A Phase II Trial of Nivolumab and Ibrutinib for Patients with Relapsed or Refractory Central Nervous System Lymphoma

Background: Central Nervous System (CNS) lymphoma is a rare and distinct subtype of diffuse large B-cell lymphoma (DLBCL). CNS lymphoma has a unique genomic profile which has similarities to the activated B-cell (ABC) subtype of DLBCL, which may speak to potential targets for therapy. These aberrancies include near uniform reliance on Toll-Like Receptor signaling, mutations of MYD88, and frequent translocation or copy number alterations of 9p24 which codes for programmed death receptor ligand 1 (PD-L1). Mutations of MYD88 may predict for response to Bruton's tyrosine kinase (BTK) inhibitors in patients with systemic DLBCL. Expression of PD1 or PD-L1, which corresponds to response with PD-targeted therapy in solid tumors, has been found on up to 90% of CNS lymphoma cases, and 60% of specimens had tumor infiltrating lymphocytes which were PD1+ (Berghoff, Clin Neuropath 2014). In addition, the majority of CNS lymphoma cases have a copy gain of 9p24.1, associated with increased expression of PD-L1 (Chapuy, Blood 2016). This suggests a potential ongoing immune reaction against CNS lymphoma, but the microenvironment and tumor conspire to render the immune response ineffective.

Ibrutinib is a BTK inhibitor which is FDA approved for multiple B-cell malignancies and is known to achieve therapeutic concentration in the cerebral spinal fluid (CSF), with activity in CNS lymphoma as a single agent and in combination with other agents. Nivolumab is a PD1 inhibitor which is FDA approved for multiple malignancies, with impressive anecdotal evidence of single agent activity in CNS lymphoma. Ibrutinib and nivolumab have been combined in other studies with modest toxicities.

Study Design and Methods: We are conducting a phase II, open label, single center clinical trial combining ibrutinib with nivolumab to treat patients with relapsed CNS lymphoma (NCT03770416). Patients are eligible if they have CNS lymphoma relapsed after or were refractory to at least 1 prior line of therapy with adequate organ and bone marrow function, are aged 18y or greater, have not received prior ibrutinib or PD1 inhibitor, and do not require persistent high dose steroids. The trial has two cohorts which will be sequentially enrolled. Cohort A begins with ibrutinib 560mg oral daily for a single 28-day cycle, followed by ibrutinib combined with nivolumab 240mg IV every 14 days. Cohort B begins with the ibrutinib and nivolumab combination during the first cycle. Patients who have at least a partial response at the conclusion of the planned 6 cycles of combined ibrutinib and nivolumab may continue therapy for up to 2 years total or until progression of disease or unacceptable toxicity occurs. Neurocognitive assays and patient reported outcome instruments are being utilized.

The primary objective is to determine the best overall response rate during the first 24 weeks of therapy. Secondary objectives will include the response rate of ibrutinib as a lead in prior to the combination, the complete response rate, landmark survival outcomes, and the safety of the combination. Exploratory analyses include assays of the blood and CSF for ctDNA and immune profiling.

The first patient was treated in February 2019, with a planned total of 40 patients to be enrolled.