No abstract

BackgroundRegulatory approval for a biosimilar product is provided on the basis of its comparability to an originator product. A thorough physicochemical and functional comparability exercise is a key element in demonstrating biosimilarity. Here we report the characterization of a proposed biosimilar rituximab (GP2013) and originator rituximab.ObjectiveTo compare GP2013 with originator rituximab using an extensive array of routine analytical and extended characterization methods.MethodsPrimary and higher order protein structures were analyzed using a variety of methods that included high-performance liquid chromatography electrospray ionization mass spectrometry (HPLC-ESI-MS), peptide mapping with UV and MS detection, circular dichroism (CD), Fourier transform infrared (FTIR) spectroscopy, hydrogen deuterium exchange (HDX) MS, 1D 1H nuclear magnetic resonance (NMR) spectroscopy, X-ray crystallography and differential scanning calorimetry (DSC). Charge and amino acid modifications were assessed using cation exchange chromatography (CEX) and peptide mapping using reversed-phase (RP) HPLC. Boronate affinity chromatography was used to determine the relative amount of glycation. Glycans were identified and quantified after 2-aminobenzamide (2-AB) labeling and separation using normal phase HPLC with fluorescence and MS detection, respectively. Glycan site occupancy was determined using reducing capillary electrophoresis with sodium dodecyl sulfate (CE-SDS). Size heterogeneity was determined using reducing and non-reducing CE-SDS, size exclusion chromatography (SEC) and asymmetric flow field flow fractionation (AF4). Biological characterization included a series of bioassays (in vitro target binding, antibody-dependent cell-mediated cytotoxicity [ADCC], complement-dependent cytotoxicity [CDC] and apoptosis) and surface plasmon resonance (SPR) Fc receptor binding assays.ResultsIntact mass analysis of GP2013 and the heavy and light chains using RP HPLC–ESI–MS revealed the expected molecular mass of rituximab. The amino acid sequence was shown to be identical between GP2013 and the originator rituximab. Further sequence confirmation using RP-HPLC-UV/MS peptide mapping showed non-distinguishable chromatograms for Lys-C digested GP2013 and originator rituximab. The higher order structure of GP2013 was shown to be indistinguishable from originator rituximab using a large panel of redundant and orthogonal methods. GP2013 and originator rituximab were comparable with regard to charge variants, specific amino acid modifications and the glycan pattern. GP2013 was also shown to have similar purity, aggregate and particle levels when compared with the originator. Functionally, and by using a comprehensive set of bioassays and binding assays covering a broad range of rituximab’s functional activities, GP2013 could not be distinguished from originator rituximab.ConclusionGP2013 was shown to be physicochemically highly similar to originator rituximab at the level of primary and higher order structure, post-translational modifications ...

