This study will compare CTAP201 with Doxercalciferol in patients with chronic kidney disease (CKD) and secondary hyperparathyroidism (SHPT), undergoing regular hemodialysis, at different dose strengths. This study will also investigate the levels of CTAP201 in the body over time and determine the safety of CTAP201.

Inclusion Criteria:

• Body mass index between 18 and 40
• On maintenance hemodialysis three times per week
• Visit 1: Serum iPTH value greater than or equal to 200 pg/mL and lower than or equal to 1000 pg/mL
• Visit 1: Serum total calcium value greater than 8.4 mg/dL and lower than 10.0 mg/dL
• Visit 1: Serum phosphorus value greater than or equal to 2.5 mg/dL and lower than or equal to 5.5 mg/dL
• Serum 25-hydroxyvitamin D level greater than or equal to 15 ng/mL
• Visit 2: Serum iPTH value greater than 300 pg/mL
• Visit 2: Serum Ca x P product less than 56 [mg/dl]2
• Willing and able to discontinue vitamin D and/or bone metabolism therapy for at least 2 weeks prior to administration of Study Drug, and length of study

Exclusion Criteria:

• Taking cytochrome P450 3A inhibitors and/or inducers
• Abnormal liver functions