Antibodies that bind to human ccr8

A method for measuring receptor occupancy (RO) of a cell membrane-bound CCR8 receptor to which a therapeutic Treg-depleting anti-CCR8 antibody binds comprising:

• (a) adding to background whole blood samples, previously exposed to various concentrations of the therapeutic antibody, a saturating concentration of the therapeutic antibody;
• (b) incubating aliquots of free, bound or fluorescence minus one (FMO) samples with buffer not containing the therapeutic antibody;
• (c) staining the samples with a core panel of antibodies to identify basic T cell markers, T cell differentiation markers, and Treg markers;
• (d) adding to the core panel
• (i) for the direct/total RO assay, an anti-idiotypic antibody for detecting bound CCR8 receptor, or
• (ii) for the indirect/total assay, two additional antibodies comprising an allophycocyanin (APC)-conjugated anti-hCCR8 antibody that competes with the therapeutic antibody, for detecting free CCR8 receptors, and an anti-hCCR8 antibody that does not compete with the therapeutic antibody, for detecting total CCR8 receptors;
• (e) lysing the red blood cells to clear the samples and analyzing the cleared samples by flow cytometry;
• and
• (f) determining the % RO for each concentration of the therapeutic antibody using the formula:
• % RO=100×[1−((free postdose/free predose)/(total postdose/total predose))].

A method for measuring a depletion in the frequency of CCR8-expressing cells in the peripheral blood of a subject undergoing treatment with an anti-CCR8 mAb, the method comprising:

• (a) determining a baseline level of expression of CCR8, and/or the frequency of CCR8-expressing cells in a first sample of whole blood or PBMCs from the subject;
• (b) administering a treatment of an anti-CCR8 mAb to the subject;
• and
• (c) determining the level of expression of CCR8, and/or the frequency of CCR8-expressing cells in a second sample of whole blood or PBMCs from the subject taken after administration of the anti-CCR8 mAb;
• wherein a decrease in the level of expression of CCR8, and/or the frequency of CCR8-expressing cells in the second sample indicates that the number of CCR8-expressing cells in the blood has been depleted.

A method for measuring a depletion in the number of tumor-infiltrating CCR8-expressing Tregs in a subject undergoing treatment, the method comprising:

• (a) determining a baseline level of expression of CCR8, and/or the frequency of CCR8-expressing Tregs, in a first sample of test tissue in or from the subject, the test tissue comprising tumor cells and tumor-infiltrating Tregs;
• (b) administering a treatment of an anti-CCR8 antibody to the subject;
• and
• (c) determining the level of expression of CCR8, and/or the frequency of CCR8-expressing Tregs, in a second sample of test tissue in or from a subject, the second test tissue taken during or after the treatment;
• wherein a decrease in the level of expression of CCR8, and/or a decrease in the frequency of CCR8-expressing Tregs, in the second sample indicates that the number of Tregs in the test tissue has been depleted.

A method for predicting the effectiveness of a therapeutic Treg-depleting antibody or an antigen-binding portion thereof in treating cancer in a subject, which method comprises:

• (a) determining the level of surface expression of CCR8, and/or the frequency of CCR8-expressing Tregs, in a test tissue in or taken from the subject, the test tissue comprising tumor cells and tumor-infiltrating Tregs;
• (b) administering the therapeutic Treg-depleting antibody or antigen-binding portion thereof the subject;
• (c) determining whether there is a decrease in the frequency of CCR8-expressing Tregs after administration of the therapeutic Treg-depleting antibody or antigen-binding portion thereof, and
• (d) predicting that the therapeutic Treg-depleting antibody or antigen-binding portion thereof will be effective in treating cancer in the subject if the decrease in the frequency of CCR8-expressing Tregs exceeds a predetermined threshold value, or
• (e) predicting that the therapeutic Treg-depleting antibody or antigen-binding portion thereof will not be effective in treating cancer in the subject if the decrease in the frequency of CCR8-expressing Tregs is less than a predetermined threshold value.

A method for treating a cancer in a subject, which method comprises:

• (a) selecting a subject that is a suitable candidate for cancer immunotherapy with a therapeutic Treg-depleting antibody or an antigen-binding portion thereof, the selecting comprising:
• (i) determining the level of surface expression of CCR8, and/or the frequency of CCR8-expressing Tregs, in a test tissue in or taken from the subject, the test tissue comprising tumor cells and tumor-infiltrating Tregs;
• (ii) administering the therapeutic Treg-depleting antibody or antigen-binding portion thereof to the subject;
• (iii) determining whether there is a decrease in the frequency of CCR8-expressing Tregs after administration of the therapeutic Treg-depleting antibody or antigen-binding portion thereof, and
• (iv) selecting the subject as a suitable candidate for immunotherapy with the therapeutic based on an assessment that a decrease in the frequency of CCR8-expressing Tregs exceeds a predetermined threshold value;
• and
• (b) administering to the selected subject a composition comprising a therapeutically effective amount of the therapeutic Treg-depleting antibody or antigen-binding portion thereof.