Combination Biologic Therapy as Initial Treatment for Follicular Lymphoma: Initial Results From CALGB 50701 - a Phase II Trial of Extended Induction Epratuzumab (anti-CD22) and Rituximab (anti-CD20)

Abstract 427

Rituximab is effective as single agent therapy in the treatment of follicular lymphoma (FL), and when combined with chemotherapy has extended remissions and survival. Epratuzumab (Immunomedics), a humanized anti-CD22 monoclonal antibody, also has single agent activity in FL, and in combination with rituximab led to durable complete responses in the treatment of patients (pts) with relapsed and refractory indolent NHL. To evaluate the hypothesis that combining a second biological agent with rituximab might improve efficacy with good tolerability, the CALGB treated 60 previously untreated pts with epratuzumab and rituximab in a multicenter phase II trial and we report here the preliminary response and toxicity findings. Rituximab was administered at 375 mg/m2 iv weekly for four weeks, then every 8 weeks for four additional doses for a total of 8 doses over 9 months. Epratuzumab, was given at 360 mg/m2 two days before the first rituximab dose to assess toxicity. From week 2 on, epratuzumab was given before the rituximab on the same day for a total of 8 doses over 9 months. Fifty-seven evaluable pts were enrolled between May 2008 and September 2009. FLIPI scores at study entry were 13 (22%) low; 28 (47.5%) intermediate; and 18 (30.5%) high. Fifty-three pts completed all therapy through month 9. One pt was taken off therapy due to progression after month 5. One pt died during induction from line sepsis. Two pts were taken off study due to adverse events, 1 during induction (grade 4 thrombosis and MI), 1 following month 5 (dyspnea, hypoxia and pulmonary NOS). All other toxicities were grade 3 or lower, including fatigue (grade 3 3%, grade 2 17%), nodal pain (grade 3 5%, grade 2 8%), and cytokine release and pruritis (grade 2, 5% each). To date, there have been 19 CRs (33.3%), 29 PRs (50.9%)(ORR 84.2%); 9 (15.8%) had stable disease. All 19 CR patients completed all treatment. The mean time to CR was 9 months. Two patients progressed after a period of stable disease, and 25 of the 29 patients who achieved PR remain in response. All 19 CRs also remain in remission at this point with a median follow-up of 0.82 years (range 0.52 to 2.0). FLIPI score was not predictive of response. The CR rate in low risk pts was 31%, 44% in intermediate risk and 18% in high risk pts. There was a trend toward higher CR rate among patients with FcgR2A His (n=10, CR 60%) and to a lower CR rate among those with FcgR2A Arg (n=14, CR 14.3%). Correlations with PET scan at week 3, with tissue biomarkers and to statin use are being analyzed. Rituximab and epratuzumab is an effective and very well tolerated regimen with an ORR of 84% in previously untreated patients with follicular lymphoma.