Peptide Antagonism and T Cell Receptor Interactions with Peptide-MHC Complexes

AbstractWe describe antagonist peptides that specifically inhibit cytolytic activity of T cell clones and lines that express the antigen-specific receptor of CD8+ T lymphocyte clone 2C, which recognizes peptides in association with syngeneic (Kb) and allogeneic (Ld) MHC proteins. Addition of an antagonist peptide that can bind to Kb on 2C cells decreased the tyrosine phosphorylation of CD3 ζ chains elicited by prior exposure of the cells to an agonist peptide-Kb complex. Contrary to previous agonist-antagonist comparisons, the 2C T cell receptor had higher affinity for an antagonist peptide-Kb complex than for a weak agonist peptide-Kb complex. This difference is considered in light of evidence that antigen-specific receptor affinity values can be substantially higher when determined with the receptor on live cells than with the receptor in cell-free systems

Phase I Study of the Bifunctional Fusion Protein Bintrafusp Alfa in Asian Patients with Advanced Solid Tumors, Including a Hepatocellular Carcinoma Safety‐Assessment Cohort

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selection of the recommended phase 2 dose for bintrafusp alfa a bifunctional fusion protein targeting tgf β and pd l1

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465 Bintrafusp alfa in combination with chemotherapy in patients with stage IV NSCLC: safety and pharmacokinetic results of the INTR@PID LUNG 024 study

BackgroundBintrafusp alfa is a first-in-class bifunctional fusion protein composed of the extracellular domain of the TGF-βRII receptor (a TGF-β "trap") fused to a human IgG1 mAb blocking PD-L1. Here we report cumulative safety and pharmacokinetic (PK) results from the global, phase 1b/2 INTR@PID LUNG 024 study (NCT03840915), which evaluated bintrafusp alfa in combination with chemotherapy (CT) in patients with stage IV NSCLC.MethodsAdult patients with stage IV nonsquamous or squamous NSCLC and an ECOG PS ≤1 were included. Cohorts A, B, and C included patients with no prior systemic therapy; patients in cohort D had disease that progressed with previous anti–PD-(L)1 therapy. Cohorts received bintrafusp alfa 2400 mg every 3 weeks intravenously in combination with CT for 4 cycles (A [nonsquamous only]: cisplatin or carboplatin + pemetrexed; B: carboplatin + nab-paclitaxel or paclitaxel; C: cisplatin or carboplatin + gemcitabine; D: docetaxel) followed by bintrafusp alfa maintenance (monotherapy or in combination with pemetrexed in cohort A) for up to 31 cycles. The primary objective of this study was to evaluate the safety of bintrafusp alfa in combination with CT. Dose-limiting toxicities (DLTs) were assessed during a 3-week observation period. Serial samples were drawn to assess serum concentration and calculate PK parameters by noncompartmental analysis.ResultsAs of the May 5, 2021, data cutoff, 70 patients received bintrafusp alfa in combination with CT. Of 35 patients included in the DLT analysis, 4 experienced 1 DLT according to a safety monitoring committee (data cutoff May 5, 2021; A: n=1/8; B: n=1/8; C: n=0/8; D: n=2/11). Cumulative safety data are reported in table 1. PK data were available for 67 patients (A: n=38; B: n=9; C: n=8; D: n=12). PK profiles were similar across cohorts and between patients who did and did not experience a DLT. Observed bintrafusp alfa first-cycle exposures (Cmax, AUC, and Ctrough) were consistent with the published population PK (popPK) model.1Abstract 465 Table 1Safety results from the INTR@PID LUNG 024 studyConclusionsThe safety profile of bintrafusp alfa in combination with CT was manageable and similar to that reported for ICIs in combination with CT, with the exception of TGF-β–related skin lesions known to occur with TGF-β inhibition. No new safety signals were identified and there were no treatment-related deaths. The PK profile was consistent with the predicted monotherapy popPK model, suggesting no victim DDI potential for bintrafusp alfa with CT.AcknowledgementsThe authors thank the patients and their families, investigators, co-investigators, and the study teams at each of the participating centers, at the healthcare business of Merck KGaA, Darmstadt, Germany, and at EMD Serono, Billerica, Massachusetts, USA.Trial RegistrationNCT03840915ReferenceWilkins JJ, Vugmeyster Y, Dussault I. Population pharmacokinetic analysis of bintrafusp alfa in different cancer types. Adv Ther 2019;36:2414–2433.Ethics ApprovalThe trial was approved by each site's independent ethics committee

Avelumab in paediatric patients with refractory or relapsed solid tumours: dose-escalation results from an open-label, single-arm, phase 1/2 trial

