In a few years, Portola Pharmaceuticals (NASDAQ:PTLA) might be selling a leading thrombosis prophylactic, as well as a much needed antidote for the medication. In an effort to bring its antidote to the market quickly, the company may also benefit Bristol-Myers Squibb (NYSE:BMY), Pfizer (NYSE:PFE), Bayer AG, and Johnson & Johnson. Lets take a look at the company's experimental drugs and see how this scenario could play out.

A simpler anticoagulant
Portola Pharmaceuticals may soon turn the world of blood thinners on its head. Less than a year after its IPO, the company has an oral once-daily inhibitor of Factor Xa, named betrixaban, in a pivotal Phase 3 trial for the prevention of blood clots known as venous thromboembolisms (VBTs).

After various types of surgery, patients are typically given enoxaparin as an injection in a hospital setting. The drug itself is safe, but keeping it at an effective level in the bloodstream is difficult. Due to this difficulty, the therapy is typically stopped when they're sent home. Far too often, patients then develop blood clots that pose serious health risks and require rehospitalization.

Betrixaban is a pill that can be taken once daily to continue prevention of VBTs without extensive monitoring. So far, it appears to maintain effective levels in the bloodstream without going overboard. Payers often penalize hospitals if patients are rehospitalized shortly after their discharge. If approved, betrixaban is likely to be very widely prescribed, saving health care providers a bundle.

Inhibition on... inhibition off
Trying to prevent blood clots can create as many problems as it solves. Patients are often treated with Factor Xa inhibitors, like betrixaban, suffer uncontrolled bleeding episodes or require emergency surgery. In either case, the ability to switch off the inhibition of clotting factors can save a life. Unfortunately, physicians do not have an effective switch, but Portola is developing the first.

Portola's most groundbreaking candidate is andexanet alfa, a recombinant protein designed to reverse the anticoagulant activity of Factor Xa inhibitors. Last May, this therapy became the first to demonstrate such a reversal is possible in a clinical study.

Bizarre blood triangles
In the clinical trial mentioned above patients were injected with the anticoagulant Eliquis, which is marketed by Bristol-Myers Squibb and Pfizer. During a more recent proof-of-concept study, patients were dosed with Xarelto, from marketed by Bayer and Johnson & Johnson's subsidiary Janssen.

Andexanet alfa is entering uncharted territory as the first Factor Xa inhibitor antidote. If it wins approval in the future, there's a good chance that regulators will sanction its use in combination with specific anticoagulants, like Xarelto and Eliquis. This could provide a much needed boost to Eliquis, which has been something of a disappointment so far.

Currently, Portola is working under collaboration agreements with all four companies, but recently updated the deal with Bristol-Myers and Pfizer. The partners will work together through phase 3 studies with Eliquis, and any US or EU approvals of andexnet alfa. Some of the details are a bit hazy. What's clear so far, is that Portola will retain full rights to andexanet alfa, and will be entitled to development and regulatory milestone payments from Bristol-Myers and Pfizer. Most importantly for Bayer and Janssen, the partnership is non-exclusive.

Foolish final take
While it seems like things will work out well for all involved, I think Portola has struck a favorable deal with its partners. In effect, the company will get paid to develop a drug, for which it retains full rights. Milestone payments, and possibly sales of andexanet alfa should provide the cash to develop its own long lasting, oral anticoagulant. With just 10 months as a publicly traded company, this young biotech's future won't be without some volatility, but is looking very positive over the long-term.

Editor's Note: A previous version of this article incorrectly stated that the FDA prevented Portola from using its anticoagulant in andexanet alfa studies. The article has been updated and the Fool regrets the error.