Receptor Occupancy Research Articles

Amphetamine pretreatment blunts dopamine-induced D2/D3-receptor occupancy by an arrestin-mediated mechanism: A PET study in internalization compromised mice

While all reversible receptor-targeting radioligands for positron emission tomography (PET) can be displaced by competition with an antagonist at the receptor, many radiotracers show limited occupancies using agonists even at high doses. [11C]Raclopride, a D2/D3 receptor radiotracer with rapid kinetics, can identify the direction of changes in the neurotransmitter dopamine, but quantitative interpretation of the relationship between dopamine levels and radiotracer binding has proven elusive. Agonist-induced receptor desensitization and internalization, a homeostatic mechanism to downregulate neurotransmitter-mediated function, can shift radioligand-receptor binding affinity and confound PET interpretations of receptor occupancy. In this study, we compared occupancies induced by amphetamine (AMP) in drug-naive wild-type (WT) and internalization-compromised β-arrestin-2 knockout (KO) mice using a within-scan drug infusion to modulate the kinetics of [11C]raclopride. We additionally performed studies at 3 h following AMP pretreatment, with the hypothesis that receptor internalization should markedly attenuate occupancy on the second challenge, because dopamine cannot access internalized receptors. Without prior AMP treatment, WT mice exhibited somewhat larger binding potential than KO mice but similar AMP-induced occupancy. At 3 h after AMP treatment, WT mice exhibited binding potentials that were 15 % lower than KO mice. At this time point, occupancy was preserved in KO mice but suppressed by 60 % in WT animals, consistent with a model in which most receptors contributing to binding potential in WT animals were not functional. These results demonstrate that arrestin-mediated receptor desensitization and internalization produce large effects in PET [11C]raclopride occupancy studies using agonist challenges.

Elucidating the cellular determinants of targeted membrane protein degradation by lysosome-targeting chimeras.

Targeted protein degradation can provide advantages over inhibition approaches in the development of therapeutic strategies. Lysosome-targeting chimeras (LYTACs) harness receptors, such as the cation-independent mannose 6-phosphate receptor (CI-M6PR), to direct extracellular proteins to lysosomes. In this work, we used a genome-wide CRISPR knockout approach to identify modulators of LYTAC-mediated membrane protein degradation in human cells. We found that disrupting retromer genes improved target degradation by reducing LYTAC recycling to the plasma membrane. Neddylated cullin-3 facilitated LYTAC-complex lysosomal maturation and was a predictive marker for LYTAC efficacy. A substantial fraction of cell surface CI-M6PR remains occupied by endogenous M6P-modified glycoproteins. Thus, inhibition of M6P biosynthesis increased the internalization of LYTAC-target complexes. Our findings inform design strategies for next-generation LYTACs and elucidate aspects of cell surface receptor occupancy and trafficking.

In vivo photopharmacology with light-activated opioid drugs

Traditional methods for site-specific drug delivery in the brain are slow, invasive, and difficult to interface with recordings of neural activity. Here, we demonstrate the feasibility and experimental advantages of invivo photopharmacology using "caged" opioid drugs that are activated in the brain with light after systemic administration in an inactive form. To enable bidirectional manipulations of endogenous opioid receptors invivo, we developed photoactivatable oxymorphone (PhOX) and photoactivatable naloxone (PhNX), photoactivatable variants of the mu opioid receptor agonist oxymorphone and the antagonist naloxone. Photoactivation of PhOX in multiple brain areas produced local changes in receptor occupancy, brain metabolic activity, neuronal calcium activity, neurochemical signaling, and multiple pain- and reward-related behaviors. Combining PhOX photoactivation with optical recording of extracellular dopamine revealed adaptations in the opioid sensitivity of mesolimbic dopamine circuitry in response to chronic morphine administration. This work establishes a general experimental framework for using invivo photopharmacology to study the neural basis of drug action.

Does Slow and Steady Win the Race? Rates of Antipsychotic Discontinuation, Antipsychotic Dose, and Risk of Psychotic Relapse.

