Ibrutinib Monotherapy in Relapse or Refractory Primary CNS Lymphoma (PCNSL) and Primary Vitreo-Retinal Lymphoma (PVRL). Result of the Interim Analysis of the iLOC Phase II Study from the Lysa and the French LOC Network

RATIONAL

Primary CNS lymphoma (PCNSL) is a diffuse large B-cell lymphoma (DLBCL), predominantly of non-germinal center (non-GC) subtype, carrying a pejorative prognosis. Constitutive activation of the NF-kB pathway via mutations in B cell receptor (BCR) pathway (CD79B) and mutation of MYD 88 and TBL1XR1 plays an important role in PCNSL. Ibrutinib, an inhibitor of BCR signaling, has been found to have significant therapeutic activity in relapsed or refractory non-CNS non-GC DLBCL.

METHODS

In this prospective, multicenter, open-label phase II, we enrolled immuno-competent patients over 18 with a refractory or relapse of PCNSL or primary vitreo-retinal lymphoma (PVRL) of DLBCL type. The treatment consisted in ibrutinib monotherapy given orally at 560 mg daily until disease progression or unacceptable toxicity. Additional corticosteroids treatment was allowed during the first 4 weeks of treatment in case of a threatening or symptomatic edema. Therapeutic responses were assessed according to the international primary CNS lymphoma collaborative group (IPCG) criteria. The primary objective of the study was the disease control (DC) rate (CR + CRu + PR + SD) after two months of treatment. This study is a two-stage Simon's design. Patients were evaluable for response if they received > 90 % of the expected dose during the first month of treatment. An interim analysis for futility was planned when 18 patients were evaluable for response. P0 and P1 hypotheses were < 10 % and > 30 % respectively. A total of 35 evaluable patients are required for the final analysis. Exploratory ancillary studies are planned and consist in dosage of ibrutinib in the cerebrospinal fluid after one cycle of treatment, and correlation of therapeutic response with mutational status of the disease. This study is registered with ClinicalTrials.gov, number NCT02542514.

RESULTS

BetweenSeptember 25, 2015 and June 30, 2016, 52 patients were recruited in 10 French centers of the French LOC network for PCNSL. The interim analysis was done on the first 18 patients evaluable for response (median age: 70 y, range 49-80). At initial diagnosis, diagnoses were PCNSL (n = 12) and PVRL (n = 6). Patients were included in the study for a relapse (n = 13) or a progressive disease (n = 5). At time of inclusion in the study, disease status was PCNSL (n = 11) and PVRL or isolated intra-ocular relapse of a PCNSL (n = 7). ECOG performance status was 0, 1 and 2 in 4, 10 and 4 patients respectively. All the patients had previously received high-dose methotrexate-based chemotherapy. Four patients had previously received high-dose chemotherapy followed by autologous stem cell transplantation. Patients had received 1, 2 or 3 prior treatments in 12, 5 and 1 cases respectively. Three patients had a concomitant meningeal involvement. Five patients received concomitant corticosteroids during the first month of treatment. At the time of analysis (median follow-up = 6.6 months), nine patients discontinued ibrutinib after a median duration of 3 months (range, 0.9 -6.4) because of a disease progressive(n = 8) or a concurrent illness (n=1). Median number of treatment cycles was 5 (range, 1-9). One patient experienced a pulmonary aspergillosis with a favorable outcome. No hemorrhagic complication was reported. Five patients died due to disease progression (n = 4), and concurrent illness (n = 1). After two months of treatment, a DC was achieved in 15/18 patients (83 %, IC 95 %, [59-96%]) (complete and unconfirmed complete response: n =3; partial response: n = 7; stable disease: n =5).

CONCLUSION

In this interim analysis, Ibrutinib monotherapy demonstrated a high DC rate of 83%, including 56% objective responses in patients with relapse/refractory PCNSL or PVRL. Regarding safety, Ibrutinib might be a risk factor for aspergillosis in this population of PCNSL patients, otherwise not exposed to fungal infection. A security warning was sent to all the investigators for a close monitoring of infections. The second cohort of patients has been recruited. Thirty-three patients are currently on study treatment. The final analysis of the iLOC study is awaited to confirm these encouraging results and better define the positioning of ibrutinib in the therapeutic strategy of PCNSL and PVR patients.