Receptor Extracellular Domain Research Articles

Bifunctional anti-PD-L1/TGF-βRII agent SHR-1701 plus chemotherapy as first-line treatment for advanced esophageal squamous cell carcinoma (ESCC): Survival results of a phase II trial.

411 Background: Recently, several clinical trials have demonstrated synergistic efficacy by combining immune checkpoint inhibitors (ICIs) with chemotherapy. However, only a subset of patients (pts) derived benefits. Combining ICIs with agents blocking immunosuppressive pathway may expand the clinical benefit of ICIs to more pts. Transforming growth factor β (TGF-β) participates in tumor immune escape. SHR-1701, a novel bifunctional fusion protein consisting of a monoclonal antibody targeting PD-L1 fused with the extracellular domain of TGF-β receptor II, was evaluated in a phase II trial (ChiCTR2000039909) to assess its efficacy and safety when combined with chemotherapy for pts with unresectable locally advanced, recurrent or metastatic ESCC in China. Methods: This trial enrolled treatment-naive pts with histologically or cytologically confirmed unresectable locally advanced, recurrent, or metastatic ESCC. Eligible pts received SHR-1701 (30mg/kg, iv, d1, q3w) in combination with up to six cycles of albumin-bound paclitaxel (125mg/m 2 , iv, d1, d8, q3w) and cisplatin (75mg/m 2 , iv, d1, q3w). For those without progressive disease, maintenance treatment was administered with SHR-1701 monotherapy until disease progression or unacceptable toxicity. The primary endpoint was objective response rate (ORR). Secondary endpoints included progression-free survival (PFS), overall survival (OS), disease control rate (DCR) and safety. Results: At the data cut-off, March 1, 2024, 24 pts had received at least one dose of the study treatment and were included in both the intention-to-treat (ITT) analysis and safety analysis sets. 3 and 12 pts achieved confirmed complete and partial responses, respectively. The confirmed ORR was 62.5% and DCR was 87.5%. With a median follow-up of 20.8 months (95% CI, 15.5-NR), the median duration of response was 9.1 months (95% CI, 6.9-NR). The median PFS was 10.8 months (95% CI, 7.8-NR) and the median OS was 26.1 months (95% CI, 8.6-NR). 12-month PFS and OS rates were 41.4% (95% CI, 22.5-76) and 64.8% (95% CI, 47.8-87.9), respectively. Grade 3-4 treatment-related adverse events occurred in 11 (45.8%) pts and no treatment-related death was observed. Conclusions: The results highlighted that SHR-1701 plus chemotherapy as first-line therapy maintained long-term, durable survival benefit in pts with advanced ESCC. Clinical trial information: ChiCTR2000039909.

Chimeric cytokine receptor TGF-β RⅡ/IL-21R improves CAR-NK cell function by reversing the immunosuppressive tumor microenvironment of gastric cancer.

Gastric cancer remains a significant global health burden, characterized by regional variations in incidence and poor survival prospects in advanced stages. Natural killer (NK) cells play a crucial role in the body's anti-cancer defense, and chimeric antigen receptor (CAR)-NK cell therapy is gaining attention as a cutting-edge and promising treatment method. This study aims to tackle the challenge of TGF-β-mediated tumor immune evasion within the immunosuppressive tumor microenvironment by designing a novel chimeric cytokine receptor TRII/21 R, which consists of extracellular domains of TGF-β receptor II (TRII) and transmembrane and intracellular domains of IL-21 receptor (21 R) and can convert the immunosuppressive signal from TGF-β in the tumor microenvironment (TME) into an NK cell activation signal through the IL-21R-STAT3 pathway. We successfully constructed NKG2D-CAR-NK cells expressing TRII/21 R and demonstrated strong anti-tumor activity against cancer cells both in vitro and in vivo. The co-expression of TRII/21 R in CAR-NK cells enhanced the cytotoxicity, promoted proliferation and survival capabilities, and reduced the expression of exhaustion markers. In the xenograft mouse model, TRII/21R-CAR-NK cells significantly inhibited tumor growth and improved the survival rate of tumor-bearing mice compared to the mice receiving control CAR-NK cells. Additionally, TRII/21 R co-expression enhanced NK cells' infiltration, activation, and persistence within the tumor, indicating a robust anti-tumor response mediated by the JAK-STAT3 signaling pathway. This study underscores the therapeutic potential of TRII/21R-modified CAR-NK cells as a breakthrough strategy for combating cancer.

