idelalisib + rituximab + lenalidomide

This drug is an investigational combination therapy comprising **idelalisib** (an oral small molecule inhibitor of PI3K delta), **rituximab** (an anti-CD20 monoclonal antibody), and **lenalidomide** (an oral immunomodulatory agent), studied for the treatment of relapsed or refractory indolent lymphomas, particularly follicular lymphoma and mantle cell lymphoma. Idelalisib blocks the delta isoform of phosphatidylinositol 3-kinase, inhibiting B cell receptor signaling and downstream survival pathways. Rituximab targets CD20 on B lymphocytes, inducing antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity, and direct apoptosis. Lenalidomide acts via cereblon-mediated degradation of transcription factors, leading to anti-tumor activity, and enhances immune cell function and antibody-dependent cytotoxicity. While each agent and certain doublets (lenalidomide + rituximab, idelalisib + rituximab) show efficacy and manageable safety as monotherapies or doublets, the triplet was tested in Phase I trials for relapsed/refractory follicular and mantle cell lymphoma but was halted prematurely due to unacceptable toxicity including severe hepatotoxicity, hypotension, sepsis, and rash, thus limiting further development of this specific triplet combination[1].