Adverse Events, Patterns of Tumor Lysis Syndrome Prophylaxis and Management, and Dosing Patterns in a Large Cohort of Venetoclax Treated CLL Patients in Community and Academic Settings

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washington; swedish; swedish cancer


Introduction: Venetoclax (Ven), an oral BCL2 inhibitor, is approved for the treatment (tx) of relapsed/refractory (R/R) chronic lymphocytic leukemia (CLL). Ven is generally well tolerated, and side effects observed in clinical trials have been consistent with other CLL tx. Clinical trials using the approved dose escalation schedule report negligible rates of clinical tumor lysis syndrome (TLS). We aimed to understand rates of select adverse events (AEs) including cytopenias, infections, and TLS in CLL patients (pts) treated with Ven in community and academic settings. To do so, we examined 297 pts with CLL who received Ven, either alone or paired, in this multicenter, international study.

Methods: We conducted a retrospective cohort study of Ven treated pts with CLL across at 15 academic (n=169) and 51 community (n=128) centers outside of the clinical trial setting. This study represents a collaboration between US centers, CLL Collaborative Study of Real World Evidence (CORE), and UK CLL Forum. Demographics, baseline disease characteristics, Ven dosing, TLS risk (per FDA Ven label) and prophylaxis, and AEs were collected. Lab vs. clinical TLS was defined by Howard criteria. PFS was estimated by Kaplan Meier methodology. All comparisons were descriptive.

Results: Of the 297 pts examined, median age at Ven initiation was 67 (range 37-91). The group was 69% male, 96% had R/R CLL, and 45% had del17p. Baseline characteristics stratified by practice setting are included in Table 1. 80% received Ven as monotherapy while 20% received it paired with another agent (anti-CD20 mAb (75%), ibrutinib (8.5%), other (16.5%)). All pts were treated outside of clinical trials.

During dose escalation, 81% achieved a 400 mg dose and 65% maintained 400 mg following escalation (cyp3A4 use unknown). TLS risk was low in 40%, intermediate (int) in 32%, and high risk in 28%. CT scan prior to Ven initiation was performed in 62%. At least one hospitalization occurred for 56% of low, 80% of int, and 88% of high risk pts (63% of the total cohort). Table 1 describes the distribution of TLS risk and frequency of hospitalizations in academic, community centers. TLS prophylactic measures were available for a subset of pts. Allopurinol was used for 91% (n=68/75) of low, 93% (n=52/56) of int, and 94% (n=29/31) of pts at high risk for TLS. Rasburicase was used for 27% (n=28/102) of low, 42% (n=34/81) of int, and 72% (n=57/79) of high risk pts. Normal saline was used in 85% (n=62/73) of low, 88% (n=49/56) of int, and 97% (n=30/31) of high risk pts. TLS occurred in 8.4% of pts (n=25/297). Three lab and 2 clinical events occurred in low risk pts, 7 lab and 3 clinical events in int risk pts, and 7 lab and 3 clinical events in high risk pts. Of pts with TLS, 1 has discontinued Ven. Of pts with clinical TLS, all were hospitalized, received allopurinol and normal saline, and 28% received rasburicase. 72% with TLS had creatinine clearance <80 mg/mL vs. 44% who did not have TLS (p=0.02). One int risk pt received hemodialysis. One death from TLS (previously reported) was observed in a pt hospitalized with rapid disease progression and tx-related neutropenia re-challenged with 400 mg Ven after dose interruption without dose escalation.

Select AEs were neutropenia (ANC<1000) 39.6%, thrombocytopenia (plt <100) 29.2%, infection 25%, neutropenic fever 7.9%, and diarrhea (>7 stools/day) 6.9%. For the subset who received Ven paired, AEs were not increased: 35% neutropenia, 29% thrombocytopenia, 22% infection, 6.3% neutropenic fever, and 6.4% diarrhea. TLS was observed in 3.4% of pts who received Ven paired vs. 9.3% who received Ven monotherapy. 29% pts required ≥1 dose reduction and 32% had ≥1 dose interruption. Median length of dose interruption was 7 days (range 1 - 132). 22 pts (7.4%) discontinued Ven due to an AE. PFS was similar in pts with ≥1 dose interruption vs. 0, pts who required dose interruption ≥8 days vs. <8 days, and pts who achieved a stable Ven dose of <400 mg vs. 400 mg (Figure 1).

Conclusions: Ven was well tolerated in this cohort; AE rates were similar to those reported in clinical trials. Both academic and community sites employed TLS prophylaxis consistent with FDA/EMA recommendations resulting in a small proportion of clinical TLS events (<3%). Of note, Ven paired with another agent did not appear to result in increased rates of AEs and TLS events. Dose reduction and interruptions were consistent with clinical experience with other novel agents though these did not appear to impact PFS.

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