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Vepdegestrant is an oral proteolysis-targeting chimera (PROTAC) estrogen receptor (ER) degrader that directly harnesses the ubiquitin-proteasome system. In this phase 3, open-label, randomized trial, we enrolled patients with ER-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer who had received one previous line of cyclin-dependent kinase 4 and 6 inhibitor therapy plus one line of endocrine therapy (and up to one additional line of endocrine therapy). Patients were randomly assigned in a 1:1 ratio to receive vepdegestrant at a dose of 200 mg orally once every day of each 28-day cycle or fulvestrant at a dose of 500 mg, administered intramuscularly, on day 1 and day 15 of cycle 1 and on day 1 of subsequent cycles, with randomization stratified according to -mutation status and presence or absence of visceral disease. The primary end point was progression-free survival as assessed by blinded independent central review among the patients with mutations and among all the patients who underwent randomization. Progression-free survival was estimated with Kaplan-Meier methods and hazard ratios with a stratified Cox proportional-hazards model. A total of 624 patients underwent randomization; 313 were assigned to receive vepdegestrant, and 311 to receive fulvestrant. Among the 270 patients with mutations, the median progression-free survival was 5.0 months (95% confidence interval [CI], 3.7 to 7.4) with vepdegestrant and 2.1 months (95% CI, 1.9 to 3.5) with fulvestrant (hazard ratio, 0.58 [95% CI, 0.43 to 0.78]; P<0.001). Among all the patients, the median progression-free survival was 3.8 months (95% CI, 3.7 to 5.3) with vepdegestrant and 3.6 months (95% CI, 2.6 to 4.0) with fulvestrant (hazard ratio, 0.83 [95% CI, 0.69 to 1.01]; P = 0.07). Adverse events of grade 3 or higher occurred in 23.4% of the patients in the vepdegestrant group and in 17.6% of the patients in the fulvestrant group. Adverse events led to treatment discontinuation in 2.9% and 0.7% of the patients, respectively. Among patients with ER-positive, HER2-negative advanced breast cancer, vepdegestrant was associated with significantly longer progression-free survival than fulvestrant in the subgroup with mutations but not in the full patient population. (Funded by Pfizer and Arvinas Estrogen Receptor; VERITAC-2 ClinicalTrials.gov number, NCT05654623.).

In Alzheimer's disease (AD), tau undergoes abnormal post‐translational modifications and aggregations. Impaired intracellular degradation pathways further exacerbate the accumulation of pathological tau. A new strategy – targeted protein degradation – recently emerged as a modality in drug discovery where bifunctional molecules bring the target protein close to the degradation machinery to promote clearance. Since 2016, this strategy has been applied to tau pathologies and attracted broad interest in academia and the pharmaceutical industry. However, a systematic review of recent studies on tau degradation mechanisms is lacking. Here we review tau degradation mechanisms (the ubiquitin–proteasome system and the autophagy–lysosome pathway), their dysfunction in AD, and tau‐targeted degraders, such as proteolysis‐targeting chimeras and autophagy‐targeting chimeras. We emphasize the need for a continuous exploration of tau degradation mechanisms and provide a future perspective for developing tau‐targeted degraders, encouraging researchers to work on new treatment options for AD patients. Highlights Post‐translational modifications, aggregation, and mutations affect tau degradation. A vicious circle exists between impaired degradation pathways and tau pathologies. Ubiquitin plays an important role in complex degradation pathways. Tau‐targeted degraders provide promising strategies for novel AD treatment.

Depression and anxiety disorders are associated with increased release of peripheral cytokines; however, their functional relevance remains unknown. Using a social stress model in mice, we find preexisting individual differences in the sensitivity of the peripheral immune system that predict and promote vulnerability to social stress. Cytokine profiles were obtained 20 min after the first social stress exposure. Of the cytokines regulated by stress, IL-6 was most highly up-regulated only in mice that ultimately developed a susceptible behavioral phenotype following a subsequent chronic stress, and levels remained elevated for at least 1 mo. We confirmed a similar elevation of serum IL-6 in two separate cohorts of patients with treatment-resistant major depressive disorder. Before any physical contact in mice, we observed individual differences in IL-6 levels from ex vivo stimulated leukocytes that predict susceptibility versus resilience to a subsequent stressor. To shift the sensitivity of the peripheral immune system to a pro- or antidepressant state, bone marrow (BM) chimeras were generated by transplanting hematopoietic progenitor cells from stress-susceptible mice releasing high IL-6 or from IL-6 knockout (IL-6 ⁻/⁻) mice. Stress-susceptible BM chimeras exhibited increased social avoidance behavior after exposure to either subthreshold repeated social defeat stress (RSDS) or a purely emotional stressor termed witness defeat. IL-6 ⁻/⁻ BM chimeric and IL-6 ⁻/⁻ mice, as well as those treated with a systemic IL-6 monoclonal antibody, were resilient to social stress. These data establish that preexisting differences in stress-responsive IL-6 release from BM-derived leukocytes functionally contribute to social stress-induced behavioral abnormalities. Significance Depression and anxiety have been linked to increased inflammation. However, we do not know if inflammatory status predates onset of disease or whether it contributes to depression symptomatology. We report preexisting individual differences in the peripheral immune system that predict and promote stress susceptibility. Replacing a stress-naive animal’s peripheral immune system with that of a stressed animal increases susceptibility to social stress including repeated social defeat stress (RSDS) and witness defeat (a purely emotional form of social stress). Depleting the cytokine IL-6 from the whole body or just from leukocytes promotes resilience, as does sequestering IL-6 outside of the brain. These studies demonstrate that the emotional response to stress can be generated or blocked in the periphery, and offer a potential new form of treatment for stress disorders.

