Résumé
Abstract 3655
Obinutuzumab (GA101) is a type II glycoengineered, humanized anti-CD20 monoclonal antibody that has increased antibody-dependent cellular cytotoxicity and direct cell death activity but lower complement-dependent cytotoxicity compared with type I anti-CD20 antibodies such as rituximab and ofatumumab. GA101 is in clinical development for the treatment of lymphoma and chronic lymphocytic leukemia. The Phase I/II study BO20999 has evaluated the efficacy and safety of GA101 monotherapy in patients with relapsed/refractory aggressive non-Hodgkin's lymphoma (aNHL). Here, we report updated Phase II results including progression-free survival (PFS) and best overall response (BOR).
Patients (n = 40) were randomized to receive GA101 (D1, D8 and D22, then 3-weekly for total of 9 infusions) at either a high dose (1,600 mg on D1 and D8, then 800 mg thereafter; 1,600/800 mg cohort; n = 19), or a flat low dose of 400 mg (400/400 mg cohort; n = 21).
Baseline patient characteristics were similar for both cohorts (Table 1). The median observation time for all patients was 9.5 months (0.3–26.1 months). BOR rates are given in Table 2, with 8/25 diffuse large B-cell lymphoma (DLBCL) patients (32%) and 4/15 mantle cell lymphoma (MCL) patients (27%) responding to GA101. Among the patients with rituximab-refractory disease, a response was observed in 1/13 patients (7.7%) and 4/12 patients (33.3%) treated in the 400/400 mg and 1,600/800 mg cohorts, respectively. Of these, 4 patients (1,600/800 mg cohort) had a response duration > 6 months, with 2 patients having an ongoing response (response duration: 9.8, 16.5+, 19.5 and 20.0+ months). Median PFS for patients with DLBCL (Figure 1) was 1.9 months (range: 0.3–15.7 months) for the 400/400 mg cohort and 2.7 months (range: 0.2–22.3) months) for the 1,600/800 mg cohort (hazard ratio: 0.70; 95% CI: 0.30–1.66). For the DLBCL subgroup, response duration was 3.1, 3.1+, 5.8, 16.5+ and 19.5 months for the 5 responders in the 1,600/800 mg cohort, compared with 6.3, 8.6 and 9.8 months for the 3 responders in the 400/400 mg cohort. Individual response data indicated that 2 MCL patients had an ongoing response for ≥ 20 months (20.0 and 20.4 months). GA101 was well tolerated in both cohorts. Infusion-related reactions (IRRs; all grades) were the most common adverse event (AE), occurring in 81% of patients in the 400/400 mg cohort and 68% of patients in the 1600/800 mg cohort. Grade 3/4 AEs occurring in >5% of patients across both cohorts included IRRs (10%), tumor lysis syndrome (10%), cardiac failure (not treatment-related; 10%), anemia (14%) and thrombocytopenia (14%) in the 400/400 mg cohort and IRRs (5%) and anemia (5%) in the 1,600/800 mg cohort.Table 1.Baseline patient characteristicsCharacteristic400/400 mg (n = 21)1,600/800 mg (n = 19)All (n = 40)Median age, years (range)70 (43–80)72 (22–85)71 (22–85)Histology, nDLBCL101525MCL11415Median number of prior treatments, n (range)4 (1–17)3 (1–6)3 (1–17)Previous rituximab, n211940Rituximab refractory*, n131225Prior stem cell transplant, n268DLBCL, diffuse large B-cell lymphoma; MCL, mantle cell lymphoma.*Rituximab refractory defined as patients who had a response of < 6 months or who failed to respond to a rituximab-containing regimen (rituximab monotherapy or in combination with chemotherapy) at any point during their treatment history.Table 2.Best overall response according to diagnosis and cohortDLBCLMCLResponse, n (%)400/400 mg (n = 10)1,600/800 mg (n = 15)400/400 mg (n = 11)1,600/800 mg (n = 4)Complete response (CR)0 (0.0)3 (20.0)2 (18.2)0 (0.0)CR unconfirmed1 (10.0)0 (0.0)0 (0.0)0 (0.0)Partial response2 (20.0)2 (13.3)0 (0.0)2 (50.0)Stable disease1 (10.0)1 (6.7)3 (27.3)0 (0.0)Progressive disease5 (50.0)9 (60.0)6 (54.5)2 (50.0)No response assessment1 (10.0)0 (0.0)0 (0.0)0 (0.0)DLBCL, diffuse large B-cell lymphoma; MCL, mantle cell lymphoma.Figure 1.Progression-free survival for patients with diffuse large B-cell lymphomaFigure 1. Progression-free survival for patients with diffuse large B-cell lymphoma
In conclusion, GA101 shows encouraging single-agent efficacy in these heavily pretreated patients with relapsed/refractory aNHL (DLBCL or MCL). A Phase III trial of rituximab plus CHOP vs GA101 plus CHOP in first-line DLBCL has recently started.