Ofatumumab maintenance therapy appears to prolong progression-free survival (PFS) in patients with relapsed chronic lymphocytic leukemia (CLL), according to final results from the PROLONG study (ClinicalTrials.gov Identifier: NCT01039376) published in Blood Cancer Journal.

PROLONG was an international, multicenter, open-label, randomized, phase 3 study on ofatumumab maintenance in patients with CLL in complete remission (CR) or with partial remission (PR) after second- or third-line treatment. The primary end point was PFS.

Overall, 480 patients with CLL in CR or PR after second- or third-line treatment were randomly assigned to receive either ofatumumab (300 mg in week 1, then 1000 mg every 8 weeks for up to 2 years) or no additional treatment (observation).

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At median follow-up of 40.9 months, median PFS was 34.2 months with ofatumumab and 16.9 months with observation (hazard ratio [HR], 0.55; 95% CI, 0.43-0.70; P <.0001). Median time to next treatment was 37.4 months with ofatumumab and 27.6 months with observation (HR, 0.72; 95% CI, 0.57-0.91; P =.0044). Median overall survival (OS) had not yet been reached; however, OS was similar in both arms (HR, 0.99; 95% CI, 0.72-1.37).

The number of adverse events of any grade (87% vs 70%) was higher in the ofatumumab arm compared with the observation arm, as was the number and grade 3 or higher adverse events (62% vs 51%). Of grade 3 or higher adverse events, the most common were neutropenia (ofatumumab, 23%; observation, 10%), pneumonia (ofatumumab, 13%; observation, 12%), and febrile neutropenia (ofatumumab, 6%; observation, 4%).

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There were 4 deaths reported in the ofatumumab arm and 6 deaths reported in the observation arm up to 60 days after the last treatment; no deaths were considered to be related to ofatumumab treatment.

“Ofatumumab maintenance significantly prolonged progression-free survival in patients with relapsed CLL and was well tolerated,” the researchers concluded.


  1. van Oers M, Smolej L, Petrini M, et al. Ofatumumab maintenance prolongs progression-free survival in relapsed chronic lymphocytic leukemia: final analysis of the PROLONG study [published online December 4, 2019]. Blood Cancer J. doi:10.1038/s41408-019-0260-2

This article originally appeared on Hematology Advisor