Dual targeting of BTK and BCL2 enhances apoptosis in marginal zone lymphoma models: preclinical activity of BGB-16673 and sonrotoclax

BackgroundBTK and BCL2 represent key therapeutic targets in B-cell lymphomas, including marginal zone lymphoma (MZL). Here, we evaluated the novel BTK degrader BGB-16673, and the second-generation BCL2 inhibitor sonrotoclax in a panel of MZL cell lines, including models with acquired resistance to BTK, BCL2 and PI3K inhibitors, as single agents and in combination. MethodsCytotoxicity, transcriptomic changes, apoptosis, and protein expression were assessed for BGB-16673 alone and in combination with venetoclax, sonrotoclax, bendamustine, selinexor, lenalidomide, and tazemetostat. ResultsBGB-16673 demonstrated single-agent activity in selected MZL cell lines, inducing BTK degradation and transcriptional repression of BCR signaling and MYC targets. Its transcriptional and phenotypic effects overlapped with those of zanubrutinib but also included specific modulation of oxidative phosphorylation genes. Combination studies revealed that BGB-16673 synergized with other targeted agents, achieving the best results with sonrotoclax, venetoclax, bendamustine, lenalidomide, and rituximab. The mechanism of action of the combination with the BCL2 inhibitors was further evaluated. The combination with sonrotoclax consistently enhanced apoptosis across MZL models, outperforming venetoclax in potency in most cell lines. Sonrotoclax showed over 10-fold higher activity than venetoclax in three MZL lines and demonstrated synergistic interaction with BGB-16673. Mechanistically, the combination leads to BTK degradation and modulation of anti-apoptotic proteins such as BCL2, MCL1, and BCL-XL. ConclusionOur findings underscore the potential of BGB-16673 as a therapeutic agent, both as a monotherapy and in combination regimens, for treating MZL patients. Additionally, the results also identify the second-generation BCL2 inhibitor sonrotoclax as another drug to be explored in the same patient populations.