Lantibiotics are ribosomally synthesized peptide antibiotics containing the amino acids lanthionine (Lan) and methyllanthione (MeLan) as the most important and characteristic post-translational modification.[1] Work on the in vitro characterization of the enzymatic processing of lantibiotics, in particular for the formation of lanthionine, was described in reports on lacticin 481 [2] and haloduracin.[3] Recently, we identified a new family of lantibiotics, named labyrinthopeptins, which are produced by the actinomycete Actinomadura namibiensis DSM 6313. [4][5][6] The structure elucidation of labyrinthopeptin A2 (Scheme 1) mainly performed by X-ray crystallography highlighted a new amino acid, named labionin (Lab) (Scheme 1). Labionin is a triamino acid with a 2S,4S,8R configuration, and consists of a central quarternary carbon atom with a lanthionine motif and an unusual methylene bridge, which establishes a covalent link to a further amino acid moiety. This structure facilitates the formation of two rings in a linear peptide. Bioactivity assays revealed that labyrinthopeptin A2 has an excellent efficacy against neuropathic pain in an in vivo mouse model (ED 50 = 50 mg kg À1 ). The additionally found labyrinthopeptins A1 and A3 have been proposed as analogues of the A2 structure containing different amino acid constituents and an alternated ring size of the lanthionine motif.[4]The overall identification and sequencing of the gene cluster revealed only five genes which could be assigned to the biosynthesis of labyrinthopeptins. These contained two structural genes (labA1/A2) as precursors of labyrinthopeptin A1/ A3 and A2, two genes with sequence similarity to ATPdependent ABC transporters for the putative peptide export (labT1 and labT2), and one gene (labKC) for a putative modifying enzyme.[4] LabKC (MW = 95 kDa) is a two-domain protein consisting of an N-terminally conserved domain with features of an eukaryotic Ser/Thr protein kinase and a C-terminal domain with low sequence homology to LanC cyclases. In comparison to LanC cyclases, important active site residues, such as the zinc binding motif identified for the nisin cyclase, are missing in LabKC. [7] Moreover, the amino acid sequence of LabKC shows high homology to the SapB modifying enzyme RamC and to sequences from gene clusters of a considerable number of sequenced actinomycete strains (Supporting Information). [4,8] Therefore, we assign labyrinthopeptins as type-III lantibiotics.Herein we present the first in vitro reconstitution of the pre-labyrinthopeptin A2 biosynthesis in which a C À C bond formation is catalyzed by LabKC. This reaction involves the unprecedented requirement of guanosine triphosphate (GTP) for the phosphorylation and dehydratation reaction of serines. In other in vitro syntheses of lantibiotics adenosine triphosphate (ATP) and not GTP is used. [2,3] From the obtained data a biosynthetic model has been deduced. To our knowledge, this is the first time that GTP has been shown to act as a cosubstrate in the formation of lanthionine-ty...

Streptomyces toyocaensis produces A47934, a teicoplanin-like type-IV glycopeptide with antibiotic activity against methicillin-resistant Staphylococcus aureus. A47934 differs from the type-I vancomycin glycopeptides, which possess a tricyclic peptide backbone, by the presence of an additional ring closure between the aromatic amino acids 1 and 3. To elucidate the order of crosslinking reactions, P450 mono-oxygenase-inactivation mutants (DeltastaF, DeltastaG, DeltastaH, and DeltastaJ) of the A47934 producer were generated, and the accumulated intermediates were analyzed. Thus, the formation of each crosslink could unambiguously be assigned to a specific oxygenase. The structure of the released intermediates from the wild-type nonribosomal peptide synthetase assembly line facilitated the determination of the cyclization order. Unexpectedly, the additional ring closure in A47934, catalyzed by StaG, is the second oxygenase reaction.

No abstract

The nonribosomal peptide synthetase PF1022-synthetase (PFSYN) synthesises the cyclooctadepsipeptide PF1022 from the building blocks D-lactate, D-phenyllactate and N-methylleucine. The substrate tolerance of PFSYN for hydroxy acids was probed by in vitro screening of a set of aliphatic and aromatic alpha-D-hydroxy acids with various structural modifications in the side chain. Thus, new PF1022 derivatives for example, propargyl-D-lactyl-PF1022 and beta-thienyl-D-lactyl-PF1022 were generated. The promiscuous behaviour of PFSYN towards aliphatic and aromatic alpha-D-hydroxy acids is considerably larger than that of related enniatin synthetase (ESYN) and thus gives rise to the enzymatic generation of various new PF1022 derivatives.

Don't do it by halves: Genetic engineering of non‐ribosomal peptide synthetases (NRPSs) by module (M) exchange (I) and deletion (II) has previously resulted in amino acid exchange and deletion of the synthesized peptide metabolite. Here we report for the first time the insertion (III) of one complete module into an NRPS assembly line, resulting in an elongated peptide metabolite.

Peptid‐Irrgarten: Die Struktur des neuartigen Lantibiotikums Labyrinthopeptin A2 (siehe Bild) enthält eine zuvor unbekannte carbacyclische, posttranslational modifizierte Aminosäure, die Labionin genannt wurde. Im Anschluss an die Strukturaufklärung gelang die Identifizierung des Biosynthesegenclusters der Labyrinthopeptine. Labyrinthopeptin A2 zeigt eine ausgeprägte In‐vivo‐Wirksamkeit (Verminderung taktiler Allodynie) in der Maus in einem Nervenverletzungsmodell.