Otlertuzumab is a humanized monospecific antibody built on Aptevo’s ADAPTIR modular protein therapeutic platform.  It targets CD37, a cell surface protein that is expressed on the surface of normal and transformed B cells, and also recently discovered to be present on the surface of T-cell lymphomas. CD37 has been implicated in diverse cellular processes including cell adhesion, proliferation, differentiation, motility, and tumor invasion.  Otlertuzumab mediates the death of CD37-expressing cells through various mechanisms including direct cell death, antibody-dependent cell-mediated cytotoxicity (ADCC), and phagocytosis.

Otlertuzumab is currently in Phase 2 clinical development and is being investigated for the treatment of peripheral T cell lymphoma (PTCL).   The Phase 2 study, which is ongoing, is an open-label, proof-of-concept evaluation of the safety and efficacy of otlertuzumab in combination with bendamustine in patients with relapsed or refractory peripheral T-cell lymphomas (PTCL).  Up to 24 patients will be enrolled in the study.  The primary endpoint is response rate, evaluable by the 2017 International Working Group consensus response evaluation criteria in lymphoma (RECIL 2017).

Otlertuzumab has previously been studied in a randomized Phase 2 study which demonstrated the efficacy and tolerability of otlertuzumab, combined with bendamustine, in relapsed chronic lymphocytic lymphoma (CLL).  In this study there was a significant increase in median progression free survival, from approximately 10 to 16 months in patients receiving the combination of otlertuzumab and bendamustine.