Aptevo Therapeutics Doses First Patient in IXINITY Clinical Trial for Potential Pediatric Label Expansion

Clinical Data Intended to be Used to Support Pediatric Label Expansion for IXINITY

Approximately 1/3 of U.S. Hemophilia B Patients are Under Twelve Years of Age; Pediatric Approval Could Significantly Increase the Addressable Patient Population for IXINITY

SEATTLE, WA / ACCESSWIRE / January 30, 2020 / Aptevo Therapeutics Inc. (NASDAQ:APVO), a biotechnology company focused on developing novel oncology and hematology therapeutics, today announced that the company has begun dosing patients in a Phase 4 clinical trial to evaluate the safety and efficacy of IXINITY® [Coagulation Factor IX (Recombinant)] in previously treated patients under 12 years of age with hemophilia B.

Launched in the United States in 2015 and wholly-owned by Aptevo, IXINITY is an intravenous recombinant factor IX therapeutic for use in people 12 years of age or older with hemophilia B, a hereditary bleeding disorder characterized by a deficiency of clotting factor IX in the blood. According to the World Federation of Hemophilia ‘Report on the Annual Global Survey 2017' approximately 34% of people treated for hemophilia B in the U.S. are 12 years of age or younger.1

"Initiation of the clinical study of IXINITY in younger patients is the next step expanding treatment options for patients with hemophilia B," said Mike Adelman, Senior Vice President, Commercial Operations. "This study, together with the introduction of a 3000 IU range vial last year, reinforces that Aptevo is continuing to execute on new initiatives that will support further growth of IXINITY. According to industry estimates, the addressable U.S. patient population for IXINITY could increase by up to one-third if we are successful in obtaining a pediatric label expansion in the U.S."

A subset of clinical data from the Phase 3 program to support the registration of IXINITY in the U.S. was previously presented by Aptevo. This analysis was drawn from pooled data of 2 prospective, multi-center, non-randomized, open-label studies of 12 children with hemophilia B under the age of 12 years. The data showed that IXINITY appeared to be well tolerated in this pilot subject population and had results comparable to those from the overall patient population studied in the Phase 3 clinical trial of IXINITY.

The current Phase 4 clinical trial is expected to enroll up to 22 patients to evaluate the safety, efficacy, pharmacokinetics and immunogenicity of IXINITY over a period of at least 50 exposure days in patients with hemophilia B who are younger than 12 years of age.

"We are very encouraged by the pediatric subset data from the Phase 3 IXINITY program and are excited to begin this latest study of IXINITY," continued Mr. Adelman. "We look forward to completing this current study and pursuing potential future licensure of IXINITY for the approximately one-third of hemophilia B patients in the U.S who are not included in our present label."

1Source: World Federation of Hemophilia Report on the Annual Global Survey, 2017 (Publication Date: October 2018)

About Hemophilia B

Hemophilia B is a congenital bleeding disorder caused by a deficiency of coagulation factor IX. It affects approximately 1:25,000 male births, with approximately 4,000 persons affected in the U.S. The clinical spectrum may include spontaneous or trauma-induced bleeding into joints, muscles, and soft tissues, resulting in joint damage, reduction in mobility, and severe arthritis, all of which negatively impact health-related quality of life. The primary aim of care is to prevent and treat bleeding by replacing the deficient clotting factor.

About IXINITY

IXINITY is indicated for the control and prevention of bleeding episodes and for perioperative management for adults and children ≥12 years of age with hemophilia B. IXINITY is not indicated for induction of immune tolerance in patients with hemophilia B. IXINITY contains recombinant coagulation factor IX (trenonacog alfa). Trenonacog alfa is a purified single chain glycoprotein derived from Chinese hamster ovary (CHO) cells and has an amino acid sequence that is comparable to the Thr148 allelic form of plasma-derived factor IX. No human or animal proteins are added during any stage of manufacturing or formulation of IXINITY. The recombinant factor IX is purified by a chromatography purification process. The process includes three validated steps for virus inactivation and removal. The process also includes a validated manufacturing step to reduce the presence of CHO proteins in the final drug product.