Superantigens (SAgs) are potent exotoxins secreted by Staphylococcus aureus and Streptococcus pyogenes. They target a large fraction of T cell pools to set in motion a \"cytokine storm\" with severe and sometimes life-threatening consequences typically encountered in toxic shock syndrome (TSS). Given the rapidity with which TSS develops, designing timely and truly targeted therapies for this syndrome requires identification of key mediators of the cytokine storm's initial wave. Equally important, early host responses to SAgs can be accompanied or followed by a state of immunosuppression, which in turn jeopardizes the host's ability to combat and clear infections. Unlike in mouse models, the mechanisms underlying SAg-associated immunosuppression in humans are ill-defined. In this work, we have identified a population of innate-like T cells, called mucosa-associated invariant T (MAIT) cells, as the most powerful source of pro-inflammatory cytokines after exposure to SAgs. We have utilized primary human peripheral blood and hepatic mononuclear cells, mouse MAIT hybridoma lines, HLA-DR4-transgenic mice, MAIThighHLA-DR4+ bone marrow chimeras, and humanized NOD-scid IL-2Rγnull mice to demonstrate for the first time that: i) mouse and human MAIT cells are hyperresponsive to SAgs, typified by staphylococcal enterotoxin B (SEB); ii) the human MAIT cell response to SEB is rapid and far greater in magnitude than that launched by unfractionated conventional T, invariant natural killer T (iNKT) or γδ T cells, and is characterized by production of interferon (IFN)-γ, tumor necrosis factor (TNF)-α and interleukin (IL)-2, but not IL-17A; iii) high-affinity MHC class II interaction with SAgs, but not MHC-related protein 1 (MR1) participation, is required for MAIT cell activation; iv) MAIT cell responses to SEB can occur in a T cell receptor (TCR) Vβ-specific manner but are largely contributed by IL-12 and IL-18; v) as MAIT cells are primed by SAgs, they also begin to develop a molecular signature consistent with exhaustion and failure to participate in antimicrobial defense. Accordingly, they upregulate lymphocyte-activation gene 3 (LAG-3), T cell immunoglobulin and mucin-3 (TIM-3), and/or programmed cell death-1 (PD-1), and acquire an anergic phenotype that interferes with their cognate function against Klebsiella pneumoniae and Escherichia coli; vi) MAIT cell hyperactivation and anergy co-utilize a signaling pathway that is governed by p38 and MEK1/2. Collectively, our findings demonstrate a pathogenic, rather than protective, role for MAIT cells during infection. Furthermore, we propose a novel mechanism of SAg-associated immunosuppression in humans. MAIT cells may therefore provide an attractive therapeutic target for the management of both early and late phases of severe SAg-mediated illnesses.

Across the animal kingdom, gastrulation represents a key developmental event during which embryonic pluripotent cells diversify into lineage-specific precursors that will generate the adult organism. Here we report the transcriptional profiles of 116,312 single cells from mouse embryos collected at nine sequential time points ranging from 6.5 to 8.5 days post-fertilization. We construct a molecular map of cellular differentiation from pluripotency towards all major embryonic lineages, and explore the complex events involved in the convergence of visceral and primitive streak-derived endoderm. Furthermore, we use single-cell profiling to show that Tal1 −/− chimeric embryos display defects in early mesoderm diversification, and we thus demonstrate how combining temporal and transcriptional information can illuminate gene function. Together, this comprehensive delineation of mammalian cell differentiation trajectories in vivo represents a baseline for understanding the effects of gene mutations during development, as well as a roadmap for the optimization of in vitro differentiation protocols for regenerative medicine. Single-cell profiling is used to create a molecular-level atlas of cell differentiation trajectories during gastrulation and early organogenesis in the mouse.

