Venetoclax therapy in chronic lymphocytic leukaemia patients relapsed after allogeneic haematopoietic stem cell transplantation.

Allogeneic hematopoietic stem cell transplantation (alloHSCT) remains an option for young and fit chronic lymphocytic leukaemia (CLL) patients with high-risk disease features. However, allotransplanted patients are generally excluded from clinical trials, making data regarding the use of venetoclax after alloHSCT extremely rare. We report data from 7 CLL patients who received venetoclax after alloHSCT among 53 Italian centers. These patients underwent alloHSCT between 2006 and 2021 after failing chemoimmunotherapy (7/7), ibrutinib (5/7) and/or idelalisib (1/7). Of note, 3/7 patients had already received venetoclax-based therapy before alloHSCT. Post-allo HSCT venetoclax treatment resulted safe, with adverse events not different from what reported in clinical trials. Importantly, no meaningful impact on graft versus host disease (GvHD) course was observed: 4/7 patients with pre-existing chronic GvHD had no exacerbation after venetoclax start, and only one patient developed GvHD during venetoclax therapy, that was managed as per standard clinical practice. Concerning efficacy, 5/7 patients presented a clinical response to venetoclax, with two patients achieving an undetectable minimal residual disease. To our knowledge, this is the largest reported series of CLL patients treated with venetoclax after alloHSCT. In these heavily pretreated and high-risk patients, previous alloHSCT did not compromise the feasibility of venetoclax therapy, that lacked unexpected toxicities and did not exacerbate GvHD.