Table 2.

Characteristics of low clearance methods.

Methods	Hepatocyte relay	HepatoPac	Hurel
Hepatocyte density (million cells/mL)	Any, typically 0.5–2	0.0752	0.3053,54
Incubation time	4 h/relay, accumulatively 20 h for 5 relays	Up to 7 days without media change52	3 days53,54
CLint, app lower limit (μL/min/million cells)a	0.58 (0.5 million cells/mL) 0.14 (2 million cells/mL)	0.49 (7-day incubation at 0.07 million cells/mL)	0.27 (3-day incubation at 0.30 million cells/mL)
CLint, app, scaled lower limit (mL/min/kg)b	1.5 (0.5 million cells/mL, 20 h) 0.36 (2 million cells/mL, 20 h)	1.2 (7-day incubation at 0.07 million cells/mL)	0.67 (3-day incubation at 0.30 million cells/mL)
Enzyme activity compared to suspension hepatocytes	Same as suspension hepatocytes	Higher UGT and AKR activities from mouse fibroblast Lower activities of CYP2D6, AO and FMO55	Higher UGT and AKR activities from mouse fibroblast Lower activities of CYP2D6, AO and FMO55
Donors	Single or pooled	Single or pooled	Single or pooled
Preclinical species	Any	Any	Any
Coculture	None	Mouse fibroblasts	Proprietary non-parenchymal stromal cell line56
Plate format	Standard	Micropatterned plates	Standard

^aCL_{int, app} = ln2/(t_{1/2, max})/cell density × 1000 (μL/min/million cells)⁵⁷. Maximum measurable t_1/2 (t_1/2,max) is twice incubation time⁵⁸.

^bCL_{int, app, scaled} = CL_{int, app} × 21 × 120/1000 (mL/min/kg)⁵⁷.