Antipsychotics are recommended for prevention of relapse in schizophrenia. It is unclear whether increased risk of relapse following antipsychotic discontinuation is predominantly associated with an absolute magnitude of dose reduction or rate of antipsychotic reduction. Establishing the responsible mechanism is important because prolonged withdrawal schedules have been suggested to reduce risk of relapse. Individual patient data from antipsychotic discontinuation studies were obtained. We estimated the occupancy of receptors over time using half-lives and median effective dose ED50 values obtained from pharmacokinetic and receptor occupancy studies. Hazard ratios for relapse events were calculated using Cox proportional hazards models to assess the influence of formulation (oral, 1-monthly, and 3-monthly injections). The change in hazard ratio over time was estimated, and the effect of time-varying covariates was calculated, including rate of occupancy reduction and absolute receptor occupancy. Five studies including 1388 participants with schizophrenia were identified (k = 2: oral, k = 2: 1-monthly injection, k = 1: 3-monthly injection). Withdrawal of long-acting injectable medication did not lead to a lower hazard ratio compared with withdrawal of oral medication, and this included the period immediately following randomization. Hazard ratios were not associated with the rate of decline of receptor occupancy; however, they were associated with reduced absolute occupancy in trials of long-acting injections (P = .038). Antipsychotic discontinuation is associated with an increased risk of psychotic relapse, related to receptor occupancy. Although relapse does not appear to be related to the rate of discontinuation, gradual discontinuation strategies may allow for easier antipsychotic reinstatement in case of symptomatic worsening.

OR33-02 The Effects Of Timing And Patterns Of Hormone Stimulation On Single Molecule Dynamics And Gene Regulation In Vivo

Abstract Disclosure: D.A. Stavreva: None. L. Hoang: None. K. Wagh: None. R. Chari: None. A. Upadhyaya: None. G.L. Hager: None. Even though most studies on hormonal signaling are performed under continuous stimulation, secretion of many hormones follows a circadian pattern, comprised of periodic (ultradian) pulses with short duration. Using glucocorticoid receptor (GR) signaling as a model system we have previously demonstrated that receptor occupancy of regulatory elements precisely tracks the hormonal pulses resulting in cyclic GR-mediated transcription (gene pulsing) (Stavreva et al., NCB 2009). Using various genomic approaches, we have also uncovered the impact of ultradian and constant stimulation on the lifetimes of chromatin accessibility and long-range promoter/enhancer interactions (Stavreva et al., Genome Res. 2015). By visualizing RNA synthesis from single-copy GR-regulated transcription sites (TSs) we demonstrated treatment-specific RNA bursting patterns. Moreover, our single molecule tracking (SMT) experiments showed that transcription factor (TF) dynamics determine burst duration and frequency (Stavreva et al., 2019). To further study the in vivo dynamics of various TFs we tagged the endogenous GR as well as the estrogen, progesterone receptor (ER and PR, respectively), and the large Pol II subunit (Rpb1) with Halo tag in MCF7 cells. We use SMT in combination with other microscopy and biochemical approaches to i) map the dynamics of TFs in response to constant and ultradian hormone stimulations, and ii) determine their effects on transcription regulation. These studies will help us better understand the importance of timing and pattern of hormone treatment for proper gene regulation in different physiological contexts. Presentation: Sunday, June 18, 2023

Sintilimab Injection Combination with Concurrent Chemoradiotherapy (cCRT) in Patients with Localized Esophageal Squamous Cell Carcinoma: A Prospective, Multi-Center, Single-Arm Trial in Progress

