Alligator Bioscience and Aptevo Therapeutics Present New Preclinical Data for ALG.APV-527 at the Society for Immunotherapy of Cancer (SITC) 33rd Annual Meeting

Data Show That ALG.APV-527 Selectively Activates and Enhances Tumor-directed T-cell and Natural Killer (NK) Cell Responses

Targets 5T4 Cancer Antigen Present on Many Types of Solid Tumors

Lund, Sweden and Seattle, WA – November 9, 2018 – Alligator Bioscience (Nasdaq Stockholm: ATORX), a biotechnology company developing antibody-based pharmaceuticals for tumor-directed immunotherapy, and Aptevo Therapeutics Inc. (Nasdaq: APVO), a biotechnology company focused on developing novel immuno-oncology and hematology therapeutics, today announced that new preclinical data for ALG.APV-527 are being presented at the Society for Immunotherapy of Cancer's (SITC) 33rd Annual Meeting being held in Washington, D.C., November 9-11, 2018.

ALG.APV-527 is a new immunotherapeutic candidate for the treatment of a variety of 5T4-positive solid tumors. It is designed to induce signaling through the co-stimulatory receptor 4-1BB (CD137), which is present on activated cytotoxic T cells and natural killer (NK) cells.  Once activated, it is designed to promote potent and selective tumor-directed immune activation in the presence of 5T4 antigen-expressing tumor cells, which are present on many different types of solid tumors.

The preclinical data show that ALG.APV-527 localizes to 5T4 positive tumors and selectively stimulates and enhances tumor-directed T cell and NK cell responses, displaying potent anti-tumor effects. Notably, the preclinical in vitro data demonstrated that in the presence of 5T4-positive cells, ALG.APV-527:

  • Increases CD8+ cytotoxic T cells’ ability to secrete the pro-inflammatory cytokine IFN-gamma production, but only in the presence of human tumor cells that display 5T4 at their surface
  • Enhances the cytotoxic profile of NK cells

Additionally, these new data confirm that 5T4 antigen is present on a wide range of tumor types. 5T4-positive tumor cells were detected in tumor samples from NSCLC (non-small cell lung cancer), head and neck, mesothelioma-, pancreatic-, bladder-, renal- and ovarian cancer, but not in normal tissues such as liver or heart.

“The latest preclinical data further strengthen ALG.APV-527’s potential to localize to 5T4-expressing tumors, where it selectively can activate the immune system and enhance tumor specific T cell or NK activation at the tumor site, potentially providing a favorable safety profile while enhancing efficacy.  We are currently compiling a preclinical package with the goal of submitting a clinical trial application (CTA) in late 2019,” said Christina Furebring, Ph.D., Senior Vice President Research at Alligator.

“Our novel bispecific candidate, ALG.APV-527, continues to show promising results in preclinical in vitro and in vivo studies. Featuring target-driven T cell activation, optimized stability, an antibody-like serum half-life of 9 days, and good manufacturing properties. Aptevo and Alligator believe that ALG.APV-527 has the potential to be a unique anti-cancer therapeutic for the treatment of numerous 5T4-expressing solid tumors with high unmet medical need.  We look forward to filing the CTA next year and commencing clinical study of this promising immunotherapy,” said Jane Gross, Ph.D., Chief Scientific Officer for Aptevo.    

The Alligator/Aptevo poster presentation, entitled “Potent Tumor-Directed T Cell Activation and Tumor Inhibition Induced by a 4-1BB x 5T4 ADAPTIR™ Bispecific Antibody is being presented today November 9, 2018 from 12:45pm  – 2:45 pm and 6:30 pm – 8:30 pm ET.

For further information, please visit

About ALG.APV-527
ALG.APV-527 is a bispecific antibody (4-1BB x 5T4) intended for tumor-directed treatment of solid cancers. ALG.APV-527 was built using Aptevo’s ADAPTIR™ bispecific platform and combines binding domains sourced from the ALLIGATOR-GOLD® human scFV library. The ALG.APV-527 bispecific antibody consists of two parts, one part activating tumor-specific T cells through the co-stimulatory receptor 4-1BB, the other part binding to the 5T4 protein displayed on the surface of tumor cells. This enables the immune-activating effect of ALG.APV-527 to be directed specifically to the tumor and not against normal tissue.

About Alligator Bioscience
Alligator Bioscience is a clinical-stage biotechnology company developing tumor-directed immuno-oncology antibody drugs. Alligator’s growing pipeline includes five lead clinical and preclinical drug candidates (ADC-1013, ATOR-1015, ATOR-1017, ALG.APV-527 and ATOR-1144). ADC-1013 (JNJ-7107) is licensed to Janssen Biotech, Inc., part of J&J, for global development and commercialization. Alligator’s shares are listed on Nasdaq Stockholm (ATORX). The Company is headquartered in Lund, Sweden, and has approximately 50 employees. For more information, please visit

About Aptevo Therapeutics Inc.
Aptevo Therapeutics Inc. is a clinical-stage biotechnology company focused on 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 to treat cancer or autoimmune diseases.  Aptevo has two ADAPTIR antibody candidates currently in clinical development and a broad pipeline of novel investigational-stage bispecific antibody candidates focused in immuno-oncology and autoimmune disease and inflammation. For more information, please visit

Safe Harbor Statement for Aptevo
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 13, 2018, as amended, 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.

For Further Information:

Alligator Bioscience
Cecilia Hofvander, Director Investor Relations & Communications
Phone +46 46 286 44 95.

This information is such information as Alligator Bioscience AB (publ) is obliged to make public pursuant to the EU Market Abuse Regulation. The information was submitted for publication, through the agency of the contact person set out above, at 6:00 am CET on November 9, 2018.

Aptevo Therapeutics
Stacey Jurchison, Sr. Director, Investor Relations and Corporate Communications
Phone:  206-859-6628

Updated 2018-11-09