Obinutuzumab (GA101) in Combination with Pixantrone for the Treatment of Patients with Relapsed Aggressive B-Cell Lymphoma: Report on an Ongoing Phase II Trial (GOAL)

Background: Prognosis of diffuse large B-cell lymphoma (DLBCL) and other aggressive lymphoma entities has improved with the advent of Rituximab, and R-CHOP-21 and variants is SOC. Nevertheless, a substantial proportion of patients fail first line treatment. Salvage therapies are often effective. However, no more than 25-50% achieve a long term remission even when consolidative high dose chemotherapy (HDT) followed by hematopoietic stem cell transplantation (SCT) is applied. In case of failure or intolerance to HDT, regimen like Gemcitabine/Oxaliplatin are applied but show limited efficacy, indicating the need for new treatments. Obinutuzumab (GA101) is a type II anti-CD20 antibody. Superiority of Obinutuzumab could be demonstrated in xenograft models of mantle cell lymphoma and DLBCL. Although desirable, cumulative dose-related, progressive cardiotoxicity eliminates anthracyclins from higher treatment lines. With Pixantrone, a drug structurally related to anthracyclines and especially anthracenediones, a re-exposition against this drug class has been shown to be feasible. In 70 heavily pre-treated patients, a best ORR of 40% (20% CR/CRu) was observed (Pettengell et al). Experiences from further antibody drug combinations lead to the assumption that the effects of Pixantrone will be augmented by a monoclonal antibody without increasing toxicity. We thus initiated a trial combining both agents for the first time. The trial has opened in Q4/2015 and recruitment is ongoing. Overall, a total of up 70 patients will be enrolled for a number of 64 evaluable patients. Primary endpoint will be the objective overall response rate, with secondary endpoints being safety, PFS and OS.

Methods: this is a multicenter, national, prospective trial. Inclusion criteria: patients were eligible if they had histologically proven DLBCL, FL grade IIIb or transformed indolent lymphoma, CD20 positive disease, no curative option available, relapsed disease, measurable disease, ECOG < 3, sufficient bone marrow reserve, no severe concomitant diseases and given informed consent. There was no upper limit or prior treatment lines. Treatment consisted of Pixantrone 50mg/m² day 1, 8 and 15 of each cycle, Obinutuzumab 1000 mg flat dose day 1, 8 and 15 of cycle one and day 1 of each subsequent cycle. A total of 6 cycles was planned with interim staging after 3 cycles.

Results: 24 patients (pts) have been included until now. Concerning clinical characteristics, all were caucasian, 12 were female and the other 12 male and median age was 75 years. Most of the patients suffered from DLBCL (18 pts, 82%). Median number of prior therapies was 2 (1 to 6). Until now 55 evaluable cycles of chemotherapy (median 2 cycles (0 to 6)) have been performed. At this time, the treatment seems to be well tolerated, with no unforeseen side effects. Observed toxicity was predominantly hematologic. The following hematologic adverse events of grade 3/4 were noted: leukopenia (4 pts, 17%), neutropenia (6 pts, 25%), granulocytopenia (1 pts, 4%), as well as thrombocytopenia (2 pts). Non-hematologic grade 3/4 adverse events were observed in at least two patients: hypertension (2 pts) and pelvic pain (2 pts). Response: currently, best responses were 4 PR, 1 SD, and 8 PD in 13 patients evaluable so far. Four patients died, all after progression of lymphoma.

Summary: the combination of Obinutuzumab and Pixantrone seems to be feasible and safe with early signs of efficacy. Updated results of this trial in progress with a focus on safety will be presented.