Esophageal cancer had accounted for the sixth highest incidence and the fourth highest death rate in China. The predominant histological subtype is esophageal squamous cell carcinoma (ESCC). At initial diagnosis, more than half of patients with ESCC are unfit for surgery. An accepted alternative to surgery is concurrent chemoradiotherapy (cCRT); however, many patients experience local recurrence or distant metastasis after cCRT. Therefore, innovative therapies are needed. Sintilimab is a fully human IgG4 monoclonal antibody, exhibiting the highest affinity for human PD-1 and a lower off-rate, the PD-1 receptor occupancy of sintilimab on circulating T cells is superior. In previous studies, sintilimab, alone and in combination with chemotherapy, was generally well tolerated and had antitumor activity in patients with advanced ESCC. This prospective, single-arm study (NCT04602013) is designed to explore the efficacy of Sintilimab in combination with cCRT. Eligible patients have histologically confirmed localized ESCC for whom cCRT is suitable and surgery is unsuitable/ declined; patients couldn't have received prior chemoradiotherapy. Approximately 53 Chinese patients from 5 centers will be to receive sintilimab (body weight <60kg: 3mg/kg IV Q3W; body weight ≥60kg: 200mg IV Q3W) in combination with cisplatin (25 mg/m2 IV on Days 1-3 of each 3-week cycle) plus paclitaxel for injection (albumin bound) (180 mg/m2). and radiotherapy at a total dose of 60Gy. Duration of treatment will be up to 12 months for sintilimab, including two cycles for concurrent administration of chemotherapy and radiotherapy. Progression-free survival (PFS), assessed by a Blinded Independent Review Committee per RECIST v1.1, is the primary endpoint of the study. Secondary efficacy endpoints include overall response rate, duration of response, and overall survival. Incidence and severity of adverse events (CTCAE V5.0) and patient-reported outcomes of health-related quality of life are additional secondary endpoints. A total of 17 patients have completed sintilimab injection combination with concurrent chemoradiotherapy,17/53 (32%). Objective response rate (ORR) 62.5% and a median progression free survival (mPFS) 17 months. 1-year overall survival (OS) 88.2%. The most common AEs included granulocytopenia (43.7%), thrombo -cytopenia (56.2%), radiation esophagitis (50%), nausea and vomiting (50%), and immune pneumonia (18.7%). Of these AEs greater than grade 3 granulocytopenia (25.0%), thrombocytopenia (35.0%), radiation esophagitis (12.5%), and nausea and vomiting (31.3%), and one patient developed grade 3 immune pneumonia (6.2%), which recovered with treatment. The treatment of sintilimab with CCRT is safe and effective for localized ESCC patients, even with high-dose radiotherapy (60Gy). This study may help to address the unmet need for new therapeutic options for patients with localized ESCC.

A pilot study of cerebral metabolism and serotonin 5-HT2A receptor occupancy in rats treated with the psychedelic tryptamine DMT in conjunction with the MAO inhibitor harmine.

Rationale: The psychedelic effects of the traditional Amazonian botanical decoction known as ayahuasca are often attributed to agonism at brain serotonin 5-HT2A receptors by N,N-dimethyltryptamine (DMT). To reduce first pass metabolism of oral DMT, ayahuasca preparations additionally contain reversible monoamine oxidase A (MAO-A) inhibitors, namely β-carboline alkaloids such as harmine. However, there is lacking biochemical evidence to substantiate this pharmacokinetic potentiation of DMT in brain via systemic MAO-A inhibition. Objectives: We measured the pharmacokinetic profile of harmine and/or DMT in rat brain, and tested for pharmacodynamic effects on brain glucose metabolism and DMT occupancy at brain serotonin 5-HT2A receptors. Methods: We first measured brain concentrations of harmine and DMT after treatment with harmine and/or DMT at low sub-cutaneous doses (1mg/kg each) or harmine plus DMT at moderate doses (3mg/kg each). In the same groups of rats, we also measured ex vivo the effects of these treatments on the availability of serotonin 5-HT2A receptors in frontal cortex. Finally, we explored effects of DMT and/or harmine (1mg/kg each) on brain glucose metabolism with [18F]FDG-PET. Results: Results confirmed that co-administration of harmine inhibited the formation of the DMT metabolite indole-3-acetic acid (3-IAA) in brain, while correspondingly increasing the cerebral availability of DMT. However, we were unable to detect any significant occupancy by DMT at 5-HT2A receptors measured ex vivo, despite brain DMT concentrations as high as 11.3µM. We did not observe significant effects of low dose DMT and/or harmine on cerebral [18F]FDG-PET uptake. Conclusion: These preliminary results call for further experiments to establish the dose-dependent effects of harmine/DMT on serotonin receptor occupancy and cerebral metabolism.

Extended duration of treatment using reduced-frequency dosing of anti-PD-1 therapy in patients with advanced melanoma and Merkel cell carcinoma.

