TABLE 2

PK parameters for FST315, FST-Fc, and FST-ΔHBS-Fc in C57Bl6 mice after a single 3 mg/kg i.v. or s.c. administration

Plasma concentrations determined using validated antigen capture ELISAs and determined from noncompartmental PK analyses.

Protein	Route	T_max	C_max	AUC_0-last	AUC_0-∞	CL	V_ss	t_1/2_β	%F
Protein	Route	h	ng/ml	ng•h/ml	μg•h/ml	ml/h/kg	ml/kg	h	%F
FST315	i.v.	0.5	344.6	532.4	569.4	5268.8	15,052	1.2	n/a
FST315	s.c.	1	155.8	476.7	482.1	6222.6	ND	1.5	90
FST-Fc	i.v.	0.083	13,759	186,677	189,664	15.9	160	57	n/a
FST-Fc	s.c.	5	1204	96,215	104,874	28.2	ND	61	52
FST-ΔHBS-Fc	i.v.	0.083	54,922	856,448	924,963	3.3	118	104	n/a
FST-ΔHBS-Fc	s.c.	24	5541	344,130	388,867	7.6	ND	104	40

AUC, area under the curve; CL, clearance; ELISA, enzyme-linked immunosorbent assay; F, bioavailability; FST-Fc, follistatin 315 murine IgG₁ Fc fusion; FST-ΔHBS-Fc, follistatin 315 heparan sulfate binding deficient mutant murine IgG₁ Fc fusion; FST315, human follistatin 315 isoform; n/a, not applicable; ND, cannot be determined from noncompartmental PK analyses; T_max, time of maximal observed plasma concentration; t_1/2_β, elimination half-life; V_ss, volume of distribution at steady state.