CC-122 Exhibits Potent Anti-Lymphoma Activity in Combination with Obinutuzumab through Cell Autonomous and Antibody Dependent Cell Mediated Cytotoxicity

Background: CC-122 modulates the CRL4 E3 ligase complex, which results in recruitment and degradation of Aiolos and Ikaros. This results in cell autonomous anti-lymphoma and immunomodulatory effects on T and NK-cell function; such as increased expression of activation markers and cytokine production such as IFN-γ and TNF-α (Gandhi, ASH 2012). Single agent CC-122 is currently in a Phase I clinical trial for diffuse large B-cell lymphoma (DLBCL), multiple myeloma, and solid tumors (NCT01421524) and in combination with obinutuzumab (GA101) in DLBCL and indolent non-Hodgkin lymphoma (iNHL) (NCT02417285). We sought to understand the effects of combining CC-122 with anti-CD20 monoclonal antibody obinutuzumab (GA101) in in vitro and in vivo models of DLBCL and follicular lymphoma (FL).

Methods: Apoptosis and cell toxicity was measured by Annexin V/ToPro-3 flow cytometry and CellTiter Glo luciferase assays, respectively.  Antibody dependent cellular cytotoxicity (ADCC) was measured by anti-CD3 stimulated peripheral blood mononuclear cells (PBMCs) treated with vehicle or 100 nM CC-122 for 3 days. Prior to co-culture, target tumor cells were incubated with  vehicle or GA101 for 1 hour, washed and incubated with  treated PBMCs for an additional 4 hours followed by an apoptosis assay. DOHH2 and OCI-LY10 xenograft models were analyzed in C.B-17/Icr-Prkdcscid/IcoIcr mice, which retain NK cells, and CC-122 was dosed at 30 mg/kg, qd days (days 1-5 out of a 7 day schedule).

Results: In the DOHH2 FL cell line, the percentage of Annexin V and ToPro-3 positive DOHH2 cells treated with 40 nΜ CC-122 or 1000 ng/mL GA101 was 35% and 40%, respectively. The combination of CC-122 and GA101 resulted in a synergistic enhancement with 82% cell death (theoretical additivity = 61%). Treatment of RL FL cells with 40 nΜ CC-122 or 2000 ng/mL GA101 resulted in 14% and 12% apoptotic cells, respectively. CC-122 combined with GA101 showed a synergistic enhancement of 44% cell death (theoretical additivity = 24.2%). In ADCC assays, DOHH2 cells incubated with vehicle treated PBMCs demonstrated 14% apoptosis. DOHH2 cells treated with 1000 ng/ml GA101 and vehicle treated PBMCs exhibited 42% apoptosis. The addition of CC-122 (100 nM) treated PBMCs to GA101 treated DOHH2 cells increased the level of ADCC to 57%. Similarly, CC-122 treatment of PBMCs co-cultured with GA101 treated RL cells led to increased levels of apoptosis by ADCC (75.7%) compared to DMSO treated PBMC with GA101 treated RL cells (62.8%) and vehicle treated co-cultures (33.9%).

In a DOHH2 xenograft model, the mean tumor volume (MTV) for vehicle treated controls was 2818 mm³ at the conclusion of the study, compared to CC-122 MTV of 1568 mm³ (44% tumor growth inhibition (TGI)). GA101 monotherapies at 0.5 and 3 mg/kg once weekly yielded dose-related MTVs of 1576 mm³ (44% TGI) and 826 mm³ (71% TGI), respectively. CC-122 in combination with GA101 at 0.5 mg/kg resulted in a MTV of 694 mm³ (75% TGI), whereas the combination of CC-122 with GA101 at 3 mg/kg yielded a MTV of 493 mm³ (83% TGI). All regimens produced TGI that was statistically different from vehicle treated controls (p≤0.001).

In 2 DLBCL cell lines (OCI-LY10, ABC-DLBCL and WSU-DLCL2, GCB-DLBCL), CC-122 treatment induced apoptosis with an IC50 ranging from 100 to 300 nΜ. Cell toxicity of either single agent CC-122, GA101 or a combination of the two was measured.  OCI-LY10 and WSU-DLCL2 cells treated with 40 nΜ CC-122 reduced viability by 20% and 15%, respectively. OCI-LY10 and WSU-DLCL2 cells treated with 2000 ng/mL GA101 reduced viability by 46% and 62%, respectively. The combination of CC-122 with GA101 in either cell line resulted in additive effects of 58% and 68%, respectively. 

In the OCI-LY10 xenograft model, CC-122 demonstrated no significant reduction in MTV compared to vehicle. Single agent GA101 at 0.5 and 2.5 mg/kg once weekly yielded dose-related reduction in TGI’s of 30.5% and 49.2%, respectively. CC-122 in combination with GA101 at 0.5 mg/kg resulted in 47% TGI), whereas the combination of CC-122 with GA101 at 2.5 mg/kg yielded a 94.5% TGI.

Conclusion: Together, these data demonstrate that CC-122 has potent cell autonomous and immunomodulatory activities and that the addition of GA101 provides a synergistic effect in FL and is additive in DLBCL when compared to either as single agents. These data provide pre-clinical proof of concept that a combination of CC-122 and GA101 in the treatment of DLBCL and iNHL may be clinically beneficial.