Investors

Trial Advancing on Schedule with Dosing in Cohort 6 Set to Begin Shortly;
Dose Levels Now Entering Potential Therapeutic Range
No Evidence of Dose-Limiting Toxicities Observed in Cohort 5
No Evidence of Drug-Induced Anti-Drug Antibodies Observed to Date

SEATTLE, WA / ACCESSWIRE / March 16, 2020 / Aptevo Therapeutics Inc. (NASDAQ:APVO), a biotechnology company focused on developing novel immuno-oncology therapeutics based on its proprietary ADAPTIR™ bispecific technology platform, today provided an update on its ongoing Phase 1/1b clinical trial of APVO436, a novel anti-CD123 x anti-CD3 targeted investigational bispecific antibody therapy being evaluated for the treatment of acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS.)

At present, dosing in cohorts 1 through 5 has been completed with dosing in cohort 6 scheduled to begin shortly. A total of 19 patients have been enrolled and treated with APVO436 to date. No evidence of dose-limiting toxicities was observed in the latest dose cohort (cohort 5.) A dose-limiting toxicity was observed in 1 of 6 patients in cohort 4. Also, importantly, no evidence of drug-induced anti-drug antibodies (ADA) has been observed in the 17 patient blood samples analyzed to date.

One patient in the study with a diagnosis of MDS is currently finishing an 8^th cycle of dosing. Preliminary analysis showed that this patient has achieved a disease assessment of "marrow complete response," which is defined as a bone marrow with ≤ 5% myeloblasts and a decrease ≥ 50% over pretreatment. Changes in peripheral blood measurements are reported separately and this particular patient continues to require platelet and red blood cell transfusions. Aptevo cautions that these data are preliminary.

"The evolving data from our Phase 1 study of APVO436 continues to look promising," said Marvin L. White, President and Chief Executive Officer. "While still preliminary, we are encouraged by the early evidence of a clinical response observed with APVO436 for a patient in cohort 4. Notably, we believe this is a subtherapeutic dose, so the potential clinical activity observed is especially intriguing. Importantly, we are now in a critical phase of the study, as pharmacokinetic modelling suggests that dosing in cohorts 5 through 8 is in a therapeutic range, which could result in potential clinical activity of the drug. We look forward to continuing the dose escalation and monitoring potential clinical responses as we advance through the upcoming dose cohorts."

Aptevo believes that its differentiated ADAPTIR bispecific technology platform has the potential to offer a more convenient and cost-effective solution compared to other immunotherapies such as CAR-T therapies. While CAR-T therapies have proven effective in generating robust and durable treatment responses, they remain challenging and expensive to manufacture and administer to patients. In contrast, bispecific technologies represent a simpler, more competitive ‘off-the-shelf' solution in the rapidly advancing field of cancer immunotherapy.

About APVO436

APVO436 is an optimized bispecific antibody candidate designed to simultaneously target CD123 and CD3 and redirect T-cell cytotoxicity to the tumor. It is currently being evaluated in a Phase 1/1b open-label, dose-escalation study evaluating the safety and pharmacokinetic profile. APVO436 was built on Aptevo's proprietary ADAPTIR protein therapeutic platform. Focused on generating novel, targeted bispecific antibody-based immunotherapies for cancer the ADAPTIR platform offers key advantages over other bispecific formats, derived in part from the flexible and modular nature of the ADAPTIR structure. These advantages include: (i) achieving potent biological activity and extended half-life while retaining desirable manufacturing characteristics; (ii) unique properties for redirecting T-cell cytotoxicity (RTCC) compared to other bispecific platforms, including a favorable cytokine release profile; (iii) ability to achieve target-dependent induction of RTCC at lower concentrations than other bispecific antibody formats; and (iv) flexibility to build ADAPTIR candidates with diverse mechanisms of action, including RTCC, and targeted cytokine release and others.

About Aptevo Therapeutics Inc.

Aptevo Therapeutics Inc. is a clinical-stage biotechnology company focused on developing novel immunotherapies for the treatment of cancer. The Company's lead clinical candidate, APVO436, and preclinical candidates, ALG. APV-527 and APVO603 were developed based on the Company's versatile and robust ADAPTIR™ modular protein technology platform. The ADAPTIR platform is 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