Lenalidomide Enhances the Biological Activity of Galiximab Against Non-Hogkin’s Lymphoma In Vitro and In Vivo.

Lenalidomide, a thalidomide analog, has dual anti-tumor activities against B-cell lymphomas and other hematological malignancies by inducing direct apoptosis in malignant cells and modulating the tumor microenviroment (angiogenesis inhibition) or the host immune response. We previously demonstrated that lenalidomide enhances rituximab-mediated antibody dependent cellular cytotoxicity (ADCC). In our current work we further studied the effects of combining lenalidomide with galiximab (IDEC114), a primatized anti-CD80 monoclonal antibody, which is undergoing clinical testing in B-cell lymphoma. To this end a panel of rituximab-sensitive or rituximab-resistant B-cell lymphoma cell lines was exposed in vitro to lenalidomide (10μg/ml) or DMSO (0.01%) with our without galiximab (10μg/ml) or isotype control antibody (10μg/ml) and incubated at 37°C, 5%CO₂ over five days. Changes in DNA synthesis were determined by measuring [3H]-thymidine uptake at 24 and 48 hrs. To asses changes in galiximab-mediated ADCC, peripheral blood mononuclear cells (PBMCs) isolated from healthy volunteers were incubated with lenalidomide or control for 72 hrs. Subsequently, NHL cells were labeled with ⁵¹Cr and then exposed to galiximab or isotype control (10mg/ml) and PBMCs (Effector:Target ratio, 40:1). For in vivo studies, 6–8 week old SCID mice were inoculated with 1×10⁶ Raji cells via tail vein injection and after a period of 72 hours, in order to allow for tumor engraftment, animals were divided into four cohorts (control, lenalidomide alone, galiximab alone, and lenalidomide + galiximab). Lenalidomide was administered intraperitoneally (i.p) at 0.5mg/kg/dose on days +3, +4, +8, +9, +13, +14, +18 and +19. Galiximab was administered via tail vein injection at 10mg/kg/dose on days +5, +10, +15 and +20. Difference in survival between treatment groups was performed by Kaplan-Meier analysis.

Results: In vitro exposure of various NHL cells to lenalidomide for five consecutive days enhanced the anti-proliferative effects of galiximab against Raji cells (40% of growth inhibition) when compared to Galiximab (15% growth inhibition) or Lenalidomide (14% growth inhibition) at 24 hrs. Similar results were observed in other cell lines. In addition, an improvement in galiximab-associated ADCC was observed in lenalidomide-exposed NHL cells. In vivo treatment of SCID mice with lenalidomide in combination with galiximab led to prolongation of the median survival (39 days, 35–42 95% C.I.) compared to galiximab (28 days, 26–29 95% C.I.) or Lenalidomide (23 days, 22–25 95% C.I.) alone ((p<0.01).

Conclusions: Our current research demonstrates that Lenalidomide when added to galiximab has augmented in vitro antitumor activity (i.e, antiproliferation and ADCC) and synergistic effects in vivo (i.e., prolongation of survival compared to either monotherapy). Our promising preclinical results of the unique combination of lenalidomide plus galiximab supports future evaluation of this doublet as a clinical trial.

(Supported by USPHS grant PO1-CA103985 from the National Cancer Institute.)