A Multi-Center, Non-Randomized Phase 2 Study of Ofatumumab in Combination with ICE-Chemotherapy (O-ICE) in Patients with Relapsed/Refractory Diffuse Large B-Cell Lymphoma (DLBCL)

Background

Patients (pts) with DLBCL who have received rituximab (R) antibody in the first-line setting, have poorer treatment outcomes when they are re-treated with R-chemotherapy in the salvage setting. Resistance to R may have developed. Ofatumumab (O) is a human monoclonal antibody against CD 20 that targets a different epitope than R. We hypothesized that replacing R with O in second line setting may overcome R resistance. The primary end-point of this ongoing phase II study is the objective response rate (ORR) following two cycles of O in combination with ICE (Ifosfamide, Carboplatin and Etoposide) or O-ICE. Secondary end points include the assessments of the safety and tolerability of the combination, progression-free (PFS) and overall survival (OS).

Methods

This was a multi-center, non-randomized phase II open label study. Pts with histologically confirmed DLBCL who failed or were refractory to first line R-based anthracycline therapy were eligible. Pts were accrued according to a 2-stage Simon’s Optimal Design at the National Cancer Centre Singapore and 3 medical centres in South Korea; Samsung Medical Centre, Ajou University Hospital and Soonchunhyang University Hospital. Stage 1 will enrol 24 pts and if 14 or more pts respond, we will proceed to stage 2 where another 37 pts would be recruited. Pts receive 3-weekly ICE (Ifosfamide 5g/m2 on day 2, Carboplatin AUC = 5 on day 2, Etoposide 100 mg/m2 day 1-3) and O (1000 mg), infused on day 1 and 8 of cycle 1, and thereafter only on day 1 of each cycle. A restaging scan is performed after cycle 2. Pts who are candidates for high dose chemotherapy (HDC) and autologous stem cell rescue (ASCR) would receive additional 1 or 2 more cycles of O-ICE before stem cell mobilization. Pts who are not candidates for HDC and ASCR would receive up to 6 cycles of O-ICE.

Results

A total of 24 pts with a median age of 54.5 years (27-75) were enrolled. Among them, 14 (58%) were male and 14 (58%) had stage III/IV disease. A median of 4 (2-6) courses of O-ICE was administered and 11 pts underwent HDC+ASCR. The ORR after 2 cycles was 58.3%; complete response (CR) 29.2% and partial response (PR) 29.2%. On treatment completion, the best ORR became 62.5% (CR = 37.5%, PR = 25%). Grade 1/2 non-hematologic toxicities, independent of relation to study drug, occurring in at least 20% of pts included nausea (50%), pain (50%), fatigue (42%), rash (42%), anorexia (33%), vomiting (33%), diarrhea (25%), edema (29%), fever (21%), pruritus (21%), cough (21%) and paresthesia (21%). Grade 3/4 toxicities included neutropenia (50%), thrombocytopenia (71%) and 4 anemia (54%). Febrile neutropenia occurred in 12.5% and no treatment related deaths were reported. The median follow up time was 8.2months (95% CI 5.3-14.0). The median PFS was 8.2months (95% CI 4.2-17.8) and the median OS was not reached (95% CI 8.6-not reached).

Conclusion

The study regimen met the predefined threshold of 14 responding pts in stage 1. The ORR of O-ICE was comparable to that of RICE in the CORAL study and this result is significant considering that all pts in this study had received R prior to study entry. Together with the tolerability data and promising activity, continuation of study enrolment in stage 2 has started.