Receptor Occupancy Research Articles

Quantification of receptor binding from response data obtained at different receptor levels: a simple individual sigmoid fitting and a unified SABRE approach

Methods that allow quantification of receptor binding (occupancy) by measuring response (effect) data only are of interest as they can be used to allow characterization of binding properties (e.g., dissociation constant, Kd) without having to perform explicit ligand binding experiments that require different setups (e.g., use of labeled ligands). However, since response depends not just on the binding affinity-determined receptor occupancy, but also on receptor activation, which is affected by ligand efficacy (plus constitutive activity, if present), and downstream pathway amplification, this requires the acquisition and fitting of multiple concentration-response data. Here, two alternative methods, which both are straightforward to implement using nonlinear regression software, are described to fit such multiple responses measured at different receptor levels that can be obtained, for example, by partial irreversible receptor inactivation (i.e., Furchgott method) or different expression levels. One is a simple method via straightforward fitting of each response with sigmoid functions and estimation of Kd from the obtained Emax and EC50 values as Kd = (Emax·EC′50 − E′max·EC50)/(Emax − E′max). This is less error-prone than the original Furchgott method of double-reciprocal fit and simpler than alternatives that require concentration interpolations, thus, should allow more widespread use of this so-far underutilized approach to estimate binding properties. Relative efficacies can then be compared using Emax·Kd/EC50 values. The other is a complex method that uses the SABRE receptor model to obtain a unified fit of the multiple concentration-response curves with a single set of parameters that include binding affinity Kd, efficacy ε, amplification γ, and Hill coefficient n. Illustrations with simulated and experimental data are presented including with activity data of three muscarinic agonists measured in rabbit myocardium.

In vivo Characterization of the Opioid Receptor-Binding Profiles of Samidorphan and Naltrexone in Rats: Comparisons at Clinically Relevant Concentrations.

The atypical antipsychotic olanzapine is approved for the treatment of schizophrenia and bipolar I disorder; however, weight gain and metabolic dysregulation associated with olanzapine therapy have limited its clinical utility. In clinical studies, treatment with the combination of olanzapine and the opioid receptor antagonist samidorphan (OLZ/SAM) mitigated olanzapine-associated weight gain while providing antipsychotic efficacy similar to that of olanzapine. Although samidorphan is structurally similar to the opioid receptor antagonist naltrexone, the two differ in their pharmacokinetics and in vitro binding affinities to mu, delta, and kappa opioid receptors (MOR, DOR, and KOR, respectively). The objective of this series of nonclinical studies was to compare the in vivo binding profiles of samidorphan and naltrexone and their receptor occupancies at MOR, DOR, and KOR in rat brains. Male rats were injected with samidorphan or naltrexone to obtain total and unbound plasma and brain concentrations representing levels observed in humans at clinically relevant oral doses. Subsequently, samidorphan and naltrexone brain receptor occupancy at MOR, DOR, and KOR was measured using ultra-performance liquid chromatography and high-resolution accurate-mass mass spectrometry. A dose-dependent increase in samidorphan occupancy was observed at MOR, DOR, and KOR (EC50: 5.1, 54.7, and 42.9 nM, respectively). Occupancy of naltrexone at MOR (EC50: 15.5 nM) and KOR was dose dependent; minimal DOR occupancy was detected. At the clinically relevant unbound brain concentration of 23.1nM, samidorphan bound to MOR, DOR, and KOR with 93.2%, 36.1%, and 41.9% occupancy, respectively. At 33.5 nM, naltrexone bound to MOR and KOR with 79.4% and 9.4% occupancy, respectively, with no binding at DOR. At clinically relevant concentrations, samidorphan occupied MOR, DOR, and KOR, whereas naltrexone occupied only MOR and KOR. The binding profile of samidorphan differs from that of naltrexone, with potential clinical implications.

Human FSH Glycoform α-Subunit Asparagine52 Glycans: Major Glycan Structural Consistency, Minor Glycan Variation in Abundance.

