Phase 2 study of tabalumab, a human anti-B-cell activating factor antibody, with bortezomib and dexamethasone in patients with previously treated multiple myeloma

In this double-blind, Phase 2 study, 220 patients with relapsed/refractory multiple myeloma were randomly assigned 1:1:1 to receive placebo (N�=�72), tabalumab 100�mg (N�=�74), or tabalumab 300�mg (N�=�74), each in combination with dexamethasone 20�mg and subcutaneous bortezomib 1�3�mg/m² on a 21-day cycle. No significant intergroup differences were observed among primary (median progression-free survival [mPFS]) or secondary efficacy outcomes. The mPFS was 6�6, 7�5 and 7�6�months for the tabalumab 100, 300�mg and placebo groups, respectively (tabalumab 100�mg vs. placebo Hazard ratio (HR) [95% confidence interval (CI)]�=�1�13 [0�80–1�59], P�=�0�480; tabalumab 300�mg vs. placebo HR [95% CI]�=�1�03 [0�72–1�45], P�=�0�884). The most commonly-reported treatment-emergent adverse events were thrombocytopenia (37%), fatigue (37%), diarrhoea (35%) and constipation (32%). Across treatments, patients with low baseline BAFF (also termed TNFSF13B) expression (n�=�162) had significantly longer mPFS than those with high BAFF expression (n�=�55), using the 75th percentile cut-off point (mPFS [95% CI]�=�8�3 [7�0–9�3] months vs. 5�8 [3�7–6�6] months; HR [95% CI]�=�1�59 [1�11–2�29], P�=�0�015). Although generally well tolerated, PFS was not improved during treatment with tabalumab compared to placebo. A higher dose of 300�mg tabalumab did not improve efficacy compared to the 100�mg dose. Nonetheless, BAFF appears to have some prognostic value in patients with multiple myeloma.