Purpose: The B-cell receptor (BCR) pathway plays a central role in signal transduction pathways that regulate survival, activation, proliferation, and differentiation of B-lineage lymphoid cells. Btk is a key regulator of the BCR signaling pathway and abberant BCR signaling has been implicated in the survival of malignant B-cells. Recent studies indicate that targeting Btk may be effective in the treatment of B-cell malignancies. ONO-4059 is a highly potent and selective oral Btk inhibitor with an IC50 in the sub-nmol/L range. Previous studies with ONO-4059 (formerly known as ONO-WG-307; AACR 2012) demonstrated that Btk-mediated signaling through Akt and PKD is a critical role for the survival of activated B-cell-like (ABC) sub-type of diffuse large B cell lymphoma (DLBCL) cell lines [TMD-8]. It was also of interest to determine the extent of gene expression changes induced in TMD-8 cells after treatment with ONO-4059. To understand the effects of ONO-4059 on gene transcription, we analyzed the gene expression patterns of ONO-4059 in the TMD-8 xenograft model.

Methods: TMD-8 cells were implanted subcutaneously into SCID mice and ONO-4059 was administered orally, twice a day (BID) in two groups of animals, at doses of 3 and 10 mg/kg. When the mean tumour volumes reached 100-200mm3, treatment was initiated daily for 14 days. After the final treatment of ONO-4059, the total RNAs were extracted from frozen re-sected tumour tissue specimens, which comprised of 10 samples at each dose, along with 10 vehicle tissue samples. Microarray analysis was conducted by Agilent technology.

Results: The inhibitory level of P-Btk achieved indicates profound anti-proliferative activity of ONO-4059 in the TMD-8 model. Gene expression studies demonstrated that ONO-4059 affects a core set of genes which contains 9 down-regulated and 8 up-regulated genes in a dose-dependent manner. CXCL-10 is the prominent regulated gene that is down-regulated after ONO-4059 treatment and CXCL-10 has been shown to be involved in the pathological processes of human disorders, such as, infectious diseases, inflammatory and autoimmune diseases as well as cancer. From a publicly available microarray database, CXCL-10 expression has been shown to be up-regulated in lymphoma patients, suggesting that CXCL-10 may be a potential biomarker for ONO-4059 in the treatment of B-cell malignancies.

Conclusion: Our data show that ONO-4059 has potent anti-tumour activity in a ABC-DLBCL xenograft model and that ONO-4059 achieves active tumor exposures as measured by P-Btk in vivo. ONO-4059 is currently being developed in a Phase I clinical trial for the treatment of B-cell malignancies. Additional work is now underway to determine whether the combining ONO-4059 with other targeted agents affects CXCL-10 expression.

Citation Format: Tomoko Yasuhiro, Toshio Yoshizawa, Shingo Hotta, Yuko Ariza, Yoshiko Ueda, Ryohei Kozaki, Joseph Birkett. ONO-4059, a novel oral Bruton's tyrosine kinase (Btk) inhibitor that demonstrates potent pharmacodynamic activity through Phosphorylated Btk (P-Btk) inhibition, in addition to effective anti-tumour activity in a TMD-8 (DLBCL) xenograft model. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2452. doi:10.1158/1538-7445.AM2013-2452