Ibrutinib in Combination with R-Gemox-D in Patients with Relapsed or Refractory Diffuse Large B-Cell Lymphoma: Phase II Clinical Trial of the Geltamo Group

BACKGROUND

Patients with relapsed or refractory diffuse large B-cell lymphoma (DLBCL), non-candidates for autologous stem-cell transplantation (ASCT), have few treatment options. Ibrutinib is an oral Bruton’s tyrosine kinase inhibitor that has shown increased antitumor activity in patients with DLBCL of different subtype from germinal center B-cell like (non-GCB). In the present phase II clinical trial (NCT02692248), we investigated the efficacy and toxicity of the combination of Ibrutinib with the R-GEMOX-D regimen (rituximab, gemcitabine, oxaliplatin and dexamethasone), in patients with non- GCB DLBCL.

METHODS

We included patients with histological diagnosis of non-GCB DLBCL (according to Hans algorithm), with relapsed or refractory disease after at least 1 line of immunochemotherapy and non-candidates for ASCT. Patients received an induction treatment consisting of 6 (in case of complete remission [CR] after cycle 4) or 8 (in case of partial response [PR] or stable disease after cycle 4) cycles of R-GEMOX-D at standard doses every 2 weeks, in combination with ibrutinib (560 mg daily), followed by a maintenance treatment with ibrutinib for a maximum of 2 years. The primary objective was to evaluate the overall response rate (ORR) after 4 cycles, and the secondary objectives were: CR rate, progression-free survival (PFS), overall survival (OS) and toxicity. Analyses were performed in the intention to treat population (data cut-off 10^th April 2020).

RESULTS

Sixty-four patients (59.4% male) were included between March 2016 and November 2018. Median age was 67 (25-84) years. Patients had received a median of 2 previous lines of treatment; 56.3% were refractory (<PR) to the last regimen, whereas 43.7% had relapsed disease after a previous CR. Eleven (17.2%) patients had received a previous ASCT. IPI at study entry was 0-1, 2-3, and 4-5 in 9.4%, 67.2%, and 20.3% of patients, respectively (missing data in 2 patients).

Of the 64 patients who started study treatment, 44 and 35 patients, respectively, were evaluated for response after 4th cycle and at the end of induction. Twenty-four (37%) patients started maintenance with ibrutinib, 7 of whom continue or have completed it. Causes of withdrawal from the trial (n=57) were progression (n=40), adverse event (n=6), transplantation (n=5), withdrawal of consent (n=3) and other causes (n=3).

ORR and CR rate after 4^th cycle were 53.2% and 35.9%, respectively. Patients with relapsed disease had significantly higher ORR (67.9% vs 41.7%, p=0.037) and CR rate (57.1% vs 19.4%, p=0.002) than patients with refractory disease. At the end of induction, ORR and CR rate were 35.9% and 29.7%, respectively.

After a median follow-up of 22 months (range: 1 to 39 months), the estimated 2-year PFS and OS were 21% and 25%, respectively (Figure 1A and 1B), being significantly better in patients with relapsed disease (Figure 1C and 1D). In the multivariate analysis, status of lymphoma at study entry significantly influenced PFS (HR 0.45; 95% CI 0.25-0.82; p=0.009) and OS (HR 0.51; 95% CI 0.27-0.94; p=0.0031) independently from the IPI and the number of previous treatment lines.

The most frequent adverse events (AE) (present in at least 20% of patients) were thrombocytopenia (67.2%), diarrhea (51.6%), neutropenia (46.9%), anemia (37.5%), fatigue (34.4%), nausea (29.7%) and paresthesia (20.3%). The most frequent grade 3-5 AE (present in at least 10% of patients) were thrombocytopenia (46.9%), neutropenia (35.9%), diarrhea (15.6%) and anemia (14.1%). Three patients presented a grade 5 AE, two of them related (aspergillosis and pneumonia, respectively) and one unrelated (heart failure).

CONCLUSIONS

The combination of ibrutinib with R-GEMOX-D as salvage therapy for patients with non-GCB DLBCL is associated with high response rates, especially in relapsed patients. The vast majority of refractory patients progress very early, so this regimen could be considered as a bridge to other consolidation therapies. Biological studies analyzing cell of origin by gene expression profiling, minimal residual disease and mutational spectrum are in progress.