Botulinum neurotoxin-specific capture agents, compositions, and methods of using and making
The present application provides stable peptide-based Botulinum neurotoxin (BoNT) serotype A capture agents and methods of use as detection and diagnosis agents and in the treatment of diseases and disorders. The application further provides methods of manufacturing BoNT serotype A capture agents using iterative on-bead in situ click chemistry.
1. A method of synthesizing a capture agent to a target comprising the steps of:
(a) selecting a linker to connect an anchor ligand to a secondary ligand, wherein the anchor ligand and the secondary ligand were previously determined to bind to the same target at different binding sites representing distinct epitopes, wherein the linker is selected based on the distance between the binding site of the anchor ligand and the binding site of the secondary ligand,
wherein the anchor ligand and the secondary ligand bind their respective binding sites on the target in an orientation such that the target can promote 1,3-dipolar cycloaddition between an acetylene group on one of the anchor ligand or secondary ligand and an azide group on the other of the anchor ligand or secondary ligand to form a triazole linkage in the absence of a separate catalyst, wherein for the cycloaddition reaction one of the azide group or the acetylene group is connected to the anchor ligand or secondary ligand via the selected linker; and
(b) synthesizing a capture agent comprising the anchor ligand, the secondary ligand, and the selected linker, thereby generating the capture agent, wherein the dissociation constant of the capture agent for binding to the target is lower than the dissociation constant of either the anchor ligand or the secondary ligand for binding to the target.
2. The method of claim 1 , wherein the linker has a length that is within 10% of the distance between the anchor ligand and the secondary ligand when both ligands are bound to the target.
3. A method of synthesizing a capture agent for inhibiting SNAP-25 cleavage mediated by botulinum neurotoxin serotype A protein in one or more neurons, wherein the botulinum neurotoxin serotype A protein comprises a heavy chain and a light chain, wherein the light chain comprises an enzymatic active site, comprising
(a) selecting an anchor ligand that specifically binds to the enzymatic active site of the botulinum neurotoxin serotype A protein;
(b) selecting a secondary ligand that specifically binds at a distinct epitope from the anchor ligand within 5-10 angstroms on the botulinum neurotoxin serotype A protein; and
(c) linking the anchor ligand and secondary ligand together,
wherein the secondary ligand must bind to an epitope so that it specifically binds to an occluded conformation of the botulinum neurotoxin serotype A holotoxin, thereby synthesizing the capture agent for inhibiting SNAP-25 cleavage mediated by botulinum neurotoxin serotype A protein in one or more neurons.
4. The method of claim 3 , wherein the linking of the anchor ligand and the secondary ligand is performed using a linker.
5. The method of claim 4 , wherein the linker has a length that is between 100 and 110% of the distance between the anchor ligand and the secondary ligand when both ligands are bound to the botulinum neurotoxin serotype A protein.
6. A method of targeting adjacent epitopes on a single protein comprising
(a) identifying an anchor ligand that binds to a first epitope and a secondary ligand that binds to a second epitope, wherein the first and second epitopes are adjacent on the single protein;
(b) screening the anchor ligand and secondary ligand against a linker library based on affinity of the combined anchor ligand, linker and secondary ligand to bind the single protein; and
(c) selecting a linker to connect the anchor ligand to the secondary ligand, thereby targeting adjacent epitopes of the single protein by generating a capture agent that targets adjacent epitopes on the single protein, wherein the dissociation constant of the capture agent for binding to the target protein is lower than the dissociation constant of either the anchor ligand or the secondary ligand for binding to the target protein.
7. The method of claim 6 , wherein the adjacent epitopes are 5-10 angstroms apart on the single protein when the single protein is folded.
8. The method of claim 4 , wherein the linker has a length that is between 100 and 110% of the distance between the anchor ligand and the secondary ligand when both ligands are bound to the first and second epitopes, respectively.
9. The method of claim 4 , wherein the linker is a tripeptide.
10. The method of claim 4 , wherein the anchor ligand, secondary ligand, or both, are linked to the linker via a 1,4-substituted-1,2,3-triazole residue (Tz4) or via a 1,5-substituted-1,2,3-triazole residue (Tz5).
11. The method of claim 1 further comprising, prior to selecting the linker, the steps of:
(i) identifying an anchor ligand and a secondary ligand that bind to the same target peptide at distinct epitopes;
(ii) identifying the binding sites of the anchor ligand and the secondary ligand on the target peptide; and
(iii) calculating the distance between the binding site of the anchor ligand and the secondary ligand.
12. The method of claim 1 , wherein the target is a protein.
13. The method of claim 1 , wherein the anchor ligand is identified by binding to an epitope on the target.
14. The method of claim 1 , wherein the secondary ligand is identified by binding to an epitope on the target.
15. The method of claim 1 further comprising, prior to selecting the linker, identifying the anchor ligand, the secondary ligand, and the binding sites of the anchor ligand and the secondary ligand on the target.
16. The method of claim 1 further comprising, prior to selecting the linker, calculating the distance between the binding site of the anchor ligand and the binding site of the secondary ligand.
17. The method of claim 1 , wherein the capture agent further comprises a tertiary ligand.