Safety and Pharmacokinetic Assessment of the FIC CLDN18.2/4-1BB Bispecific Antibody in Rhesus Monkeys.

Gastric cancer is one of the most common cancers worldwide, particularly in China, with over half a million new cases and over 400 thousand deaths in 2022. Zolbetuximab, a first-in-class investigational monoclonal antibody (mAb) targeting tumor-associated antigen CLDN18.2 which is highly expressed on gastric cancer cells, was recently reported to meet the primary endpoint in Phase III trial as first-line treatment in CLDN18.2 positive and HER2-negative gastric cancers. In the present study, we developed a humanized bispecific antibody (bsAb) CLDN18.2/4-1BB named PM1032. PM1032 activates immune cells via CLDN18.2 mediated crosslinking of 4-1BB, a potent stimulator of T/NK cells. It induced strong immunological memory in multiple tumor-bearing animal models, indicating significant potential as an effective treatment for CLDN18.2 positive cancers such as gastric cancer. Since liver and gastrointestinal (GI) related toxicities were reported in 4-1BB and CLDN18.2 targeting programs during the clinical development, respectively, extensive pharmacokinetics (PK) and safety profile characterization of PM1032 was performed in rhesus monkeys. PM1032 had a half-life comparable to a conventional IgG1 mAb, and serum drug concentration increased in a dose-dependent pattern. Furthermore, PM1032 was generally well tolerated, with no significant abnormalities observed in toxicity studies, including the liver and stomach. In summary, PM1032 demonstrated good PK and an exceptional safety profile in rhesus monkeys supporting further investigation in clinical studies.

Insulin signaling establishes a developmental trajectory of adipose regulatory T cells.

Systematic characterizations of adipose regulatory T (Treg) cell subsets and their phenotypes remain uncommon. Using single-cell ATAC-sequencing and paired single-cell RNA and T cell receptor (TCR) sequencing to map mouse adipose Treg cells, we identified CD73hiST2lo and CD73loST2hi subsets with distinct clonal expansion patterns. Analysis of TCR-sharing data implied a state transition between CD73hiST2lo and CD73loST2hi subsets. Mechanistically, we revealed that insulin signaling occurs through a HIF-1α-Med23-PPAR-γ axis to drive the transition of CD73hiST2lo into a CD73loST2hi adipose Treg cell subset. Treg cells deficient in insulin receptor, HIF-1α or Med23 have decreased PPAR-γ expression that in turn promotes accumulation of CD73hiST2lo adipose Treg cells and physiological adenosine production to activate beige fat biogenesis. We therefore unveiled a developmental trajectory of adipose Treg cells and its dependence on insulin signaling. Our findings have implications for understanding the dynamics of adipose Treg cell subsets in aged and obese contexts.

Generation of a safe and efficacious llama single-domain antibody fragment (vHH) targeting the membrane-proximal region of 4-1BB for engineering therapeutic bispecific antibodies for cancer.

BACKGROUND: The discovery of checkpoint inhibitors towards cytotoxic T-lymphocyte protein 4 (CTLA-4) and programmed cell death protein 1 (PD-1) has been revolutionary for the treatment of cancers. These therapies have only offered an average of 20%-30% response rates across the tumor spectrum and the combination of agonists towards the tumor-necrosis superfamily members, such as 4-1BB and CD40, has shown potent efficacy in preclinical studies; however, these agonists have exhibited high degrees of toxicity with limited efficacy in human trials. In this study, we have generated a single-domain antibody towards a unique epitope of 4-1BB that limits its potential on-target toxicity while maintaining sufficient potency. This 4-1BB binder is ideal for use in the engineering of multispecific antibodies to localize 4-1BB activation within the tumor microenvironment, as shown here by a anti-PD-L1/4-1BB bispecific candidate (PM1003). METHODS: To determine the functional activity of the 4-1BB- and PD-L1-binding elements of PM1003, in vitro luciferase reporter and primary cell assays were used to test the potency of programmed cell death 1 ligand 1 (PD-L1) blockade and PD-L1-mediated 4-1BB activation via cross-bridging. X-ray crystallography was conducted to resolve the binding epitopes of the respective binding arms, and accurate binding kinetics were determined using standard affinity measurement techniques. Human 4-1BB and/or PD-L1 knock-in mice were used in cancer models for testing the in vivo antitumor efficacy of PM1003, and safety was evaluated further. RESULTS: PM1003 shows potent activation of 4-1BB and blockade of PD-L1 in cell-based assays. 4-1BB activation was exerted through the bridging of PD-L1 on target cells and 4-1BB on effector cells. No PD-L1-independent activation of 4-1BB was observed. Through X-ray crystallography, a unique binding epitope in the cysteine-rich domain 4 (CRD4) region was resolved that provides high potency and potentially low on-target toxicity as determined by primary immune cell assays and toxicity evaluation in vivo. CONCLUSIONS: A unique single-domain antibody was discovered that binds to the CRD4 domain of 4-1BB. When incorporated into a 4-1BB/PD-L1 bispecific (PM1003), we have shown the potent inhibition of PD-L1 activity with 4-1BB agonism upon cross-bridging with PD-L1 in vitro. Antitumor activity with minimal toxicity was found in vivo. Thus, PM1003 is a uniquely differentiating and next generation therapeutic agent for cancer therapy.