Indications and Important Risk Information

IXINITY [Coagulation Factor IX (Recombinant)] Lyophilized Powder for Solution for Intravenous Injection is a coagulation factor IX (recombinant) indicated in adults and children ≥ 12 years of age with hemophilia B for control and prevention of bleeding episodes, and for perioperative management. IXINITY is not indicated for induction of immune tolerance in patients with hemophilia B. IXINITY is contraindicated in patients who have known hypersensitivity to IXINITY or its excipients, including hamster protein.

Hypersensitivity reactions, including anaphylaxis, may occur following IXINITY administration. Discontinue use of IXINITY if hypersensitivity symptoms occur and initiate appropriate treatment. Regularly evaluate patients for the development of factor IX inhibitors by appropriate clinical observations and laboratory tests. If expected factor IX activity plasma levels are not attained, or, if bleeding is not controlled as expected with a certain dose, perform an assay that measures factor IX inhibitor concentration. An association between the occurrence of a factor IX inhibitor and allergic reactions has been reported. Individuals with factor IX inhibitors may be at increased risk of severe hypersensitivity reactions or anaphylaxis if re-challenged.

Nephrotic syndrome may occur with IXINITY. Nephrotic syndrome has been reported following attempted immune tolerance induction in hemophilia B patients with factor IX inhibitors and a history of allergic reactions. Thromboembolism may occur when using IXINITY (e.g., pulmonary embolism, venous thrombosis, and arterial thrombosis). Patients may develop hypersensitivity to hamster (CHO) protein as IXINITY contains trace amounts. The most common adverse drug reaction observed in >2% of patients in clinical trials was headache.

Please see full Prescribing Information at www.IXINITY.com.

About Aptevo Therapeutics Inc.

Aptevo Therapeutics Inc. is a clinical-stage biotechnology company focused on developing novel oncology and hematology therapeutics to meaningfully improve patients' lives. Aptevo has a commercial product, IXINITY® coagulation factor IX (recombinant), approved and marketed in the United States for the treatment of hemophilia B, and a versatile core technology – the ADAPTIR™ modular protein technology platform capable of generating highly-differentiated bispecific antibodies with unique mechanisms of action for the treatment of different types of cancer. For more information, please visit www.aptevotherapeutics.com

Safe Harbor Statement

This press release includes forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Any statements, other than statements of historical fact, including, without limitation, statements regarding potential milestone payments, Aptevo's outlook, financial performance or financial condition, Aptevo's technology and related pipeline, collaboration and partnership opportunities, commercial portfolio, milestones, and any other statements containing the words "believes," "expects," "anticipates," "intends," "plans," "forecasts," "estimates," "will" and similar expressions are forward-looking statements. These forward-looking statements are based on Aptevo's current intentions, beliefs and expectations regarding future events. Aptevo cannot guarantee that any forward-looking statement will be accurate. Investors should realize that if underlying assumptions prove inaccurate or unknown risks or uncertainties materialize, actual results could differ materially from Aptevo's expectations. Investors are, therefore, cautioned not to place undue reliance on any forward-looking statement. Any forward-looking statement speaks only as of the date of this press release, and, except as required by law, Aptevo does not undertake to update any forward-looking statement to reflect new information, events or circumstances.

There are a number of important factors that could cause Aptevo's actual results to differ materially from those indicated by such forward-looking statements, including a deterioration in Aptevo's business or prospects; adverse developments in research and development; adverse developments in the U.S. or global capital markets, credit markets or economies generally; and changes in regulatory, social and political conditions. Additional risks and factors that may affect results are set forth in Aptevo's filings with the Securities and Exchange Commission, including its most recent Annual Report on Form 10-K, as filed on March 18, 2019 and its subsequent reports on Form 10-Q and current reports on Form 8-K. The foregoing sets forth many, but not all, of the factors that could cause actual results to differ from Aptevo's expectations in any forward-looking statement.

Contact:

Aptevo Therapeutics
Stacey Jurchison
Senior Director, Investor Relations and Corporate Communications
206-859-6628
JurchisonS@apvo.com

SOURCE: Aptevo Therapeutics Inc.

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