Impact of Venetoclax Treatment Schedule on Hematologic Recovery and Treatment Response in AML Patients Unfit for Intensive Chemotherapy.

(1) Background: The combination of venetoclax and hypomethylating agents (HMAs) is a standard first-line regimen for acute myeloid leukemia (AML) patients unfit for intensive chemotherapy. Since venetoclax-HMAs are usually administered until progression and delayed hematologic recovery is one of the limiting toxicities, cyclic administration including 7-14-day breaks is recommended. However, whether longer venetoclax schedules lead to higher response rates and how venetoclax pharmacokinetics correlate with toxicity and efficacy remains unclarified. In this single-center retrospective study, we analyzed how venetoclax plasma levels and treatment duration impact hematologic toxicity and treatment responses. (2) Methods: We analyzed the safety and efficacy of venetoclax-HMA combination regimens in a cohort of AML patients unfit for intensive chemotherapy treated at our institution between June 2020 and September 2023. The primary endpoint was the correlation between venetoclax plasma levels or administration schedule with hematologic recovery after the first cycle. Secondary endpoints included the following clinical outcomes: correlation with complete response (CR) status, progression-free survival, and overall survival. (3) Results: Within our cohort of 75 AML patients, we found no correlation between venetoclax plasma peak and trough levels, or venetoclax treatment duration (≤ or >14 days), and hematologic toxicity. Patients receiving shorter venetoclax schedules (≤14 days) had similar CR rates compared to patients treated with longer schedules. (4) Conclusions: Our results suggest that shorter (≤14 days) venetoclax schedules may have no negative impact on tumor responses in AML patients receiving venetoclax and HMA combinations. However, prospective validation studies would be required to confirm these findings.