Follicle-stimulating hormone (FSH), an α/β heterodimeric glycoprotein hormone, consists of functionally significant variants resulting from the presence or absence of either one of two FSHβ subunit N-glycans. The two most abundant variants are fully-glycosylated FSH24 (based on 24 kDa FSHβ band in Western blots) and hypo-glycosylated FSH21 (21 kDa band, lacks βAsn24 glycans). Due to its ability to bind more rapidly to the FSH receptor and occupy more FSH binding sites than FSH24, hypo-glycosylated FSH21 exhibits greater biological activity. Endoglycosidase F1-deglycosylated FSH bound to the complete extracellular domain of the FSH receptor crystallized as a trimeric complex. It was noted that a single biantennary glycan attached to FSHα Asn52 might preemptively fill the central pocket in this complex and prevent the other two FSH ligands from binding the remaining ligand-binding sites. As the most active FSH21 preparations possessed more rapidly migrating α-subunit bands in Western blots, we hypothesized that Asn52 glycans in these preparations were small enough to enable greater FSH21 receptor occupancy in the putative FSHR trimer model. Highly purified hFSH oligosaccharides derived from each FSH subunit, were characterized by electrospray ionization-ion mobility-collision-induced dissociation (ESI-IM-CID) mass spectrometry. FSHβ glycans typically possessed core-linked fucose and were roughly one third bi-antennary, one third tri-antennary and one third tetra-antennary. FSHα oligosaccharides largely lacked core fucose and were bi- or tri-antennary. Those αAsn52 glycans exhibiting tetra-antennary glycan m/z values were found to be tri-antennary, with lactosamine repeats accounting for the additional mass. Selective αAsn52 deglycosylation of representative pituitary hFSH glycoform Superdex 75 gel filtration fractions followed by ESI-IM-CID mass spectrometry revealed tri-antennary glycans predominated even in the lowest molecular weight FSH glycoforms. Accordingly, the differences in binding capacity of the same receptor preparation to different FSH glycoforms are likely the organization of the FSH receptor in cell membranes, rather than the αAsn52 oligosaccharide.

The Neurokinin-1 Receptor: Structure Dynamics and Signaling

Substance P (SP), the first isolated neuropeptide, belongs to the family of tachykinin peptides and is the natural ligand of neurokinin-1 receptors (NK-1R), also named SP receptors. The undecapeptide activates the receptor after specifically binding to the protein and triggers intracellular signals leading to different biochemical events and subsequent physiological responses. This study reviews the main architectural features of this receptor, its interaction with natural and synthetic ligands, and the functional conformational states adopted after interacting with ligands and effector G proteins. The analysis of the main intracellular signaling pathways turned on by the activation of NK-1 receptors reveals the participation of different proteins supporting metabolic changes and genetic and epigenetic regulations. Furthermore, the analysis of receptor occupancy and receptor downregulation and internalization represents a complex and estimable field for basic and clinical research focused on the role of SP in physiopathology. Profound knowledge of the structural dynamics of NK-1R may help develop and assay new selective synthetic non-peptide antagonists as potential therapeutic agents applied to various pathologies and symptoms.

Relationship of tafamidis binding site occupancy, transthyretin stabilization, and disease modification in tafamidis treated transthyretin amyloid cardiomyopathy patients