Optimal duration of treatment (DoT) with immune checkpoint inhibitors (ICI) in metastatic cancers remains unclear. Many patients, especially those without radiologic complete remission, develop progressive disease after ICI discontinuation. Extending DoT with ICI may potentially improve efficacy outcomes but presents major logistical and cost challenges with standard frequency dosing (SFD). Receptor occupancy data supports reduced frequency dosing (RFD) of anti-PD-1 antibodies, which may represent a more practical and economically viable option to extend DoT. We conducted a retrospective study of patients with metastatic melanoma and Merkel cell carcinoma (MCC), who received ICI at RFD administered every 3months, after initial disease control at SFD. We evaluated efficacy, safety, and cost-savings of the RFD approach in this cohort. Between 2014 and 2021, 23 patients with advanced melanoma (N = 18) or MCC (N = 5) received anti-PD-1 therapy at RFD. Median DoT was 1.1years at SFD and 1.2years at RFD. The 3year PFS after start of RFD was 73% in melanoma and 100% in MCC patients, which compare favorably to historical control rates. In the subset of 15 patients who received at least 2years of therapy, total savings amounted to $1.1 million in drug costs and 384h saved despite the extended DoT (median 3.4years), as compared to the calculated cost of 2years at SFD. ICI administration at RFD can allow extension of treatment duration, while preserving efficacy and reducing logistical and financial burden. RFD approach deserves further exploration in prospective clinical trials.

An assessment of the effects of neurokinin1 receptor antagonism against nausea and vomiting: Relative efficacy, sites of action and lessons for future drug development.

A broad-spectrum anti-vomiting effect of neurokinin1 receptor antagonists (NK1 RA), shown in pre-clinical animal studies, has been supported by a more limited range of clinical studies in different indications. However, this review suggests that compared with vomiting, the self-reported sensation of nausea is less affected or possibly unaffected (depending on the stimulus) by NK1 receptor antagonism, a common finding for anti-emetics. The stimulus-independent effects of NK1 RAs against vomiting are explicable by actions within the central pattern generator (ventral brainstem) and the nucleus tractus solitarius (NTS; dorsal brainstem), with additional effects on vagal afferent activity for certain stimuli (e.g., highly emetogenic chemotherapy). The central pattern generator and NTS neurones are multifunctional so the notable lack of obvious effects of NK1 RAs on other reflexes mediated by the same neurones suggests that their anti-vomiting action is dependent on the activation state of the pathway leading to vomiting. Nausea requires activation of cerebral pathways by projection of information from the NTS. Although NK1 receptors are present in cerebral nuclei implicated in nausea, and imaging studies show very high receptor occupancy at clinically used doses, the variable or limited ability of NK1 RAs to inhibit nausea emphasizes: (i) our inadequate understanding of the mechanisms of nausea; and (ii) that classification of a drug as an anti-emetic may give a false impression of efficacy against nausea vs. vomiting. We discuss the potential mechanisms for the differential efficacy of NK1 RA and the implications for future development of drugs that can effectively treat nausea, an area of unmet clinical need.

Antipsychotic dose, dopamine D2 receptor occupancy and extrapyramidal side-effects: a systematic review and dose-response meta-analysis.

Antipsychotic drugs differ in their propensity to cause extrapyramidal side-effects (EPS), but their dose-effects are unclear. Therefore, we conducted a systematic review and dose-response meta-analysis. We searched multiple electronic databases up to 20.02.2023 for fixed-dose studies investigating 16 second-generation antipsychotics and haloperidol (all formulations and administration routes) in adults with acute exacerbations of schizophrenia. The primary outcome was the number of participants receiving antiparkinsonian medication, and if not available, the number of participants with extrapyramidal side-effects (EPS) and the mean scores of EPS rating scales were used as proxies. The effect-size was odds ratio (ORs) compared with placebo. One-stage random-effects dose-response meta-analyses with restricted cubic splines were conducted to estimate the dose-response curves. We also examined the relationship between dopamine D2 receptor (D2R) occupancy and ORs by estimating occupancies from administrated doses. We included data from 110 studies with 382 dose arms (37193 participants). Most studies were short-term with median duration of 6 weeks (range 3-26 weeks). Almost all antipsychotics were associated with dose-dependent EPS with varied degrees and the maximum ORs ranged from OR = 1.57 95%CI [0.97, 2.56] for aripiprazole to OR = 7.56 95%CI [3.16, 18.08] for haloperidol at 30 mg/d. Exceptions were quetiapine and sertindole with negligible risks across all doses. There was very low quality of findings for cariprazine, iloperidone, and zotepine, and no data for clozapine. The D2R occupancy curves showed that the risk increased substantially when D2R occupancy exceeded 75-85%, except for D2R partial agonists that had smaller ORs albeit high D2R occupancies. In conclusion, we found that the risk of EPS increases with rising doses and differs substantially in magnitude among antipsychotics, yet exceptions were quetiapine and sertindole with negligible risks. Our data provided additional insights into the current D2R therapeutic window for EPS.

