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Methoxy polyethylene glycol (mPEG) is attached to many proteins, peptides, nucleic acids and nanomedicines to improve their biocompatibility. Antibodies that bind PEG are present in many individuals and can be generated upon administration of pegylated therapeutics. Anti-PEG antibodies that bind to the PEG "backbone" can accelerate drug clearance and detrimentally affect drug activity and safety, but no studies have examined how anti-methoxy PEG (mPEG) antibodies, which selectively bind the terminus of mPEG, affect pegylated drugs. Here, we investigated how defined IgG and IgM monoclonal antibodies specific to the PEG backbone (anti-PEG) or terminal methoxy group (anti-mPEG) affect pegylated liposomes or proteins with a single PEG chain, a single branched PEG chain, or multiple PEG chains. Large immune complexes can be formed between all pegylated compounds and anti-PEG antibodies but only pegylated liposomes formed large immune complexes with anti-mPEG antibodies. Both anti-PEG IgG and IgM antibodies accelerated the clearance of all pegylated compounds but anti-mPEG antibodies did not accelerate clearance of proteins with a single or branched PEG molecule. Pegylated liposomes were primarily taken up by Kupffer cells in the liver, but both anti-PEG and anti-mPEG antibodies directed uptake of a heavily pegylated protein to liver sinusoidal endothelial cells. Our results demonstrate that in contrast to anti-PEG antibodies, immune complex formation and drug clearance induced by anti-mPEG antibodies depends on pegylation architecture; compounds with a single or branched PEG molecule are unaffected by anti-mPEG antibodies but are increasingly affected as the number of PEG chain in a structure increases. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Erythropoiesis stimulating agents (ESA) are widely used for hemoglobin correction in patients suffering from renal anemia. However, their beneficial non-hematopoietic effects on renal deterioration have not been adequately assessed. The Primavera study is the first prospective, controlled trial to assess whether ESA treatment could ameliorate progression of chronic kidney disease (CKD) in non-anemic patients. Primavera is a single-blind, 24-month trial in which patients are randomized to placebo or to C.E.R.A., a continuous erythropoietin receptor activator. Patients with type 2 diabetes or who have undergone kidney transplantation are eligible to enter the study if they have CKD stage III (estimated GFR [eGFR] 30–59mL/min/1.73m2), urinary albumin to creatinine ratio (UACR) ≥50g/g and ≤1500g/g, or total urine protein ≥50mg/24h and ≤1500mg/24h, and hemoglobin 11–14g/dL. The primary efficacy endpoint is the change in eGFR from baseline to month 24. Secondary efficacy endpoints are the changes in UACR, serum cystatin C and serum creatinine from baseline. Safety endpoints include adverse events and discontinuation due to pre-specified adverse events. An interim analysis will be performed after all patients have completed the first year. The planned sample size is 400 patients (200 type 2 diabetics, 200 transplant recipients) conferring 90% power to detect a prespecified significant difference of 1.5mL/min/1.73m2 in the annual reduction in eGFR between treatment groups. The results of Primavera are expected in 2013. [Copyright &y& Elsevier]