Background: We report dose-escalation results from an open-label, phase 1/2 trial evaluating avelumab (anti-PD-L1) in paediatric patients with refractory/relapsed solid tumours. Methods: In phase 1, patients aged \u3c 18 years with solid (including central nervous system [CNS]) tumours for which standard therapy did not exist or had failed were enrolled in sequential cohorts of 3–6 patients. Patients received avelumab 10 or 20 mg/kg intravenously every 2 weeks. Primary endpoints were dose-limiting toxicities (DLTs) and grade ≥ 3 treatment-emergent adverse events (AEs). Results: At data cut-off (27 July 2021), 21 patients aged 3–17 years had received avelumab 10 mg/kg (n = 6) or 20 mg/kg (n = 15). One patient had three events that were classified as a DLT (fatigue with hemiparesis and muscular weakness associated with pseudoprogression; 20 mg/kg cohort). Grade ≥ 3 AEs occurred in five (83%) and 11 (73%) patients in the 10 and 20 mg/kg cohorts, respectively, and were treatment-related in one patient (7%; grade 3 [DLT]) in the 20 mg/kg cohort. Avelumab exposure in paediatric patients receiving 20 mg/kg dosing, but not 10 mg/kg, was comparable or higher compared with approved adult dosing (10 mg/kg or 800 mg flat dose). No objective responses were observed. Four patients with CNS tumours (20 mg/kg cohort) achieved stable disease, which was ongoing in two patients with astrocytoma at cut-off (for 24.7 and 30.3 months). Conclusion: In paediatric patients with refractory/relapsed solid tumours, avelumab monotherapy showed a safety profile consistent with previous adult studies, but clinical benefits were limited

MHC and the proteasome-ubiquitin pathway in T cell development

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 2002.Includes bibliographical references.The essential role of classical MHC molecules in T cell development as well as the proteasome role in antigen processing for MHC-mediated antigen presentation to T cells is well established. However, the contribution of nonclassical MHC molecules, the signals evoked by the MHC-TCR interactions, the signaling role of the proteasome-mediated proteolysis, and the regulation of the proteasome-ubiquitin proteolysis remain to be clarified. Here we address these more subtle but essential aspects of T cell development. We obtained mice deficient for MHC molecules encoded by the H-2K and H-2D genes. KbDb -/- mice have greatly reduced numbers of mature CD8+ T cells, indicating that selection of CD8+ T cells can not be compensated for by [beta]2m-associated molecules other than classical H-2K and D locus products. Spleen cells from KbDb -/- mice generate strong CD8+ MHC class I-specific responses after in vivo priming. Thus, a minor population of CD8+ T cells arises in the complete absence of classical MHC class I molecules. KbDb -/- animals also have self-tolerant natural killer (NK) cells that retain their cytotoxic potential. We utilize a fetal thymic organ culture (FTOC) system with a panel of proteasome inhibitors to implicate the proteasome in thymocyte apoptosis and negative selection. We find that proteasome inhibitors do not completely block but rather delay both dexamethasone- and antigen-triggered thymocyte apoptosis. We also show that proteasome activity is increased in apoptotic thymocytes,(cont.) as visualized by active site labeling of proteasomal D subunits, indicating that proteasome functions as a positive regulator in thymocyte death cascade. We show that the deubiquitinating enzyme USP7 (HAUSP) is specifically and uniquely processed in apoptotic thymocytes. USP7 protein is highly expressed in thymus, spleen, and brain and is very similar in men and mice. Processing of USP7 does not occur in caspase 3-/- thymocytes but caspase 3 does not cleave USP7 directly. Our results suggest that thymocyte apoptosis leads to a modification of a deubiquitinating enzyme and may provide an additional link between the proteasome-ubiquitin pathway and the caspase cascade during programmed cell death.by Yulia Vugmeyster.Ph.D

Pharmacokinetics and lung distribution of a humanized anti-RAGE antibody in wild-type and RAGE-/- mice

A neutralizing antibody to the receptor for the advanced glycation end products (anti-RAGE Ab) was developed as a potential treatment of acute and chronic inflammatory conditions. Previous pharmacology studies demonstrated efficacy of the anti-RAGE antibody in a mouse model of sepsis. We examined pharmacokinetics and lung distribution of [125I]anti-RAGE Ab in RAGE-/- and wild-type (129S5) mice following single IV administration. Serum pharmacokinetics of [125I]anti-RAGE Ab was similar in RAGE-/- and 129S5 mice, with the total body clearance of 0.3 mL/hr/kg and the elimination half-life of 11–12 days, suggesting the target expression had limited impact on overall elimination of [125I]anti-RAGE Ab from mice. [125I]Anti-RAGE Ab accumulated in the lung of 129S5 mice, with ∼4% of total dose retained in the lung at days 6–27 and the lung AUC0-∞ of ∼300% of that in serum. The SDS-PAGE analysis suggested that most of retained lung radioactivity was attributed to intact antibody. No accumulation of radioactivity was observed in the lung of RAGE-/- mice, indicating that lung uptake of [125I]anti-RAGE Ab was target-dependent in wild-type mice. These data suggest that the anti-RAGE Ab was able to localize to the site of RAGE expression, the lung, and support the findings in the previous pharmacology studies