Synthesis of uniformly defined molecular weight mannosylated dextrans and derivatives thereof
Inventors
Arnold, Jeffrey • Ralph, David A.
Assignees
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Publication Number
US-11859023-B2
Publication Date
2024-01-02
Expiration Date
Abstract
Disclosed herein is method for conjugating a metal chelating agent to a functionalized dextran by reacting a chelator with an aminated dextran backbone, where the chelator comprises a one, and only one, derivatized carboxylic acid group to form a chelator-dextran complex. In certain aspects, the dextran-chelator complex is substantially free of intra- or intermolecular crosslinking. In certain aspects, the functionalized dextran is an amine dextran, an alkynyl dextran, or a thiol dextran. In exemplary implementations, the functionalized dextran is an amine dextran. In further embodiments, one and only one carboxylic acid group on the chelating agent is derivatized as a N-hydroxysuccinimide (NHS) ester.
Core Innovation
The invention relates to conjugating a metal chelating agent to a functionalized dextran by reacting a chelator with an aminated dextran backbone, where the chelator comprises a plurality of carboxylic acid groups. Only one carboxylic acid group is activated to form a chelator-dextran complex, while the additional carboxylic acid group(s) are each conjugated to a protecting group. The resulting dextran-chelator complex is substantially free of intra- or intermolecular crosslinking.
The description identifies shortcomings of prior tilmanocept preparation in which activation of unprotected multi-acid chelators can cause intra- and intermolecular crosslinking, increasing molecular weight and polydispersity index, and degrading biodistribution and imaging sensitivity. In contrast, the disclosed approach is directed to more uniform monomeric constructs by preventing crosslinking and oligomerization during chelator attachment to the dextran backbone.
The disclosed constructs include mannosylated dextrans, including tilmanocept, and the metal chelators DTPA or DOTA conjugated via a strategy that uses only one derivatized or activated carboxylic acid group on the chelator. Representative structures and comparisons are described using molecular weight distributions by MWCO fractionation and imaging studies to contrast non-crosslinked lower molecular weight constructs against crosslinked tilmanocept with higher observed molecular weight.
Claims Coverage
The partial content includes two independent claims. The claims focus on formation of a substantially non-crosslinked chelator-dextran complex by activating only one chelator carboxylic acid group while protecting the remaining acids, and on a subsequent synthesis sequence for removing protecting groups and adding mannose moieties through amidate linkage to the dextran backbone.
Single activated carboxylic acid chelator conjugation with protected remaining acids
Reacting a chelator with an aminated dextran backbone, wherein the chelator comprises a plurality of carboxylic acid groups, wherein only one carboxylic acid group is activated to form a chelator-dextran complex, and wherein the additional carboxylic acid group(s) are each conjugated to a protecting group, wherein the dextran-chelator complex is substantially free of intra- or intermolecular crosslinking.
Mannose addition to chelator-dextran complex via amidate linkage with protected multi-acid chelator precursor
Synthesizing an amine dextran by reacting a chelator with an aminated dextran backbone, wherein the chelator comprises a plurality of carboxylic acid groups, each conjugated to a protecting group with the exception of only one carboxylic acid derivatized as a single activated mono-N-hydroxysuccinimide (NHS) ester, to form a chelator-dextran complex; removing the protecting groups from each of the plurality of carboxylic acid groups; and adding a plurality of mannose moieties to the chelator dextran complex through amidate linkage to the dextran backbone.
Across the independent claims, the inventive focus is formation of a substantially non-crosslinked chelator-dextran complex by activating only one chelator carboxylic acid group while protecting the remaining acids, followed in a separate synthesis claim by removing protecting groups and adding mannose moieties through amidate linkage to the dextran backbone.
Stated Advantages
Dextran-chelator complex is substantially free of intra- or intermolecular crosslinking.
Improved localization is associated with non-crosslinked lower molecular weight constructs versus crosslinked tilmanocept with higher observed molecular weight in imaging comparisons.
Non-crosslinked constructs are associated with improved biodistribution and imaging sensitivity relative to prior crosslinking-prone preparation.
Documented Applications
CD206 targeting using mannose moieties in mannosylated dextrans, including tilmanocept, evaluated by PET/CT and SPECT/CT imaging comparisons.
Assessment of molecular weight distributions using MWCO fractionation to compare non-crosslinked constructs versus crosslinked tilmanocept.
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