Publication Date:
2014-12-06
Description:
Introduction. Patients with B-cell lymphomas harboring the oncogenic MYD88 L265P mutation have poor response to standard of care regimens such as R-CHOP (Fernandez-Rodriguez et al, Leukemia, 2014, Jun 6). These patients also have not responded well to new therapies under development, including BTK inhibitors (Wilson et al, Blood 2012; 120). The MYD88 L265P oncogenic mutation has been shown to over-activate TLR7- and TLR9-mediated signaling pathways, including NF-κB, IRAK1/4 and STAT3, which in turn promote cell survival and proliferation (Lim et al., AACR 2013, Abstract #2332). Our approach to a potential treatment of B-cell lymphomas harboring the MYD88 L265P mutation is to block TLR7- and TLR9-mediated signaling through use of a TLR antagonist. IMO-8400 is an antagonist of TLR7, TLR8, and TLR9 that inhibits cell signaling and induces apoptosis specifically in B-cell lymphoma cell lines harboring the MYD88 L265P mutation (Bhagat et al, AACR 2014, Abstract #2570). IMO-8400 is currently in clinical development for the treatment of relapsed/refractory patients with Waldenström’s macroglobulinemia (WM) and diffuse large B-cell lymphoma (DLBCL). Methods. The current preclinical studies were designed to evaluate the combination of IMO-8400 with rituximab, which is a key component of R-CHOP. The studies were conducted in xenograft models of the activated B-cell like (ABC) DLBCL cell line OCI-Ly10 and the WM cell line MWCL-1, both positive for the MYD88 L265P mutation. For the ABC-DLBCL model, OCI-Ly10 cells were implanted s.c in NOD-SCID mice on day 0 and treatment was initiated on day 9 when mean tumor volume reached ~200 mm3. For the WM model, MWCL-1 cells were implanted s.c. in NOD-SCID mice on day 0 and treatment was initiated on day 6 when mean tumor volume reached ~250 mm3. In both models, the tumor-bearing mice were treated with PBS (control group), IMO-8400 (25 mg/kg, i.p.), rituximab (10 mg/kg, i.p.) or a combination of the two agents. IMO-8400 was administered twice per week for 3 weeks and continued further as maintenance treatment once per week. Rituximab was administered twice per week for three weeks in the ABC-DLBCL model whereas it was given only on days 3, 6, and 9 in the WM model. Results. Treatment of tumor-bearing animals with IMO-8400 or rituximab alone and in combination was well tolerated in both the models. In the ABC-DLBCL model, tumor growth inhibition compared to PBS control was 91.3% in the combination therapy group vs. 40.8% with IMO-8400 alone (p
Print ISSN:
0006-4971
Electronic ISSN:
1528-0020
Topics:
Biology
,
Medicine
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