Neoadjuvant SHR-1701 (a bifunctional anti-PD-L1/TGF-βRII agent) combined with chemoradiotherapy for resectable locally advanced esophageal squamous cell carcinoma (ESCC): A phase II trial.

410 Background: Neoadjuvant chemotherapy or chemoradiotherapy followed by surgery is the standard of care for resectable locally advanced ESCC. SHR-1701, a new bifunctional fusion protein composed of a monoclonal antibody against PD-L1 fused with the extracellular domain of TGF-β receptor II, may enhance antitumor activity in combination with neoadjuvant standard therapies in ESCC patients (pts). The aim of this phase II trial is to determine the safety and efficacy of neoadjuvant chemoradiotherapy plus SHR-1701 followed by esophagectomy in pts with locally advanced resectable ESCC. Methods: Pts with resectable thoracic ESCC, diagnosed as clinical stage of cT1b-cT2N+M0 or cT3-cT4aNxM0 per AJCC 8th were eligible. Preoperative therapy included SHR-1701 (30 mg/kg every 3 weeks for 2 cycles), albumin paclitaxel (50 mg/m 2 , once a week for 5 weeks), carboplatin (AUC=2, once a week for 5 weeks) and radiotherapy (41.4Gy in 23 fractions). Following esophagectomy, pts received SHR-1701 up to 1 year. The primary endpoint was pathological complete response (pCR) rate in the per-protocol population. Secondary endpoints included R0 resection rate, major pathological response (MPR) rate, disease free survival (DFS) and safety. Results: Between Dec. 2021 and Feb. 2023, 43 pts were screened and 41 met the inclusion criteria, among whom the clinical stage I, II, III, and IVa at baseline were 1 (2.4%), 8 (19.5%), 31 (75.6%), and 1 (2.4%), respectively. All 41 pts received neoadjuvant SHR-1701 combined with chemoradiotherapy. As of Mar. 2024, 30 pts underwent surgery, and all achieved R0 resection. There was no in-hospital and postoperative 30-day mortality. 9 (30.0%) pts achieved pCR in both primary tumor and lymph nodes (ypT0N0), and 12 (40.0%) pts had complete pathological response of the primary tumor with residual disease in lymph nodes alone (ypT0N+). Treatment-related adverse events (TRAEs) occurred in all pts, and most of TRAEs were grade 1-2. Notable toxicity included pneumonitis (31.7%) and anastomotic leak (12.2%). Conclusions: The addition of SHR-1701 to neoadjuvant chemoradiotherapy in ESCC demonstrated promising efficacy with acceptable toxicity, and might be a promising approach for neoadjuvant treatment. Clinical trial information: ChiCTR2000041562.

Post-Selection Design of Aptamers: Comparative Study of Affinity of the DNA Aptamers to Recombinant Extracellular Domain of Human Epidermal Growth Factor Receptors.

The current work presents comparative assessment of affinity of the designed DNA aptamers for extracellular domain of the human epidermal growth factor receptor (EGFR*). The affinity data of the 20 previously published aptamers are summarized. Diversity of the aptamer selection methods and techniques requires unification of the comparison algorithms, which is also necessary for designing aptamers used in the post-selection fitting to the target EGFR* protein. In this study affinities of the DNA aptamers from two families, U31 and U2, previously obtained by Wuetal. from the same selection [Wuetal. (2014) PLoS One, 9, e90752] and their derivatives- GR20, U2s, and Gol1 obtained by us through rational design, were compared. Affinity of the aptamers to EGFR* was measured by two different methods: a solution-phase technique- fluorescence polarization of FAM-labeled aptamers, and by a kinetic method using biolayer interferometry technique with aptamers immobilized on the surface. Unlike the values of equilibrium dissociation constants obtained through titration and expressed in units of protein concentration, analysis of the titration curve profiles themselves and kinetics of interaction proved to be more informative. This allowed us to identify how even subtle changes in the aptamers and their structures affect affinity. Hypotheses regarding the "structure-function" relationships and recognition mechanisms were formulated. The data obtained for the set of aptamer constructs are critical for moving forward to examination of aptamer interactions with EGFR on the cell surface.

Targeting C797S mutations and beyond in non-small cell lung cancer-a mini-review.