The melanocortin receptor signaling system and its role in neuroprotection against neurodegeneration: Therapeutic insights.

The melanocortin signaling system consists of the melanocortin peptides, their distinctive receptors, accessory proteins, and endogenous antagonists. Melanocortin peptides are small peptide hormones that have been studied in a variety of physiological and pathological conditions. There are five types of melanocortin receptors, and they are distributed within the central nervous system and in several tissues of the periphery. The G protein-coupled melanocortin receptors typically signal through adenylyl cyclase and other downstream signaling pathways. Depending on the ligand, surface expression of melanocortin receptor, receptor occupancy period, related proteins, the type of cell, and other parameters, the signaling pathways are complicated and pleiotropic. While it is known that all five melanocortin receptors are coupled to Gs, they can also occasionally couple to Gq or Gi. Both direct and indirect neuroprotection are induced by the melanocortin signaling system. Targeting several of the components of the melanocortin signaling system (ligands, receptors, accessory proteins, signaling effectors, and regulators) may provide therapeutic opportunities. Activation of the melanocortin system improves different functional traits in neurodegenerative diseases. There is a potential for additional melanocortin system interventions by interfering with dimerization or dissociation. This review aims to discuss the melanocortin receptor signaling system and its role in neuroprotection, as well as its therapeutic potential.

Trazodone and chlorpromazine a proposal treatment for syndrome post-finasteride and syndrome of post-selective serotonin reuptake inhibitors (post-SSRI)

Erectile dysfunction caused by medications are probably caused by the disconnection of synaptic circuits responsible for linking libido to erection. For instance, it is well known that sexual dysfunction may occur in patients treated with antidepressants like selective serotonin reuptake inhibitors, syndrome known as (post-SSRI). A similar side effect has been also reported during treatment with finasteride, an inhibitor of the enzyme 5alpha-reductase, for androgenetic alopecia. Interestingly, sexual dysfunction persists in both cases after drug discontinuation. Trazodone is a multifunctional drug with hypnotic actions at low doses due to blockade of 5-HT2A receptors, as well as H1 histamine receptors and α1 adrenergic receptors therefore this drug can cause severe priaprism as a side effect and in many cases causing penile necrosis or permanent loss of erectile function. Thus the antipsychotic like chlorpromazine also induce priapism because the alpha receptor occupancy property of those drugs. Therefore we propose that these drugs can restore libido synaptic circuits, and trazodone or antipsychotic drugs such as chlorpromazine can also be a treatment for post-finasteride syndrome and post-SSRI.

A Doubly Dissipative System Driven by Chemical and Radiative Stimuli.

The operation of a dissipative network composed of two or three different crown-ether receptors and an alkali metal cation can be temporally driven by the use (combined or not) of two orthogonal stimuli of a different nature. More specifically, irradiation with light at a proper wavelength and/or addition of an activated carboxylic acid, are used to modulate the binding capability of the above crown-ethers towards the metal ion, allowing to control over time the occupancy of the metal cation in the crown-ether moiety of a given ligand. Thus, application of either or both of the stimuli to an initially equilibrated system, where the metal cation is distributed among the crown-ether receptors depending on the different affinities, causes a programmable change in the receptor occupancies. Consequently, the system is induced to evolve to one or more out-of-equilibrium states with different distributions of the metal cation among the different receptors. When the fuel is exhausted or/and the irradiation interrupted, the system reversibly and autonomously goes back to the initial equilibrium state. Such results may contribute to the achievement of new dissipative systems that, taking advantage of multiple and orthogonal stimuli, are featured with more sophisticated operating mechanisms and time programmability.

Effect of GR205171 on autonomic dysreflexia induced by colorectal distension in spinal cord injured rats.

