Method for measuring reactivity of FVIII
The inventors produced substances that neutralize the activity of a bispecific antibody having an activity of functionally substituting for FVIII, and undertook the construction of methods for measuring the reactivity of FVIII that can ensure accuracy even in the presence of this bispecific antibody. As a result, the inventors discovered that in APTT-based one-stage clotting assay, FVIII activity in the plasma of a hemophilia A patient can be evaluated accurately, and also that in APTT-based Bethesda assay, FVIII inhibitor titer in the plasma of a hemophilia A patient carrying a FVIII inhibitor can be evaluated accurately.
1. A method for determining a level of coagulation factor VIII (FVIII) activity or FVIII inhibitor titer in a sample from a patient who had been treated with a bispecific antibody functionally substituting for FVIII, the method comprising:
(i) providing an in vitro sample derived from blood of the patient and containing the bispecific antibody, wherein the bispecific antibody is any one of the bispecific antibodies recited below, in which a first polypeptide is associated with a third polypeptide and a second polypeptide is associated with a fourth polypeptide:
a bispecific antibody in which the first polypeptide is an H chain consisting of the amino acid sequence of SEQ ID NO: 9, the second polypeptide is an H chain consisting of the amino acid sequence of SEQ ID NO: 11, and the third and fourth polypeptides are identical L chains, each consisting of the amino acid sequence of SEQ ID NO: 10; or
a bispecific antibody in which the first polypeptide is an H chain consisting of the amino acid sequence of SEQ ID NO: 36, the second polypeptide is an H chain consisting of the amino acid sequence of SEQ ID NO: 37, and the third and fourth polypeptides are identical L chains, each consisting of the amino acid sequence of SEQ ID NO: 38;
(ii) contacting the sample with one or more antibodies that neutralize the bispecific antibody so that it does not functionally substitute for FVIII; and
(iii) assaying the sample to determine a level of FVIII activity or a level of FVIII inhibitor titer in the sample, wherein at least one of the one or more antibodies that neutralize the bispecific antibody is selected from the group consisting of:
(A) an antibody having a heavy chain variable region comprising a CDR 1 comprising the amino acid sequence of SEQ ID NO: 12, a CDR2 comprising the amino acid sequence of SEQ ID NO: 13, and a CDR3 comprising the amino acid sequence of SEQ ID NO: 14; and a light chain variable region comprising a CDR1 comprising the amino acid sequence of SEQ ID NO: 18, a CDR2 comprising the amino acid sequence of SEQ ID NO: 19, and a CDR3 comprising the amino acid sequence of SEQ ID NO: 20,
(B) an antibody having a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 1 and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 2,
(C) an antibody having a heavy chain variable region comprising a CDR 1 comprising the amino acid sequence of SEQ ID NO: 24, a CDR2 comprising the amino acid sequence of SEQ ID NO: 25, and a CDR3 comprising the amino acid sequence of SEQ ID NO: 26; and a light chain variable region comprising a CDR1 comprising the amino acid sequence of SEQ ID NO: 30, a CDR2 comprising the amino acid sequence of SEQ ID NO: 31, and a CDR3 comprising the amino acid sequence of SEQ ID NO: 32, and
(D) an antibody having a heavy chain variable region comprising the amino acid sequence of SEQ ID NO: 3 and a light chain variable region comprising the amino acid sequence of SEQ ID NO: 4.
2. The method of claim 1 , wherein step (ii) comprises contacting the sample with a combination of two antibodies that neutralize the bispecific antibody, the two antibodies being the antibodies of (A) and (C).
3. The method of claim 2 , wherein, following the contacting step, the sample is assayed for FVIII activity.
4. The method of claim 3 , wherein the FVIII activity is assayed with a one-stage clotting assay or a thrombin generation assay.
5. The method of claim 2 , wherein, following the contacting step, the sample is assayed for FVIII inhibitor titer.
6. The method of claim 5 , wherein the FVIII inhibitor titer is assayed with a Bethesda assay, an ELISA, or a Nijmegen Bethesda assay.
