Method for Uses of Protein Precursors as Prodrugs
The present invention provides compositions useful as prodrugs and methods for making the same. The compositions include a fusion protein having a first delivery domain and a second protein precursor domain linked together via a linker sequence. The delivery domain is a protein capable of facilitating entry to a target cells via the endocytotic pathway, such as transferrin. The protein precursor is a prohormone or a profactor, such as proinsulin. Methods of this invention include the steps of selecting a protein suitable as the delivery domain, constructing a vector to encode the fusion protein, and expressing the fusion protein in a suitable expression host.
1 . A fusion protein useful as a prodrug, comprising:
a first delivery domain linked by a linker sequence to a second protein precursor domain comprising a protein precursor useful as a therapeutic agent,
wherein said first delivery domain is a protein capable of facilitating entry to a target cell via the endocytotic pathway, and said second protein precursor domain is a prohormone or a profactor.
2 . The fusion protein of claim 1 , wherein said first delivery domain is transferrin.
3 . The fusion protein of claim 2 , wherein said second protein precursor domain is proinsulin.
4 . The fusion protein of claim 3 , wherein said target cell is liver cell.
5 . A method for delivering a protein precursor prodrug, comprising:
forming a fusion protein comprising a first delivery domain linked to a second protein precursor domain; and
introducing said fusion protein to a patient in need of the prodrug.
6 . The method of claim 5 , wherein said first delivery domain is a transferrin.
7 . The method of claim 5 , wherein said prodrug is proinsulin.
8 . The method of claim 5 , wherein said linker sequence is a leucine-glutamate dipeptide.
9 . A method for forming a fusion protein useful as a prodrug, comprising:
selecting a protein useful as a delivery domain for a protein precursor;
constructing a vector encoding said delivery domain linked to said protein precursor via a suitable linker sequence; and
expressing said fusion protein in a suitable expression host.
10 . The method of claim 9 , wherein said delivery domain is transferrin.
11 . The method of claim 9 , wherein said protein precursor is proinsulin.
12 . The method of claim 9 , wherein said linker sequence is leucine-glutamate dipeptide.
13 . A method for extending plasma half-life of a protein precursor domain, comprising:
conjugating said protein precursor domain to a transferrin domain prior to introducing said protein precursor into said plasma,
whereby said transferrin domain acts as a half-life extending element to extend the plasma half-life of the protein precursor domain.
14 . The method of claim 13 , wherein said protein precursor is a prohormone or a profactor.
15 . The method of claim 13 , wherein said protein precursor is proinsulin.
16 . A method for extending a therapeutic effect of a protein precursor in a subject, comprising:
conjugating said protein precursor to a transferrin domain to form a fusion protein,
whereby said transferrin domain acts as a stabilizing element to extend the therapeutic effects of the protein precursor in the subject.
17 . The method of claim 16 , wherein said protein precursor is a prohormone or a profactor.
18 . The method of claim 16 , wherein said protein precursor is proinsulin.