Abstract Introduction Tafamidis inhibits progression of transthyretin (TTR) amyloid cardiomyopathy (ATTR-CM) by binding TTR tetramer and inhibiting its dissociation to monomers which can denature and result in amyloid fibril formation and deposition in cardiac tissue. Purpose While the phase 3 ATTR-ACT clinical data clearly demonstrated efficacy, quantification of TTR stabilization in patients and the degree to which the approved dose captures the full potential of the mechanism has yet to be assessed. Methods Isothermal titration calorimetry and subunit fraction exchange were used to determine affinities to the two binding sites on TTR. These values were used to develop a model of tafamidis binding to TTR in plasma that was applied to individual patient data to calculate TTR binding site occupancy and the change in total TTR levels induced by TTR stabilization. Population pharmacodynamic (PD) models were developed for three measures of disease progression, plasma NT-proBNP levels, Kansas City Cardiomyopathy Questionnaire – Overall Score (KCCQ-OS), and six-minute walk test (6MWT) distance, to evaluate patient response with the degree of TTR occupancy. Results In vitro binding data of wild-type TTR confirmed tafamidis binds two sites of TTR with negative cooperativity and provided precise estimates of the binding affinity to TTR and albumin. Modeling individual patient data of tafamidis exposure and increased TTR plasma levels using the in vitro derived binding affinity values confirms single site binding is consistent with complete tetramer stabilization. Patients given 80 mg tafamidis meglumine, the clinically approved dose for ATTR-CM, had a 92% reduction in unbound, unstabilized TTR, which correlated with a 53% decrease in NT-proBNP elevation, a 56% decrease in KCCQ-OS worsening and a 49% reduced decline in the 6MWT. For 100% receptor occupancy and stabilization, the expected effects on these measures are 58%, 61%, and 54% for NT-proBNP, KCCQ-OS, and 6MWT, respectively. Conclusions These results demonstrate a quantitative relationship between TTR stabilization, the mechanism of action of tafamidis, and accepted laboratory and patient-based outcomes in ATTR-CM. These results also support the value of TTR stabilization as a clinically beneficial treatment option which maintains the protein in its physiologically active form within the body. Funding Acknowledgement Type of funding sources: Private company. Main funding source(s): This study was sponsored by Pfizer.

S793 Full Target Engagement With Saturation of α4β7 Integrin Receptor Occupancy Resulting in Changes in Subset of Lymphocytes by MORF-057 Following 200 Mg Daily Dosing in Healthy Subjects

S793 Full Target Engagement With Saturation of α4β7 Integrin Receptor Occupancy Resulting in Changes in Subset of Lymphocytes by MORF-057 Following 200 Mg Daily Dosing in Healthy Subjects

First-in-human phase I/II, open-label study of the anti-OX40 agonist INCAGN01949 in patients with advanced solid tumors

BackgroundOX40 is a costimulatory receptor upregulated on antigen-activated T cells and constitutively expressed on regulatory T cells (Tregs). INCAGN01949, a fully human immunoglobulin G1κ anti-OX40 agonist monoclonal antibody, was designed...

MM-071 Subcutaneous (SC) Isatuximab (Isa) Administration by an On-Body Delivery System (OBDS) in Combination With Pomalidomide-Dexamethasone (Pd) in Relapsed/Refractory Multiple Myeloma (RRMM) Patients: Interim Phase 1b Study Results

SC Isa delivery would optimize convenience of administration. Prior results showed SC Isa administered by syringe pump has efficacy and safety profiles comparable to IV Isa; recommended Phase 2 dose (RP2D) 1400 mg (IMW21 P-207). Evaluate safety, pharmacokinetics (PK), and efficacy of SC vs IV Isa+Pd Design: Multicenter Phase 1b study. RRMM patients after ≥2 prior treatment lines. Patients randomized 2:1 to SC1000mg or IV10mg/kg and to SC1400mg or IV. Expansion cohort was implemented with SC Isa administered at RP2D via OBDS (wearable bolus injector applied to abdomen). Primary endpoints were safety, including injection site (IS) reactions (ISRs), and PK. 56 patients were randomized and treated: 12 IV, 12 SC1000, 10 SC1400, 22 OBDS. At study entry, ISS stage II-III: IV 67%, SC1000 33%, SC1400 60%, OBDS 50%. On January 20th, 2022, 33% IV, 25% SC1000, 50% SC1400, 86% OBDS patients remained on treatment. Due to sequential accrual, median follow-up (FU; in mo) was longer in IV (20.6) and SC1000 (23.8) than SC1400 (18.1) and OBDS (6.5). Infusion reactions (IRs) were infrequent (≤10% in each cohort, Grade [G] 2), at first IV/SC infusion/injection, with no IRs in OBDS. Local tolerability of OBDS was very good; 5 (22.7%) patients experienced 7 ISR episodes, (G1) of 305 administrations (2.3%): 5 IS erythemas, 1 IS hemorrhage, 1 IS induration. Median duration of OBDS was 10 min. Lower percentage of ≥G3 treatment-related adverse events in OBDS (77%) vs other cohorts (≥80%) may be due to shorter FU. Overall response rate: IV and SC1000 66.7%, SC1400 80.0%, OBDS 77.3%, SC1400+OBDS 78.1%; ≥very good partial response ranged between 40%-50%, complete response 13-25%, partial response 16-40% across cohorts; longer FU is needed for OBDS. Median PFS was: IV 22 mo, SC1000 12.5 mo, SC1400 and OBDS not reached. PK and CD38 receptor occupancy in OBDS were consistent with SC1400. SC Isa via OBDS shows safety profile consistent with IV; with no IRs and excellent tolerability. Efficacy in SC cohorts was comparable to Phase 3 ICARIA. Isa SC administration by OBDS is well-tolerated, requires a short injection duration, and provides a handsfree option.

