Population Pharmacokinetic Analysis of Sparsentan in Healthy Volunteers and Patients with Focal Segmental Glomerulosclerosis

Sparsentan is a single-molecule dual endothelin angiotensin receptor antagonist (DEARA) currently under investigation as a treatment for focal segmental glomerulosclerosis (FSGS) and IgA nephropathy (IgAN). A population pharmacokinetic (PK) analysis was performed to characterize the PKs of sparsentan and to evaluate the impact of FSGS disease characteristics and co-medications as covariates on sparsentan PKs. Blood samples were collected from 236 healthy volunteers, 16 subjects with hepatic impairment, and 194 primary and genetic FSGS patients enrolled in nine studies ranging from phase I to phase III. Sparsentan plasma concentrations were determined using validated liquid chromatography-tandem mass spectrometry with a lower limit of quantitation of 2 ng/mL. Modeling was conducted with the first-order conditional estimation with η-ϵ interaction (FOCE-1) method in NONMEM. A total of 20 covariates were tested using a univariate forward addition and stepwise backward elimination analysis with significance level of p < 0.01 and p < 0.001, respectively. A two-compartment model with first-order absorption and an absorption lag time with proportional plus additive residual error (2 ng/mL) described sparsentan PKs. A 32% increase of clearance due to CYP3A auto-induction occurred at steady-state. Covariates retained in the final model included formulation, cytochrome P450 (CYP) 3A4 inhibitor co-administration, sex, race, creatinine clearance, and serum alkaline phosphatase. Moderate and strong CYP3A4 inhibitors comedications increased area under the concentration-time curve by 31.4% and 191.3%, respectively. This population PK model of sparsentan suggests that dose adjustments may be warranted for patients taking moderate and strong CYP3A4 inhibitors concomitantly, but other covariates analyzed may not require dose adjustments.