated CD8⁺ T cells from tumors and secondary lymphoid organs and submitted them to T cell receptor (TCR) and total mRNA sequencing. We found an extremely diverse repertoire of more than 40 000 unique TCR sequences, but the ten most abundant TCRs accounted for >60% of CD8⁺ T-cell clones in the tumor. AH1-specific TCRs were consistently found among the most abundant sequences. AH1-specific T cells in the tumor had a tissue-resident memory phenotype. Treatment with L19-mIL12 led to overexpression of IL-12 receptor and of markers of cell activation and proliferation. These data suggest that the antitumor response driven by antibody-cytokine fusions proceeds through an oligoclonal expansion and activation of tumor-infiltrating CD8⁺ T cells.

Antibody-Cytokine Fusions: Versatile Products for the Modulation of Anticancer Immunity

The remarkable clinical success of immune-checkpoint inhibitors for the treatment of a growing number of cancer types has sparked interest in the discovery of novel forms of immunotherapy, which may be used alone or in combination. In this context, cytokine-based therapeutics are well poised to play a role in modern cancer therapy. This article focuses on antibody-cytokine fusion proteins (also called "immunocytokines") as one class of biopharmaceuticals that can substantially improve the therapeutic index and, thus, the applicability of cytokine products. In many preclinical settings, antibodies can be used to preferentially deliver many (but not all) types of cytokines to primary and metastatic tumor lesions. The antibody-based delivery of certain proinflammatory payloads (such as IL2, IL12, and TNF) to the tumor microenvironment can lead to a dramatic potentiation of their anticancer activity. However, although some fusion proteins have advanced to late-stage clinical trials, much work remains to be done in order to fully characterize the mechanism of action and the pharmaceutical potential of immunocytokines in the clinical setting. Various factors contribute to in vivo performance, including the target antigen, the antibody properties, the nature of the payload, the format of the fusion protein, the dose, and schedule, as well as their use in combination with other therapeutic modalities. Protein engineering opportunities and insights in cancer immunology are contributing to the development of next-generation immunocytokine products and of novel therapeutic concepts, with the goal to increase antitumor activity and reduce systemic toxicity (a common problem for cytokine-based biopharmaceuticals).

Targeting glioblastoma with novel immunocytokines

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Background: There is an urgent need for novel treatment options for patients with glioblastoma, the most frequent malignant primary brain tumor. In contrast to other types of cancer, immunotherapeutic approaches have so far not been successful against glioblastoma. Converting the glioma microenvironment from a "cold" and immunosuppressive status into a more "hot" and immunopermissive phenotype may allow for clinically meaningful anti-tumor immune responses. Methods: We explored the activity of novel immunocytokines based on the L19 antibody, specific to a tumor-associated epitope of extracellular fibronectin, for the targeted delivery of three pro-inflammatory cytokines (IL-2, IL-12, TNF) to the microenvironment of gliomas. Following an extensive preclinical assessment in 2 orthotopic immunocompetent mouse glioma models, we used a fully-human L19-hTNF fusion protein to treat human patients with recurrent glioblastoma. Results: Intravenous administration of L19-mIL12 or L19-mTNF prolonged survival and cured a proportion of tumor-bearing mice while no effect was seen with L19-IL2. When L19-mIL12 or L19-mTNF were administered to glioma-bearing RAG−/− mice, no therapeutic activity was observed which suggests adaptive immunity as an underlying mechanism. On a mechanistic level, both immunocytokines induced the infiltration of the tumor site with lymphocytes and promoted the expression of pro-inflammatory cytokines in the tumor microenvironment. In addition, L19-mTNF induced tumor necrosis. Based on these preclinical findings, we initiated a phase I/II clinical trial with a fully-human L19-hTNF fusion protein for patients with isocitrate dehydrogenase (IDH1R132H) wildtype WHO Grade III or IV glioma at first relapse (NCT03779230). Treatment was safe and well tolerated in the first three glioblastoma patients. Administration of L19-hTNF resulted in reduced regional blood perfusion in the tumor region and was associated with more necrotic areas within the tumor as well as an increased number of tumor-infiltrating CD4 and CD8 T cells. Conclusions: The data obtained with the comprehensive preclinical characterization and subsequent clinical translation form the basis for future studies with immunocytokines as novel treatment option for patients with malignant brain tumors. Clinical trial information: NCT03779230 .