Studying Telmisartan Plasma Exposure, Kidney Distribution, Receptor Occupancy, and Response in Patients With Type 2 Diabetes Using [11 C]Telmisartan.

The angiotensin receptor blocker telmisartan slows progression of kidney disease in patients with type 2 diabetes (T2D), yet many patients remain at high risk for progressive kidney function loss. The underlying mechanisms for this response variation might be attributed to differences in angiotensin-1 receptor occupancy (RO), resulting from individual variation in plasma drug exposure, tissue drug exposure, and receptor availability. Therefore, we first assessed the relationship between plasma telmisartan exposure and urinary-albumin-to-creatinine-ratio (UACR) in 10 patients with T2D and albuminuria (mean age 66 years, median UACR 297 mg/g) after 4 weeks treatment with 80 mg telmisartan once daily. Increasing telmisartan exposure associated with a larger reduction in UACR (Pearson correlation coefficient (PCC)=-0.64, P=0.046, median change UACR: -40.1%, 95% confidence interval (CI): -22.9 to -77.4%, mean telmisartan area under the curve (AUC)=2927.1 ng·hour/mL, 95% CI: 723.0 to 6501.6 ng·hour/mL). Subsequently, we assessed the relation among plasma telmisartan exposure, kidney distribution, and angiotensin-1 RO in five patients with T2D (mean age 60 years, median UACR 72 mg/g) in a separate positron emission tomography imaging study with [11 C]Telmisartan. Individual plasma telmisartan exposure correlated with telmisartan distribution to the kidneys (PCC=0.976, P=0.024). A meaningful RO could be calculated in three patients receiving 120 mg oral telmisartan, and although high exposure seems related to higher RO, with AUC0-last of 31, 840, and 274 ng·hour/mL and corresponding RO values 5.5%, 44%, and 59%, this was not significant (P=0.64). Together these results indicate, for the first time, a relationship among interindividual differences in plasma exposure, kidney tissue distribution, RO, and ultimately UACR response after telmisartan administration.

PEGylation of anti-MerTK Antibody Modulates Ocular Biodistribution.

Here, we explore whether PEGylation of antibodies can modulate their biodistribution to the eye, an organ once thought to be immune privileged but has recently been shown to be accessible to IV-administered large molecules, such as antibodies. We chose to PEGylate an anti-MerTK antibody, a target with known potential for ocular toxicity, to minimize biodistribution to retinal pigment epithelial cells (RPEs) in the eye by increasing the hydrodynamic volume of the antibody. We used site-specific conjugation to an engineered cysteine on anti-MerTK antibody to chemically attach 40-kDa branched or linear PEG polymers. Despite reduced binding to MerTK on cells, site-specifically PEGylated anti-MerTK retained similar potency in inhibiting MerTK-mediated macrophage efferocytosis of apoptotic cells. Importantly, we found that PEGylation of anti-MerTK significantly reduced MerTK receptor occupancy in RPE cells in both naïve mice and MC-38 tumor-bearing mice, with the branched PEG exhibiting a greater effect than linear PEG. Furthermore, similar to unconjugated anti-MerTK, PEGylated anti-MerTK antibody triggered type I IFN response and exhibited antitumor effect in syngeneic mouse tumor studies. Our results demonstrate the potential of PEGylation to control ocular biodistribution of antibodies.

