Belimumab induces early and sustained resolution of lupus thrombocytopenia

Belimumab has well-established efficacy in improving overall SLE disease activity and preventing flares and organ damage. Belimumab effects have been demonstrated across organ domains but have not been reported in detail for haematological manifestations. We investigated the efficacy of belimumab in thrombocytopenia and leucopenia in patients with SLE.

Anonymised data on haematological parameters from five phase III randomised controlled clinical trials of belimumab were provided by GSK. These datasets included 1769 patients treated with belimumab and 1144 patients who received placebo, on top of standard therapy. We selected patients with active thrombocytopenia or leucopenia at baseline and compared sustained resolution of symptoms from the time of resolution through week 52 by means of log-rank tests.

At baseline, thrombocytopenia and leucopenia were present in 39 and 346 belimumab-treated patients and 25 and 203 placebo recipients, respectively. Thrombocytopenia resolved earlier with belimumab versus placebo, starting from week 2 on therapy and in a higher proportion of belimumab-treated patients (p=0.0267). One-third (13/39) of belimumab-treated and 8% (2/25) of placebo-receiving patients reached persistent resolution. In contrast to thrombocytopenia, observed improvements in leucopenia were slower, with no apparent difference between belimumab and placebo.

This post hoc analysis of data from five large phase III RCTs suggests a benefit from belimumab compared with placebo in the haematological domain. A benefit from belimumab was seen in improving thrombocytopenia, but not leucopenia. While mild leucopenia is rarely clinically relevant, the data on thrombocytopenia will inform differential therapeutic decisions in patients with active SLE.