Preclinical pharmacology. To determine whether blocking substance P signaling attenuates the hypertension and bradycardia evoked by colorectal distension (CRD) in spinal cord injured (SCI) rats. University laboratory in Pennsylvania, U.S.A. Tachykinin NK1 receptor antagonists were administered 30 min prior to CRD three weeks after complete spinal cord transection at the 4th thoracic (T4) level. The dose range, route of administration, and pretreatment time was based on published data demonstrating occupancy of brain NK1 receptors in rodents. Subcutaneous (SC) administration of 10-30 mg/kg GR205171 ((2S,3S)-N-[[2-methoxy-5-[5-(trifluoromethyl)tetrazol-1-yl]phenyl]methyl]-2-phenylpiperidin-3-amine dihydrochloride) reduced CRD-induced hypertension and bradycardia by 55 and 49%, respectively, compared with pretreatment values. There was no effect of GR205171 on resting blood pressure or heart rate. In contrast, the same dose range of CP-99,994 ((2S,3S)-N-[(2-methoxyphenyl)methyl]-2-phenyl-3-piperidinamine dihydrochloride) had no effect on CRD-induced cardiovascular responses. The effective dose range of GR205171 to alleviate autonomic dysreflexia is consistent with the blockade of NK1 receptors on pelvic sensory afferents in the lumbosacral spinal cord, which may in turn prevent the over-excitation of sympathetic preganglionic neurons (SPNs) that regulate blood pressure and heart rate. The findings provide preclinical support for the utility of NK1 receptor antagonists to treat autonomic dysreflexia in people with SCI. The difference in the effects of the two NK1 receptor antagonists may reflect the ~200-fold lower affinity of CP-99,994 than GR205171 for the rat NK1 receptor.

Therapeutic Reference Range for Olanzapine in Schizophrenia: Systematic Review on Blood Concentrations, Clinical Effects, and Dopamine Receptor Occupancy.

Therapeutic Reference Range for Olanzapine in Schizophrenia: Systematic Review on Blood Concentrations, Clinical Effects, and Dopamine Receptor Occupancy.

A 20-Year Research Overview: Quantitative Prediction of Hepatic Clearance Using the In Vitro-In Vivo Extrapolation Approach Based on Physiologically Based Pharmacokinetic Modeling and Extended Clearance Concept.

Understanding the extended clearance concept and establishing a physiologically based pharmacokinetic (PBPK) model are crucial for investigating the impact of changes in transporter and metabolizing enzyme abundance/functions on drug pharmacokinetics in blood and tissues. This mini-review provides an overview of the extended clearance concept and a PBPK model that includes transporter-mediated uptake processes in the liver. In general, complete in vitro and in vivo extrapolation (IVIVE) poses challenges due to missing factors that bridge the gap between in vitro and in vivo systems. By considering key in vitro parameters, we can capture in vivo pharmacokinetics, a strategy known as the top-down or middle-out approach. We present the latest progress, theory, and practice of the Cluster Gauss-Newton method, which is used for middle-out analyses. As examples of poor IVIVE, we discuss "albumin-mediated hepatic uptake" and "time-dependent inhibition" of OATP1Bs. The hepatic uptake of highly plasma-bound drugs is more efficient than what can be accounted for by their unbound concentration alone. This phenomenon is referred to as "albumin-mediated" hepatic uptake. IVIVE was improved by measuring hepatic uptake clearance in vitro in the presence of physiologic albumin concentrations. Lastly, we demonstrate the application of Cluster Gauss-Newton method-based analysis to the target-mediated drug disposition of bosentan. Incorporating saturable target binding and OATP1B-mediated hepatic uptake into the PBPK model enables the consideration of nonlinear kinetics across a wide dose range and the prediction of receptor occupancy over time. SIGNIFICANCE STATEMENT: There have been multiple instances where researchers' endeavors to unravel the underlying mechanism of poor in vitro-in vivo extrapolation have led to the discovery of previously undisclosed truths. These include 1) albumin-mediated hepatic uptake, 2) the target-mediated drug disposition in small molecules, and 3) the existence of a trans-inhibition mechanism by inhibitors for OATP1B-mediated hepatic uptake of drugs. Consequently, poor in vitro-in vivo extrapolation and the subsequent inquisitiveness of scientists may serve as a pivotal gateway to uncover hidden mechanisms.