A novel biparatopic hybrid antibody-ACE2 fusion that blocks SARS-CoV-2 infection: implications for therapy.

In the absence of a proven effective vaccine preventing infection by SARS-CoV-2, or a proven drug to treat COVID-19, the positive results of passive immune therapy using convalescent serum provide a strong lead. We have developed a new class of tetravalent, biparatopic therapy, 89C8-ACE2. It combines the specificity of a monoclonal antibody (89C8) that recognizes the relatively conserved N-terminal domain of the viral Spike (S) glycoprotein, and the ectodomain of ACE2, which binds to the receptor-binding domain of S. This molecule shows exceptional performance in vitro, inhibiting the interaction of recombinant S1 to ACE2 and transduction of ACE2-overexpressing cells by S-pseudotyped lentivirus with IC50s substantially below 100 pM, and with potency approximately 100-fold greater than ACE2-Fc itself. Moreover, 89C8-ACE2 was able to neutralize authentic viral infection in a standard 96-h co-incubation assay at low nanomolar concentrations, making this class of molecule a promising lead for therapeutic applications.

Structure, heterogeneity and developability assessment of therapeutic antibodies.

Increasing attention has been paid to developability assessment with the understanding that thorough evaluation of monoclonal antibody lead candidates at an early stage can avoid delays during late-stage development. The concept of developability is based on the knowledge gained from the successful development of approximately 80 marketed antibody and Fc-fusion protein drug products and from the lessons learned from many failed development programs over the last three decades. Here, we reviewed antibody quality attributes that are critical to development and traditional and state-of-the-art analytical methods to monitor those attributes. Based on our collective experiences, a practical workflow is proposed as a best practice for developability assessment including in silico evaluation, extended characterization and forced degradation using appropriate analytical methods that allow characterization with limited material consumption and fast turnaround time.

Analytical comparability study of recombinant monoclonal antibody therapeutics.

Process changes are inevitable in the life cycle of recombinant monoclonal antibody therapeutics. Products made using pre- and post-change processes are required to be comparable as demonstrated by comparability studies to qualify for continuous development and commercial supply. Establishment of comparability is a systematic process of gathering and evaluating data based on scientific understanding and clinical experience of the relationship between product quality attributes and their impact on safety and efficacy. This review summarizes the current understanding of various modifications of recombinant monoclonal antibodies. It further outlines the critical steps in designing and executing successful comparability studies to support process changes at different stages of a product's lifecycle.

Forced degradation of recombinant monoclonal antibodies: A practical guide.

Forced degradation studies have become integral to the development of recombinant monoclonal antibody therapeutics by serving a variety of objectives from early stage manufacturability evaluation to supporting comparability assessments both pre- and post- marketing approval. This review summarizes the regulatory guidance scattered throughout different documents to highlight the expectations from various agencies such as the Food and Drug Administration and European Medicines Agency. The various purposes for forced degradation studies, commonly used conditions and the major degradation pathways under each condition are also discussed.

Accidental Burn by Intentional Laxative Use.