Non-small cell lung cancer (NSCLC) represents over 80% of lung cancer cases and has a high mortality worldwide, however, targeting common epidermal growth-factor receptor (EGFR) alterations (i.e., del19, L858R) has provided a paradigm shift in the treatment of NSCLC. Uncommon EGFR mutations, however, show variable efficacy to EGFR-targeted drugs depending on the molecular alterations within exons 18-21 which underlying biological mechanism are far from being clear. The substitution mutations of G719X in exon 18, L861Q in exon 21, S768I in exon 20, and exon 20 insertions are the most frequent mutations among the uncommon mutations. The development of fourth-generation EGFR-tyrosine kinase inhibitor (TKIs) has gained increased interest as these drugs are able to inhibit resistance mutations (e.g., C797S) often detected in NSCLC patients' resistance to third-generation EGFR TKIs. BDTX-1535 is an orally bioavailable, brain-penetrating, mutation-selective, irreversible EGFR inhibitor with significant antitumour activity in NSCLCs and glioblastomas (phase I/II trials ongoing). It is a fourth-generation EGFR inhibitor that was found to overcome resistance to osimertinib in preclinical models and has shown promising activity in NSCLC patients harbouring C797S mutations. In experimental models BDTX-1535 was found to inhibit all common EGFR mutations and more than 50 of uncommon mutations including T790M, C797S, L718X, E709X, S784F, V834L and A289V, however, exon 20 insertions are inhibited to a much lesser extent. In addition, mutations in the extracellular domain of the EGF receptor (e.g., EGFRvII, III, IV) can be blocked as well. It should be noted that in up to 50% of all NSCLC patients who progress following osimertinib or other EGFR TKI therapy no underlying resistance mechanism can be identified suggesting that non-mutational signal transduction pathways may also be operative, and intratumoural heterogeneity has been found to be a major contributor to resistance and it consists of three main mechanisms: (I) drug-tolerant persister (DTP) cells, (II) chromosomal instability, and (III) extrachromosomal extracellular DNA (ecDNA) (seen in over 50% of NSCLCs) suggesting that novel EGFR TKIs will include many challenges in sufficiently targeting on-target resistance mechanisms. The development of novel drugs that can overcome TKI resistance in NSCLC patients harbouring the C797S mutation and beyond is, therefore, eagerly warranted.

Functional implications of the exon 9 splice insert in GluK1 kainate receptors

Kainate receptors are key modulators of synaptic transmission and plasticity in the central nervous system. Different kainate receptor isoforms with distinct spatiotemporal expressions have been identified in the brain. The GluK1-1 splice variant receptors, which are abundant in the adult brain, have an extra fifteen amino acids inserted in the amino-terminal domain (ATD) of the receptor resulting from alternative splicing of exon 9. However, the functional implications of this post-transcriptional modification are not yet clear. We employed a multi-pronged approach using cryogenic electron microscopy, electrophysiology, and other biophysical and biochemical tools to understand the structural and functional impact of this splice insert in the extracellular domain of GluK1 receptors. Our study reveals that the splice insert alters the key gating properties of GluK1 receptors and their modulation by the cognate auxiliary Neuropilin and tolloid-like (Neto) proteins 1 and 2. Mutational analysis identified the role of crucial splice residues that influence receptor properties and their modulation. Furthermore, the cryoEM structure of the variant shows that the presence of exon 9 in GluK1 does not affect the receptor architecture or domain arrangement in the desensitized state. Our study thus provides the first detailed structural and functional characterization of GluK1-1a receptors, highlighting the role of the splice insert in modulating receptor properties and their modulation.

Functional implications of the exon 9 splice insert in GluK1 kainate receptors.

Kainate receptors are key modulators of synaptic transmission and plasticity in the central nervous system. Different kainate receptor isoforms with distinct spatiotemporal expressions have been identified in the brain. The GluK1-1 splice variant receptors, which are abundant in the adult brain, have an extra fifteen amino acids inserted in the amino-terminal domain (ATD) of the receptor resulting from alternative splicing of exon 9. However, the functional implications of this post-transcriptional modification are not yet clear. We employed a multi-pronged approach using cryogenic electron microscopy, electrophysiology, and other biophysical and biochemical tools to understand the structural and functional impact of this splice insert in the extracellular domain of GluK1 receptors. Our study reveals that the splice insert alters the key gating properties of GluK1 receptors and their modulation by the cognate auxiliary Neuropilin and tolloid-like (Neto) proteins 1 and 2. Mutational analysis identified the role of crucial splice residues that influence receptor properties and their modulation. Furthermore, the cryoEM structure of the variant shows that the presence of exon 9 in GluK1 does not affect the receptor architecture or domain arrangement in the desensitized state. Our study thus provides the first detailed structural and functional characterization of GluK1-1a receptors, highlighting the role of the splice insert in modulating receptor properties and their modulation.

