The Aurora A Kinase Inhibitor, Alisertib, Has Broad Activity In Nonclinical Models Of T-Cell Lymphoma and Is Highly Synergistic With Romidepsin, But Not With Pralatrexate Or The Proteasome Inhibitor, Ixazomib

Aurora A kinase (AAK), a serine-threonine protein kinase, regulates mitotic entry, spindle formation, and cytokinesis. Alisertib is a selective AAK investigational inhibitor with demonstrated clinical activity in acute myeloid leukemia, peripheral t-cell lymphoma (PTCL), DLBCL and other heme-lymphatic cancers. Here we report the cytotoxicity and apoptotic effect of Alisertib  in a panel of T-cell-derived lymphoma cell-lines (TCL) (CTCL, HTLV+, T-ALL) and B-cell lymphoma cell-lines (DLBCL-ABC, DLBCL-GCB, MCL) alone and in combination with romidepsin, pralatrexate (PDX) and ixazomib, a  proteasome inhibitor.

Single agent concentration and time effect relationships were generated for 8 TCL, 4 DLBCL (2 ABC, 2 GCB) and 4 MCL cell-lines. The mean IC₅₀ of alisertib in TCL was 350 nM (range 100-1000nM) and in B-cell lymphoma lines (DLBCL, MCL) was 200 nM (range 20-300 nM) at 48 hours, measured by growth inhibition. In all cell lines evaluated, there was a consistent 2-log fold decrease in IC₅₀ values at 72 hours.  Combination studies evaluating synergy were performed testing schedule, concentration, and time effect relationships. Interestingly, simultaneous exposure of combined alisertib and romidepsin at their IC₁₀, IC_20, and IC₃₀ demonstrated marked synergy in TCL. Deepest synergy was observed at 72 hours with synergy coefficients ranging from 0.2 to 0.7. This synergistic interaction was restricted to the TCL cell-lines, with no benefit demonstrated in DLBCL or MCL cell lines. (Table 1) Similarly, alisertib did not demonstrate synergy in TCL, DLBCL or MCL cell lines at any concentration, combination, or time schedule  with PDX  or ixazomib (simultaneous incubation of alisertib + PDX, 24 hour pre-exposure alisertib followed by PDX, 24 hour pre-exposure PDX followed by alisertib; simultaneous incubation of alisertib + ixazomib).

Evidence for apoptosis was confirmed for alisertib in combination with romidepsin in the TCL cell-line, H9 after 48 hours of exposure by increased caspase 3 and PARP cleavage,  acetylated H3 expression, and decreased Cyclin B1, P27, and BCL2 expression; suggesting that cell death occurred through apoptosis.  AnnexinV/propridium iodide via FACS analysis confirmed induction of apoptosis.

These data support the observation that alisertib produces broad single-agent activity in models of TCL and demonstrates marked synergy with romidepsin. Interestingly this effect is restricted to TCL and there is no synergistic effect with ixazomib or PDX in TCL.  Further evaluation of the mechanism of action with alisertib in combination with romidepsin as well as in vivo modeling of these combinations is ongoing.