Development of a Bruton's Tyrosine Kinase (Btk) Inhibitor, ONO-WG-307: Efficacy in ABC-DLBCL Xenograft Model – Potential Treatment for B-Cell Malignancies,

ONO-WG-307 is a small molecule inhibitor that covalently binds to Btk. Signals from B cell receptors (BCR) play a central role in signal transduction pathways regulating survival, activation, proliferation, and differentiation of B-lineage lymphoid cells. BCR signaling is implicated in the survival of malignant B cells and recent studies indicate that targeting Btk, an essential component of the BCR pathway, may be effective in the treatment of B-cell lymphoma. The activated B-cell-like (ABC) subtype of diffuse large B-cell lymphoma (DLBCL) correlates with poor prognosis and new therapies, preferably chemo-sparing therapies, or as add-on to existing treatment regimens are required to help treat patients with ABC-DLBCL. Therefore, Btk constitutes an interesting therapeutic target, thus the activity of ONO-WG-307 was evaluated in an ABC-DLBCL xenograft model.

Tumor cells (TMD-8) were implanted subcutaneously into female SCID mice. Tumors were allowed to grow to a volume of 100–200 mm³ before the mice were randomized into groups based on tumor size. ONO-WG-307 was administered orally at doses up to 10 mg/kg bid. Tumors were measured two or three times weekly after initiation of treatment, and tumor volumes were determined using the formula volume (=width²xlength)/2. Animals were euthanized when the tumors reached a maximum volume of 2,000 mm³ or after a maximum period of 2 months. In parallel, an exploratory pharmacodynamic marker of Btk inhibition (Phosphorylated-Btk [P-Btk]) was also investigated in vivo.

Treatment with ONO-WG-307 resulted in a dose-dependent inhibition of tumor growth in a TMD-8 xenograft model. Furthermore, parallel analysis of a pharmacodynamic marker, P-Btk, supported that Btk was inhibited and the level of P-Btk inhibition was correlated with the decreased tumor volumes observed in the TMD-8 model.

ONO-WG-307 is a highly potent and selective oral Btk inhibitor with evidence of efficacy in the ABC-DLBCL xenograft model, with Btk inhibition further supported using a PD marker. Given the need to treat and overcome disease resistance especially in ABC-DLBCL, the use of a Btk inhibitor is a novel, mechanistic approach to treating B cell malignancies. Additional work is underway, combining ONO-WG-307 with chemotherapy and other targeted agents.

No relevant conflicts of interest to declare.