Merck acquired ArQule for $2.7B (closed January 2020) for its lead asset ARQ 531, a reversible, non-covalent BTK inhibitor now developed as nemtabrutinib (MK-1026). As of late 2025 the asset has advanced into multiple registrational Phase 3 BELLWAVE trials in CLL/SLL (incl. a head-to-head BELLWAVE-011 vs ibrutinib/acalabrutinib), though it remains pre-approval with no pivotal efficacy readout.