Fresh on the heels of winning Food and Drug Administration (FDA) approval in December for what could be its first blockbuster drug, Ionis Pharmaceuticals (NASDAQ:IONS) should find out this quarter if another one of its drugs has what it takes.

Advancing to market

In December, Ionis and collaboration partner Biogen won FDA approval for Spinraza, the first FDA-approved treatment for spinal muscular atrophy (SMA), a life-threatening genetic disease.

Soon, Ionis' collaboration partner GlaxoSmithKline (NYSE:GSK) will report phase 3 trial results for another one of its drugs: IONIS-TTR Rx.

Scientists work together in a lab on next-generation medicine.

Image source: Getty Images.

IONIS-TTR Rx is in development for the treatment of familial amyloid polyneuropathy (FAP), a debilitating and fatal disease caused by a progressive buildup of amyloid plaque deposits in the peripheral nerves, as well as in the heart and kidneys.

If IONIS-TTR Rx is effective and safe in FAP patients, GlaxoSmithKline plans on filing for FDA approval, and if it's eventually approved for sale by regulators, it could become a needle-moving source of royalty revenue for Ionis. According to SEC filings, Ionis will receive tiered royalties of up to the mid-teen percentages on IONIS-TTR Rx sales.

Initially, IONIS-TTR Rx approval would be for use in FAP patients, but it may also prove to be effective in TTR amyloid cardiomyopathy (FAC) patients, and if so, it would significantly increase its addressable patient population.

Over half of the patients participating in GlaxoSmithKline's FAP study also have FAC, and depending on the safety profile in FAC patients, GlaxoSmithKline could rekindle its plans to initiate a phase 3 trial for IONIS-TTR Rx in FAC.

Last year, GlaxoSmithKline decided to hold off on initiating a IONIS-TTR Rx phase 3 study in FAC patients after the FDA said it had some safety concerns about IONIS-TTR Rx in FAC patients. Conceivably, if those safety concerns are adequately addressed by results from the FAP study, then GlaxoSmithKline could pursue an eventual approval in FAC, increasing IONIS-TTR Rx's addressable market by tens of thousands of patients. 

Ionis estimates there are about 10,000 patients with FAP and about 40,000 patients with FAC worldwide. Survival rates for both FAP and FAC are poor, so there's a significant need for new treatment options like IONIS-TTR Rx, which could make it a top seller.

Looking forward

It's anyone's guess if the phase 3 FAP trial will be a success, or if it is, that it will support a phase 3 trial in FAC.

Nevertheless, if IONIS-TTR Rx pans out, it would be an important win for Ionis because it could add meaningful revenue to the company as soon as next year. IONIS-TTR Rx has patent protection until 2031, so eventual commercialization could be a key tailwind to this company's long-term profitability. Because of this, investors will want to keep close tabs on Ionis press releases in the coming weeks.

Todd Campbell has no position in any stocks mentioned. His clients may have positions in the companies mentioned. The Motley Fool owns shares of and recommends Biogen and Ionis Pharmaceuticals. The Motley Fool has a disclosure policy.