6584 Background: In Study 406, the anti-CD20 monoclonal antibody ofatumumab (ofa), given as monotherapy over 6 months, showed 47% overall response rate (ORR) in patients (pts) with chronic lymphocytic leukemia (CLL) refractory to fludarabine and alemtuzumab (FA-ref), or to fludarabine with bulky (>5cm) lymphadenopathy (BF-ref). The effects of ofa retreatment (retx) and maintenance (mt) are unknown. Methods: Pts who responded to ofa and then progressed or had stable disease (SD) in Study 406, were offered retx in Study 416 (NCT00802737; GSK/Genmab) with ofa 1 x 300 mg + 7 x 2000 mg weekly followed by mt with ofa 2000 mg monthly for up to 2 years (if SD or better). Primary endpoint was ORR (1996 NCI-WG). Safety and time to event outcomes were also assessed. Results: Of 29 pts enrolled, 7 had SD and 22 had partial response (PR) and progressed in Study 406. Pts were defined per Study 406: 17 FA-ref, 11 BF-ref, 1 “other”. Pretreatment characteristics were similar between groups. Pts received a median of 12 doses (range 3-32); 86% had 8 doses, 3% received all 32 doses. 72% of pts had infusion-related adverse events (AEs), 41% at 1st infusion, mostly grade 1-2. The most common grade >3 AE occurring up to 60 days after last tx was infection (38%); the most common was pneumonia (17%). 3 pts (10%) had fatal infections, all bronchopneumonia. Clinical efficacy is shown in Table. Comparative analysis to Study 406 is ongoing. Conclusions: The response to ofatumumab (ofa) as induction retreatment and progression-free survival in this limited number of pts was similar to 1st treatment (Study 406). Ofa maintenance had some clinical benefit for pts with advanced CLL. Ofa was well-tolerated with no unexpected toxicities. [Table: see text]