OBJECTIVE: The purpose of this study was to present a case report and review the relevant literature on laxative-induced dermatitis being mistaken for scald injury and child abuse. CASE: A 33-month-old girl presented with partial thickness burn to the buttocks and perineum, which were suspected to be caused by child abuse. On further investigation, the parents had been administering large doses of laxatives to the child for chronic constipation. DISCUSSION: Child abuse by burning has characteristic physical examination findings, which differ from the pattern of laxative-induced dermatitis that has been reported in the literature. Diapers appear to be a risk factor for laxative-induced dermatitis. Surprisingly, the dose of laxative does not correlate with the severity of the burn injury. All physicians must be aware of the possibility of laxative-induced dermatitis mimicking scald burn injury to the buttocks. Parents should be educated about the risk of administering over-the-counter laxatives to children.

Squamous Cell Carcinoma-related Oncogene (SCCRO) Family Members Regulate Cell Growth and Proliferation through Their Cooperative and Antagonistic Effects on Cullin Neddylation.

SCCRO (squamous cell carcinoma-related oncogene; also known as DCUN1D1) is a highly conserved gene that functions as an E3 in neddylation. Although inactivation of SCCRO in yeast results in lethality, SCCRO(-/-) mice are viable. The exclusive presence of highly conserved paralogues in higher organisms led us to assess whether compensation by SCCRO paralogues rescues lethality in SCCRO(-/-) mice. Using murine and Drosophila models, we assessed the in vivo activities of SCCRO and its paralogues in cullin neddylation. We found that SCCRO family members have overlapping and antagonistic activity that regulates neddylation and cell proliferation activities in vivo. In flies, both dSCCRO and dSCCRO3 promote neddylation and cell proliferation, whereas dSCCRO4 negatively regulates these processes. Analysis of somatic clones showed that the effects that these paralogues have on proliferation serve to promote cell competition, leading to apoptosis in clones with a net decrease in neddylation activity. We found that dSCCRO and, to a lesser extent, dSCCRO3 rescue the neddylation and proliferation defects promoted by expression of SCCRO4. dSCCRO and dSCCRO3 functioned cooperatively, with their coexpression resulting in an increase in both the neddylated cullin fraction and proliferation activity. In contrast, human SCCRO and SCCRO4 promote, and human SCCRO3 inhibits, neddylation and proliferation when expressed in flies. Our findings provide the first insights into the mechanisms through which SCCRO family members cooperatively regulate neddylation and cell proliferation.

High throughput solution-based measurement of antibody-antigen affinity and epitope binning.

Advances in human antibody discovery have allowed for the selection of hundreds of high affinity antibodies against many therapeutically relevant targets. This has necessitated the development of reproducible, high throughput analytical techniques to characterize the output from these selections. Among these characterizations, epitopic coverage and affinity are among the most critical properties for lead identification. Biolayer interferometry (BLI) is an attractive technique for epitope binning due to its speed and low antigen consumption. While surface-based methods such as BLI and surface plasmon resonance (SPR) are commonly used for affinity determinations, sensor chemistry and surface related artifacts can limit the accuracy of high affinity measurements. When comparing BLI and solution equilibrium based kinetic exclusion assays, significant differences in measured affinity (10-fold and above) were observed. KinExA direct association (k(a)) rate constant measurements suggest that this is mainly caused by inaccurate k(a) measurements associated with BLI related surface phenomena. Based on the kinetic exclusion assay principle used for KinExA, we developed a high throughput 96-well plate format assay, using a Meso Scale Discovery (MSD) instrument, to measure solution equilibrium affinity. This improved method combines the accuracy of solution-based methods with the throughput formerly only achievable with surface-based methods.

Heterogeneity of monoclonal antibodies.

Heterogeneity of monoclonal antibodies is common due to the various modifications introduced over the lifespan of the molecules from the point of synthesis to the point of complete clearance from the subjects. The vast number of modifications presents great challenge to the thorough characterization of the molecules. This article reviews the current knowledge of enzymatic and nonenzymatic modifications of monoclonal antibodies including the common ones such as incomplete disulfide bond formation, glycosylation, N-terminal pyroglutamine cyclization, C-terminal lysine processing, deamidation, isomerization, and oxidation, and less common ones such as modification of the N-terminal amino acids by maleuric acid and amidation of the C-terminal amino acid. In addition, noncovalent associations with other molecules, conformational diversity and aggregation of monoclonal antibodies are also discussed. Through a complete understanding of the heterogeneity of monoclonal antibodies, strategies can be employed to better identify the potential modifications and thoroughly characterize the molecules.

Progression of emergency medicine resident productivity.

