Single-Arm Phase II Study of MOR208 Combined with Lenalidomide in Patients with Relapsed or Refractory Diffuse Large B-Cell Lymphoma: L-Mind

Introduction: The CD19 antigen is broadly and homogeneously expressed across different B-cell malignancies, including diffuse large B-cell lymphoma (DLBCL). MOR208 is an Fc-enhanced, humanized, monoclonal antibody that targets CD19, leading to natural killer (NK) cell-mediated antibody-dependent cytotoxicity, macrophage-mediated antibody-dependent phagocytosis and direct cytotoxicity. The immunomodulatory drug, lenalidomide (LEN), has both antiproliferative and antiangiogenic effects, and can stimulate the activity of immune effectors, such as NK cells. MOR208 and LEN have each shown single agent activity in patients with relapsed or refractory (R-R) DLBCL. In addition, MOR208 and LEN have shown synergy in in vitro and in vivo lymphoma models. We present results of an ongoing, multicenter phase II study designed to assess the safety and efficacy of MOR208 combined with LEN in patients with R-R DLBCL (NCT02399085).

Methods:Patients >18 years of age diagnosed with DLBCL, an Eastern Cooperative Oncology Group performance status 0-2, and adequate organ function, who had relapsed after or were refractory to at least one but not more than three prior systemic therapies, including at least one CD20-targeting regimen, and who were not candidates for high-dose chemotherapy (HDC) and autologous stem cell transplantation (ASCT), were eligible. Patients with primary refractory disease (defined as no response to or progression during or within 6 months after completion of frontline therapy for DLBCL) were excluded. Treatment comprises up to twelve 28-day cycles of MOR208, administered intravenously at a dose of 12 mg/kg weekly during cycles 1-3 (plus a loading dose on day 4 of cycle 1), and every second week during cycles 4-12. LEN was administered orally at a daily dose of 25 mg on days 1-21 of each cycle, for up to 12 cycles. Patients who were progression-free after 12 cycles received MOR208 every second week until progression. The primary endpoint is the objective response rate (ORR), centrally assessed, as per the International Working Group criteria 2007, incorporating PET-based imaging. Secondary endpoints include ORR as per investigator assessment, duration of response (DoR), progression-free survival (PFS) and overall survival (OS), safety, and analysis of outcomes by cell of origin and other biomarkers.

Results: As of November 2017, 81 patients had been enrolled and recruitment is complete. We report here updated preliminary results with a data cutoff of 5 June 2018. Median age was 72 years (range 41-87); 40 (49%) patients had received ≥2 prior lines of therapy (median 2, range 1-4); 31 (38%) had rituximab refractory disease; 33 (41%) were refractory to the previous line of therapy, 43 (53%) had Ann Arbor stage ≥III disease; and 42 (52%) had an International Prognostic Index of 3-5 at study entry, indicating poor prognosis. The most common treatment-emergent adverse events (any grade/grade ≥3) were neutropenia in 39/35 (48%/43%) patients, thrombocytopenia in 26/14 (32%/17%), anemia in 25/7 (31%/9%), diarrhea in 24/1 (30%/1%), pyrexia in 18/1 (22%/1%) and asthenia in 16/2 (20%/2%) patients. Thirty-four (42%) patients required dose reduction with LEN, 58 (72%) patients overall could stay on a daily LEN dose of 20 mg or higher. Based on investigator assessments, complete and partial responses were observed in 27 (33%) and 20 (25%) patients, respectively, resulting in an ORR of 58%. A further 12 (15%) patients had stable disease. With a median follow-up of 12 months, the median PFS was 16.2 months (95% CI: 6.3-not reached [NR]). Responses were durable with a median DoR not reached (95% CI: NR-NR) and 70% of responding patients were without progression at 12 months (Kaplan-Meier estimate). A significant proportion of patients (37/81; 46%) are still on study treatment, with 19 having been treated for over 12 months. Median OS has not been reached (95% CI: 18.6-NR); the 12-month OS rate was 73% (95% CI: 63-85).

Conclusions: MOR208 in combination with LEN has shown highly encouraging activity in patients with R-R DLBCL who were ineligible for HDC and ASCT and who had a poor prognosis. These results indicate a significant improvement in outcome for these patients who have very limited treatment options. MOR208 plus LEN was well tolerated in this population, without evidence of additive toxicity. Treatment and follow-up are currently ongoing, as are cell of origin and other biomarker analyses.