Effect of 22 Novel Cytochrome P450 2D6 (CYP2D6) Variants Found in the Chinese Population on Hemangeol Metabolism In Vitro.

BACKGROUND AND OBJECTIVES: Hemangeol, approved for the treatment of proliferative infantile hemangiomas requiring systemic therapy, is metabolized by cytochrome P450 2D6 (CYP2D6), which is a highly polymorphic enzyme that metabolizes a large number of drugs. More than 100 CYP2D6 allelic variants have been reported so far, including 22 novel variants that discovered in our lab in the Chinese population. Our study aimed to probe the enzymatic activity of these variants toward hemangeol in vitro with recombinant microsomes that expressed in sf21 insect cells using a baculovirus-mediated expression system.

METHODS: The wild-type CYP2D6.1 and other variants (CYP2D6.2, CYP2D6.10 and 22 novel CYP2D6 variants) were incubated with 1-200 μM hemangeol for 50 min at 37 °C. Then the products were extracted, and signal detection was performed by high-performance liquid chromatography with fluorescence detector.

RESULTS: All of the variants exhibited changed apparent Michaelis-Menten constant (Km) or maximum velocity of the reaction (V max ) values compared with that of wild-type protein. The intrinsic clearances (V max /Km) were significantly decreased by 0.37 to 42.74 %. However, CYP2D6.92 and CYP2D6.96 showed no or minimal enzymatic activity as no concentration of 4'-hydroxypropranolol was detected.

CONCLUSIONS: The comprehensive in vitro assessment of CYP2D6 variants provides significant insights into allele-specific activity towards hemangeol in vivo.