Designing drug occupancy studies with PET neuroimaging: Sample size, occupancy ranges and analytical methods

Molecular neuroimaging is today considered essential for evaluation of novel CNS drugs; it is used to quantify blood-brain barrier permeability, verify interaction with key target and determine the drug dose resulting in 50% occupancy, IC50. In spite of this, there has been limited data available to inform on how to optimize study designs.Through simulations, we here evaluate how IC50 estimation is affected by the (i) range of drug doses administered, (ii) number of subjects included, and (iii) level of noise in the plasma drug concentration measurements. Receptor occupancy is determined from PET distribution volumes using two different methods: the Lassen plot and Likelihood estimation of occupancy (LEO). We also introduce and evaluate a new likelihood-based estimator for direct estimation of IC50 from PET distribution volumes.For estimation of IC50, we find very limited added benefit in scanning individuals who are given drug doses corresponding to less than 40% receptor occupancy. In the range of typical PET sample sizes (5–20 subjects) each extra individual clearly reduces the error of the IC50 estimate.In all simulations, likelihood-based methods gave more precise IC50 estimates than the Lassen plot; four times the number of subjects were required for the Lassen plot to reach the same IC50 precision as LEO.

754P A phase I/IIa dose escalation study of AFM24 in patients with epidermal growth factor receptor-expressing (EGFR) solid tumors: Results from phase I

AFM24 is an EGFR/CD16A bispecific innate cell engager binding to natural killer (NK) cells and macrophages, inducing potent antibody mediated cytotoxicity and phagocytosis of tumor cells in vitro. This phase 1 study evaluated the safety, immunogenicity, pharmacokinetics (PK) and pharmacodynamics (PD) of AFM24 in patients (pts) with metastatic, treatment refractory solid tumors known to express EGFR. AFM24 was given intravenously QW at 14–720 mg in 28-day cycles until disease progression, intolerable toxicity, investigator’s discretion, or patient withdrawal. As of March 2022, 34 pts were treated with AFM24; median (range) age 58 (29–81) years; prior therapies 4 (2–11); total AFM24 doses given 8 (1–29). Tumor types included mainly colorectal (18/34; 12 KRAS mutant) and non-small cell lung cancer (8/34; 7 EGFR mutant). AFM24-related treatment-emergent adverse events (TEAEs) included infusion-related reactions (IRR, 25/34), nausea (8/34), and acneiform dermatitis (7/34). Seven pts had AFM24-related, transient, reversible G3–4 TEAEs (2 G3 IRRs, 1 G3 hypertension, 1 G3 dermatitis acneiform, 4 ≥G3 lymphocytopenia); there were no on-study deaths. One dose-limiting toxicity occurred at 40 mg (G3 IRR). The maximum tolerated dose has not been reached. Stable disease (SD) was observed in 10/27 evaluable pts; 4 pts had SD for ≥4 months. Dose proportional increase in PK was observed at doses ≥320 mg. CD16A receptor occupancy on circulating blood cells was dose-dependent and appeared to level off between 320–480 mg. Comprehensive PD studies of cytokines (including TNFα, IFNγ) and immune cells in peripheral blood and tumor biopsies indicated activation of the innate as well as the adaptive immune system starting at 160 mg. From these findings, the recommended phase 2 dose was determined at 480 mg. Treatment is ongoing in 4 pts (final data at ESMO). AFM24 was well-tolerated and enrollment into disease specific cohorts at 480 mg has begun. Early biomarker data demonstrate target engagement with expected immune activation. Studies are also evaluating AFM24 in combination with atezolizumab, or with autologous NK cells exploring its potential to activate the innate immune response.

782TiP Reduced frequency immune checkpoint inhibition in cancers (REFINE): A multi-arm phase II trial testing reduced intensity immunotherapy in different cancers

Immune checkpoint inhibitors (ICI) have revolutionised cancer treatment, resulting in long-term durable responses. In advanced disease, ICIs are administered every 2-6 weeks i.v. until cancer progression or unacceptable toxicity, which is often several years’ treatment. Physiological efficacy of anti-PD-1 antibodies (maximal receptor occupancy) is seen at lower doses than those in routine use. Pharmacodynamic studies indicate sustained target occupancy of >70% for at least 2 months, despite half-lives of 2-3 weeks.