Development of the novel amylin and calcitonin receptor activators by peptide mutagenesis

The amylin peptide hormone receptor is the complex of the calcitonin peptide hormone receptor and an accessory protein. The calcitonin receptor activation controls calcium homeostasis, while it also functions as the main component of the amylin receptor. Amylin receptor activation in brains controls blood glucose and appetite. Currently, non-selective amylin and calcitonin receptor activators have been tested for body weight reduction to treat obesity. Here, multiple peptide activators for human amylin and calcitonin receptors were developed by introducing comprehensive mutagenesis to rat amylin peptide. The rat amylin peptide C-terminal fragment that interacts with amylin receptor extracellular domain was used to screen for affinity-enhancing mutations. Up to twelve mutational combinations were found to significantly increase peptide affinity both for amylin and calcitonin receptor extracellular domains by over 100-fold. Using these affinity-enhancing mutations, three representative rat amylin analogs with thirty-seven amino acids were made to test the potency increase for amylin and calcitonin receptor activation. All three mutated rat amylin analogs showed significant potency increases by 5- to 10-fold compared to endogenous rat amylin. These mutated peptide activators also showed higher potency for human amylin and calcitonin receptor activation than a clinically available amylin receptor activator pramlintide. These amylin and calcitonin receptor activators developed in this study may be useful as the valuable pharmacological tools that activate amylin receptors in cell-based systems.

Modulation of amylin and calcitonin receptor activation by hybrid peptides

Calcitonin peptide hormone controls calcium homeostasis by activating the calcitonin receptor. When the calcitonin receptor forms a complex with an accessory protein, the complex functions as the receptors for another peptide hormone amylin. The amylin receptors are the drug target for diabetes and obesity treatment. Since human amylin can produce aggregates, rat amylin that does not form aggregates has been commonly used for research. Interestingly, calcitonin originated from salmons was reported to interact with human amylin receptors with higher affinity/potency than endogenous rat amylin. Here, the peptide hybrid was made of a rat amylin N-terminal fragment and a salmon calcitonin C-terminal fragment. This novel hybrid peptide showed higher potency for human amylin receptor 1/2 activation by 6- to 8-fold than endogenous rat amylin. To further examine the role of the peptide C-terminal fragment in receptor activation, another hybrid peptide was made where salmon calcitonin N-terminal 21 amino acids were fused with rat amylin C-terminal 11 amino acids. The rat amylin C-terminal fragment was previously reported to have relatively low affinity for calcitonin receptor extracellular domain. As expected, this calcitonin-amylin hybrid peptide decreased the potency for calcitonin receptor activation by 3-fold compared to salmon calcitonin. The hybrid strategy used in this study significantly changed the peptide potency for amylin and calcitonin receptor activation. These results provide insight into the role of peptide C-terminal fragments in modulating amylin and calcitonin receptor activation.

Selective targeting of oncogenic hotspot mutations of the HER2 extracellular domain.

Oncogenic mutations in the extracellular domain (ECD) of cell-surface receptors could serve as tumor-specific antigens that are accessible to antibody therapeutics. Such mutations have been identified in receptor tyrosine kinases including HER2. However, it is challenging to selectively target a point mutant, while sparing the wild-type protein. Here we developed antibodies selective to HER2 S310F and S310Y, the two most common oncogenic mutations in the HER2 ECD, via combinatorial library screening and structure-guided design. Cryogenic-electron microscopy structures of the HER2 S310F homodimer and an antibody bound to HER2 S310F revealed that these antibodies recognize the mutations in a manner that mimics the dimerization arm of HER2 and thus inhibit HER2 dimerization. These antibodies as T cell engagers selectively killed a HER2 S310F-driven cancer cell line in vitro, and in vivo as a xenograft. These results validate HER2 ECD mutations as actionable therapeutic targets and offer promising candidates toward clinical development.

Aging by autodigestion.

