This extension study of subjects previously enrolled in studies CTAP101-CL-3001 or CTAP101-CL-3002 allows long term evaluation of the safety and efficacy of CTAP101 Capsules in reducing elevated intact parathyroid hormone (iPTH) and correcting vitamin D insufficiency in stage 3 or 4 chronic kidney disease patients.

Only subjects previously enrolled in studies CTAP101-CL-3001 or CTAP101-CL-3002 are eligible to participate in this extension study. This is a phase 3, open-label study of CTAP101 Capsules, with and without add-on vitamin D hormone therapy.

Inclusion Criteria:

• Completed either of the phase 3 double-blind, placebo-controlled studies, CTAP101-CL-3001 or CTAP101-CL-3002
• Taking no more than 1000 mg/day of elemental Ca and willing/able to remain on this dose for the duration of the study
• Taking no more than 1600 IU/dose vitamin D (ergocalciferol or cholecalciferol) therapy and willing/able to remain on a stable dose of vitamin D during the study
• Willing and able to comply with study instructions and to commit to all clinic visits for the duration of the study
• Female subjects of childbearing potential must be neither pregnant nor lactating and must have a negative urine pregnancy test
• All female subjects of childbearing potential and male subjects with female partners of childbearing potential must agree to use effective contraception (eg, implants, injectables, combined oral contraceptives, intrauterine device, sexual abstinence, vasectomy or vasectomized partner) for the duration of the study
• Have the ability to read and understand subject Informed Consent Form (ICF). Subjects or their legal representatives must sign the ICF.

Exclusion Criteria:

• Use of pharmacological dose of ergocalciferol and cholecalciferol (monthly equivalent of 50,000 IU or 1250 µg, eg, Drisdol®) or bisphosphonate therapy
• Use of other bone metabolism therapy (with the exception of stable doses of bisphosphonates and denosumab [Xgeva® and Prolia®]) that may interfere with study endpoints
• Concomitant serious illness or medical condition, such as malignancy, human immunodeficiency virus, significant gastrointestinal or hepatic disease or cardiovascular event or hepatitis that in the opinion of the investigator may worsen and/or interfere with participation in the study
• Neurological/psychiatric disorder, including psychotic disorder or dementia, or any condition reason which, in the opinion of the investigator makes adherence to a treatment or follow-up schedule unlikely
• Known or suspected hypersensitivity to any of the constituents of either investigational product (CTAP101) or adjunctive vitamin D hormone therapy

Intent to treat population: includes subjects receiving CTAP101 capsules only in the extension trial (up to 6 months total active therapy, subjects receiving up to 12 months receiving CTAP101 capsules (6 months in the previous trials and up to 6 months in the extension) with or without being randomized to CTAP101 capsules plus adjunctive therapy.

6 months from initiation of treatment through end of treatment