This Day On The Street
Continue to site right-arrow
ADVERTISEMENT
This account is pending registration confirmation. Please click on the link within the confirmation email previously sent you to complete registration.
Need a new registration confirmation email? Click here
$1 buys you full access to ALL of TheStreet's Subscription Services! Learn More

Portola Pharmaceuticals Announces New Phase 2 Results Confirming Immediate, Dose-Dependent And Well-Tolerated Reversal Of Anticoagulation Activity Of XARELTO(R) (rivaroxaban) With Andexanet Alfa (PRT4445*), Investigational Factor Xa Inhibitor Reversal Agent

Stocks in this article: PTLA

NEW ORLEANS and SOUTH SAN FRANCISCO, Calif., Dec. 9, 2013 (GLOBE NEWSWIRE) -- Portola Pharmaceuticals (Nasdaq:PTLA) today announced additional results of a Phase 2 proof-of-concept study that showed andexanet alfa's ability to immediately reverse the anticoagulation activity of XARELTO ® (rivaroxaban) through the administration of a short intravenous bolus. The data also showed that this reversal can be prolonged if needed by a continuous infusion. Andexanet alfa was well tolerated, with no serious adverse events reported. The data were presented at the 55th American Society of Hematology (ASH) Annual Meeting in New Orleans by lead investigator Mark Crowther, M.D., M.Sc., associate chair, Department of Medicine, McMaster University, Hamilton, Ontario.

Andexanet alfa has the potential to be a first-in-class universal antidote designed to reverse the anticoagulant activity of Factor Xa inhibitors in patients who experience an uncontrolled bleeding episode or who require emergency surgery. By the year 2020, Portola estimates that the number of patients presenting to the hospital who could benefit from an antidote may approach 500,000 in the United States, Japan and the five largest European Union countries alone. In November 2013, andexanet alfa was designated as a breakthrough therapy by the U.S. Food and Drug Administration.

"We have now shown that andexanet alfa produces immediate, dose-dependent and well-tolerated reversal of multiple Factor Xa inhibitors. Andexanet alfa's unique flexibility to provide short-term reversal through the administration of an intravenous bolus or sustained reversal by the addition of an extended infusion is critical in covering the multiple clinical scenarios where a reversal agent is needed," said John T. Curnutte, M.D., Ph.D., executive vice president of research and development for Portola. "Importantly, we believe andexanet alfa's highly specific mechanism of action may minimize complications that can be associated with agents that have off-target activity."

Phase 2 Study Design and Results

The randomized, double-blind, placebo-controlled, cohort dose-escalation Phase 2 proof-of-concept study treated healthy volunteers with an oral dose of XARELTO ® at 20 mg once daily for six days and then randomized 36 volunteers in a 6:3 ratio to andexanet alfa in four different dosing cohorts. The first three cohorts received a single IV bolus of andexanet alfa at 210 mg, 420 mg or 600 mg, respectively. A fourth cohort received a single IV bolus of andexanet alfa at 720 mg followed by a 4 mg/minute infusion for one hour.

Immediately following completion of the 210 mg, 420 mg, 600 mg and 720 mg bolus doses of andexanet alfa, anti-Factor Xa activity decreased dose-dependently by 20 percent, 53 percent, 70 percent and 81 percent, respectively, from the pre-andexanet alfa level and returned to placebo levels approximately two hours after treatment. In parallel, the plasma concentrations of unbound XARELTO ® were decreased by 32 percent, 51 percent, 75 percent and 70 percent respectively, relative to pre-andexanet alfa values. XARELTO ®-induced inhibition of thrombin generation and prolongation of both prothrombin time and activated clotting time approached normal levels with andexanet alfa in a dose-dependent manner.

Safety data showed that andexanet alfa was well tolerated, with no thrombotic events or serious adverse events reported. No antibodies to Factor Xa or Factor X were observed in this or other Phase 2 studies, which have included a total of more than 80 volunteers.

1 of 3

Select the service that is right for you!

COMPARE ALL SERVICES
Action Alerts PLUS
Try it NOW

Jim Cramer and Stephanie Link actively manage a real portfolio and reveal their money management tactics while giving advanced notice before every trade.

Product Features:
  • $2.5+ million portfolio
  • Large-cap and dividend focus
  • Intraday trade alerts from Cramer
  • Weekly roundups
TheStreet Quant Ratings
Try it NOW
Only $49.95/yr

Access the tool that DOMINATES the Russell 2000 and the S&P 500.

Product Features:
  • Buy, hold, or sell recommendations for over 4,300 stocks
  • Unlimited research reports on your favorite stocks
  • A custom stock screener
  • Upgrade/downgrade alerts
Stocks Under $10
Try it NOW

David Peltier, uncovers low dollar stocks with extraordinary upside potential that are flying under Wall Street's radar.

Product Features:
  • Model portfolio
  • Stocks trading below $10
  • Intraday trade alerts
  • Weekly roundups
Dividend Stock Advisor
Try it NOW

Jim Cramer's protege, David Peltier, identifies the best of breed dividend stocks that will pay a reliable AND significant income stream.

Product Features:
  • Diversified model portfolio of dividend stocks
  • Alerts when market news affect the portfolio
  • Bi-weekly updates with exact steps to take - BUY, HOLD, SELL
Real Money Pro
Try it NOW

All of Real Money, plus 15 more of Wall Street's sharpest minds delivering actionable trading ideas, a comprehensive look at the market, and fundamental and technical analysis.

Product Features:
  • Real Money + Doug Kass Plus 15 more Wall Street Pros
  • Intraday commentary & news
  • Ultra-actionable trading ideas
Options Profits
Try it NOW

Our options trading pros provide daily market commentary and over 100 monthly option trading ideas and strategies to help you become a well-seasoned trader.

Product Features:
  • 100+ monthly options trading ideas
  • Actionable options commentary & news
  • Real-time trading community
  • Options TV
To begin commenting right away, you can log in below using your Disqus, Facebook, Twitter, OpenID or Yahoo login credentials. Alternatively, you can post a comment as a "guest" just by entering an email address. Your use of the commenting tool is subject to multiple terms of service/use and privacy policies - see here for more details.
Submit an article to us!
DOW 17,810.06 +91.06 0.51%
S&P 500 2,063.50 +10.75 0.52%
NASDAQ 4,712.97 +11.1030 0.24%

Brokerage Partners

Rates from Bankrate.com

  • Mortgage
  • Credit Cards
  • Auto

Free Newsletters from TheStreet

My Subscriptions:

After the Bell

Before the Bell

Booyah! Newsletter

Midday Bell

TheStreet Top 10 Stories

Winners & Losers

Register for Newsletters
Top Rated Stocks Top Rated Funds Top Rated ETFs