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Cancer cachexia is a highly prevalent condition associated with poor quality of life and reduced survival 1 . Tumor-induced perturbations in the endocrine, immune and nervous systems drive anorexia and catabolic changes in adipose tissue and skeletal muscle, hallmarks of cancer cachexia 2 – 4 . However, the molecular mechanisms driving cachexia remain poorly defined, and there are currently no approved drugs for the condition. Elevation in circulating growth differentiation factor 15 (GDF15) correlates with cachexia and reduced survival in patients with cancer 5 – 8 , and a GDNF family receptor alpha like (GFRAL)–Ret proto-oncogene (RET) signaling complex in brainstem neurons that mediates GDF15-induced weight loss in mice has recently been described 9 – 12 . Here we report a therapeutic antagonistic monoclonal antibody, 3P10, that targets GFRAL and inhibits RET signaling by preventing the GDF15-driven interaction of RET with GFRAL on the cell surface. Treatment with 3P10 reverses excessive lipid oxidation in tumor-bearing mice and prevents cancer cachexia, even under calorie-restricted conditions. Mechanistically, activation of the GFRAL–RET pathway induces expression of genes involved in lipid metabolism in adipose tissues, and both peripheral chemical sympathectomy and loss of adipose triglyceride lipase protect mice from GDF15-induced weight loss. These data uncover a peripheral sympathetic axis by which GDF15 elicits a lipolytic response in adipose tissue independently of anorexia, leading to reduced adipose and muscle mass and function in tumor-bearing mice. Pharmacological inhibition of GFRAL–RET signaling in preclinical tumor models supports the therapeutic potential for reversing GDF15-dependent cachexia in people with cancer.

GDNF receptor alpha-like is a brainstem-restricted receptor for growth and differentiation factor 15, regulating appetite and body weight in non-homeostatic conditions by activating the emergency circuit response to disease and toxin stresses. Brainstem receptor regulates body mass loss Growth and differentiation factor 15 (GDF15) acts on feeding centres in the brain to cause anorexia, leading to loss of both lean and fat mass and eventually cachexia. GDF15 levels rise in response to tissue stress and injury, and higher levels are associated with weight loss in numerous chronic human diseases, including cancer. Bernard Allan and colleagues now show that glial cell-derived neurotrophic factor (GDNF) receptor alpha-like (GFRAL) is a GDF15 receptor in the brainstem. The structure of GDF15 and its interaction with GFRAL together with biochemical experiments and analysis of Gfral knockout mice demonstrate that regulation of body weight by GFRAL is independent of previously characterized pathways. Unlike hormones from gut and adipose tissue that activate receptors mostly in the hypothalamus, GDF15 increases in response to tissue damage and activates GFRAL-expressing neurons in the brainstem. Gfral knockout mice overate under stressed conditions and were resistant to chemotherapy-induced anorexia and weight loss. These findings provide therapeutic opportunities for disorders with altered energy demands. Under homeostatic conditions, animals use well-defined hypothalamic neural circuits to help maintain stable body weight, by integrating metabolic and hormonal signals from the periphery to balance food consumption and energy expenditure 1 , 2 . In stressed or disease conditions, however, animals use alternative neuronal pathways to adapt to the metabolic challenges of altered energy demand 3 . Recent studies have identified brain areas outside the hypothalamus that are activated under these ‘non-homeostatic’ conditions 4 , 5 , 6 , but the molecular nature of the peripheral signals and brain-localized receptors that activate these circuits remains elusive. Here we identify glial cell-derived neurotrophic factor (GDNF) receptor alpha-like (GFRAL) as a brainstem-restricted receptor for growth and differentiation factor 15 (GDF15). GDF15 regulates food intake, energy expenditure and body weight in response to metabolic and toxin-induced stresses; we show that Gfral knockout mice are hyperphagic under stressed conditions and are resistant to chemotherapy-induced anorexia and body weight loss. GDF15 activates GFRAL-expressing neurons localized exclusively in the area postrema and nucleus tractus solitarius of the mouse brainstem. It then triggers the activation of neurons localized within the parabrachial nucleus and central amygdala, which constitute part of the ‘emergency circuit’ that shapes feeding responses to stressful conditions 7 . GDF15 levels increase in response to tissue stress and injury, and elevated levels are associated with body weight loss in numerous chronic human diseases 8 , 9 . By isolating GFRAL as the receptor for GDF15-induced anorexia and weight loss, we identify a mechanistic basis for the non-homeostatic regulation of neural circuitry by a peripheral signal associated with tissue damage and stress. These findings provide opportunities to develop therapeutic agents for the treatment of disorders with altered energy demand.

