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What: Shares of Portola Pharmaceuticals (NASDAQ:PTLA), a clinical-stage biopharmaceutical company focused on developing therapies for thrombosis and other hematologic diseases, dropped by more than 22% as of 11:00 a.m. EST today after the company released data from a phase 3 trial that failed to impress investors.

So what: Portola released top-line results from its Phase 3 APEX trial today, which was a study designed to test how well its experimental drug compound Betrixaban prevented blood blots in acute medically ill patients when compared to the current standard of care, which is Sanofi's (NASDAQ:SNY) injectable drug Lovenox. 

The trial divided the 7,513 patients enrolled in the study into three separate cohorts, and Portola was hoping to show a statically significant improvement in each of them. Patients in cohorts 2 and 3 did manage to show a statistically significant improvement as their p-values came in below the critical threshold level of 0.05. However, patients in cohort 1 achieved a p-value of 0.054, which was a bit higher than the critical threshold level, so the company was not able to call the data statistically significant. 

Now what: Despite the miss, Portola's CEO Bill Lis still believes the rest of the data was strong enough to support a regulatory for Betrixaben. In the release, he stated: The markets are not looking kindly on the news, hence why shares are getting slammed today.

We believe the overall robustness of the efficacy and safety results in this high-risk patient population, including the positive net clinical benefit observed, provide ample evidence to support the submission of an NDA later this year.

Lis' confidence likely stems from the study data that showed Betrixaban was able to reduce the relative risk of venous thromboembolism, or VTE, when compared to Lovenox's in all three of the cohort groups by at least 19%. Since there are more than 1 million cases of VTE reported annually in the G7 countries, and 150,000 patients die from the disease, it's possible regulators might be willing to overlook the small miss and allow the drug to be marketed anyway.

However, despite management's confidence in Betrixaban, Portola's near-term future just got a little bit murkier. Since investors were banking on Betrixaban to eat into a significant slice of the $1.7 billion in sales Sanofi rang up on Lovenox in 2014, it's understandable that shares were sold off today.

Portola still has ambitions to one day become a player in the $10 billion market for anticoagulants, and those dreams still might come true, but given the increased uncertainty, here, I think it makes sense to wait until we have more information before we call this dip a buying opportunity.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.