Azido-PEG4-carbonylaminophenyl 3,6-di-O-(α-D-mannopyranosyl)-α-D-mannopyranoside is supplied as a synthetic glycosidic active pharmaceutical ingredient for oral and injectable formulation development. The model identifier is the full systematic chemical name rather than a proprietary trade code: the molecule is composed of an α-D-mannopyranoside core substituted at the 3- and 6-positions with α-D-mannopyranosyl residues, connected through a carbonylaminophenyl junction to a discrete tetraethylene glycol spacer carrying a terminal azide. The azide group supports bioorthogonal conjugation through copper(I)-catalysed alkyne-azide cycloaddition and strain-promoted alkyne-azide cycloaddition, while the branched trimannosyl head group presents three mannose units in a defined geometry suitable for mannose-receptor-directed applications. The product is manufactured under ICH Q7 conditions and is released with certificates covering residual solvents, elemental impurities, water content, and microbiological quality. The intended dosage forms include tablet, capsule, granule, and injection; oral and injectable grades differ primarily in endotoxin control, particle-size distribution, and container closure documentation. Because the molecule contains a terminal azide and a discrete tetraethylene glycol chain, its handling and formulation boundaries are distinct from unprotected mannose, polydisperse PEGylated mannans, and azide-free mannosides.

Specification framework and release parameters

The release specification for a synthetic glycosylated PEG linker of this class is structured around the decision-tree requirements of ICH Q6A and relevant pharmacopoeial general chapters. Identity is confirmed by high-resolution electrospray ionisation mass spectrometry and one- and two-dimensional NMR; infrared spectroscopy is recorded against a qualified reference spectrum under Ph. Eur. 2.2.24. The terminal azide produces an IR asymmetric stretch near 2100 cm⁻¹, which is monitored as an identity band. Chromatographic purity is determined by HPLC with charged aerosol detection because the molecule lacks a strong UV chromophore apart from the phenyl carbonyl segment. Residual solvents are controlled against ICH Q3C limits; for this synthetic route, methanol, dichloromethane, acetonitrile, and dimethylformamide are the principal solvents monitored. Elemental impurity risk is assessed according to ICH Q3D, and compliance with USP <232> and USP <233> is verified by inductively coupled plasma–mass spectrometry. Water content is determined by Karl Fischer titration and is maintained below 0.5% w/w for injectable-grade material because excess moisture accelerates hydrolysis of the glycosidic bonds and can reduce azide stability during melt processing.

For injectable-grade lots, bioburden is monitored before aseptic processing, and the bacterial endotoxin limit is not a single fixed value but is calculated from the maximum intended dose according to USP <85>. For a parenteral product with a dose of 100 mg per 70 kg patient, the corresponding endotoxin limit calculated with a 5 EU/kg threshold is approximately 3.5 EU/mg; this value changes with dose and route of administration. Water-free handling is maintained because the tetraethylene glycol segment can absorb atmospheric moisture during open transfer. Pre-drying under vacuum at 40 °C is applied when water content approaches the release limit after extended storage.

In oral solid dosage form development, the compound is handled as a low-dose component; direct addition to a tumble blender without geometric pre-blending can produce content uniformity failures on high-speed rotary tablet presses. For tablet and capsule manufacture, the API is first passed through a 250 µm screen and pre-dispersed in lactose monohydrate or mannitol in a low-shear blender before final mixing with magnesium stearate. Blend uniformity acceptance value is not more than 15.0 according to USP <905>. Aqueous granulation should be limited to short dwell times because the tetraethylene glycol chain lowers the wet-mass glass transition and can cause sticking on high-shear granulator walls. Published data for this exact azido-PEG4 trimannoside in twin-screw wet granulation is limited; transfer from batch high-shear equipment should be supported by feasibility studies measuring torque, granule particle-size distribution, and residual water. The API is less hygroscopic than unprotected mannose, but storage above 60% relative humidity can increase water uptake and reduce flowability. Over-lubrication with magnesium stearate beyond 10 min in a bin blender should be avoided unless dissolution testing under USP <711> demonstrates no delay in release.