RNA synthesis using in vitro transcription by phage T7 RNA polymerase allows preparation of milligram quantities of RNA for biochemical, biophysical and structural investigations. Previous purification approaches relied on gel electrophoretic or gravity-flow chromatography methods. We present here a protocol for the in vitro transcription of RNAs and subsequent purification using fast-performance liquid chromatography. This protocol greatly facilitates production of RNA in a single day from transcription to purification.

Nature 550, 255–259 (2017); doi:10.1038/nature24042 Owing to an error during the production process, in Fig. 2c of this Letter, all four groups of mice were incorrectly labelled as ‘WT’ (wild type), but the two groups on the left (filled and open blue boxes) should have been labelled ‘WT’, whereas the two groups on the right (filled and open yellow boxes) should have been labelled ‘KO’ (knockout), as in the key for Fig. 2b. The original Letter has been corrected online.

Circulating proteins are common targets for the discovery of occupancy-based inhibitors including monoclonal antibodies. Effective inhibition of target pathogenicity with blocking approaches, however, is often challenged by target parameters that lead to insufficient occupancy and/or incomplete pharmacology limited by only single site binding. Extracellular targeted protein degradation approaches, such as lysosomal targeting chimeras (LYTACs), offer an opportunity to minimize these challenges by an event-driven mechanism that selectively, thoroughly and irreversibly eliminates drivers of disease. First generation LYTACs, designed to traffic to the lysosome, show limited durability since the therapeutic is degraded along with the target protein of interest. Here we describe cataLYTACs, which overcome this limitation by combining stabilized asialoglycoprotein (ASGPR) ligands, pH-sensitive target binding and recycling via the neonatal Fc receptor (FcRn). These cataLYTACs degraded superstoichiometric levels of a target protein, IgE, in vitro and demonstrated deep and sustained clearance of human IgE in mouse models. In non-human primates, cataLYTACs resulted in >98% clearance of circulating endogenous IgE for 2 weeks and outperformed the standard of care blocking antibody, omalizumab (Xolair), in both free IgE elimination and duration of action. CataLYTACs represent a new therapeutic modality for a wide range of disease states driven by circulating factors, with the potential for superior efficacy and duration of action compared to traditional inhibitors.Competing Interest StatementC.K., N.A.L., R.M.L., T.C., C.L.C., S.G., K.T.A., K.H.D., C.K.F., D.J.H., R.K., D.L., S.R., D.A.L., S.M.M., J.S.I., S.T.S., E.D.T. and M.J.S. are employees of Lycia Therapeutics Inc. R.M.L., I.E.J., K.T.A., K.H.D., D.L., T.T., R.Y., D.A.L., S.M.M., J.G.L. and S.T.S. are shareholders of Lycia Therapeutics Inc. R.W.H. and C.L. are employees of Thermo Fisher Scientific Inc. J.G.L. is a founder and employee of Chempiric Consulting, LLC. C.K., M.J.S., I.E.J., D.H.L., S.R., R.Y., D.A.L., J.S.I., J.G.L., S.T.S., E.D.T. and N.A.L. are inventors on provisional patent applications related to this work.