Eblasakimab, a novel IL-13 receptor alpha 1 monoclonal antibody, blocks STAT6 phosphorylation with low dose in human volunteers

Eblasakimab is a first-in-class monoclonal antibody under investigation for the treatment of atopic dermatitis (AD), which targets IL-13Rα1, a subunit of the Type 2 receptor complex. IL-13Rα1 stimulates phosphorylation of signal transducer and activator of transcription 6 (STAT6) to drive inflammation. This brief report investigates the mechanistic basis of eblasakimab and its effects on IL-13Rα1 signaling as part of a phase 1a, open-label, single ascending dose study. Single ascending doses of eblasakimab were administered by intravenous or subcutaneous injection to healthy male volunteers. The impact of eblasakimab on IL-13Rα1 receptor occupancy and STAT6 phosphorylation was assessed in participant blood monocytes. No serious treatment emergent adverse events were reported. Eblasakimab effectively blocked the IL-13Rα1 receptor and inhibited STAT6 phosphorylation with single doses of 3 mg/kg intravenously and 300 mg subcutaneously. Results support further clinical development of eblasakimab as a novel biologic for AD, with potential for 2- to 4-week dosing regimens.

Characterization of a Novel M4 PAM PET Radioligand [11C]PF06885190 in Nonhuman Primates (NHP).

Muscarinic acetylcholine receptors (mAChR), including M4, draw attention as therapeutic targets for several neurodegenerative diseases including Alzheimer's disease (AD). PET imaging of M4 positive allosteric modulator (PAM) allows qualification of the distribution as well as the expression of this receptor under physiological conditions and thereby helps to assess the receptor occupancy (RO) of a drug candidate. In this study, our aims were (a) to synthesize a novel M4 PAM PET radioligand [11C]PF06885190 (b) to evaluate the brain distribution of [11C]PF06885190 in nonhuman primates (NHP) and (c) to analyze its radiometabolites in the blood plasma of NHP. Radiolabeling of [11C]PF06885190 was accomplished via N-methylation of the precursor. Six PET measurements were performed using two male cynomolgus monkeys, where three PET measurements were at baseline, two after pretreatment with a selective M4 PAM compound CVL-231 and one after pretreatment with donepezil. The total volume of distribution (VT) of [11C]PF06885190 was examined using Logan graphical analysis with arterial input function. Radiometabolites were analyzed in monkey blood plasma using gradient HPLC system. Radiolabeling of [11C]PF06885190 was successfully accomplished and the radioligand was found to be stable in the formulation, with radiochemical purity exceeding 99% 1 h after the end of the synthesis. [11C]PF06885190 was characterized in the cynomolgus monkey brain where a moderate brain uptake was found at the baseline condition. However, it showed fast wash-out as it dropped to half of the peak at around 10 min. Change of VT from baseline was around -10% after pretreatment with a M4 PAM, CVL-231. Radiometabolite studies showed relatively fast metabolism. Although sufficient brain uptake of [11C]PF06885190 was observed, these data suggest that [11C]PF06885190 might have too low specific binding in the NHP brain to be further applied in PET imaging.

Development of a quantitative systems pharmacology (QSP) model to support dose optimization of DS-1103a (anti SIRPa antibody) in combination with trastuzumab deruxtecan in patients with cancer.

