A Phase I/II Trial of Intratumoral CpG, Local Low-Dose Radiation, and Oral Ibrutinib in Patients with Low-Grade B-Cell Lymphoma

Background: In situ vaccination for the treatment of cancer aims to trigger an immune response locally that propagates systemically. We have shown that local treatment with intratumoral CpG (a TLR9 agonist) and low-dose radiation can elicit antitumor immune responses and global tumor shrinkage in patients with low-grade lymphoma (Brody, J Clin Oncol, 2010; Frank, Cancer Discov, 2018). Ibrutinib is a small molecule that compromises B cell survival by inhibiting Bruton's tyrosine kinase (BTK) but also modulates T cell phenotypes by inhibiting interleukin-2-inducible T-cell kinase (ITK). Specifically, there is evidence for ibrutinib-induced skewing of CD4 T-cells toward a Th1 phenotype, which would be expected to promote anti-tumor immunity (Dubovsky, Blood, 2013). In a mouse model of lymphoma, systemic ibrutinib plus intratumoral CpG was curative of systemic disease in all treated mice, an effect that was fully T-cell dependent (Sagiv-Barfi, Blood, 2015). Study Design: To test the hypothesis that ibrutinib will enhance the efficacy of in situ vaccination via its effects on T-cells, we initiated a phase I/II clinical trial combining oral ibrutinib (560mg), intratumoral CpG (SD-101, 3mg) and local low-dose radiation in patients with recurrent low-grade lymphoma (NCT02927964). Patients with follicular lymphoma, marginal zone lymphoma, or indolent mantle cell lymphoma relapsed or refractory to at least one line of prior therapy and with at least one superficial disease site accessible for injection and one independent measurable disease site are eligible. Patients with significant autoimmune disease, recent stroke or intracranial hemorrhage, and those requiring anticoagulation with vitamin K antagonists or chronic treatment with strong CYP3A inhibitors are excluded. The primary outcome of the study is determination of safety of the combination treatment. Secondary outcomes include overall response rate, progression-free survival, and correlative studies of tumor and blood immune populations. Fourteen patients have been enrolled thus far, with a goal enrollment of 21-30 patients. Treatment consists of two consecutive days of low-dose (2 Gy) radiation to the chosen treatment site, followed by 5 weekly injections of CpG into that same site. Daily oral ibrutinib is begun one day after the second CpG injection. CT scans are performed at 3, 6, 12, 18, and 24 months. Common Terminology Criteria for Adverse Events (CTCAE) are used to track treatment-emergent safety events, and Lugano criteria (Cheson, J Clin Oncol, 2014) are used to assess response to therapy. Correlative Studies: Fine needle aspirates (FNAs) are obtained from CpG-injected and non-injected sites pre-treatment and at weeks 2 and 6. Peripheral blood samples are obtained pre-treatment and weeks 2, 4, 6, and at all response assessment timepoints. When available, tumor cells from an excisional biopsy pre-treatment are viably preserved. FNAs and peripheral blood samples from pre-treatment and at weeks 2 and 6 are being analyzed by both flow cytometry and single cell RNA sequencing. For patients for whom viably preserved tumor cells are available, these are co-cultured with autologous peripheral blood T cells in an in vitro immune response assays to test for tumor-specific T-cell activation. Summary: This innovative study combines in situ vaccination and ibrutinib-induced T-cell modulation and incorporates serial sampling of multiple tumors and peripheral blood using minimally invasive procedures, analyzed by methods that allow for deep profiling of treatment-induced changes. This study is ongoing and currently accruing at the Stanford Cancer Center. Download : Download high-res image (247KB) Download : Download full-size image Disclosures Khodadoust: Corvus Pharmaceuticals: Research Funding. 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