Sonrotoclax: the first new BCL-2 inhibitor in a decade

On May 13, 2026 the FDA granted accelerated approval to sonrotoclax (Beqalzi, BeOne Medicines) for adults with relapsed or refractory mantle cell lymphoma after at least two prior lines, including a Bruton’s tyrosine kinase (BTK) inhibitor. It is the first new BCL-2 inhibitor the agency has approved in roughly a decade — venetoclax, the only other one, was approved in 2016. For a target class that spent thirty years being called undruggable, a second approved molecule is a genuine event.

What BCL-2 does, and why blocking it kills cancer cells

BCL-2 is an anti-apoptotic protein. It sits on the outer mitochondrial membrane and acts as a brake on the intrinsic (mitochondrial) apoptosis pathway. It does this by binding and sequestering pro-apoptotic partners — the BH3-only sensors like BIM and BID, and the pore-forming effectors BAX and BAK — through a hydrophobic surface groove that recognizes their BH3 alpha-helix. As long as BCL-2 keeps those partners tied up, the cell cannot trigger the mitochondrial outer-membrane permeabilization step that commits it to death.

Many B-cell malignancies survive precisely because they overexpress BCL-2 and lean on it to stay alive — they are, in the field’s phrase, “addicted” to it. A drug that plugs the BH3-binding groove displaces the sequestered pro-apoptotic proteins, and the cell, already primed to die, finally does. Molecules that work this way are called BH3 mimetics: they imitate the BH3 helix that the groove evolved to bind.

From venetoclax to sonrotoclax

Venetoclax (ABT-199) was the proof of concept. Souers et al. (2013) described a reverse-engineered, BCL-2-selective BH3 mimetic that drove tumor regression while sparing platelets — platelets depend on the related protein BCL-xL, and the earlier dual BCL-2/BCL-xL compound navitoclax had caused dose-limiting thrombocytopenia by hitting it. Selectivity for BCL-2 over BCL-xL was the whole design problem, and venetoclax solved it well enough to reach the clinic.

• Venetoclax (Venclexta) — AbbVie/Genentech, FDA approved 2016. First-in-class oral BCL-2 inhibitor; backbone of CLL and AML regimens.
• Sonrotoclax (Beqalzi, BGB-11417) — BeOne Medicines, FDA accelerated approval May 13, 2026. A second-generation BCL-2 inhibitor designed for higher potency and a cleaner selectivity profile, now the first BCL-2 agent approved specifically in mantle cell lymphoma.

The trial behind the approval

Approval rested on BGB-11417-201 (NCT05471843), a single-arm, multicenter study of 103 adults with relapsed or refractory MCL who had already received anti-CD20-based therapy and a BTK inhibitor. The overall response rate was 52% (95% CI 42–62%), responses came fast at a median 1.9 months, and the median duration of response was 15.8 months. As with most single-arm accelerated approvals, the readout is response rate rather than survival; continued approval is expected to hinge on confirmatory data. Like venetoclax, sonrotoclax carries a multi-week dose ramp-up to manage the risk of tumor lysis syndrome, because killing a large bulk of lymphoma cells quickly floods the blood with their contents.

Why this matters for the MCL treatment ladder

Mantle cell lymphoma is an aggressive B-cell non-Hodgkin lymphoma driven by the t(11;14) translocation that overexpresses cyclin D1. Covalent BTK inhibitors reshaped its treatment, but patients progress, and once a BTK inhibitor fails, options have been thin. Sonrotoclax slots in specifically after BTK-inhibitor failure, attacking survival through a completely different node — apoptosis rather than B-cell receptor signaling. That mechanistic orthogonality is the point: a tumor that has learned to live without functional BTK signaling has not necessarily lost its dependence on BCL-2.

The resistance question docking can probe

BH3-mimetic resistance has a structural face. In venetoclax-treated CLL, Blombery et al. (2019) identified the recurrent BCL2 Gly101Val (G101V) mutation in patients progressing on the drug: the valine sits in the BH3-binding groove and reduces venetoclax binding without abolishing the protein’s normal job. It is the same story Liganx readers will know from kinases — a single residue swap in the binding pocket that costs the drug a fold or two of affinity while sparing the target’s function. Whether a second-generation binder like sonrotoclax holds its grip against groove mutations is exactly the kind of wild-type-versus- mutant comparison that matters more than any single absolute score.

Try the docking yourself

BCL-2 is not yet in the Liganx target catalog, but the rung directly before sonrotoclax in the MCL ladder is. Open Studio and pick BTK with the C481S mutation to dock the covalent-inhibitor resistance that pushes MCL patients toward BCL-2 therapy in the first place. Dock a covalent BTK inhibitor against wild-type and C481S BTK and watch the score collapse when the catalytic cysteine that anchors the warhead is gone — the molecular reason those patients run out of BTK options and need a drug like sonrotoclax next.

Liganx is molecular docking online: a free, browser-based platform with no install and no local GPU required. Using molecular docking to watch a resistance mutation rewrite a binding pocket is the fastest way to build intuition for why the treatment ladder is shaped the way it is.

Primary sources

• U.S. FDA. FDA grants accelerated approval to sonrotoclax for relapsed or refractory mantle cell lymphoma. (May 13, 2026). fda.gov
• Souers AJ, et al. ABT-199, a potent and selective BCL-2 inhibitor, achieves antitumor activity while sparing platelets. Nat Med 19, 202–208 (2013). doi:10.1038/nm.3048
• Blombery P, et al. Acquisition of the Recurrent Gly101Val Mutation in BCL2 Confers Resistance to Venetoclax in Patients with Progressive Chronic Lymphocytic Leukemia. Cancer Discov 9, 342–353 (2019). doi:10.1158/2159-8290.CD-18-1119