Keryx' phosphate binder set for filing following impressive Phase III

Keryx Biopharmaceuticals said it anticipates US and European regulatory submissions for Zerenex (ferric citrate; KRX-0502) in the second quarter of 2013, after reporting top-line data showing that a Phase III study investigating the treatment for hyperphosphataemia in end-stage renal disease (ESRD) patients on dialysis met the primary and all key secondary endpoints.

Some analysts believe the new data could not only help the New York City-headquartered firm differentiate its product (excluding it from certain upcoming pricing pressures) but also influence any partnerships or takeover moves. However, other analysts have questioned the Zenerex clinical database will be sufficient to secure US approval.

The announced long-term study was the final component of Keryx' Phase III registration program for the ferric iron-based phosphate binder drug candidate, and was conducted under a Special Protocol Assessment (SPA) with the US FDA.

Zerenex met the study's primary endpoint by demonstrating a statistically significant change in serum phosphorus versus placebo over the four-week efficacy assessment period of the study. Moreover, the drug met the key secondary endpoints of increasing ferritin and transferrin saturation (TSAT) and reducing the use of intravenous (iv) iron and erythropoiesis-stimulating agents (ESAs) versus the active control over the 52-week safety assessment period of the study.

According to analysts from Roth Capital , "The true differentiated data come from the secondary endpoints of iron sparing, showing significant reductions of iv iron and ESA usage." They stated, "With anticipated cost pressures in 2016 on bundling phosphate binders with dialysis costs, the differentiated profile of Zerenex has the potential to be excluded from these pricing pressures, especially with the data supporting its ability to reduce iv delivered drugs."

In addition: "Zerenex produced statistically significant increases in Ferritin, TSAT and haemoglobin levels. From a clinical standpoint this led to statistically significant reductions in iv iron usage (51.6% decrease) and ESA usage (27.1% decrease). These reductions in iv iron and ESA translate to ~$750 million in potential savings (drug costs alone) and does not take into consideration the personnel costs of administering these drugs. Therefore we believe the pharmacoeconomic benefits of this oral agent are clear should Zerenex be approved."

The Roth Capital analysts questioned what the next commercial step for Zerenex would be. "With Phase III data under SPA in hand and regulatory filings on the short term horizon, we believe this drug is an attractive asset to potential suitors," they noted. "We believe that Keryx now has the ammunition to drive either a partnership or even an ultimate takeout of the company based on Zerenex' differentiated profile."

They believe Keryx is now well positioned with Zerenex to garner both US and EU approval in 2014.

But not everyone is confident that the US FDA will be convinced.

BioMedTracker commented: "The main concern going forward is whether the clinical database will be sufficient to support approval in the US. The clinical development program for the most recently approved anti-hyperphosphataemia agent, Fosrenol, included 1507 patients with long term exposure to drug and an additional 298 patients with short term exposure. Long term exposure to Zerenex appears to be about 1050 patients, with all but 440 or so being Japanese."

Separately, the drug is expected to reach the Japanese market (where it is licensed to Japan Tobacco), in the first half of 2014 (scripintelligence.com, 8 January 2013).