Studies Challenge Standards to Improve Treatment Outcomes for Patients with Clotting Disorders

ATLANTA, Dec. 8, 2012 /PRNewswire-USNewswire/ -- Studies presented today at the 54th Annual Meeting of the American Society of Hematology (ASH) examine current treatment standards for patients with clotting disorders in an effort to improve outcomes. The studies evaluate long-held treatment standards and whether modifications in intensity and duration of therapy may offer equally effective outcomes while reducing toxicities and relapse rates. 

Although significant advances have been made in delivering new and improved therapies for clotting disorders, treatment still presents challenges; patients must balance the burden of therapy and risk of treatment-related bleeding with the threat of potentially life-threatening clotting. The studies presented today examine how simple strategies in the treatment of polycythemia vera (PV) and venous thromboembolism (VTE) may be safe and help produce more effective results in patients with these disorders.

"It is important to constantly evaluate and challenge standard treatment protocols to ensure that we are utilizing the best possible strategies to treat patients with these serious disorders," said Agnes Y. Lee, MD, moderator of the press conference and Medical Director of the Thrombosis Program and Associate Professor of Medicine at the University of British Columbia and Vancouver Coastal Health in Canada. "Additionally, as we are seeing an increasing number of patients who require ongoing, long-term treatment, it is important to find new ways to improve efficacy and lower the risks of potentially life-threatening complications that accompany these aggressive therapies."

This press conference will take place on Saturday, December 8, 2012, at 2:00 p.m. EST.

A Large-Scale Trial Testing the Intensity of Cytoreductive Therapy to Prevent Cardiovascular Events in Patients with Polycythemia Vera (CYTO-PV trial) [Abstract 4]

In the first randomized clinical trial assessing the proper target hematocrit level, or percentage of red blood cells that should be maintained in patients with polycythemia vera (PV), researchers have concluded that the current recommendation to maintain a hematocrit level of less than 45 percent is associated with a lower risk of thrombosis compared with a less aggressive treatment strategy of maintaining a hematocrit level between 45 and 50 percent.

PV is a rare blood disorder that causes the bone marrow to produce too many red blood cells, making the blood much thicker.This can dramatically increase the risk of blood clots such as deep-vein thrombosis (DVT, a blood clot that forms in a vein deep in the legs) or pulmonary embolism (PE, a blood clot in the lung) and cardiovascular events such as heart attack or stroke. Because thrombosis is the most common cause of death in patients with PV, prompt diagnosis and treatment to reduce the thickness of the blood is critical.

Patients with PV usually have elevated hematocrit levels (approximately 50 to 70%, compared with less than 50% in the general population), which puts them at a higher risk of suffering heart attacks, strokes, and DVT/PE than the general population. In order to reduce this risk, a hematocrit level of less than 45 percent is recommended and initially maintained through phlebotomies. If the hematocrit level cannot be reduced through multiple phlebotomies or disease progression is documented, patients receive hydroxyurea or chemotherapy to eliminate the excess red blood cells. While these two treatment strategies have become widely accepted for PV, until recently no prospective randomized clinical trial has confirmed whether tight control of hematocrit levels below 45 percent successfully prevents or reduces blood clots in patients with PV.

In order to assess the efficacy and safety of maintaining a hematocrit level of lower than 45 percent versus a more liberal approach (keeping hematocrit levels between 45 and 50%), investigators from Italy conducted a study comparing the two strategies among 365 patients with newly diagnosed PV. Patients in Arm A were treated aggressively to maintain hematocrit levels at less than 45 percent, while the patients in Arm B were treated to maintain levels between 45 and 50 percent. The primary composite endpoint was major clots, including stroke, heart attack, transient ischemic attacks ("mini strokes"), clots in the veins in the abdomen, DVT or PE, and cardiovascular death.

The investigators observed that the risk of developing major clots was four times higher in those patients whose hematocrit levels were kept between 45 and 50 percent than in patients whose levels were kept below 45 percent. With the more intensive regimen in Arm A, 1.1 percent of the patients had a major clot versus 4.4 percent in the less aggressive regimen in Arm B. The median hematocrit levels during follow-up were 44 percent and 48 percent, respectively. Treatment with phlebotomy, anti-clotting drugs, and hydroxyurea were comparable.

There was no difference in the safety profile between the regimens. Six patients in Arm A and one patient in Arm B developed myelofibrosis, a blood disorder that causes the bone marrow to be replaced by scar tissue. Researchers observed no statistical difference in the frequency of acute leukemias that occurred in three patients in Arm A and one patient in Arm B. 

"These data validate the notion that it is important to keep hematocrit levels below 45 percent for this population of patients who are at a high risk of developing clotting complications," said Tiziano Barbui, MD, lead author and Professor of Hematology and Scientific Director of the Research Foundation at Ospedali Riuniti di Bergamo in Italy. "The results from our study will be especially important in the development of new drugs for polycythemia vera, as we look to maintain these levels more effectively and with minimal complications."

Dr. Barbui will present this study during the Plenary Scientific Session on Sunday, December 9 at 3:05 p.m. EST at the Georgia World Congress Center in Hall B5, Level 1, Building B.

