A Safety, Pharmacokinetic & Dose-Escalation Study of KD019 in Subjects With Autosomal Dominant Polycystic Kidney Disease

Phase 1b: * Primary objective was to determine the safety of tesevatinib. * Dosing was for 28 days daily. After the 28-day treatment period, participants would, at the discretion of the investigator, continue to receive study treatment for 24 months from their first dose or until the development of unacceptable toxicity, noncompliance, or withdrawal of consent by the participant, or investigator decision. Participants might continue beyond 24 months at the discretion of the investigator after consultation with the medical monitor. * All participants received active tesevatinib study drug. * Tesevatinib is an oral once daily tablet. Tablets were 50 milligrams (mg), 100 mg and 150 mg in strength. Participants were enrolled into three sequential dosing cohort levels (50 mg, 100 mg and 150 mg.). Participants in Phase 1b had their dose increased or decreased to the maximum tolerated dose (MTD). * Study participants had magnetic resonance imaging (MRI) of the abdomen (kidneys) at Screening and 6 months thereafter to explore effects of KD019. * Echocardiogram was performed at Screening, Day 28, months 3 and 6 and every 6 months thereafter. Phase 2a: * Primary objective was to compare the annualized change in GFR in participants with ADPKD when treated with tesevatinib. * Two alternate dosing schedules were explored to determine if they were more tolerable than daily dosing when used chronically in participants with ADPKD. * Participants received study treatment for 24 months from their first dose or until the development of unacceptable toxicity, noncompliance, or withdrawal of consent by the participant, or investigator decision. Participants continued beyond 24 months at the discretion of the investigator after consultation with the sponsor. * All participants received active tesevatinib study drug. * Tablets were 50 mg, 100 mg, and 150 mg in strength. * Study participants had MRI of the abdomen (kidneys) at Screening and Month 6 visit and every 6 months after to explore effects of tesevatinib. * Echocardiogram was performed at Screening, Day 28, and Months 3 and 6 and 6 months thereafter.