730MO First-in-human phase I study of INCAGN02390, a TIM-3 monoclonal antibody antagonist in patients with advanced malignancies

TIM-3 is a transmembrane checkpoint receptor expressed on multiple immune cells that promotes an inhibitory tumor microenvironment. INCAGN02390 is a fully human Fc-engineered IgG1κ monoclonal antibody that selectively inhibits TIM-3 ligand interactions. This study is primarily aimed to determine the safety and tolerability and define the MTD or PAD of INCAGN02390 monotherapy. This is a phase 1, multicenter, open-label, dose-escalation study that enrolled pts with locally advanced or metastatic solid tumors that failed available therapies, were intolerant to treatment, or refused noncurative standard treatment. A 3+3 dose-escalation design was used; pts received intravenous INCAGN02390 Q2W in 7 dose levels (DLs): 10 mg, 30 mg, 100 mg, 200 mg, 400 mg, 800 mg, or 1600 mg. The primary endpoint was safety and tolerability. Other endpoints were PK, PD and preliminary efficacy per RECIST v1.1. Forty pts (median age, 63 y) were enrolled; 53% were male and 83% had ECOG PS 1. Lead cancer types were breast (15%), lung (13%), and colorectal (10%). 98% received prior systemic therapy (58% had prior immunotherapy). No DLT was observed and MTD was not reached. Most frequent treatment-emergent adverse events (TEAEs) were anemia (35%), back pain (30%), and fatigue (28%). Drug-related grade ≥3 TEAEs were observed in 7.5% of pts (anemia, adrenal insufficiency, and amylase increased [n=1 each]; all Gr3). One drug-related serious TEAE (adrenal insufficiency) occurred at the 1600 mg DL. One drug-unrelated fatal TEAE (multi-organ failure) occurred in the 800-mg DL. INCAGN02390 trough serum concentrations achieved steady state around Cycles 4 to 6. Maximum concentration and area under the serum concentration-time curve were linear across most DLs. Doses ≥400 mg led to trough TIM-3 receptor occupancy levels of ≥90% in peripheral blood. Disease control rate was 17.5%, with 1 confirmed partial response in a pt with an adenoid cystic carcinoma in lung. INCAGN02390 monotherapy was generally well tolerated, with linear PK. The 400 mg Q2W dose is selected for further investigation in phase 1b/2 studies in combinations with other immunotherapies (NCT04370704, NCT05287113).

Opioid antagonism in humans: a primer on optimal dose and timing for central mu-opioid receptor blockade

Non-human animal studies outline precise mechanisms of central mu-opioid regulation of pain, stress, affiliation and reward processing. In humans, pharmacological blockade with non-selective opioid antagonists such as naloxone and naltrexone is typically used to assess involvement of the mu-opioid system in such processing. However, robust estimates of the opioid receptor blockade achieved by opioid antagonists are missing. Dose and timing schedules are highly variable and often based on single studies. Here, we provide a detailed analysis of central opioid receptor blockade after opioid antagonism based on existing positron emission tomography data. We also create models for estimating opioid receptor blockade with intravenous naloxone and oral naltrexone. We find that common doses of intravenous naloxone (0.10–0.15 mg/kg) and oral naltrexone (50 mg) are more than sufficient to produce full blockade of central MOR (>90% receptor occupancy) for the duration of a typical experimental session (~60 min), presumably due to initial super saturation of receptors. Simulations indicate that these doses also produce high KOR blockade (78–100%) and some DOR blockade (10% with naltrexone and 48–74% with naloxone). Lower doses (e.g., 0.01 mg/kg intravenous naloxone) are estimated to produce less DOR and KOR blockade while still achieving a high level of MOR blockade for ~30 min. The models and simulations form the basis of two novel web applications for detailed planning and evaluation of experiments with opioid antagonists. These tools and recommendations enable selection of appropriate antagonists, doses and assessment time points, and determination of the achieved receptor blockade in previous studies.

