Earlier this month, Phase IIb results were published for Shield Therapeutics’ PT20 (ferric iron oxide adipate), an oral iron-based phosphate binder, for the treatment of hyperphosphatemia (HPT) in dialysis-dependent chronic kidney disease (CKD) patients. PT20 is a novel binder based on adipate-doped iron oxide technology, and acts as a phosphate sponge, allowing specificity and efficacy in the binding of phosphates. Its crystal structure consists of a ligand modified disrupted lattice, which provides a larger surface area and allows for higher-capacity phosphate binding. Although the CKD-HPT market has several marketed treatments available, GlobalData believes that PT20 has the potential to capture a slice of the HPT market by targeting dialysis-dependent patients who are not able to maintain recommended phosphate levels, despite treatment and adhering to restricting dietary phosphate intake.
In the double-blind, parallel-group, placebo-controlled, dose-ranging Phase IIb study involving 153 participants, the efficacy and safety of PT20 were studied in dialysis-dependent CKD patients. Patients were either treated with PT20 or placebo three times daily for 28 days, with PT20-treated patients experiencing a statistically significant and dose-dependent reduction in serum phosphate concentration. The most common AEs identified were gastrointestinal, and laboratory results indicated that there was no clinically significant increase in ferritin following treatment with PT20, an important measurement due to iron accumulation being a concern in dialysis patients treated with iron-based binders. Overall, PT20 was efficacious and generally well tolerated, with Shield Therapeutics eyeing a Phase III study in the coming years.
In 2019, a Phase III study was anticipated to begin in 2021, following the development of a new formulation of PT20. Trial initiation has now been pushed back to 2022, which will directly follow the completion of the new formulation, which is expected to start in H2 2020 and last 15–18 months. GlobalData believes if PT20 sustains such an apparently beneficial efficacy profile from its planned Phase III trial, then it could be of high clinical value to future patients against in-family iron-based binders, Vifor’s Velphoro (sucroferric oxyhydroxide) and Akebia Therapeutics’ Auryxia (ferric citrate). With that said, PT20 will be entering a highly competitive and crowded market, filled with established metal- and non-metal-based binders. There is also the potential threat from Ardelyx’s tenapanor, an inhibitor of sodium/hydrogen exchanger isoform 3 (NHE3), with the company announcing an NDA submission to the FDA for tenapanor in June for treating HPT in adult CKD patients on dialysis.