When injectable formulation requires endotoxin-controlled PEG glycosides

Injectable-grade use requires dissolution or dispersion in compendial Water for Injection with endotoxin levels below 0.25 EU/mL. The dissolution profile depends on pH and temperature; the phenyl carbonyl and tetraethylene glycol segment provide moderate aqueous solubility, but stock solutions should not be prepared above the concentration that remains free of visible precipitation after 24 h at 2–8 °C. Aseptic processing follows EU GMP Annex 1 and ISO 14644-1 cleanroom zoning; final sterile filtration is performed through a 0.22 µm polyethersulfone membrane with a 0.45 µm pre-filter. Terminal sterilisation by autoclaving at 121 °C for 15 min has not been established as a default cycle for this azide-bearing molecule; forced-degradation studies must confirm azide integrity and absence of phenyl carbamate hydrolysis before terminal sterilisation is selected. Subvisible particulate matter in the finished injection is controlled according to USP <788>, and bulk solution is filtered under positive-pressure nitrogen to reduce shear-induced aggregation of the trimannosyl head group. The container closure system for lyophilised injections should use bromobutyl rubber stoppers and glass vials meeting USP <660> and USP <381> requirements; extractables and leachables protocols aligned with Ph. Eur. 3.2.2.1 and USP <1663> should assess compatibility with the azido-PEG4 moiety.

What differentiates this azido-PEG4 trimannoside from linear PEG mannose derivatives?

The compound differs from linear PEG-mannose derivatives by the branched 3,6-di-O-(α-D-mannopyranosyl) architecture rather than a single terminal mannose. The branched trisaccharide presents three mannose residues in a geometry that can influence multivalent receptor engagement; the carbonylaminophenyl linker provides a defined junction instead of a reducible disulfide or enzymatically cleavable ester. Unlike azide-free mannosylated polymers, the terminal azide permits bioorthogonal conjugation without activation of carbohydrate hydroxyls and without reaction with free amines or thiols under normal pharmaceutical conditions. Compared with longer PEG chains, the discrete tetraethylene glycol spacer adds sufficient hydrophilicity for aqueous processing while limiting viscosity build-up in high-concentration injection solutions. The material also differs from unprotected α-D-mannopyranoside because the phenyl and tetraethylene glycol groups reduce susceptibility to glycosidase hydrolysis and modify aqueous diffusion behaviour, although the exact pharmacokinetic impact depends on the conjugated carrier. Because the tetraethylene glycol spacer is monodisperse rather than a broad polymeric distribution, the product has an exact mass and avoid the polydispersity index concerns associated with high-molecular-weight PEGylated mannosides.

Documentation for each batch includes a certificate of analysis, a residual solvent report, an elemental impurity risk assessment, and a statement of microbiological quality. Master batch records are maintained under ICH Q7 and should be disclosed in a drug master file or as the active substance section of a Common Technical Document Module 3.2.S. The retest period is assigned from accelerated and long-term stability data; without product-specific data, no fixed retest date is claimed. Batch-to-batch variance should be reviewed for residual dichloromethane, acetonitrile, and water because these parameters are sensitive to drying deviations in the final isolation step. The supplier’s release data should also include the azide-to-carbonyl NMR integration ratio to confirm that conjugation sites have been retained through synthesis and drying.

Storage, retest, and material compatibility boundaries

Storage of the API should be under inert gas in tightly closed containers at 2–8 °C, protected from light. The terminal azide is stable during short ambient transfer periods but should not be processed with concentrated mineral acids or transition-metal salts that can lead to hydrazoic acid formation; safety assessments are required before any operation involving acid pH below 2.0 or heating above 60 °C. Compatibility with common tablet excipients is generally acceptable with microcrystalline cellulose, lactose monohydrate, mannitol, and pregelatinised starch; however, materials containing oxidising agents must be excluded. For injectable formulations, leachables from silicone tubing should be considered because amphiphilic PEGylated glycosides can extract low-molecular-weight siloxanes. The compound should not be blended with phosphine-containing reagents under processing conditions that permit Staudinger ligation, because residual phosphines can consume the terminal azide. No conclusion on interchangeability with other azido-mannoside linkers can be made without head-to-head receptor-binding and purity data.

At pilot scale, high-shear blending of the pure API with magnesium stearate for more than 10 min can produce over-lubrication and delayed release from capsule contents; blending time should be validated by dissolution testing under USP <711>. For injectable processing, final product should be evaluated for pH and osmolality after addition of the API. The target pH for stability assessment is typically between 5.0 and 7.0, because acidic conditions accelerate glycosidic hydrolysis and alkaline conditions can reduce azide recovery. The osmolality contribution from the compound must be measured; it is not predictable from molecular weight alone because the tetraethylene glycol chain and mannosyl residues influence activity coefficients. The product is supplied as a single lot with a defined certificate of analysis, and any change in synthesis path, salt form, or drying protocol triggers re-evaluation of the specification and stability profile.