Two Doses of Apixaban for the Extended Treatment of Venous Thromboembolism [LBA 1]

A large study has found that the new oral anticoagulant apixaban, given at fixed doses without laboratory monitoring, may provide a simple, effective, and safe strategy for the long-term management of venous thromboembolism (VTE). Data showed that apixaban dramatically reduced patients' risk of developing potentially fatal clots without increasing their rate of major bleeding events. 

VTE is the collective name for blood clots in the deep veins of the legs (deep-vein thrombosis or DVT) or lungs (pulmonary embolism). According to the Centers for Disease Control and Prevention, approximately one-third of patients who have suffered a VTE have a recurrence within 10 years.[1] Current VTE treatments include anticoagulant drugs such as warfarin, dabigatran, and rivaroxaban that prevent blood clots from forming or growing larger. While warfarin is effective, it requires regular blood testing and dose adjustment and is associated with the risk of uncontrolled bleeding. Attempts to reduce the intensity of the anticoagulation effect of warfarin (as well as dabigatran and rivaroxaban) to lower the risk of bleeding have been ineffective, as the reduction only led to more frequent recurrent VTE without reducing bleeding risk.

While warfarin reduces the activity of several blood clotting factors, apixaban is different in that it specifically targets the activated factor X, a critically important enzyme responsible for the formation of blood clots. Also unlike warfarin, apixaban can be given in fixed doses and does not require routine laboratory monitoring. Previous studies demonstrate that patients who received a fixed, 2.5 mg dose of apixaban twice daily to prevent VTE after major orthopedic surgery experienced similar outcomes as those who received low-molecular-weight heparin (an injectible anticoagulant). Recent data also show that a twice-daily, 5.0 mg dose of apixaban was safer and more effective than warfarin to prevent stroke in patients with an irregular heart rhythm called atrial fibrillation.

To evaluate whether apixaban may be an effective and safe treatment option for the prevention of recurrent VTE, researchers initiated the AMPLIFY-Extension study, which randomized 2,500 patients with VTE who had already completed a 6-to-12 month course of anticoagulant therapy to receive one of three regimens – apixaban 2.5 mg twice daily, apixaban 5.0 mg twice daily, or placebo – for 12 months. The primary efficacy and safety study endpoints were rates of symptomatic, recurrent VTE; VTE – or cardiovascular-related death; and major bleeding.

Compared to placebo, both doses of apixaban reduced the risk of recurrent VTE and VTE-related death in study participants by approximately 80 percent. While 8.8 percent of the placebo group experienced recurrent VTE or VTE-related death, only 1.7 percent of patients in either the low-dose or high-dose apixaban groups experienced the same outcome. Treatment at either dose also reduced cardiovascular events, including stroke, heart attack, and cardiovascular-related death. Major bleeding rates associated with both the 2.5 mg and 5.0 doses of apixaban were similar to placebo (0.2%, 0.1% and 0.5%, respectively), demonstrating the safety of both doses of apixaban as a long-term VTE therapy. 

"These results indicate that apixaban – at both low and high doses – provides an attractive risk-benefit profile for use as an ongoing treatment option in patients at risk of recurrent VTE," said Giancarlo Agnelli, MD, lead author and Chair of the Steering Committee of AMPLIFY-Extension, Professor of Internal Medicine and Director of the Department of Internal and Cardiovascular Medicine and Stroke-Unit at Perugia University Hospital in Italy. "This regimen has the potential to eliminate many of the challenges we face when we treat patients with warfarin, including drug and food interactions and the need for ongoing monitoring, which can greatly simplify ongoing management of this condition." 

Dr. Agnelli will present this study during the Late-Breaking Abstracts session on Tuesday, December 11, at 7:30 a.m. EST at the Georgia World Congress Center in Hall B5, Level 1, Building B.

American Society of Hematology 54th Annual Meeting
The study authors and moderator will be available for interviews after the press conference or by telephone. Additional press briefings will take place throughout the meeting on new targeted treatment for chronic lymphocytic leukemia (CLL) and hard-to-treat blood disorders, efforts to reduce toxicity and improve survival for blood cancer therapy, and advances in stem cell technology and transplant strategies. For the complete annual meeting program and abstracts, visit www.hematology.org/2012abstracts. Follow ASH (@ASH_hematology) on Twitter (use the hashtag #ASH12 when posting tweets about the meeting) and on Facebook at www.facebook.com/AmericanSocietyofHematology for the most up-to-date information about the 2012 ASH Annual Meeting.

The American Society of Hematology (ASH) (www.hematology.org) is the world's largest professional society of hematologists dedicated to furthering the understanding, diagnosis, treatment, and prevention of disorders affecting the blood. For more than 50 years, the Society has led the development of hematology as a discipline by promoting research, patient care, education, training, and advocacy in hematology. The official journal of ASH is Blood (www.bloodjournal.org), the most cited peer-reviewed publication in the field, which is available weekly in print and online.

[1] Center for Disease Control and Prevention, "Deep Vein Thrombosis/Pulmonary Embolism (DVT/PE): Data & Statistics," http://www.cdc.gov/NCBDDD/dvt/data.html (Accessed November 2012).

SOURCE American Society of Hematology