In xenograft models using the DLBCL line SU-DHL-10, BTM-3566 once-daily oral treatment resulted in complete regression in all tumor-bearing animals. Most importantly, no subsequent tumor growth occurred for 2 weeks after cessation of therapy, indicating that treatment with BTM-3566 resulted in a durable complete remission in this model of double-hit DLBCL. Expansion studies into human DLBCL PDX models harboring a range of high-risk genomic alterations, including MYD88 mutations and MYC and BCL2 rearrangements, demonstrated response in 100% of the lines with complete tumor regression in 6 of 8 PDX models tested (Table 1).