Effects of 22 <b><i>CYP2D6</i></b> Genetic Variations Newly Identified in Chinese Population on Olanzapine Metabolism in vitro

The objective of this study was to assess the catalytic activity of 22 novel <i>CYP2D6</i> allelic variants (<i>2D6</i>*<i>87-</i>*<i>98</i>,<i> R25Q</i>,<i> F164L</i>,<i> E215K</i>,<i> F219S</i>,<i> V327M</i>,<i> D336N</i>,<i> V342M</i>,<i> R344Q</i>,<i> R440C</i> and <i>R497C</i>) to olanzapine in vitro. Their protein products expressed in <i>Spodoptera frugiperda</i> 21 (<i>Sf21</i>) insect cells were incubated with olanzapine 100-2,000 μmol/l for 30 min. The kinetic parameters of K_m, V_max and intrinsic clearance were determined by 2-hydroxymethylolanzapine, the metabolite of olanzapine mediated by <i>CYP2D6</i>, using ultra-performance liquid chromatography tandem mass spectrometry. Results showed that the kinetic parameters of 2 alleles, <i>CYP2D6</i>*<i>92</i> and <i>2D6</i>*<i>96</i>, could not be detected; 17 allelic variants, <i>CYP2D6</i>*<i>87-</i>*<i>88</i>,<i> 2D6</i>*<i>90-</i>*<i>91</i>,<i> 2D6</i>*<i>93-</i>*<i>95</i>,<i> 2D6</i>*<i>97</i>,<i> R25Q</i>,<i> F164L</i>,<i> E215K</i>,<i> F219S</i>,<i> V327M</i>,<i> V342M</i>, <i>R344Q</i>,<i> R440C </i>and<i> R497C</i>, significantly reduced the intrinsic clearance of olanzapine; 2 variants, <i>CYP2D6</i>*<i>89</i> and <i>2D6</i>*<i>98</i>, increased the intrinsic clearance of olanzapine; no difference was found in intrinsic clearance of <i>D336N</i>. Furthermore, 6 alleles, <i>CYP2D6</i>*<i>87</i>,<i> 2D6</i>*<i>88</i>,<i> 2D6</i>*<i>91</i>,<i> 2D6</i>*<i>93</i>,<i> 2D6</i>*<i>97</i> and <i>R497C</i>, exhibited higher K_m values in a range of 120.80-217.56% relative to wild-type <i>CYP2D6</i>*<i>1</i>. The research demonstrated the metabolic phenotype of the 22 novel <i>CYP2D6</i> variants for olanzapine that were different from probe drugs we used previously and might provide beneficial information to the personalized medicine of olanzapine.