A Study to Evaluate Safety, Tolerability and Efficacy of AP306 at Fixed Doses in Dialysis Participants With Hyperphosphatemia

Important Inclusion Criteria:

* Signs a written informed consent form (ICF) and is willing to comply with all study requirements in the study
* Receiving a stable hemodialysis (including hemodialysis, hemodiafiltration, and hemoadsorption) regimen, which is defined as a frequency of three times per week for at least 12 weeks before signing the ICF, and does not plan to change in the study
* Who has a blood phosphate level within the study-required range
* Who has a dialysis adequacy, assessed by single pooled Kt/V (SpKt/V, estimated with blood urea) ≥1.20, at screening or any documented value ≥1.20 within 12 weeks prior to signing the ICF
* If the participant is receiving etelcalcetide, their doses must be unchanged for at least 4 weeks prior to signing the ICF
* If the participant is receiving any of the following therapies, their doses are stable for at least 14 days prior to signing the ICF: phosphate-lowering products other than tenapanor or phosphate binders, active vitamin D and analogs, cinacalcet, calcitonin, and P-glycoprotein inhibitors
* Agreement to use highly effective contraception for women of childbearing potentially and non-sterile sexually active males throughout the study and for 90 days after the final dose of study drug

Important Exclusion Criteria:

* Pregnant or breastfeeding
* Scheduled for a living donor kidney transplant in the next 6 months, planned change to peritoneal dialysis or home hemodialysis in the study; planned relocation to another dialysis center in the study
* Any history of a non-pharmacological parathyroid intervention within 6 months prior to the ICF sign off, or planned parathyroid intervention in the study
* Blood calcium or blood intact parathyroid hormone abnormality
* Adequate organ and bone marrow function
* Acute hepatitis or significant chronic liver disease
* Any clinically significant GI disorders within 4 weeks prior to signing the ICF; or any history of gastrectomy; or any GI tract surgery (excluding appendectomy and polypectomy), within 12 weeks of signing the ICF
* Uncontrolled hypertension
* Hospitalization for cardiac or cardiocerebrovascular disease within 24 weeks prior to signing the ICF
* Significant abnormalities of QT interval and heart rhythm on an electrocardiograph (ECG) test
* Any clinically significant active infection or infestation or any treatment with systemic antimicrobial treatment within 2 weeks prior to signing the ICF
* History or presence of malignancy within 3 years prior to signing the ICF, except basal cell skin cancer, in-situ carcinoma of the cervix, and in-situ prostate cancer
* Taking moderate or strong cytochrome P450 (CYP) 3A inhibitors within 2 weeks or 5 half-lives, whichever is longer, prior to signing the ICF (topical use is allowed)
* Treatment with any investigational medication or medical device within 30 days prior to signing the ICF
* Life expectancy less than 12 months