The mechanism that triggers the progressive dysregulation of cell functions, inflammation, and breakdown of tissues during aging is currently unknown. We propose here a previously unknown mechanism due to tissue autodigestion by the digestive enzymes. After synthesis in the pancreas, these powerful enzymes are activated and transported inside the lumen of the small intestine to which they are compartmentalized by the mucin/epithelial barrier. We hypothesize that this barrier leaks active digestive enzymes (e.g. during meals) and leads to their accumulation in tissues outside the gastrointestinal tract. Using immune-histochemistry we provide evidence in young (4 months) and old (24 months) rats for significant accumulation of pancreatic trypsin, elastase, lipase, and amylase in peripheral organs, including liver, lung, heart, kidney, brain, and skin. The mucin layer density on the small intestine barrier is attenuated in the old and trypsin leaks across the tip region of intestinal villi with depleted mucin. The accumulation of digestive enzymes is accompanied in the same tissues of the old by damage to collagen, as detected with collagen fragment hybridizing peptides. We provide evidence that the hyperglycemia in the old is accompanied by proteolytic cleavage of the extracellular domain of the insulin receptor. Blockade of pancreatic trypsin in the old by a two-week oral treatment with a serine protease inhibitor (tranexamic acid) serves to significantly reduce trypsin accumulation in organs outside the intestine, collagen damage, as well as hyperglycemia and insulin receptor cleavage. These results support the hypothesis that the breakdown of tissues in aging is due to autodigestion and a side-effect of the fundamental requirement for digestion.

MG53's non-physiologic interaction with insulin receptor: lack of effect on insulin-stimulated Akt phosphorylation in muscle, heart and liver tissues.

MG53's known function in facilitating tissue repair and anti-inflammation has broad applications to regenerative medicine. There is controversy regarding MG53's role in the development of type 2 diabetes mellitus. This study aims to address this controversy - whether MG53's myokine function contributes to inhibition of insulin signaling in muscle, heart, and liver tissues. We determined the binding affinity of the recombinant human MG53 (rhMG53) to the insulin receptor extracellular domain (IR-ECD) and found low affinity of interaction with Kd (>480 nM). Using cultured C2C12 myotubes and HepG2 cells, we found no effect of rhMG53 on insulin-stimulated Akt phosphorylation (p-Akt). We performed in vivo assay with C57BL/6J mice subjected to insulin stimulation (1 U/kg, intraperitoneal injection) and observed no effect of rhMG53 on insulin-stimulated p-Akt in muscle, heart and liver tissues. Overall, our data suggest that rhMG53 can bind to the IR-ECD, however has a low likelihood of a physiologic role, as the Kd for binding is ~10,000 higher than the physiologic level of MG53 present in the serum of rodents and humans (~10 pM). Our findings question the notion proposed by Xiao and colleagues - whether targeting circulating MG53 opens a new therapeutic avenue for type 2 diabetes mellitus and its complications.

A model-based approach using GSK3772847, an anti-interleukin-33 receptor monoclonal antibody, as a showcase to predict SC administration PK and free target dynamics based on PK and total target measurements after IV administration.

Integrated modeling of the pharmacokinetic (PK) and target binding, by means of a TMDD model, can provide valuable insights into the expected pharmacodynamic (PD) effects of monoclonal antibodies (mAbs). Optimal characterization of the human PK and target binding for mAbs requires data obtained after intravenous (IV) administration which can be combined with subcutaneous (SC) data to further this characterization. Integration of free and/or total target measurements in a population TMDD model will allow quantification of target engagement which is the first step in the cascade leading to efficacy. However, the assays for determination of free target concentrations are analytically challenging and are inherently biased to overpredict the true concentrations in the presence of mAb:target complexes. For that reason, the objective of the current research was to evaluate the predictive value of free target concentrations in a TMDD model developed using PK and total target observations only. Further, a secondary objective was to demonstrate that prediction of SC data is feasible, based on an existing IV model and typical values of mAb parameters reported for SC absorption. GSK3772847, a human immunoglobulin G2 sigma isotype (IgG2f) mAb that binds to the extracellular domain of the interleukin-33 receptor (IL-33R or ST2) and neutralizes IL-33-mediated ST2 signaling, was used as a model compound for mAbs in this study.

