The Food and Drug Administration (FDA) often sends new drug applications back to pharmaceutical companies with requests for more evidence. Recently, Pfizer had the somewhat unusual experience of actually coming back with data that satisfied the agency.

The company's newly approved treatment, Vyndamax, also known as tafamidis, is priced like a rare disease drug, at around $225,000 per year. There are enough people out there suffering from the conditions it's approved for to easily drive 10-figure annual sales, but it's far from guaranteed that Pfizer will be able to take a leading share in this increasingly crowded market.

Company TTR Treatment FDA-Approved Indication
Pfizer (NYSE:PFE)  Vyndamax ATTR-CM
Alnylam Pharmaceuticals (NASDAQ:ALNY) Onpattro hATTR-PN
Akcea Therapeutics (NASDAQ:AKCA) Tegsedi hATTR-PN
Eidos Therapeutics (NASDAQ:EIDX) AG10 N/A 

Data source: Company press releases.

Vyndamax is a once-daily capsule with a lower dosage than its predecessor, Vyndaqel, which earned approval in the EU eight years ago. European sales of Vyndaqel have been so disappointing that Pfizer doesn't bother reporting them. But Vyndamax has a much better chance to break through the $1 billion-per-year annual revenue barrier after its U.S. launch -- that is, unless an experimental drug from a tiny biotech start-up continues to succeed.

Stabilizing a troublesome transporter

Transthyretin (TTR) is an important transport protein that carts thyroid hormones and vitamin A to places in the body where they're needed. Unfortunately, TTR tends to fall apart, and the little amyloid fragments that break off get stuck in all sorts of places they shouldn't be, including the heart and the peripheral nervous system. 

Vyndamax recently became the first and only TTR stabilizer to earn approval for the treatment of patients at risk of heart failure due to cardiomyopathy caused by TTR-mediated amyloidosis (ATTR-CM). This first-mover status isn't the only advantage for Pfizer's drug.

Guy in a suit clearing a hurdle.

Image source: Getty Images.

Hardly a contest

Vyndamax isn't as interesting or as effective as Onpattro and Tegsedi, both of which target RNA to prevent the production of TTR at its source. Pfizer's once-daily capsule simply helps the transporter stay together.

But Onpattro and Tegsedi are currently approved specifically to treat hereditary ATTR that leads to severe polyneuropathy (hATTR-PN). Neither is approved to treat the much larger ATTR-CM population, which means Pfizer could have that space to itself for at least a year or two. 

There are an estimated 10,000 people worldwide with hATTR-PN, which is why Alnylam is rapidly developing more new drug candidates. Alnylam also plans to begin a study in the middle of 2019 that could expand Onpattro's approval to include an estimated 40,000 hATTR-CM patients.

If Alnylam or Akcea succeed at expanding their ATTR treatments into Pfizer's turf, it still won't be a problem for the pharmaceutical giant. An estimated 400,000 people worldwide have wild-type ATTR-CM, which isn't inherited and occurs more frequently with age. Since Vyndamax is currently the only treatment available to slow the progression of wild-type ATTR-CM, Pfizer will have this population all to itself.

Trouble ahead?

Pfizer doesn't need to worry about competition for wild-type ATTR-CM patients from Alnylam or Akcea, but it does have to keep an eye on a much smaller biotech. Eidos Therapeutics made its stock market debut less than a year ago, and its lead candidate, AG10, could make a lot of trouble for Vyndamax in a few short years.

In a midstage study with both types of ATTR-CM, the average patient receiving a high dose of AG10 showed a 51% increase in serum TTR levels. Moreover, 15 out of 31 patients treated with AG10 had serum TTR levels below the normal range, and all 15 returned to the normal range after treatment with AG10.

Guy in a suit on a ladder with binoculars.

Image source: Getty Images.

Eidos has rushed AG10 into a phase 3 study that will measure how far patients treated with the drug can walk in six minutes compared to those given a placebo. According to Eidos, the FDA is willing to review an application for AG10 to treat the same patients as Vyndamax based on six-minute walk test results after 12 months of treatment. 

The average patient treated with Vyndamax lost 27 meters after 12 months of treatment against a loss of 59 meters among the placebo group. If AG10 can beat these numbers, or at least get close, the FDA appears ready to grant Eidos' candidate a conditional approval while waiting for 30-month hospitalization data to mature. At 30 months, Vyndamax reduced the risk of heart-related hospitalizations by 32%, which won't be an easy number to beat. 

Returning to growth

With the ATTR-CM patient population all to itself for at least a couple of years, Vyndamax has "future blockbuster sales" written all over it, and it's not the only young drug in Pfizer's product line on the way up. Talzenna recently earned approval to treat a cross-section of newly diagnosed breast cancer patients. Talzenna capsules reduced patients' risk of disease progression or death by 46% compared to standard care.

Pfizer's popular nerve pain drug, Lyrica, loses market exclusivity in the U.S. in June, and the sales declines that will follow will make it hard for the company to grow revenue in 2019. But after June, Pfizer will enter a six-year period when it won't have any major patent expirations. The arrival of Vyndamax in the U.S. market, plus a slate of recently launched blockbusters-to-be, could make 2020 the beginning of Pfizer's next golden age of growth.

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