Small molecule photocatalysis enables drug target identification via energy transfer

Over half of new therapeutic approaches fail in clinical trials due to a lack of target validation. As such, the development of new methods to improve and accelerate the identification of cellular targets, broadly known as target ID, remains a fundamental goal in drug discovery. While advances in sequencing and mass spectrometry technologies have revolutionized drug target ID in recent decades, the corresponding chemical-based approaches have not changed in over 50 y. Consigned to outdated stoichiometric activation modes, modern target ID campaigns are regularly confounded by poor signal-to-noise resulting from limited receptor occupancy and low crosslinking yields, especially when targeting low abundance membrane proteins or multiple protein target engagement. Here, we describe a broadly general platform for photocatalytic small molecule target ID, which is founded upon the catalytic amplification of target-tag crosslinking through the continuous generation of high-energy carbene intermediates via visible light-mediated Dexter energy transfer. By decoupling the reactive warhead tag from the small molecule ligand, catalytic signal amplification results in unprecedented levels of target enrichment, enabling the quantitative target and off target ID of several drugs including (+)-JQ1, paclitaxel (Taxol), dasatinib (Sprycel), as well as two G-protein-coupled receptors-ADORA2A and GPR40.

Postsynaptic glutamate response downregulates within presynaptic exaggerated glutamate release by activating TRPV1 in the spinal dorsal horn

Activating primary afferent TRPV1-positive (TRPV1+) fibers in the spinal dorsal horn triggers exaggerated glutamate release and induces acute pain. However, whether the glutamate postsynaptic responses on dorsal horn neurons are regulated by excessive glutamate is unknown, largely due to intrinsic technical difficulties. In the present study, capsaicin, a specific TRPV1 agonist, was used to activate TRPV1+ fibers in the spinal dorsal horn. Combining three-dimensional (3-D) holographic photostimulation and whole-cell recordings on acute spinal cord slices from adult rodents, we found that postsynaptic glutamate responses were attenuated when activating TRPV1+ fibers with capsaicin. Electron microscopy and Western blot studies found that postsynaptic GluA1 (a subtype of ionotropic glutamate receptors) on the postsynaptic membrane was decreased by acute capsaicin treatment. Therefore, postsynaptic glutamate receptor occupancy and/or downmodulation may underlie this postsynaptic attenuation. Our data thus clarify a scenario in which postsynaptic glutamate responses are largely downregulated upon TRPV1+ activation, and this change may contribute to homeostasis in the dorsal horn circuit when “acute pain” occurs.

Safety and Biological Activity of Rozibafusp alfa, a Bispecific Inhibitor of Inducible Costimulator Ligand and B Cell Activating Factor, in Patients With Rheumatoid Arthritis: Results of a Phase 1b, Randomized, Double-Blind, Placebo-Controlled, Multiple Ascending Dose Study.

ObjectiveTo assess the safety and biological activity of rozibafusp alfa, a first‐in‐class bispecific antibody–peptide conjugate targeting inducible costimulator ligand (ICOSL) and B cell activating factor (BAFF), in patients with rheumatoid arthritis (RA).MethodsThis phase 1b, double‐blind, placebo‐controlled, multiple ascending dose study included 34 patients (18–75 years; 82.4% female) with active RA (Disease Activity Score of 28 joints–C‐reactive protein [DAS28‐CRP] >2.6, on stable methotrexate) randomized 3:1 to receive rozibafusp alfa (n = 26, in four ascending dose cohorts of 70, 140, 210, and 420 mg) or a placebo (n = 8) subcutaneously once every 2 weeks for 10 weeks (six total doses), with 24 weeks of follow‐up. The primary end point was the incidence of treatment‐emergent adverse events (TEAEs). Additional assessments included serum pharmacokinetics (PK), pharmacodynamics (PD), immunogenicity, and RA disease activity measures (DAS28‐CRP, Patient Global Assessment of Disease, and Physician Global Assessment of Disease).ResultsTEAEs occurred in 96.2% and 87.5% of patients receiving rozibafusp alfa and the placebo, respectively; most were mild or moderate in severity. Two (7.7%) patients treated with rozibafusp alfa reported serious TEAEs; none were considered treatment related. Multiple doses of rozibafusp alfa showed nonlinear PK (mean t 1/2 = 4.6–9.5 days) and dose‐related, reversible PD (>90% ICOSL receptor occupancy in 210‐ and 420‐mg cohorts; reduction in naïve B cells and increase in memory B cells in all cohorts). Five (20%) patients developed anti–rozibafusp alfa antibodies, with no apparent impact on safety. RA disease activity showed greater numerical improvement from baseline with rozibafusp alfa versus the placebo in the 210‐ and 420‐mg cohorts.ConclusionMultiple ascending doses of rozibafusp alfa were well tolerated, with PK and PD reflecting dual ICOSL and BAFF blockade. Findings support further clinical evaluation of rozibafusp alfa in autoimmune disease.