Targeted degradation of cell surface and extracellular proteins via lysosomal delivery is an important means to modulate extracellular biology. However, these approaches have limitations due to lack of modularity, ease of development, restricted tissue targeting and applicability to both cell surface and extracellular proteins. We describe a lysosomal degradation strategy, termed cytokine receptor-targeting chimeras (KineTACs), that addresses these limitations. KineTACs are fully genetically encoded bispecific antibodies consisting of a cytokine arm, which binds its cognate cytokine receptor, and a target-binding arm for the protein of interest. We show that KineTACs containing the cytokine CXCL12 can use the decoy recycling receptor, CXCR7, to target a variety of target proteins to the lysosome for degradation. Additional KineTACs were designed to harness other CXCR7-targeting cytokines, CXCL11 and vMIPII, and the interleukin-2 (IL-2) receptor-targeting cytokine IL-2. Thus, KineTACs represent a general, modular, selective and simple genetically encoded strategy for inducing lysosomal delivery of extracellular and cell surface targets with broad or tissue-specific distribution. KineTACs are modular bispecific antibodies for degradation of extracellular and cell-surface proteins.

Proteolysis-targeting chimeras (PROTACs) are engineered techniques for targeted protein degradation. A bifunctional PROTAC molecule with two covalently-linked ligands recruits target protein and E3 ubiquitin ligase together to trigger proteasomal degradation of target protein by the ubiquitin-proteasome system. PROTAC has emerged as a promising approach for targeted therapy in various diseases, particularly in cancers. In this review, we introduce the principle and development of PROTAC technology, as well as the advantages of PROTACs over traditional anti-cancer therapies. Moreover, we summarize the application of PROTACs in targeting critical oncoproteins, provide the guidelines for the molecular design of PROTACs and discuss the challenges in the targeted degradation by PROTACs.

Atherosclerosis is a major cause of death and disability in cardiovascular disease. Atherosclerosis associated with lipid accumulation and chronic inflammation leads to plaques formation in arterial walls and luminal stenosis in carotid arteries. Current approaches such as surgery or treatment with statins encounter big challenges in curing atherosclerosis plaque. The infiltration of proinflammatory M1 macrophages plays an essential role in the occurrence and development of atherosclerosis plaque. A recent study shows that TRIM24, an E3 ubiquitin ligase of a Trim family protein, acts as a valve to inhibit the polarization of anti-inflammatory M2 macrophages, and elimination of TRIM24 opens an avenue to achieve the M2 polarization. Proteolysis-targeting chimera (PROTAC) technology has emerged as a novel tool for the selective degradation of targeting proteins. But the low bioavailability and cell specificity of PROTAC reagents hinder their applications in treating atherosclerosis plaque. In this study we constructed a type of bioinspired PROTAC by coating the PROTAC degrader (dTRIM24)-loaded PLGA nanoparticles with M2 macrophage membrane (MELT) for atherosclerosis treatment. MELT was characterized by morphology, size, and stability. MELT displayed enhanced specificity to M1 macrophages as well as acidic-responsive release of dTRIM24. After intravenous administration, MELT showed significantly improved accumulation in atherosclerotic plaque of high fat and high cholesterol diet-fed atherosclerotic (ApoE −/− ) mice through binding to M1 macrophages and inducing effective and precise TRIM24 degradation, thus resulting in the polarization of M2 macrophages, which led to great reduction of plaque formation. These results suggest that MELT can be considered a potential therapeutic agent for targeting atherosclerotic plaque and alleviating atherosclerosis progression, providing an effective strategy for targeted atherosclerosis therapy.

An orthogonal aminoacyl-tRNA synthetase/tRNA pair is a crucial prerequisite for site-specific incorporation of unnatural amino acids. Due to its high codon suppression efficiency and full orthogonality, the pyrrolysyl-tRNA synthetase/pyrrolysyl-tRNA pair is currently the ideal system for genetic code expansion in both eukaryotes and prokaryotes. There is a pressing need to discover or engineer other fully orthogonal translation systems. Here, through rational chimera design by transplanting the key orthogonal components from the pyrrolysine system, we create multiple chimeric tRNA synthetase/chimeric tRNA pairs, including chimera histidine, phenylalanine, and alanine systems. We further show that these engineered chimeric systems are orthogonal and highly efficient with comparable flexibility to the pyrrolysine system. Besides, the chimera phenylalanine system can incorporate a group of phenylalanine, tyrosine, and tryptophan analogues efficiently in both E. coli and mammalian cells. These aromatic amino acids analogous exhibit unique properties and characteristics, including fluorescence, post-translation modification. Orthogonal aminoacyl-tRNA synthetase/tRNA pairs are crucial for the incorporation of unnatural amino acids in a site-specific manner. Here the authors use rational chimera design to create multiple efficient pairs that function in bacterial and mammalian systems for genetic code expansion.