It was a decision a long time in the making, but the Food and Drug Administration has officially given Portola Pharmaceuticals' (NASDAQ:PTLA) AndexXa the green light. The approval ends a winding road for the company that includes a regulatory rejection, a refiling for approval, and requests for additional information. With a go-ahead finally secured, is this biotech about to become a top stock to buy?

In this clip from The Motley Fool's Industry Focus: Healthcare, analysts Kristine Harjes and Todd Campbell discuss why AndexXa matters to this company's investors.

A full transcript follows the video.

This video was recorded on May 9, 2018.

Kristine Harjes: We want to update you guys about Portola! [laughs] I hope our listeners aren't sick of hearing us talk about this. I was thinking about it earlier today, I knew that we were going to be talking about Portola, and I wish we could make a metric that had captured a ratio between the number of minutes that we've spent discussing a stock on this show relative to that stock's market cap, because Portola would be by far the highest. [laughs]

Todd Campbell: And what crazy ups and downs over the course of the last three years that you and I, and even prior, Michael, [laughs] end up talking about this company and what it was doing to try to improve upon the use of anticoagulants here and worldwide. One of the things that's made that such a roller coaster ride for Portola investors has been its factor Xa anticoagulant reversal agent, Andexxa, which had been filed for approval previously and had been rejected, then got refiled for approval, and now, finally approved.

Harjes: Yes! So, last Friday, we got the news that Andexxa was finally approved by the FDA after a very bumpy road where, honestly, it wasn't looking good. I mean, initially, when we were digging into this company, before it ever applied for approval of Andexxa, we thought the numbers looked really good. And when the application was rejected back in August of 2016, it definitely caught me by surprise. The FDA cited a need for more data demonstrating its ability to reverse factor Xa inhibitory activity. They resubmitted that application last year, but again, in December, we had more bad news when the FDA pushed back its approval decision date to get more time with the data. But, finally, sigh of relief, it was finally approved. The stock gained about 25% on the news, so it was a good day for shareholders.

This is a pretty significant approval. To put some numbers behind it, there are over 100,000 hospital admissions and 2,000 deaths in the United States every month because of bleeding events in patients taking Factor Xa inhibitors, which are this new class of blood thinners or anticoagulants that are increasingly being used in place of Warfarin to prevent stroke or pulmonary embolism and venous thromboembolism. And now, this is the first-ever approved reversal agent.

Campbell: Right. Factor Xa, they work upstream in the coagulation cascade of Warfarin, which is a vitamin K-oriented inhibitor. There's less monitoring, there's less dietary restrictions, and they've been very well received as a result. I think that investors should recognize that it's a really large market. If you look at Eliquis and Xarelto, the two biggest factor Xas that are on the market, their combined sales last year were in excess of $5 billion.

Harjes: Yeah. Which kind of leads us to what else is going on with Portola: this is actually their second approval. Their first approval was for their own factor Xa anticoagulant called Bevyxxa. That was launched back in January of this year after an approval in the summer of 2017. So, if you look at the opportunity for this company, between Bevyxxa and now Andexxa, to me, I think they're still a buy, even at current levels. They're still pretty tiny. They're, what, $2.7 billion in market cap?

Campbell: Yeah, and I think you could make an argument that both of these drugs should generate hundreds of millions of dollars each and could, potentially, at some point, end up reaching blockbuster status. Obviously, we'll need to see a couple of quarters play out and see whether or not, how widely used and embraced they are. I can't imagine, though, that if you're an ambulatory center, if you're a hospital, you're not going to stock Andexxa, especially given how widespread the use of factor Xas are and how much of a need there is to reverse bleeding in these emergency situations.

And then, as far as Andexxa, Lovenox is the drug that that one is displacing. It was approved based on trials competing against Lovenox head to head, and that drug, in its peak, was raking in, I think, $2.5-2.7 billion a year. So, you can make an argument that both of these drugs could be meaningful drugs. And that raises the question, OK, would any other company want to come in and buy Portola? There's reasons to think that there'd be synergies for a company like Bristol-Myers or Pfizer stepping up, because those are the two companies that make Eliquis. And they've also, Kristine, you may remember, licensed the rights to sell Andexxa in Japan, if it ever gets approved there.

It's an interesting story. We wanted to update everybody on it because we've talked so much about it and there's been so many puts and takes over the years.

Harjes: And we will absolutely continue to update, hopefully not excessively. But, whenever there's news, I bet we'll end up talking about it on this show.

Kristine Harjes owns shares of Portola Pharmaceuticals. Todd Campbell owns shares of Pfizer and Portola Pharmaceuticals. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.