The U.S. Food and Drug Administration granted Regeneron Pharmaceuticals' (REGN -1.69%) antibody treatment for the coronavirus authorization late last year. Unlike coronavirus vaccines, the product hasn't yet brought in billions of dollars in revenue. Regeneron reported $262 million in sales of REGEN-COV in the first quarter. And the product hasn't inspired major share gains either. Regeneron shares have increased about 5% year to date.

A new FDA decision, however, could accelerate the REGEN-COV success story. The regulatory agency last week authorized a lower dose of the antibody cocktail. And the authorization includes a change in delivery method. Regeneron now can deliver the treatment by subcutaneous injection. Originally, the authorization only covered administration by infusion. Why do these details matter? Let's take a look at two reasons why the recent regulatory decision could equal billions for Regeneron.

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1. More product ready for delivery

The U.S. government back in January increased its order for Regeneron's antibody cocktail, asking for an additional 1.25 million doses. This new order represents $2.63 billion in revenue -- if Regeneron can deliver. (The government previously offered the company a $450 million contract for the supply of 300,000 doses.)

When Regeneron announced the January deal, it expected to produce 750,000 doses by the June 30 deadline. At that point, the cocktail only was authorized at the 2,400 mg dose level. Now that the FDA has given the nod to a 1,200 mg dose, Regeneron can produce more doses more quickly, because less product is needed for each dose.

Here's how that translates into a win for Regeneron: The biotech company says that at the lower dose level it should be able to deliver at least 1 million doses. The government may accept additional doses through Sept. 30.

So, it seems very likely Regeneron can produce and deliver the full number of doses -- and benefit from the highest level of revenue possible from this contract. And that's thanks to the lower dose. This dose level also will help Regeneron manufacture more product more quickly for other customers. And importantly, less product per treatment -- half of the original dose -- should lower costs over time.

2. A path to widespread use

A major hurdle for companies making antibody treatments for COVID-19 has been the delivery method: typically by infusion in a healthcare setting.

This has meant two challenges. The first is from the professional side of things. Hospitals, overwhelmed with coronavirus patients, sometimes don't have the resources to maintain infusion centers for antibody treatments. This requires space and staff. The second point has to do with patients. Since antibodies are meant for mild to moderate cases, some patients haven't felt ill enough to take the step to go for treatment. They know the administration of infusions involves spending 20 minutes to about an hour in a healthcare setting.

"Unfortunately, to date only a fraction of patients eligible for antibody treatments have received them, which we hope will change based on this updated FDA authorization," George D. Yancopoulos, Regeneron's chief scientific officer, said when announcing the new authorization.

Injections don't require infusion centers -- or a lot of time for administration. That's good news for healthcare providers and patients. This should increase use of Regeneron's antibody cocktail. The more the treatment is used, the more governments will be willing to make bigger orders in the future. That means more revenue for Regeneron.

Regeneron's annual revenue has generally been on the rise for the past decade. And annual profit tops $3.5 billion.

REGN Net Income (Annual) Chart

REGN Net Income (Annual) data by YCharts

The company commercializes seven other products, including blockbuster eye drug Eylea. The new authorization of REGEN-COV adds the possibility of another billion-dollar product to the mix. Regeneron shares may not surge overnight on this news. But for the two reasons above and the company's product portfolio, Regeneron shares are a good bet for long-term investors.