e14509 Background: DS-1103a, an anti-human signal regulatory protein α (SIRPα) monoclonal antibody (mAb), is designed to block the SIRPα-CD47 axis “Don’t Eat Me” signal and trigger phagocytosis of tumor cells when combined with an Fc-active antitumor mAb. DS-1103a is being developed as a combination therapy with trastuzumab deruxtecan (T-DXd; DS-8201a) as the antibody-dependent cellular phagocytosis (ADCP) enabling antibody. We developed a QSP model to support the first in human (FIH) intravenous dosing (IV) based on predicted intratumoral receptor occupancy (RO) within immunological synapses (the intercellular contact zone between macrophages and cancer cells) and corresponding ADCP activity. Methods: The QSP model mechanistically integrated DS-1103a plasma pharmacokinetics (PK), tumor distribution and binding of receptors to both antibodies and their ligands to simulate RO in the tumor microenvironment (TME). A proximal pharmacodynamics pathway model was first developed to estimate the intratumoral RO required to induce desired levels of ADCP for DS-1103a+T-DXd combination therapy. A human model was then developed to integrate DS-1103a PK with derived intratumormal RO in patients considering key human pathophysiological parameters, including SIRPα expression, tumor lesion permeability, SIRPα+ cell fractions in TME, tumor capillary radius, SIRPα internalization, CD47 expression and tumor lesion size. Virtual patient simulations were conducted in various cancer types to facilitate FIH dose selection. Results: The proximal pharmacodynamics pathway model quantitatively recapitulated the dose dependent in vitro ADCP activities for DS-1103a+T-DXd combination therapy. The intratumoral RO (within synapses) required to induce desired levels of ADCP activity were also derived. The human model predicted similar dose dependent intratumoral RO in various cancer types. Virtual patient simulations indicated that a flat dose of 100 mg Q3W IV DS-1103a could achieve steady-state intratumoral RO sufficient to reach half of the maximal ADCP activity and would be a suitable FIH starting dose. The predicted steady-state intratumoral RO after a flat dose of ≥1000 mg Q3W IV DS-1103a is well above the predicted intratumoral RO threshold to achieve maximum ADCP activity. Conclusions: The QSP model mechanistically characterized DS-1103a mechanism of action and linked PK to intratumoral RO and corresponding ADCP activity in both in vitro and in vivo setting. The model was used to derive the FIH starting dose and potentially clinically effective doses for DS-1103a in combination with T-DXd. This QSP model will be integrated into a large-scale disease platform to support dose expansion and further dose optimization as new clinical data emerge.

Safety, pharmacokinetics (PK), pharmacodynamics (PD) and preliminary efficacy of AZD2936, a bispecific antibody targeting PD-1 and TIGIT, in checkpoint inhibitor (CPI)-experienced advanced/metastatic non-small-cell lung cancer (NSCLC): First report of ARTEMIDE-01.

9050 Background: PD-1 and TIGIT are implicated in cancer-related T cell immunosuppression. AZD2936 is a bispecific, humanized IgG1 (triple-mutated to minimize Fc effector function) targeting PD-1 and TIGIT. It has demonstrated encouraging activity compared to both anti-PD-1 and anti-PD-1/-TIGIT combinations in murine models. We report data from dose escalation (Part A) and an expansion cohort (Part B) of the first-in-human study ARTEMIDE-01 (NCT04995523). Methods: This open-label, multicenter study enrolled pts with advanced NSCLC who had prior CPI treatment and a PD-L1 tumor proportion score ≥1%. Part A evaluated doses of 70–1500 mg IV Q3W; Part B evaluated the recommended phase 2 dose (RP2D). Primary endpoints included safety, tolerability, dose-limiting toxicities (DLTs) and preliminary efficacy. Secondary endpoints included PK and PD, defined as percentage PD-1 and TIGIT receptor occupancy (RO). Results: As of Dec 5, 2022, 80 pts were enrolled (Part A, n=48; Part B, n=32). Pts were 62.5% male, median age 63.5 years; 72.5% had adenocarcinoma, 23.8% had squamous cell carcinoma; 96.3% had metastatic disease; and 22.5% had brain metastases. They had a median of 2 prior regimens. Median duration of therapy was 11 wks. AZD2936 was well tolerated with no DLTs. In total, 46.3% of pts had treatment-related adverse events (TRAEs), all grade 1–3; the most common were pruritus, rash and lipase increased (6.3% each). Serious TRAEs occurred in 3 pts (3.8%): immune system disorder, acute hepatitis and fatigue (n=1 each). AZD2936 systemic exposure increased in a near dose-proportional manner. Doses of ≥210 mg achieved ~90% PD-1 and TIGIT RO in peripheral T cells. The RP2D was determined to be 750 mg Q3W based on safety, preliminary efficacy, PK/PD and modeling analysis predicting intratumoral RO. Among 76 evaluable pts, 3 had a partial response and 30 had stable disease (Table). Time to response was 1.9–4.0 mos and duration of response was 2.1–6.4 mos. Conclusions: In this interim analysis, AZD2936 showed an acceptable safety profile and preliminary antitumor activity in pts with advanced/metastatic NSCLC previously treated with standard therapy including CPIs. Further exploration of AZD2936 in CPI-naïve NSCLC pts, including a randomized dose optimization cohort is ongoing. Clinical trial information: NCT04995523 . [Table: see text]