Immuno-PET Monitoring of Lymphocytes Using the CD8-Specific Antibody REGN5054.

Assessment of immune-cell subsets within the tumor immune microenvironment is a powerful approach to better understand cancer immunotherapy responses. However, the use of biopsies to assess the tumor immune microenvironment poses challenges, including the potential for sampling error, restricted sampling over time, and inaccessibility of some tissues/organs, as well as the fact that single biopsy analyses do not reflect discordance across multiple intrapatient tumor lesions. Immuno-positron emission tomography (PET) presents a promising translational imaging approach to address the limitations and assess changes in the tumor microenvironment. We have developed 89Zr-DFO-REGN5054, a fully human CD8A-specific antibody conjugate, to assess CD8+ tumor-infiltrating lymphocytes (TIL) pre- and posttherapy. We used multiple assays, including in vitro T-cell activation, proliferation, and cytokine production, and in vivo viral clearance and CD8 receptor occupancy, to demonstrate that REGN5054 has minimal impact on T-cell activity. Preclinical immuno-PET studies demonstrated that 89Zr-DFO-REGN5054 specifically detected CD8+ T cells in lymphoid tissues of CD8-genetically humanized immunocompetent mice (VelociT mice) and discerned therapy-induced changes in CD8+ TILs in two models of response to a CD20xCD3 T-cell activating bispecific antibody (REGN1979, odronextamab). Toxicology studies in cynomolgus monkeys showed no overt toxicity, and immuno-PET imaging in cynomolgus monkeys demonstrated dose-dependent clearance and specific targeting to lymphoid tissues. This work supports the clinical investigation of 89Zr-DFO-REGN5054 to monitor T-cell responses in patients undergoing cancer immunotherapy.

Relationship between subjective well-being and aripiprazole: an [11C]raclopride PET study

The dopamine blockade by antipsychotics trigger subjective dysphoria. Compared with D2 antagonists, aripiprazole, a D2 partial agonist, was expected to produce a different experience. Indeed, a previous study reported no relationship between the D2 receptor occupancy by aripiprazole and subjective dysphoria, while the D2 receptor occupancy by antagonists was associated with negative subjective experiences. This study revisited the relationship in patients treated with aripiprazole by using an inhibitory Emax model, which enables the individual drug-free binding potential and D2 receptor occupancy to be properly estimated. Eight patients with schizophrenia who have been clinically stable on aripiprazole were enrolled. Assessments including Positive and Negative Syndrome Scale (PANSS) and Subjective Well-being under Neuroleptics Scale (Kv-SWN) were administered. [11C]raclopride PET scan were conducted 2, 26, and 74 h after aripiprazole administration. Regression analysis showed a significant negative association between the D2 receptor occupancy by aripiprazole in the striatum and the Kv-SWN (R2 = 0.55, p = 0.036), but the PANSS total score was not associated with the Kv-SWN (R2 = 0.42, p = 0.080). The negative association between D2 receptor occupancy by aripiprazole and subjective well-being implies that clinicians should find the lowest effective doses of aripiprazole for clinically stable patients to improve their subjective experiences and clinical outcomes.