Assays for determining plasma kallikrein system biomarkers

1. An ex vivo activation method, comprising:

placing an activator of the plasma kallikrein (pKal) system in a plasma sample obtained from a subject to produce a mixture, wherein the activator is Factor XIIa (FXIIa);

incubating the mixture;

measuring levels of intact high molecular weight kininogen (HMWK), cleaved HMWK, or both, in the plasma sample before and after the incubation;

determining a reduction of intact HMWK in the sample after the activation and/or an elevated level of the cleaved HMWK in the sample after the activation; and

administering a therapeutic agent to the subject if the plasma sample obtained from the subject has an elevated level of the cleaved HMWK as compared to a predetermined value;

wherein the therapeutic agent is DX-2930, DX-2922, DX-88, or EpiKal-2.

2. The method of claim 1 , wherein the subject is a human patient having or at risk of having a disease associated with pKal.

3. The method of claim 2 , wherein the human patient has been subjected to a treatment of the disease.

4. The method of claim 3 , wherein the human patient has HAE and has been treated with a pKal inhibitor, which is DX-2930, DX-2922, DX-88, or EpiKal-2.

5. An ex vivo assay for determining plasma kallikrein (pKal) activity in a sample, comprising:

placing a pKal system activator and a labeled synthetic peptide substrate of pKal in a plasma sample obtained from a subject to produce a mixture, wherein the activator is Factor XIIa (FXIIa), and wherein the peptide substrate comprises a motif of PFR;

incubating the mixture;

measuring the activity of pKal in the mixture based on a cleavage rate of the substrate; and

administering a therapeutic agent to the subject if the plasma sample obtained from the subject has an elevated level of pKal activity compared to a predetermined value;

wherein the therapeutic agent is DX-2930, DX-2922, DX-88, or EpiKal-2.

6. The assay of claim 5 , wherein the labeled substrate releases a detectable signal after being cleaved by pKal and the cleavage rate of the substrate is determined based on the magnitude of the detectable signal.

7. The assay of claim 5 , wherein the subject is a human patient having or at risk of having a disease associated with pKal.

8. The assay of claim 7 , wherein the human patient has been subjected to a treatment of the disease.

9. The assay of claim 8 , further comprising evaluating the efficacy of the treatment; wherein a reduced level of pKal activity as compared to the pKal activity before the treatment or a reduced level of pKal activity over the course of the treatment indicates that the treatment is effective; and continuing the treatment on the subject, if the treatment is identified as effective.

10. The assay of claim 8 , wherein the human patient has hereditary angioedema (HAE) and has been treated with a pKal inhibitor, which is DX-2930, DX-2922, DX-88, or EpiKal-2.

11. The method of claim 2 , wherein the disease associated with pKal is hereditary angioedema (HAE).

12. The method of claim 3 , wherein the plasma sample is obtained after or during the course of the treatment.

13. The method of claim 12 , further comprising evaluating the efficacy of the treatment, and continuing the treatment on the subject who is identified as being responsive to the treatment, a reduced level of cleaved HMWK after the treatment as compared to the level of cleaved HMWK before the treatment or a reduced level of cleaved HMWK over the course of the treatment indicating that the subject is responsive to the treatment.

14. The method of claim 8 , wherein the sample is obtained after or during the course of the treatment.

15. The method of claim 7 , wherein the disease associated with pKal is hereditary angioedema (HAE).