Pom 1

Example 7

3.5×10⁴ MEL-28 cells were plated overnight at 37 degrees C. Cells were washed with Tris assay buffer to remove phosphate. 100 nM titrated down to 0.005 pM of monoclonal antibodies were incubated with cells for 30 minutes at 37 degrees C. 50 μM ATP was added and incubated for 15 minutes. Supernates were harvested and frozen. Supernates were thawed and evaluated for ATP using the EnzyLight (EnzyLight ATP Assay Kit, BioAssay Systems). Palivizumab was used as an isotype control and ARL (Tocris) and POM-1 (Alpha Aesar) used at a concentration of 100 μM are non-specific small molecule inhibitors of CD39 as positive controls.

ATP was almost undetectable after 30 minutes post ATP addition to the cells in untreated and/or isotype treated samples (see FIG. 5 A) while all of the anti-CD39 antibodies tested prevented processing of ATP in dose dependent manner (see FIG. 5 A, B). Most of the anti-CD39 antibodies tested in this assay prevented ATP processing by CD39 to a similar extent as ARL (see FIG. 5A). IC50s of anti-CD39 antibodies in ATP preservation assay ranged from 0.02-0.1 nM. Overall potency of antibodies in this assay was consistent with what was observed in Malachite Green phosphate readout assay.

Example 10

B cells were isolated from human leukopak using EasySep B cell isolation kit (STEMCELL Technologies). 5×10⁴ B cells/well were washed with Tris buffer and incubated with serially diluted (100-0.00013 nM) antibodies for 30 minutes at 37 degrees C. 50 μM ATP was added to each well and incubated with cells for 2 hrs. The supernatants were collected and analyzed in Malachite Green Assay (R&D) according to manufacturer's protocol. Phosphate released from CD39 processing of ATP was used as a readout of enzyme activity. Palivizumab was used as an isotype control and ARL (Tocris) and POM-1 (Alpha Aesar), non-specific small molecule inhibitors of CD39, were used as positive controls at 100 μM.

The antibodies were demonstrated to bind to primary human and cyno B cells (see FIG. 7) and the next step was to evaluate the inhibition of ATP hydrolysis by detection of free phosphate (Pi) using a Malachite Green Assay. The results are shown in FIG. 8 and indicate the anti-CD39 antibodies inhibit the enzymatic inhibition/dephosphorylation of ATP by primary human B cells. The ability of the antibodies to inhibit enzymatic activity was comparable regardless of high vs. low max MFI detected in the binding to human B cells (FIG. 7).

Example 8

3.5×10⁴ MEL-28 cells/well were plated and incubated with antibodies overnight at 37 degrees C. Cells were washed to remove FBS. Cells next were pre-treated with antibodies in X-VIVO 15 FBS free media overnight at 37 degrees C. ATP was then spiked in at 50 μM for 15 minutes. Supernatants were collected and analyzed using AMP-Glo kit according to manufacturer's instructions (Promega). Palivizumab was used as an isotype control and POM-1 (Alpha Aesar), a non-specific small molecule inhibitor of CD39, was used as positive control at 100 μM.

Anti-CD39 antibodies tested in overnight AMPGlo assay in MEL-28 cells demonstrated sustained inhibition of ATPase activity as indicated by decreased AMP levels present in the supernatants (see FIG. 6A) Inhibition of CD39 activity by antibodies was equivalent to or more potent compared to POM-1 treatment. The data is consistent with results obtained in CD39 short-term Malachite Green assay in MEL-28 (see FIG. 4). Antibodies tested in an overnight assay had IC50 values in an AMPGlo CD39 inhibition assay ranging from 0.01 to 0.3 nM. (see FIG. 6 B)