The combination of intratumoral CpG with systemic ibrutinib results in complete and permanent regression of both local and distant tumors.
The antitumor effect of the combination is T cell dependent.
We have designed a novel therapeutic approach for lymphoma that combines targeted kinase inhibition with in situ vaccination. Intratumoral injection of an unmethylated CG-enriched oligodeoxynucleotide (CpG), an agonist for the toll like receptor 9 (TLR9), induces the activation of NK cells, macrophages and antigen presenting cells that control tumor growth at the local site. Ibrutinib, an irreversible inhibitor of Bruton's tyrosine kinase (BTK), a key enzyme in the signaling pathway downstream of B Cell receptor (BCR), is an effective treatment against many types of B cell lymphomas. The combination of intratumoral injection of CpG with systemic treatment by ibrutinib resulted in eradication of the tumors not only in the injected site but also at distant sites. Surprisingly, this combinatorial antitumor effect required an intact T cell immune system since it did not occur in nude, scid or T cell depleted mice. Moreover, T cells from animals treated with intratumoral CpG and ibrutinib prevented the outgrowth of newly injected tumors. This result suggests that ibrutinib can induce immunogenic cell death of lymphoma cells and that concomitant stimulation of antigen-presenting cells in the tumor microenvironment by TLR ligands can lead to a powerful systemic antitumor immune response.
- Submitted August 1, 2014.
- Accepted January 30, 2015.
- Copyright © 2015 American Society of Hematology