TABLE 1

Kinetic parameters for panobinostat metabolism by recombinant human CYP2C19, CYP2D6, and CYP3A4

K_m,u, unbound K_m (corrected for the unbound fraction in the microsomes, fu_mic). The fu_mic was 1.0 for the rhCYP2C19 and rhCYP2D6 incubations (0.20 and 0.24 mg of protein/ml, respectively) and 0.99 for the rhCYP3A4 incubations (0.26 mg protein/ml), determined by ultracentrifugation (data not shown).

P450	Metabolite	K_m,uµM	V_max h⁻¹	Enzyme Efficiency	Estimation of Individual P450 Contributions to Total HLM Oxidative CL_int of Panobinostat
P450	Metabolite	K_m,uµM	V_max h⁻¹	V_max/K_m,u ml/h per nmol P450	Scaled V_max nmol/h per mg of Protein^a	Scaled CL_int,u ml/h per mg Protein	% Contribution^b
CYP2C19	Total^{^c}	6.41 ± 0.40	118 ± 1.7 (14.7)^{^d}	18.4	0.299	0.0466	6
	M9	10.8 ± 2.0	6.35 ± 0.46 (0.792)	0.588	0.0161	0.00149
	M24.2 + M24.2A	7.93 ± 0.43	120 ± 1.7 (15.1)	15.1	0.308	0.0388
CYP2D6	Total	0.554 ± 0.043	48.3 ± 0.74 (4.97)	87.2	0.0965	0.174	21
	M9	10.3 ± 5.0	2.72 ± 0.56 (0.281)	0.264	0.00546	0.000530
	M24.2 + M24.2A	0.536 ± 0.048	40.2 ± 0.71 (4.14)	75.0	0.0804	0.150
	M43.5	0.424 ± 0.042	6.41 ± 0.12 (0.661)	15.1	0.0128	0.0303
CYP3A4	Total	8.98 ± 0.44	226 ± 2.7 (44.4)	25.1	5.41	0.603	73
	M9	14.2 ± 0.99	56.8 ± 1.1 (11.1)	4.00	1.35	0.0953
	M24.2	7.49 ± 0.58	160 ± 2.8 (31.4)	21.3	3.83	0.512
	M43.5	21.0 ± 1.9	11.6 ± 0.35 (2.28)	0.552	0.278	0.0132

↵^a Scaled V_max is an estimate of the V_max for that P450 enzyme in HLM. It was calculated by dividing the V_max value in parentheses (units of nanomoles per hour per milligram of microsomal protein) from the rhP450 enzyme by the RAF values: 49.1 (CYP2C19), 51.5 (CYP2D6), 8.20 (CYP3A4), see Materials and Methods section.
↵^b The % contribution of the individual P450 enzyme to total panobinostat oxidative CL_int,u in HLM = individual P450 CL_int,u/Σ P450 CL_int,u × 100.
↵^c Total metabolism.
↵^d the value in parentheses is the V_max value with the units of nanomoles per hour milligram microsomal protein.