The role of palmitoylation of the insulin receptor in insulin resistance: A hypothesis

Palmitoylation is attachment of a palmitoyl group to the cysteine residues of a protein. The intermediary in this process is Palmitoyl CoA, which is formed during the activation of fatty acids in the beta oxidationn of the palmitic acid, consequent to the shift of the energy metabolism to beta oxidation from glycolysis, in DM2.The insulin receptor has cysteine rich domains in the cytosolic portion of the beta sub unit connected by disulfide bonds. It is hypothesized that the palmitoylation forms a thio-ester bond with cystein residues of the beta sub units of the insulin receptor. Depalmitoylation results in substitution of thiol (-SH) in place of the disulfide (S-S) bonds (S-S), due to the hydrolysis by the thio-esterase enzyme. The disulfide bonds are responsible for formation of the functional tettameric form of the insulin receptor. Consequent to the substitution of the SH group in place of S-S group, during depalmitoylation, the functional specificity of the insulin receptor is lost. This leads to the failure of conformational changes and auto- phoshorylation of the beta sub units when insulin binds to the extra cellular insulin binding receptor domain. Also failure of the cascade of phosphorylation of other signalling proteins occurs. Consequently, the failure of the intra- cellular transduction of the signals results in failure of the translocation of the GLUT 4 transporter to the cell membrane. This results in the hyperglycaemia in spite of hyper insulinemia and mo glucose enters into the cell- a state called insulin resistance in DM 2.

Effects of combined cytotoxic T-lymphocyte antigen 4 and programed death 1 ligand-receptor blockade on interferon-gamma production in bovine leukemia virus-infected cattle.

In chronic viral infections, cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) and programmed death ligand 1 (PD-L1) significantly suppress immune responses. The CTLA-4 receptor abundance in regulatory T cells showed a positive association with viral load and a negative association with interferon-gamma (IFN-γ) production in bovine leukemia virus (BLV)-infected cattle. Blocking this receptor boosted IFN-γ production, recovering immune response against this illness. In human cancer patients, not everyone responded positively to non-immunotherapy using CTLA-4 receptor antibodies. The present study analyzed the synergistic effects of CTLA-4 and PD-L1 receptor blockade on IFN-γ production in BLV+ cattle in vitro. The genes for bovine CTLA-4 and PD-L1 were artificially produced. The amino acid sequences of the extracellular receptor domains were sourced from the National Center for Biotechnology Information PubMed database. The western blotting and liquid chromatography with tandem mass spectrometry (LC-MS/MS) techniques were employed for the characterization of recombinant CTLA-4 (rCTLA-4) and recombinant PD-L1 (rPD-L1) proteins. The immunoinhibitory effects of recombinant proteins in Staphylococcus enterotoxin B (SEB)-stimulated cattle peripheral blood mononuclear cells (PBMCs) were investigated. Enzyme-linked immunosorbent assay (ELISA) was used to analyze monoclonal antibodies against rCTLA-4 and rPD-L1. Antibodies generated from peripheral blood mononuclear cells of healthy and BLV-seropositive cows were employed to evaluate their blocking capabilities. The resulting recombinant proteins specifically reacted with commercial homogeneous monoclonal antibodies (mAbs) using ELISA and anti-His-tag mAbs using western blotting. Analysis of the proteins using LC-MS/MS revealed correspondence with the sequences of rCTLA-4 and rPD-L1 located in the Mascot database. rCTLA-4 and rPD-L1 proteins inhibited IFN-γ production in bovine PBMCs of activated SEB. When PBMCs from cows were cultured with activated SEB containing rCTLA-4 and rPD-L1, the mAbs increased IFN-γ production in PBMCs. The combined cultivation of mAbs and PBMCs from BLV+ cattle enhanced IFN-γ production in the cells. These findings suggest that the combined blockade of bovine CTLA-4 and PD-L1 receptors can be used as a therapy for bovine leukemia. However, it was shown that a single PBMC sample from a BLV-positive donor did not amplify the synergistic effect. Therefore, it is necessary to perform further studies on a larger population and assessing a wider range of cytokines.

In vivo turnover and biodistribution of soluble AXL: implications for biomarker development

Soluble biomarkers are paramount to personalized medicine. However, the in vivo turnover and biodistribution of soluble proteins is seldom characterized. The cleaved extracellular domain of the AXL receptor (sAXL) is a prognostic biomarker in several diseases and a predictive marker of AXL targeting agents. Plasma sAXL reflects a balance between production in tissues with lymphatic transport into the circulation and removal from blood by degradation or excretion. It is unclear how this transport cycle affects plasma sAXL levels that are the metric for biomarker development. Radiolabeled mouse sAxl was monitored after intravenous injection to measure degradation and urinary excretion of sAxl, and after intradermal injection to mimic tissue or tumor production. sAxl was rapidly taken-up and degraded by the liver and kidney cortex. Surprisingly, intact sAxl was detectable in urine, indicating passage through the glomerular filter and a unique sampling opportunity. The structure of sAxl showed an elongated, flexible molecule with a length of 18 nm and a thickness of only 3 nm, allowing passage through the glomerulus and excretion into the urine. Intradermally injected sAxl passed through local and distant lymph nodes, followed by uptake in liver and kidney cortex. Low levels of sAxl were seen in the plasma, consistent with an extended transit time from local tissue to circulation. The rapid plasma clearance of sAxl suggests that steady-state levels in blood will sensitively and dynamically reflect the rate of production of sAxl in the tissues but will be influenced by perturbations of liver and kidney function.

