A Phase 2 interventional study of AP306 75 mg BID and AP306 125 mg BID in Hyperphosphatemia, Chronic Kidney Disease Requiring Chronic Dialysis and End Stage Renal Disease on Dialysis, sponsored by R1 Therapeutics. Recruiting at 31 sites in 2 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-08-26.
Sponsored by R1 Therapeutics · Phase 2, Interventional, and Treatment
This study is being conducted to characterize the safety, tolerability, and efficacy of AP306 at fixed doses in adults with hyperphosphatemia receiving maintenance hemodialysis.
Hyperphosphatemia, one of the most common complications of advanced chronic kidney disease, becomes increasingly prevalent as kidney function declines and is found almost universally in patients with end-stage kidney disease requiring dialysis. Hyperphosphatemia is an independent risk factor for cardiovascular outcomes, fractures, and mortality in patients with chronic kidney disease, especially in patients receiving dialysis.
AP306 is a pan-phosphate transporter inhibitor that may stop phosphate absorption in the gut, controlling hyperphosphatemia.
This is a randomized, double-blind, placebo-controlled, study to characterize the safety, tolerability, and efficacy of AP306 given daily for 8 weeks at fixed doses in adults with hyperphosphatemia receiving maintenance hemodialysis.
173 studies on the registry are indexed under Hyperphosphatemia; 16 are open to participants now.
This study's planned enrollment of 168 is above the median of 101 across 143 interventional studies indexed under Hyperphosphatemia.
Browse Hyperphosphatemia studies →This is the only study on the registry with R1 Therapeutics as lead sponsor.
Counted across the registry records on this site, refreshed daily.
Important Inclusion Criteria:
Important Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
On an ECG, the QT interval is the time the heart’s lower chambers take to activate electrically and recover in each beat. QTc is that time adjusted for heart rate (QTcF by Fridericia’s formula, QTcB by Bazett’s). Some medicines lengthen it, and a long QTc can raise the risk of a dangerous heart rhythm.
The study may name a correction formula and a limit in milliseconds, often around 450–480.
A recording of the heart’s electrical activity, taken with stickers on the chest, arms and legs. It takes a few minutes and does not hurt.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
QT and QTc
On an ECG, the QT interval is the time the heart’s lower chambers take to activate electrically and recover in each beat. QTc is that time adjusted for heart rate (QTcF by Fridericia’s formula, QTcB by Bazett’s). Some medicines lengthen it, and a long QTc can raise the risk of a dangerous heart rhythm.
The study may name a correction formula and a limit in milliseconds, often around 450–480.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ECG (electrocardiogram)
A recording of the heart’s electrical activity, taken with stickers on the chest, arms and legs. It takes a few minutes and does not hurt.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Life expectancy
The study doctor’s estimate of how long someone is likely to live. Criteria use it so that people can stay in the study long enough for it to answer its question.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Drug: AP306 75 mg BID
Drug: AP306 125 mg BID
Drug: AP306 150 mg BID
Drug: AP306 75 mg TID
Drug: AP306 100 mg TID
Drug: AP306 125 mg TID
Drug: Placebo
AP306 75 mg by mouth, twice daily (150 mg/day). Placebo given once daily. Treatment given daily for 8 weeks.
AP306 125 mg by mouth, twice daily (250 mg/day). Placebo given once daily. Treatment given daily for 8 weeks.
AP306 150 mg by mouth, twice daily (300 mg/day). Placebo given once daily. Treatment given daily for 8 weeks.
AP306 75 mg by mouth, three times daily (225 mg/day). Treatment given daily for 8 weeks.
AP306 100 mg by mouth, three times daily (300 mg/day). Treatment given daily for 8 weeks.
AP306 125 mg by mouth, three times daily (375 mg/day). Treatment given daily for 8 weeks.
Placebo given by mouth, three times daily. Treatment given daily for 8 weeks.
To investigate the ability of AP306 at different fixed doses to lower serum phosphate in participants with hyperphosphatemia receiving maintenance hemodialysis
The change in serum phosphate from baseline to the end of treatment or before the initiation of rescue therapy, or before the interruption of study drug due to serum phosphate \<2.5 mg/dL (0.81 mmol/L)
Time frame: 8 weeks
To assess the proportion of participants with serum phosphate in the target range
Achievement of serum phosphate concentrations within the target range (between 3.5 and 5.5 mg/dL \[1.13 and 1.78 mmol/L\], inclusive) at any time during the Treatment Period
Time frame: 8 weeks
To assess the change in serum phosphate from baseline to the end of the Treatment Period
The change in serum phosphate from baseline to the end of Treatment Week 8.
Time frame: 8 weeks
To assess the time to response on serum phosphate reduction
* The change in serum phosphate over time * The time to the first occurrence of serum phosphate ≤5.5 mg/dL (1.78 mmol/L) and ≤4.5 mg/dL (1.45 mmol/L)
Time frame: 8 weeks
To evaluate the pharmacokinetic (PK) characteristics of AP306
* The plasma concentration of AP306 at the following time points: baseline, after 4 weeks of treatment, and after 8 weeks of treatment * The constituent and proportion of metabolites at PK sampling time points
Time frame: 8 weeks
To evaluate the overall safety and tolerability of AP306
* The nature, frequency, and severity of all treatment emergent and serious adverse events (AEs) * The effects on laboratory values, vital signs, electrocardiogram (ECG) parameters, and Bristol Stool Form Scale
Time frame: 12 weeks
To assess the effects of AP306 on intact parathyroid hormone (iPTH) and fibroblast growth factor (FGF23) concentration
The change in iPTH and FGF23 from the baseline to the end of Treatment Week 8 (or early termination (ET) visit for those who terminate study drug), and the end of the study
Time frame: 12 weeks
Eligibility is decided by the study team. Share this record with your doctor or contact the team directly.
Contact study teamGet an email when the registry record changes — status, dates, results — or when someone posts here.
Sign in to followQuestions and observations about this study, from anyone following it. Not medical advice, and not a channel to the study team — their contact details are on the registry record.
Sign in to join the discussion. Reading takes no account; posting does. You choose a display name, and a pseudonym is the default.
Nothing here yet. If you are running this trial, taking part in it, or weighing whether to, this is the place to say so.