FDA rebuffs Amneal's Parkinson's prospect with $500M peak sales target

Amneal Pharmaceuticals’ hopes for a midyear launch of its extended-release Parkinson’s disease prospect—and a shot at a potential $500 million peak sales opportunity in the U.S.—have been put on ice.

Monday, the FDA rebuffed Amneal’s application for IPX203, an oral formulation of carbidopa/levodopa (CD/LD) featuring a mix of immediate-released CD/LD granules and extended-release LD-coated beads.

The Parkinson’s candidate leverages a unique delivery formula to increase “on” time without involuntary body movement. The goal, put simply, is to boost the duration of the drug’s therapeutic benefit over existing formulations with fewer doses.

The complete response letter from the FDA highlighted inadequate safety data on the drug’s CD component, stressing the need for additional pharmacokinetic information. The FDA didn’t spot any problem with the LD element or any issues related to efficacy or manufacturing of IPX203, Amneal pointed out in a press release.

“We plan to work closely with the FDA to address the agency’s feedback and we remain confident in bringing this new treatment to Parkinson’s patients as soon as possible,” Chirag Patel and Chintu Patel, co-CEOs at Amneal, said in a statement.

Levodopa has been the “gold standard” for Parkinson’s patients for more than half a century, though occurrences of peak-dose dyskinesia and “off” episodes form common motor complications for patients on the drug, GlobalData analyst Christie Wong explained in a note Wednesday.

“Although the drugs are common in PD, the formulation is just novel enough to require further due diligence by the agency,” Wong said.

Amneal is counting on an approval of IPX203 to maintain its competitive edge in Parkinson’s, where the company’s marketed med Rytary is expected to lose patent protection in 2028—an event which Wong says “will inevitably shrink [Amneal’s] sales.”

Amneal filed for approval of its extended-release prospect back in September, leveraging data from its successful RISE-PD study.

Still, it’s unclear just how much IPX203 will move the needle for doctors and patients. Wong cited GlobalData interviews with key opinion leaders who suggested the efficacy edge with IPX203 versus immediate-release formulations of LD wasn’t significant enough to influence treatment patterns, “particularly if IPX203 is anticipated to have premium pricing.”

IPX203 may also face competition from other novel subcutaneous levodopa delivery systems, Wong said, singling out AbbVie’s ABBV-951 and NeuroDerm’s ND0612, which tee up a continuous infusion of CD/LD and “could create additional options to control severe motor fluctuations in advanced-stage [Parkinson’s] patients.” ABBV-951 recently hit its own setback after the FDA questioned the combo’s subcutaneous pump device.

IPX203 features a disintegrant polymer for rapid dissolution of the immediate-release granules. The LD beads are coated with a sustained release polymer for slow release of the drug, a mucoadhesive polymer to keep the granules adhered to the area of absorption longer and an enteric coating to prevent the beads from disintegrating prematurely in the stomach.

While Rytary has proven to be a somewhat niche product, Amneal hopes IPX203 could unlock a much bigger opportunity in Parkinson’s. The company is targeting peak U.S. annual net sales of $300 million to $500 million, making IPX203 the greatest opportunity in its branded specialty pipeline.