OBJECTIVES: To evaluate the progression in productivity of emergency medicine (EM) residents by postgraduate year, as measured by hourly work in relative value units (RVUs). METHODS: This retrospective study was conducted at an Accreditation Council for Graduate Medical Education (ACGME)-accredited EM residency with a postgraduate year (PGY) 1-2-3 configuration. A query of an electronic billing database composed of more than 230,000 visits from academic years July 2003 to December 2006, representing at least four classes at each PGY level, was conducted. The main outcome was change in productivity in RVUs generated per hour, compared by resident PGY level. This measure encompasses not only volume of patients seen but also patient acuity in terms of evaluation and management services and procedures provided and supported by documentation adequate for coding. Descriptive statistics and Tukey's test were used for data analysis. RESULTS: Over the three-year study period, 70 EM residents were assessed at various levels of training. Productivity, as measured by mean RVUs generated per hour, was 2.51 (95% confidence interval [CI] = 2.20 to 2.82) for PGY-1 residents, 3.51 (95% CI = 3.12 to 3.90) for PGY-2 residents, and 3.61 (95% CI = 3.41 to 3.80) for PGY-3 residents (p < 0.001). Patient acuity (RVUs generated per patient) increased 5%-8% with each PGY progression: 3.05 (95% CI = 2.96 to 3.13) for PGY-1, 3.20 (95% CI = 3.09 to 3.31) for PGY-2, and 3.46 (95% CI = 3.42 to 3.50) for PGY-3 (p < 0.001). There was a statistically significant increase in productivity (p < 0.001) and acuity (p = 0.03) from PGY-1 to PGY-2, with acuity also increasing between PGY-2 and PGY-3 (p < 0.001). CONCLUSIONS: Hourly work productivity and acuity increased with experience within this ACGME-accredited EM residency. The progression in workload and acuity by PGY is measurable and commensurate with the graduated level of responsibility desired in an EM program.

Comparison of methionine oxidation in thermal stability and chemically stressed samples of a fully human monoclonal antibody.

Methionine (Met) oxidation is a major degradation pathway of protein therapeutics. Met oxidation of a fully human recombinant monoclonal antibody was investigated under both chemically stressed conditions using tert-butylhydroperoxide (tBHP) and thermal stability conditions where the sample was incubated in formulation buffer at 25 degrees C for 12 months. This antibody has one Met residue on each of the light chains and four Met residues on each of the heavy chains. In the thermal stability sample, only Met residues 256 and 432 in the Fc region were oxidized to form methionine sulfoxide, while Met residues in the Fab region were relatively stable. The susceptibility of Met residues 256 and 432 was further confirmed by incubating samples with tBHP, which has been shown to induce Met oxidation. Further analysis revealed that the susceptible Met residues of each heavy chain were randomly oxidized in samples incubated with tBHP, while in the thermal stability sample, the susceptible Met residues of one heavy chain were preferentially oxidized.

Effect of posttranslational modifications on the thermal stability of a recombinant monoclonal antibody.

The effect of oligosaccharides and C-terminal lysine residues on the thermal stability of a recombinant IgG(1) monoclonal antibody was investigated using differential scanning calorimetry (DSC). The C-terminal lysine did not appear to affect the thermal stability of this IgG(1) molecule. However, oligosaccharides, which are buried between the two CH(2) domains, provided significant stabilizing energy. Characterization of the Fab and Fc after papain digestion suggested that the stabilizing effect of oligosaccharides on this molecule was through stabilizing CH(2) domains. Oligosaccharides had little effect on the thermal stability of Fab region and CH(3) domains. It was also interesting to note that both intact IgG(1) antibody and its Fab, but not the Fc regions, appeared to form precipitate after thermal unfolding under the experimental conditions.

Characterization of the stability of a fully human monoclonal IgG after prolonged incubation at elevated temperature.

The susceptible degradation sites of therapeutic proteins are routinely assessed under accelerated conditions such as exposure to chemicals or incubation at elevated temperature or a combination of both. A fully human monoclonal IgG(1) antibody was characterized after incubation at 40 degrees C for 6 months by employing mass spectrometry and chromatography analyses. It was found that deamidation, fragmentation and N-terminal glutamate cyclization to form pyroglutamate are the major degradation pathways. Three major deamidation sites were identified and one site in a small tryptic peptide accounted for more than 80% of the total. Peptide cleavage was observed at several positions between different pairs of amino acids. Most of the cleavage sites were located in the hinge or other flexible regions of the IgG molecule.