Anthos Therapeutics Announces ~84% of Eligible Patients Have Transitioned to Abelacimab in the AZALEA-TIMI 71 Extension Study of Atrial Fibrillation Patients at a Moderate-to-High Risk of Stroke

CAMBRIDGE, MASS., June 6, 2024 – Anthos Therapeutics, Inc., a clinical-stage company developing innovative therapies for cardiovascular diseases, founded by Blackstone Life Sciences (BXLS), today provided an update on the transition of patients in the open-label extension (OLE) portion of the AZALEA-TIMI 71 study. When the independent data monitoring committee (DMC) recommended that the study be stopped early because of the substantially greater than anticipated reduction in bleeding events favoring abelacimab over rivaroxaban, they also recommended that an optional open-label extension be made available so that all eligible patients could potentially benefit from abelacimab treatment.

“The impressive bleeding reductions with abelacimab in the AZALEA-TIMI 71 study represent a potential game changer for how we treat patients with atrial fibrillation in the future, so it was no surprise when almost 84% of eligible patients, including the vast majority who had been on rivaroxaban during the trial, voluntarily decided to enter the open-label extension to receive abelacimab,” said Dr. Christian T. Ruff, MD, MPH, Principal Investigator of AZALEA-TIMI 71, the Director of General Cardiology at Brigham and Women’s Hospital, Senior Investigator of the TIMI Study Group, an Associate Member of the Broad Institute of MIT and Harvard, and an Associate Professor of Medicine at Harvard Medical School.

The initial results of the AZALEA-TIMI 71 study1 of patients with atrial fibrillation at moderate-to-high risk of stroke were presented at the American Heart Association 2023 scientific congress during a late-breaking session. For the primary endpoint, abelacimab 150 mg dosed once-monthly, demonstrated a highly significant 67% reduction in major or clinically relevant non-major bleeding.¹ In addition, there was a substantial 74% reduction in major bleeding alone and a 93% reduction in gastrointestinal (GI) bleeding, all favoring abelacimab over rivaroxaban, a standard-of-care anticoagulant.1

“We are very pleased that the open-label extension of the AZALEA-TIMI 71 study has completed its transition phase and that the vast majority of eligible patients voluntarily opted to receive abelacimab 150 mg once-monthly moving forward,” said Dr. Dan Bloomfield, Chief Medical Officer of Anthos Therapeutics. “Too many patients with diagnosed atrial fibrillation are not receiving an anticoagulant today or are taking an inappropriate dose, due to the risk or fear of bleeding, the possibility for drug-drug interactions, dosing complications due to age or renal status or just because they forget to take their daily medication. If approved, it is our hope that abelacimab will provide patients with the protection they need against blood clots, but with a placebo-like bleeding profile.”

Atrial fibrillation, or AF, is the most common type of irregular heart rhythm. The most severe complication of AF is stroke,2 which can be prevented by taking an anticoagulant, or “blood thinner.” The Centers for Disease Control and Prevention (CDC) estimates that 12.1 million people in the United States will have atrial fibrillation by 2030.3 However, data from multiple patient registries and claims-based data analyses highlight that approximately 40% to 60% of patients with atrial fibrillation are either not on an anticoagulant or are receiving a sub-therapeutic dose and are thereby not benefiting from the protection that anticoagulants provide. This underuse of anticoagulants has been cited as one of the greatest public health issues facing cardiovascular patients.4

About Abelacimab
Abelacimab is a highly selective, fully human monoclonal antibody that binds to FXI and locks it in the inactive state, preventing the formation of activated FXI (FXIa).

As a monoclonal antibody, abelacimab is not metabolized via the cytochrome P450 system or as a substrate for P-glycoprotein, meaning the risk of drug-drug interactions is very low. There is no need to adjust the dose based on age or renal/hepatic status.

Factor XI inhibition offers the promise of hemostasis-sparing anticoagulation for the prevention and treatment of arterial and venous thromboembolic events.1 Abelacimab is the only Factor XI inhibitor being studied for both conditions.

In patients with atrial fibrillation, abelacimab is planned to be dosed subcutaneously (SC) monthly to maintain near-complete inhibition in a chronic setting. It is also planned to be administered via an initial intravenous (IV) infusion for acute indications requiring immediate onset of action and then followed by subsequent monthly SC administration.