Comparative evaluation of DNA-encoded chemical selections performed using DNA in single-stranded or double-stranded format

DNA-encoded chemical libraries (DEL) are increasingly being used for the discovery and optimization of small organic ligands to proteins of biological or pharmaceutical interest. The DNA fragments, that serve as amplifiable identification barcodes for individual compounds in the library, are typically used in double-stranded DNA format. To the best of our knowledge, a direct comparison of DEL selections featuring DNA in either single- or double-stranded DNA format has not yet been reported. In this article, we describe a comparative evaluation of selections with two DEL libraries (named GB-DEL and NF-DEL), based on different chemical designs and produced in both single- and double-stranded DNA format. The libraries were selected in identical conditions against multiple protein targets, revealing comparable and reproducible fingerprints for both types of DNA formats. Surprisingly, selections performed with single-stranded DNA barcodes exhibited improved enrichment factors compared to double-stranded DNA. Using high-affinity ligands to carbonic anhydrase IX as benchmarks for selection performance, we observed an improved selectivity for the NF-DEL library (on average 2-fold higher enrichment factors) in favor of single-stranded DNA. The enrichment factors were even higher for the GB-DEL selections (approximately 5-fold), compared to the same library in double-stranded DNA format. Collectively, these results indicate that DEL libraries can conveniently be synthesized and screened in both single- and double-stranded DNA format, but single-stranded DNA barcodes typically yield enhanced enrichment factors.

Critical Evaluation of Photo-cross-linking Parameters for the Implementation of Efficient DNA-Encoded Chemical Library Selections

The growing importance of DNA-encoded chemical libraries (DECLs) as tools for the discovery of protein binders has sparked an interest for the development of efficient screening methodologies, capable of discriminating between high- and medium-affinity ligands. Here, we present a systematic investigation of selection methodologies, featuring a library displayed on single-stranded DNA, which could be hybridized to a complementary oligonucleotide carrying a diazirine photoreactive group. Model experiments, performed using ligands of different affinity to carbonic anhydrase IX, revealed a recovery of preferential binders up to 10%, which was mainly limited by the highly reactive nature of carbene intermediates generated during the photo-cross-linking process. Ligands featuring acetazolamide or p-phenylsulfonamide exhibited a higher recovery compared to their counterparts based on 3-sulfamoyl benzoic acid, which had a lower affinity toward the target. A systematic evaluation of experimental parameters revealed conditions that were ideally suited for library screening, which were used for the screening of a combinatorial DECL library, featuring 669 240 combinations of two sets of building blocks. Compared to conventional affinity capture procedures on protein immobilized on solid supports, photo-cross-linking provided a better discrimination of low-affinity CAIX ligands over the background signal and therefore can be used as a tandem methodology with the affinity capture procedures.

A universal reporter cell line for bioactivity evaluation of engineered cytokine products

Engineered cytokine products represent a growing class of therapeutic proteins which need to be tested for biological activity at various stages of pharmaceutical development. In most cases, dedicated biological assays are established for different products, in a process that can be time-consuming and cumbersome. Here we describe the development and implementation of a universal cell-based reporter system for various classes of immunomodulatory proteins. The novel system capitalizes on the fact that the signaling of various types of pro-inflammatory agents (e.g., cytokines, chemokines, Toll-like receptor agonists) may involve transcriptional activation by NF-κB. Using viral transduction, we generated stably-transformed cell lines of B or T lymphocyte origin and compared the new reporter cell lines with conventional bioassays. The experimental findings with various interleukins and with members of the TNF superfamily revealed that the newly-developed “universal” bioassay method yielded bioactivity data which were comparable to the ones obtained with dedicated conventional methods. The engineered cell lines with reporters for NF-κB were tested with several antibody-cytokine fusions and may be generally useful for the characterization of novel immunomodulatory products. The newly developed methodology also revealed a mechanism for cytokine potentiation, based on the antibody-mediated clustering of TNF superfamily members on tumor-associated extracellular matrix components.