Pretreatment evaluation of fluorescence resonance energy transfer‐based drug sensitivity test for patients with chronic myelogenous leukemia treated with dasatinib

Abstract

Tyrosine kinase inhibitors (TKI) are used for primary therapy in patients with newly diagnosed CML. However, a reliable method for optimal selection of a TKI from the viewpoint of drug sensitivity of CML cells has not been established. We have developed a FRET‐based drug sensitivity test in which a CrkL‐derived fluorescent biosensor efficiently quantifies the kinase activity of BCR‐ABL of living cells and sensitively evaluates the inhibitory activity of a TKI against BCR‐ABL. Here, we validated the utility of the FRET‐based drug sensitivity test carried out at diagnosis for predicting the molecular efficacy. Sixty‐two patients with newly diagnosed chronic phase CML were enrolled in this study and treated with dasatinib. Bone marrow cells at diagnosis were subjected to FRET analysis. The ΔFRET value was calculated by subtraction of FRET efficiency in the presence of dasatinib from that in the absence of dasatinib. Treatment response was evaluated every 3 months by the BCR‐ABL1 International Scale. Based on the ΔFRET value and molecular response, a threshold of the ΔFRET value in the top 10% of FRET efficiency was set to 0.31. Patients with ΔFRET value ≥0.31 had significantly superior molecular responses (MMR at 6 and 9 months and both MR4 and MR4.5 at 6, 9, and 12 months) compared with the responses in patients with ΔFRET value <0.31. These results suggest that the FRET‐based drug sensitivity test at diagnosis can predict early and deep molecular responses. This study is registered with UMIN Clinical Trials Registry (UMIN000006358).

Signaling Microdomains in the Spotlight: Visualizing Compartmentalized Signaling Using Genetically Encoded Fluorescent Biosensors

“…Drug resistance caused by Bcr-Abl mutations poses a growing therapeutic challenge for CML, and the authors were able to detect heterogeneous responses to both first-and second-generation drugs in cells expressing Bcr-Abl mutants. Introducing Pickles into mononuclear cells from CML patients further enabled drug efficacy predictions for individual patients, a strategy that has recently been applied for pretreatment evaluations of the clinical efficacy and safety of dasatinib (140) and nilotinib therapy (141).…”

Tailored Biosensors for Drug Screening, Efficacy Assessment, and Toxicity Evaluation

“…The result of the FRET biosensor in cells was consistent with that of the traditional formalin test in mouse, showing the ability of the biosensor for predicting the intrinsic analgesic nature of σ1 receptor ligands. Moreover, Kondo and co-workers − made an improved FRET-based biosensor. It can efficiently quantify the kinase activity of BCR-ABL from patients’ bone marrow cells and evaluate the inhibitory activity of tyrosine kinase inhibitors (TKIs) against BCR-ABL.…”