In the AZALEA-TIMI 71 study, abelacimab 150 mg dosed subcutaneously once-monthly, inhibited Factor XI by 99%.1 In a PK / PD study, abelacimab administered IV provided profound suppression of Factor XI within one hour after the start of therapy and maintained near maximal inhibition for up to 30 days.2 In a Phase 2 study published in the New England Journal of Medicine in 2021, a single intravenous dose of abelacimab after knee surgery reduced the rate of venous thromboembolism by 80%, measured 10 days after surgery, compared to enoxaparin.7

Abelacimab received a Fast Track Designation from the FDA in July 2022 for the treatment of thrombosis associated with cancer. In September 2022, abelacimab was also granted a Fast Track Designation for the prevention of stroke and systemic embolism in patients with atrial fibrillation.

Abelacimab is an investigational agent and is not approved for any indication in any country.

About the AZALEA-TIMI 71 Phase 2 Study
The AZALEA-TIMI 71 study was an event-driven, randomized, active-controlled, blinded endpoint, parallel-group study with a primary endpoint that evaluated the effect of two blinded doses of abelacimab relative to open-label rivaroxaban in patients with atrial fibrillation (AF) who are at moderate-to-high risk of stroke. The primary endpoint of the AZALEA-TIMI 71 study was the composite of the rate of major or clinically relevant non-major bleeding events. A secondary endpoint was major bleeding on its own. Patients were randomized 1:1:1 and administered subcutaneous (SC) abelacimab 150 mg once-monthly, abelacimab 90 mg once-monthly, or rivaroxaban 20 mg daily.

With a median follow-up of 21 months, spanning more than 2,000 patient-years, the AZALEA-TIMI 71 study is the largest and longest head-to-head study of a Factor XI inhibitor to provide definitive evidence of a highly significant reduction in bleeding as compared to a standard-of-care anticoagulant.

Summary of Results as Presented During the American Heart Association 2023 Scientific Sessions:1

• Primary endpoint met with a 67% reduction in major or clinically relevant non-major bleeding (CRNM) with abelacimab 150 mg compared with rivaroxaban 20 mg in patients with atrial fibrillation who are at moderate-to-high risk of stroke (P<0.001, HR 0.33, 95% Cl 0.19–0.55)
• 74% reduction in major bleeding alone with abelacimab 150 mg vs rivaroxaban 20 mg (P=0.002, HR 0.26, 95% CI 0.11-0.61)
• 93% reduction in gastrointestinal (GI) bleeding with abelacimab 150 mg vs rivaroxaban 20 mg (P=0.008, HR 0.07, 95% Cl 0.01-0.50)
• 51% reduction in net clinical outcome with abelacimab 150 mg vs rivaroxaban 20 mg (P<0.001, HR 0.49, 95% CI 0.33-0.71)
• Factor XI inhibition of ~99% with abelacimab 150 mg dosed once monthly

The AZALEA-TIMI 71 study enrolled 1,287 patients across 95 global study sites including the U.S. and Canada, Europe and Asia. The independent data monitoring committee (IDMC) recommended that the study end early because of a substantially greater than anticipated reduction in major and clinically relevant non-major bleeding in the abelacimab arms compared to rivaroxaban and a benefit:risk ratio that favored abelacimab. At the same time, the IDMC also recommend that an optional open-label extension period should be made available.

AZALEA-TIMI 71 Open-Label Extension
An optional extension period in order to provide longer-term data was included as part of the AZALEA-TIMI 71 study protocol. It could be initiated if the independent data monitoring committee (IDMC) stopped the study early due to an imbalance of bleeding substantially favoring abelacimab over rivaroxaban, and the benefit:risk clearly favored abelacimab. Investigative sites had the option of participating or not participating in the extension period. Patients who completed the end-of-treatment visit on study treatment and met the eligibility criteria for the extension period had the option to participate or not.

About the LILAC-TIMI 76 Phase 3 Study
The LILAC-TIMI 76 study is an event-driven, randomized, placebo-controlled, double-blind, parallel-group study to evaluate the efficacy and safety of abelacimab relative to placebo on the rate of ischemic stroke or systemic embolism in patients with atrial fibrillation (AF) who have been deemed to be unsuitable for currently available anticoagulation therapy. Patients in the study will be randomized to receive abelacimab 150 mg subcutaneous (SC) or matching placebo once monthly. The study is targeting to enroll approximately 1,900 patients from more than 400 sites in North America, Europe, Latin America, the Middle East and Asia.