Structural characterization and biological activity evaluation of Magnoflorine alkaloid, a potential anticonvulsant agent

Magnoflorine (MGF), an isoquinoline alkaloid, emerges as a quaternary aporphine alkaloid derived from L-tyrosine amino acid, found in families Magnoliaceae plants and it presents important biological activity being noted for its effect on the nervous system. In this work, a deep study of structural, vibrational and electronic properties has been carried out for the MGF. From Potential Energy Surface (PES) scan the most stable conformer of alkaloid was identified and geometrical parameters were determined by Density Functional Theory (DFT) using B3LYP/6–311++G** method. A complete vibrational assignment of the normal modes was theoretical and experimentally achieved from FT-IR and Raman spectroscopies and scaled SQM methodology. Electronic transitions observed in UV–visible spectrum in aqueous medium were identified using TD-DFT methodology, with the π→π* transition being the most probable UV signal. The MEPs, the electric charge distribution along with the HOMO and LUMO frontier orbitals were analyzed and the GAP energy values justified the stability of the molecule in aqueous medium. The molecular electrostatic potential map reveals the most favourable region for electrophilic attack on MGF. Molecular docking was used to analyze the anxiolytic biological activity of the title molecule on the GABAA receptor. The results suggest an intermolecular binding capability of MFG toward both intracellular and extracellular domains of GABAA receptor, and the extracellular domain presents a higher affinity by alkaloid. Finally, the biological study infers that MGF could be used as a potential anxiolytic compound.

Antibody fragments targeting the extracellular domain of follicular stimulating hormone receptor for contraception in male dogs and cats

The increased LH levels resulting from the absence of negative feedback after castration has been linked to long-term health issues. A need exists for an alternative contraceptive agent that functions without interfering the LH pathways. This study aimed to develop antibody fragments against the follicular-stimulating hormone receptor (anti-FSHr) using phage-display technology and evaluate its effects on Sertoli cell functions. Phage clones against the extracellular domain of dog and cat FSHr selected from an antibody fragment phagemid library were analyzed for binding kinetics by surface plasmon resonance. Sertoli cells were isolated from testes of adult animals (five dogs and five cats). Efficacy test was performed by treating Sertoli cell cultures (SCCs) with anti-FSHr antibody fragments compared with untreated in triplicates. Expressions of androgen binding protein (ABP), inhibin subunit beta B (IHBB) and vascular endothelial growth factor A (VEGFA) mRNA in SCCs were quantified by RT-qPCR. The results demonstrated that the molecular weight of the purified dog and cat anti-FSHr antibody fragment was 25 kDa and 15 kDa, respectively. Based on protein molecular weight, the antibody fragment of dogs and cats was therefore, so-called single-chain variable fragments (scFv) and nanobody (nb), respectively. The binding affinity with dissociation constant (KD) was 2.32 × 10−7 M and 2.83 × 10−9 M for dog and cat anti-FSHr antibody fragments, respectively. The cross-binding kinetic interactions between the dog anti-FSHr scFv and the cat ECD of FSHr could not be fitted to the curves to determine the binding kinetics. However, the cross-binding affinity KD between the cat anti-FSHr nb and the dog ECD FSHr was 1.75 × 10−4 M. The mRNA expression of ABP, IHBB and VEGFA in SCCs was less (P < 0.05) in both dogs (12.26, 4.07 and 5.11 folds, respectively) and cats (39.53, 14.07 and 20.29 folds, respectively) treated with anti-FSHr antibody fragments, indicating the Sertoli cell functions were suppressed. In conclusion, this study demonstrated the establishment of species-specific antibody fragments against FSHr in SCCs for dogs and cats. The fragment proteins illustrate potential to be developed as non-surgical contraceptive agent targeting FSHr in companion animals.

