RESUMEN
Deficiency in the adipose-derived hormone leptin or leptin receptor signaling causes class 3 obesity in individuals with genetic loss-of-function mutations in leptin or its receptor LEPR and metabolic and liver disease in individuals with hypoleptinemia secondary to lipoatrophy such as in individuals with generalized lipodystrophy. Therapies that restore leptin-LEPR signaling may resolve these metabolic sequelae. We developed a fully human monoclonal antibody (mAb), REGN4461 (mibavademab), that activates the human LEPR in the absence or presence of leptin. In obese leptin knockout mice, REGN4461 normalized body weight, food intake, blood glucose, and insulin sensitivity. In a mouse model of generalized lipodystrophy, REGN4461 alleviated hyperphagia, hyperglycemia, insulin resistance, dyslipidemia, and hepatic steatosis. In a phase 1, randomized, double-blind, placebo-controlled two-part study, REGN4461 was well tolerated with an acceptable safety profile. Treatment of individuals with overweight or obesity with REGN4461 decreased body weight over 12 weeks in those with low circulating leptin concentrations (<8 ng/ml) but had no effect on body weight in individuals with higher baseline leptin. Furthermore, compassionate-use treatment of a single patient with atypical partial lipodystrophy and a history of undetectable leptin concentrations associated with neutralizing antibodies to metreleptin was associated with noteable improvements in circulating triglycerides and hepatic steatosis. Collectively, these translational data unveil an agonist LEPR mAb that may provide clinical benefit in disorders associated with relatively low leptin concentrations.
Asunto(s)
Resistencia a la Insulina , Lipodistrofia Generalizada Congénita , Animales , Ratones , Humanos , Leptina/uso terapéutico , Ensayos de Uso Compasivo , Receptores de Leptina/metabolismo , Lipodistrofia Generalizada Congénita/tratamiento farmacológico , Obesidad/tratamiento farmacológico , Anticuerpos/uso terapéutico , Peso CorporalRESUMEN
Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disorder whose most debilitating pathology is progressive and cumulative heterotopic ossification (HO) of skeletal muscles, ligaments, tendons, and fascia. FOP is caused by mutations in the type I BMP receptor gene ACVR1, which enable ACVR1 to utilize its natural antagonist, activin A, as an agonistic ligand. The physiological relevance of this property is underscored by the fact that HO in FOP is exquisitely dependent on activation of FOP-mutant ACVR1 by activin A, an effect countered by inhibition of anti-activin A via monoclonal antibody treatment. Hence, we surmised that anti-ACVR1 antibodies that block activation of ACVR1 by ligands should also inhibit HO in FOP and provide an additional therapeutic option for this condition. Therefore, we generated anti-ACVR1 monoclonal antibodies that block ACVR1's activation by its ligands. Surprisingly, in vivo, these anti-ACVR1 antibodies stimulated HO and activated signaling of FOP-mutant ACVR1. This property was restricted to FOP-mutant ACVR1 and resulted from anti-ACVR1 antibody-mediated dimerization of ACVR1. Conversely, wild-type ACVR1 was inhibited by anti-ACVR1 antibodies. These results uncover an additional property of FOP-mutant ACVR1 and indicate that anti-ACVR1 antibodies should not be considered as therapeutics for FOP.
Asunto(s)
Miositis Osificante , Osificación Heterotópica , Receptores de Activinas Tipo I/genética , Receptores de Activinas Tipo I/farmacología , Anticuerpos/inmunología , Humanos , Ligandos , Mutación , Miositis Osificante/genética , Osificación Heterotópica/genética , Osificación Heterotópica/patología , Transducción de Señal/genéticaRESUMEN
Methamphetamine (Meth) is abused by over 35 million people worldwide. Chronic Meth abuse may be particularly devastating in individuals who engage in unprotected sex with multiple partners because it is associated with a 2-fold higher risk for obtaining HIV and associated secondary infections. We report the first specific evidence that Meth at pharmacological concentrations exerts a direct immunosuppressive effect on dendritic cells and macrophages. As a weak base, Meth collapses the pH gradient across acidic organelles, including lysosomes and associated autophagic organelles. This in turn inhibits receptor-mediated phagocytosis of antibody-coated particles, MHC class II antigen processing by the endosomal-lysosomal pathway, and antigen presentation to splenic T cells by dendritic cells. More importantly Meth facilitates intracellular replication and inhibits intracellular killing of Candida albicans and Cryptococcus neoformans, two major AIDS-related pathogens. Meth exerts previously unreported direct immunosuppressive effects that contribute to increased risk of infection and exacerbate AIDS pathology.
Asunto(s)
Presentación de Antígeno/efectos de los fármacos , Estimulantes del Sistema Nervioso Central/toxicidad , Células Dendríticas/efectos de los fármacos , Macrófagos Peritoneales/efectos de los fármacos , Metanfetamina/toxicidad , Fagocitosis/efectos de los fármacos , Animales , Presentación de Antígeno/inmunología , Células de la Médula Ósea/efectos de los fármacos , Células de la Médula Ósea/inmunología , Candida albicans/inmunología , Fraccionamiento Celular , Células Cultivadas , Cloroquina/farmacología , Cryptococcus neoformans/inmunología , Células Dendríticas/microbiología , Células Dendríticas/fisiología , Femenino , Terapia de Inmunosupresión , Macrófagos Peritoneales/microbiología , Macrófagos Peritoneales/fisiología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Fagocitosis/inmunologíaRESUMEN
Diverse physiological and therapeutic insults that increase the amount of unfolded or misfolded proteins in the endoplasmic reticulum (ER) induce the unfolded protein response, an evolutionarily conserved protective mechanism that manages ER stress. Glucose-regulated protein 78/immunoglobulin heavy-chain binding protein (GRP78/BiP) is an ER-resident protein that plays a central role in the ER stress response and is the only known substrate of the proteolytic A subunit (SubA) of a novel bacterial AB(5) toxin. Here, we report that an engineered fusion protein, epidermal growth factor (EGF)-SubA, combining EGF and SubA, is highly toxic to growing and confluent epidermal growth factor receptor-expressing cancer cells, and its cytotoxicity is mediated by a remarkably rapid cleavage of GRP78/BiP. Systemic delivery of EGF-SubA results in a significant inhibition of human breast and prostate tumor xenografts in mouse models. Furthermore, EGF-SubA dramatically increases the sensitivity of cancer cells to the ER stress-inducing drug thapsigargin, and vice versa, demonstrating the first example of mechanism-based synergism in the action of a cytotoxin and an ER-targeting drug.