Antibody-like peptides for quantifying therapeutic antibodies

1. A process for quantifying one or more therapeutic antibodies in a sample of an individual comprising the steps of:

a) adding to a test sample which contains therapeutic antibodies a known amount of one or more labeled forms of a labeled chimeric non-therapeutic antibody-like protein, whereby a pre-proteolysis sample is provided,

b) subjecting the pre-proteolysis sample to an enzyme proteolysis, so as to provide a proteolysis sample comprising (i) proteolysis labeled peptides derived from the labeled antibody-like proteins and (ii) proteolysis peptides derived from the therapeutic antibody contained in the test sample,

c) determining by mass spectrometric analysis the ratio between (i) one or more selected proteolysis labeled peptides and (ii) one or more corresponding proteolysis peptides derived from said therapeutic antibody,

d) calculating from the ratio determined at step c) the amount of said therapeutic antibody in the test sample;

characterized in that the labeled chimeric non-therapeutic antibody-like protein is structurally similar to a plurality of reference therapeutic antibodies, and comprises an enzyme cleavable peptide sequence of a hypervariable region derived from each one of said plurality of reference therapeutic antibodies.

2. A process for quantifying one or more therapeutic antibodies in a sample of an individual comprising the steps of:

a) adding to a test sample which contains therapeutic antibodies a known amount of a composition comprising a labeled chimeric non-therapeutic antibody-like protein, whereby a pre-proteolysis sample is provided,

b) subjecting the pre-proteolysis sample to an enzyme proteolysis, so as to provide a proteolysis sample comprising (i) proteolysis labeled peptides derived from the labeled antibody-like proteins and (ii) proteolysis peptides derived from the therapeutic antibody contained in the test sample,

c) determining by mass spectrometric analysis the ratio between (i) one or more selected proteolysis labeled peptides and (ii) one or more corresponding proteolysis peptides derived from said therapeutic antibody,

d) calculating from the ratio determined at step c) the amount of said therapeutic antibody in the test sample;

characterized in that the labeled chimeric non-therapeutic antibody-like protein is structurally similar to a plurality of reference therapeutic antibodies, and comprises an enzyme cleavable peptide sequence of a hypervariable region derived from each one of said plurality of reference therapeutic antibodies.

3. The process according to claim 1 , wherein the chimeric antibody-like protein is labelled with a stable isotope.

4. The process according to claim 1 , wherein the reference therapeutic antibodies are selected from the group consisting of:

human antibodies, humanized antibodies, bispecific antibodies, chimeric antibodies, Fab, and single domain antibodies.

5. The process according to claim 1 , wherein the peptide sequence(s) derived from reference therapeutic antibodies are:

in the hypervariable region of a heavy chain of said antibody-like protein; and/or

in the hypervariable region of a light chain of said antibody-like protein.

6. The process according to claim 1 , wherein a hypervariable region of said antibody-like protein comprises more than one polypeptide sequence of a hypervariable region derived from said reference therapeutic antibodies.

7. The process according to claim 1 , wherein the reference antibodies are selected from the group consisting of: lnfliximab, Adalimumab, Rituximab, Golimumab, Vedolizumab, Certolizumab, Etanercept, Secukinumab, Cetuximab, Bevacizumab, Nivolumab, Ipilimumab, Atezolizumab, Durvalumab, Avelumab, Trastuzumab, Pertuzumab, Panitumumab, Natalizumab, Pembrolizumab.

8. The process according to claim 1 , wherein the labeled chimeric non-therapeutic antibody-like protein comprises:

a) a heavy chain in which a variable region comprises at least one sequence selected from the group consisting of: SEQ ID NO 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, and 33; and/or

b) a light chain in which a variable region comprises at least one sequence selected from the group consisting of: SEQ ID NO 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, and 34.

9. The process according to claim 1 , wherein the labeled chimeric non-therapeutic antibody-like protein has at least one variable region and at least one constant region.

10. The process according to claim 1 , wherein the labeled chimeric non-therapeutic antibody-like protein is structurally similar to an antibody selected from the group consisting of: a IgG, a IgM, a IgE, a IgA, and a IgD antibody.

11. The process according to claim 1 , wherein the labeled chimeric non-therapeutic antibody-like protein is structurally similar to a IgG antibody.

12. The process according to claim 1 , wherein the labeled chimeric non-therapeutic antibody-like protein is structurally similar to a IgG1 or a IgG4 antibody.

13. The process according to claim 1 , wherein the reference antibodies are selected from the group consisting of: Ipilimumab, Nivolumab, Atezolimumab, Durvalumab, Pembrolizumab, or Avelumab.

14. The process according to claim 2 , wherein the reference antibodies are selected from the group consisting of: Ipilimumab, Nivolumab, Atezolimumab, Durvalumab, Pembrolizumab, or Avelumab.

15. The process according to claim 1 , wherein the reference antibodies are selected from the group consisting of: Ipilimumab, Nivolumab, or Pembrolizumab.