TKI Dose Optimization Based on Therapeutic Drug Monitoring（TDM) with Encouraging Outcomes and Well-Tolerated for Chronic Myeloid Leukaemia Patients

Background Imatinib, nilotinib, and dasatinib are tyrosine kinase inhibitors (TKIs) that have become first-line treatments for Philadelphia chromosome-positive chronic myeloid leukemia (CML). Series studies indicated TKIs had a high therapeutic index, which led to the registration of these medications at fixed doses. Therapeutic drug monitoring (TDM) is a strategy for dosage optimization to provide individual treatment through dose adjustment to improve efficacy or avoid TKI-related adverse events (AEs).

Objective We prospectively analyzed the outcome based on trough plasma concentrations (Cmin) to manage TKI dosage optimization during imatinib, nilotinib, and dasatinib therapy in patients with CML by 12 months. The primary efficacy endpoint was the rate of MMR at 12 months, the secondary endpoints included the cumulative rate of significant AEs defined as grade 3/4 fluid retention, all grade pleural effusion and pulmonary hypertension, grade 3/4 bilirubin increased, and grade 3/4 hematological toxicity related to TKIs within the first 12 months of therapy.

Methods We examined 204 CML patients treated with imatinib, nilotinib, or dasatinib in the first line for CML-CP. We used high-performance liquid chromatography-tandem mass spectrometry (UPLC/MS-MS) to detect the Cmin of TKIs. Dasatinib or imatinib Cmin (24±3h post-dose) and nilotinib Cmin (12±3 h post-dose) were assessed after 7~10 days of therapy. We set the Cmin of imatinib at 1000~1500 ng/mL and that of nilotinib at 600~800 ng/mL, dasatinib at 1~3 ng/ml, respectively.

Results Imatinib group (n = 67), Nilotinib group (n = 72), and Dasatinib group (n = 65), respectively. The initial dose of imatinib was 400mg qd, based on Cmin of imatinib was 900~1100ng/mL, there were 17 patients with dose reduction(1 case with 100mg qd, 5 cases with 200mg qd, 11 cases with 300mg qd) and 2 patients increased dose to 500mg qd; The initial dose of nilotinib was 300mg bid, based on Cmin of imatinib was 600~800ng/mL, there were 21 patients with dose reduction( 4 cases with 150mg bid, 16 cases with 450mg daily, 1 cases with 150mg qd) and 1 patients increased to 400mg bid; the initial dose of dasatinib was 100mg qd, based on Cmin of dasatinib was1~3 ng/ml, there were 32 patients with dose reduction(1 case with 20mg qd, 4 cases with 40mg qd, 20 cases with 50mg qd, 7 cases with 70mg qd ). Among the patients treated with imatinib, dasatinib, and nilotinib, no statistically significant associations were observed between gender, age, ELT scores, and plasma trough concentration (p>0.05). Early molecular reaction (EMR BCR: ABL(IS) <10%) was achieved by 83.6% (95% confidence interval [CI], 74.6%-92.5%) in the imatinib group, 87.7% (95% CI, 80.0%-95.4%) in the nilotinib group, and 83.3% (95% CI, 75.0%-91.7%) in the dasatinib group of patients at 3 months. The incidence of MMR at 12 months was 82.1% (95% CI, 73.1%-93.0%) in the imatinib group, 73.8% (95% CI, 64.6%-84.6%) in the nilotinib group, and 75.0% (95% CI, 65.3%-84.7%) in the dasatinib group, respectively. The cumulative incidence of grade 3/4 hematological toxicity was 7.8% (16/204), all-grade pleural effusion was 23.1% (15/65) in the dasatinib group, grade 3/4 bilirubin increased was 6.9% (5/72) in the nilotinib group, and there were no patients with pulmonary hypertension.

Conclusion There are large individual differences in plasma trough concentrations in CML patients taking TKIs, the TKI dosage should be adjusted based on target plasma concentrations to maximize efficacy and minimize the incidence of adverse events.