A phase I/II open label, multicenter study to assess the safety, tolerability, pharmacokinetics, and efficacy of HB0028 in patients with advanced solid tumors.

2528 Background: HB0028 is a bifunctional fusion protein consisting of an anti-PD-L1 IgG1 single domain antibody and TGF-β RII receptor extracellular domain (TGFβRII-ECD). This is the first dose escalation and expansion phase I/II study to evaluate the safety and preliminary anti-tumor activity of HB0028 in advanced solid tumors. Methods: In the phase I portion of the study, the patients (pts) with advanced solid tumor were enrolled, and an accelerated titration followed by a standard 3+3 design was applied to dose escalation. The objectives were toxicity evaluation, maximum tolerable dose (MTD), and recommended phase 2 dose (RP2D). Eligible pts with advanced solid cancers of any histologic subtype, and ECOG performance status ≤ 1 were treated with HB0028 (0.3mg, 1mg, 3mg, 10mg, 20mg, Q3W), until unacceptable toxicity or disease progression. Radiologic tumor assessments (by RECIST v1.1) were performed every 6 weeks while on treatment. Results: 16 pts [12 females and 4 males; ECOG 0/1, 9/7; median age 52 years (range 36 – 60)] were enrolled in phase I (0.3 mg/kg [n = 1], 1 mg/kg [n = 3], 3 mg/kg [n = 3], 10 mg/kg [n = 3], 20 mg/kg [n = 6]). Median number of prior lines of systemic therapy was 2 (range 1-4). 8(50%) pts received and progressed upon prior anti-PD-1/L1 therapy. All pts had measurable metastatic disease. No DLT and Death occurred. MTD was not reached. As of DEC 25,2023, among 16 patients' safety data are evaluable for toxicity. Any grade treatment‐related adverse events (TRAEs) occurred in 15 subjects (93.8%), with 2 subjects (12.5%) reported with ≥ Grade 3 (G3 Anemia and G3 γ-glutamyltransferase). The most common TRAEs (all grades) were AST increased (n = 4, 25%), anemia (n = 7, 43.8%) and infusion-related response (n = 5, 31.3%). Two SAEs (G2 AST increased and G3 Neoplastic fevers) were reported, only AST increased was considered as possibly related to study drug, but recovered shortly. The efficacy data cutoff date of DEC 25,2023, 16 patients are evaluable for radiologic response. 1 subject with cervical cancer in HB0028 20 mg/kg group had a partial response (PR), 3 subjects (liver cancer, lung cancer, left submandibular gland cancer) had stable disease (SD) and 12 subjects had progressive disease (PD). The ORR per RECIST 1.1 by investigator was 6.25% (1/16; 95% CI, 0%-30.2%), and the DCR was 25% (4/16; 95% CI, 7.3%-52.4%). Durable clinical benefit (SD for &gt; 32 weeks) was seen in 1 subject with malignant tumor in the left submandibular gland. To date, 2 responders are still on treatment. Conclusions: HB0028 was generally well tolerated, and therapy provided modest antitumor activity in patients with heavily pretreated advanced solid tumors. Based on these data, a phase II prospective clinical trial is being planned in specific cancer. Clinical trial information: NCT06223308 .

Impact of secretin receptor homo-dimerization on natural ligand binding

Class B G protein-coupled receptors can form dimeric complexes important for high potency biological effects. Here, we apply pharmacological, biochemical, and biophysical techniques to cells and membranes expressing the prototypic secretin receptor (SecR) to gain insights into secretin binding to homo-dimeric and monomeric SecR. Spatial proximity between peptide and receptor residues, probed by disulfide bond formation, demonstrates that the secretin N-terminus moves from adjacent to extracellular loop 3 (ECL3) at wild type SecR toward ECL2 in non-dimerizing mutants. Analysis of fluorescent secretin analogs demonstrates stable engagement of the secretin C-terminal region within the receptor extracellular domain (ECD) for both dimeric and monomeric receptors, while the mid-region exhibits lower mobility while docked at the monomer. Moreover, decoupling of G protein interaction reduces mobility of the peptide mid-region at wild type receptor to levels similar to the mutant, whereas it has no further impact on the monomer. These data support a model of peptide engagement whereby the ability of SecR to dimerize promotes higher conformational dynamics of the peptide-bound receptor ECD and ECLs that likely facilitates more efficient G protein recruitment and activation, consistent with the higher observed functional potency of secretin at wild type SecR relative to the monomeric mutant receptor.