PET imaging with PD-L1 binding polypeptides
Provided herein are novel 10 Fn3 domains which specifically bind to PD-L1, as well as imaging agents based on the same for diagnostics.
1. A method of visualizing Programmed Death Ligand-1 (PD-L1) protein in a subject, comprising:
(a) administering to the subject a radiolabeled PD-L1 imaging agent at a dose of about 3-10 mCi (100-333 MBq);
(b) conducting a PET scan of the subject about 30-120 minutes after administering the imaging agent and obtaining an image; and
(c) visualizing the presence of the PD-L1 protein in the subject from the image,
wherein the imaging agent comprises a radiolabeled prosthetic group conjugated to an anti-PD-L1 adnectin by a bifunctional chelating agent, wherein the radiolabeled prosthetic group has the following structure:
wherein the 18 F is ortho to the N atom, x is an integer from 1 to 8, and wherein the anti-PD-L1 adnectin comprises BC, DE, and FG loops comprising amino acid sequences selected from the group consisting of:
(i) SEQ ID NOs: 6, 7, and 8, respectively;
(ii) SEQ ID NOs: 21, 22, and 23, respectively;
(iii) SEQ ID NOs: 36, 37, and 38, respectively;
(iv) SEQ ID NOs: 51, 52, and 53, respectively;
(v) SEQ ID NOs: 66, 67, and 68, respectively;
(vi) SEQ ID NOs: 81, 82, and 83, respectively; or
(vii) SEQ ID NOs: 97, 98, and 99, respectively.
2. The method of claim 1 , wherein the subject has at least one tumor.
3. The method of claim 2 , comprising comparing the uptake of the imaging agent in the at least one tumor and in background tissue, wherein the presence of PD-L1 in the at least one tumor above the background tissue is indicative that the PD-L1 is expressed in the at least one tumor and that the subject is likely to respond to treatment with a PD-1 or PD-L1 antagonist.
4. The method of claim 1 , wherein the radiolabel is a radioactive PET tracer.
5. The method of claim 1 , wherein the anti-PD-L1 adnectin comprises an amino acid sequence at least 80% identical to an amino acid sequence selected from the group consisting of: SEQ ID NOs: 5, 20, 35, 50, 65, 80 or 96.
6. The method of claim 1 , wherein the anti-PD-L1 adnectin comprises an amino acid sequence at least 80% identical to an amino acid sequence selected from the group consisting of: SEQ ID NOs: 9-15, 24-30, 39-45, 54-60, 69-75, 84-91, and 100-107.
7. The method of claim 1 , wherein the structure of the 18 F-radiolabeled prosthetic group is,
8. The method of claim 1 , wherein the structure of the 18 F-radiolabeled prosthetic group is,
9. The method of claim 1 , wherein the structure of the 18 F-radiolabeled prosthetic group is
10. The method of claim 1 , wherein the bifunctional chelating agent is a cyclooctyne comprising a reactive group that forms a covalent bond with an amine, carboxyl, carbonyl or thiol functional group on the protein.
11. The method of claim 1 , wherein the imaging agent has a structure as set forth below:
wherein X is an anti-PD-L1 adnectin comprising the amino acid sequence of any one of SEQ ID NOs: 13, 28, 43, 58, 73, 88, and 104.
12. The method of claim 11 , wherein the anti-PD-L1 adnectin comprises the amino acid sequence set forth in SEQ ID NO: 88.
13. The method of claim 11 , wherein the anti-PD-L1 adnectin comprises the amino acid sequence set forth in SEQ ID NO: 104.