7. The method of claim 2 , wherein the patient is a human patient who has a disease involving hemorrhagic symptoms, and to whom the bispecific antibody has been administered as a treatment for the disease, prior to obtaining the blood from the patient.
8. The method of claim 7 , wherein, after the contacting step, the sample is assayed to determine FVIII activity.
9. The method of claim 8 , wherein the FVIII activity determined in the sample is compared to FVIII activity in a control sample derived from blood obtained from a human subject who does not have the disease, and wherein the comparison provides an indication of the disease's severity in the patient.
10. The method of claim 7 , wherein, after the contacting step, the sample is assayed to determine FVIII inhibitor titer.
11. The method of claim 10 , wherein the patient is a hemophilia A patient whose plasma comprises an FVIII inhibitor.
12. The method of claim 7 , wherein a formulation comprising FVIII was administered to the patient, prior to obtaining the blood from the patient.
13. The method of claim 1 , wherein step (ii) comprises contacting the sample with a combination of two antibodies that neutralize the bispecific antibody, the two antibodies being the antibodies of (B) and (D).
14. The method of claim 13 , wherein, following the contacting step, the sample is assayed for FVIII activity.
15. The method of claim 14 , wherein the FVIII activity is assayed with a one-stage clotting assay or a thrombin generation assay.
16. The method of claim 13 , wherein, following the contacting step, the sample is assayed for FVIII inhibitor titer.
17. The method of claim 16 , wherein the FVIII inhibitor titer is assayed with a Bethesda assay, an ELISA, or a Nijmegen Bethesda assay.
18. The method of claim 1 , wherein one of the one or more antibodies that neutralize the bispecific antibody binds to a Fab comprising the variable regions of SEQ ID NOs: 9 and 10.
19. The method of claim 1 , wherein one of the one or more antibodies that neutralize the bispecific antibody binds to a Fab comprising the variable regions of SEQ ID NOs: 11 and 10.
20. The method of claim 1 , wherein one of the one or more antibodies is the antibody of (A).
21. The method of claim 1 , wherein one of the one or more antibodies is the antibody of (B).
22. The method of claim 1 , wherein one of the one or more antibodies is the antibody of (C).
23. The method of claim 1 , wherein one of the one or more antibodies is the antibody of (D).
24. The method of claim 1 , wherein, following the contacting step, the sample is assayed for FVIII activity.
25. The method of claim 24 , wherein the FVIII activity is assayed with a one-stage clotting assay or a thrombin generation assay.
26. The method of claim 1 , wherein, following the contacting step, the sample is assayed for FVIII inhibitor titer.
27. The method of claim 26 , wherein the FVIII inhibitor titer is assayed with a Bethesda assay, an ELISA, or a Nijmegen Bethesda assay.
28. The method of claim 1 , wherein the patient is a human patient who has a disease involving hemorrhagic symptoms, and to whom the bispecific antibody has been administered as a treatment for the disease, prior to obtaining the blood from the patient.
29. The method of claim 28 , wherein, after the contacting step, the sample is assayed to determine FVIII activity.
30. The method of claim 29 , wherein the FVIII activity determined in the sample is compared to FVIII activity in a control sample derived from blood obtained from a human subject who does not have the disease, and wherein the comparison provides an indication of the disease's severity in the patient.
31. The method of claim 28 , wherein, after the contacting step, the sample is assayed to determine FVIII inhibitor titer.
32. The method of claim 28 , wherein a formulation comprising FVIII was administered to the patient, prior to obtaining the blood from the patient.
33. The method of claim 28 , wherein the patient is selected from the group consisting of a hemophilia A patient, an acquired hemophilia A patient, and a von Willebrand disease patient.
34. The method of claim 31 , wherein the patient is a hemophilia A patient whose plasma comprises an FVIII inhibitor.