Aptevo Therapeutics Provides Pipeline Update

• Breast cancer patient who improved from a progressive disease diagnosis to an over nine-month sustained stable disease diagnosis has now successfully transitioned to a higher dose level, accessing the potential for greater clinical benefit in the ALG.APV-527 clinical trial
  • Cohort 5 dosing imminent, trial more than 50% enrolled
• APVO436 Phase 1b/2 dose optimization trial initiation expected 1H 2024
  • Premier CRO, Prometrika, engaged as partner for dose optimization trial to evaluate APVO436 in frontline AML in combination with venetoclax + azacitidine in venetoclax naïve patients
• APVO711 demonstrates its ability to induce tumor killing properties in preclinical studies
  • APVO711 dual mechanism checkpoint inhibitor with unique precision targeting capabilities progressing towards IND

SEATTLE, WA / ACCESSWIRE / April 10, 2024 / Aptevo Therapeutics Inc. (NASDAQ:APVO), a clinical-stage biotechnology company focused on developing novel immune-oncology therapeutics based on its proprietary ADAPTIR™ and ADAPTIR-FLEX™ platform technologies, today announced advancements in both clinical programs and one preclinical program.

A heavily pretreated breast cancer patient, enrolled in the ALG.APV-527 Phase 1 open-label, multi-center, multi-cohort trial for the treatment of multiple solid tumor types, entered the trial and improved from progressive disease to long-lasting stable disease (SD) while on therapy. The patient has remained on study for more than nine months and been successfully transitioned to a higher dose level, which may allow for increased clinical benefit. The trial is more than 50% enrolled and dosing in cohort five (of six) is imminent.

"I'm encouraged by the promise that ALG.APV-527 brings to the treatment of solid tumor patients. Witnessing a patient maintaining a stable disease, especially for more than nine months, and then moving to a higher dose level within a Phase 1 trial is uncommon, but we believe it can be therapeutically beneficial for this patient and is a testament to the drug's clinical potential," stated Dirk Huebner, MD, Chief Medical Officer at Aptevo.

The Company is on track to initiate part 1 of its upcoming two-part Phase 1b/2 trial in 1H 2024. The study will further evaluate APVO436 for the treatment of acute myeloid leukemia (AML). Aptevo has partnered with premier CRO, Prometrika, for the upcoming study. The first part is a dose optimization trial evaluating standard of care venetoclax + azacitidine along with APVO436 as a frontline treatment for AML patients. It is planned as an open-label, multi-center, multi-cohort study. The trial will evaluate safety/tolerability and efficacy of the triplet combination at multiple dose levels.

The therapeutic combination of venetoclax + azacitidine + APVO436 was selected based on outcomes from the Company's dose expansion trial that showed promising outcomes across all categories of evaluation including safety, efficacy, and duration of remission.

"We are eager to initiate the next phase of development in support of lead candidate APVO436 as a therapeutic option in combination therapy for the treatment of AML," said Marvin White, President and CEO of Aptevo. "APVO436 results have been positive across the board. For example, we demonstrate an exemplary safety profile, noting that patients experienced cytokine release syndrome at rates that are about one-third the benchmarks demonstrated in literature. Similarly, efficacy results demonstrate clinical responses that are almost double the benchmarks in literature. We anticipate that our dose optimization results will reinforce our growing body of data and demonstrate the clinical potential of APVO436 in patients with frontline AML."

APVO711 is currently progressing through preclinical evaluation intended to target a broad range of solid tumors. The Company continues to move this anticancer checkpoint inhibitor with added dual mechanism of action functionality toward the clinic. Key learnings to date include:

• APVO711 imparts beneficial attributes to both antigen presenting cells and T cells that boost the immune response targeted at controlling tumor cells
• Experiments in cultured cells have confirmed that APVO711 enhances tumor cell killing by T cells
• In vivo studies have confirmed that APVO711 reduces the size of PD-L1-expressing tumors

"We are pleased with the progress we have made to date in preclinical studies for our dual mechanism checkpoint inhibitor APVO711. This PD-L1 x CD40 molecule, represents an anticancer approach that combines a checkpoint inhibitor with a potent immune mediator. This innovative therapeutic strategy holds promise for unleashing the full potential of the immune system to combat cancer, offering new hope for patients in need of more effective treatments," said Michelle H. Nelson, Ph.D., Director of Immunobiology at Aptevo Therapeutics.

More About the Programs

ALG.APV-527
ALG.APV-527 is a conditional 4-1BB agonist bispecific that is designed for activation only upon simultaneous binding to 4-1BB and 5T4. It is designed to target cancer cells by activating both T cells and natural killer cells and is intended to bind to tumor-specific antigens while sparing healthy cells and maximizing immune response. This has the potential to be clinically important because 4-1BB can stimulate the immune cells (antitumor-specific T cells and NK cells) involved in tumor control, making 4-1BB a particularly compelling target for cancer immunotherapy. The compound is currently being evaluated for multiple solid tumor types in a multi-center, dose escalation trial that is more than 50% enrolled.

Additional promising preliminary data includes:

• In addition to the patient described above, a second heavily pretreated breast cancer patient who was progressing prior to enrolling in the trial has sustained long lasting stable disease and remained on study drug for seven months. Analysis demonstrated measurable level of drug in circulation (pharmacokinetic) and reproducible elevation of serum pharmacodynamic markers with dosing, suggesting the drug is biologically active
• Treatment to date has been overall well-tolerated, and a maximum tolerated dose has not yet been determined, dose-escalation in higher-dose cohorts is ongoing as the Company moves into cohort five (of six)
• ALG.APV-527 has been measurable in all patients with plasma concentration of ALG.APV-527 consistent with the administered dose
• Biomarker analyses indicate the expression of the targets (4-1BB and 5T4) in tumor biopsies and confirm biological activity of ALG.APV-527

"We are excited by the emerging data from the ALG.APV-527 clinical trial, indicating biological activity and generating stable disease even at the lowest dose levels tested in heavily pretreated patients. This molecule is engineered to target cancer cells while preserving healthy tissues, all the while amplifying a specific immune response. We eagerly anticipate sharing forthcoming data and continuing to unveil the immense potential of this bispecific candidate in the solid tumor space," expressed Dirk Huebner, MD, Chief Medical Officer at Aptevo.

APVO436
Aptevo's wholly owned lead proprietary drug candidate, APVO436 is targeting AML and is differentiated by design to redirect the immune system of the patient to destroy leukemic cells and leukemic stem cells expressing the target antigen CD123, which is a compelling target for AML due to its overexpression on leukemic stem cells and AML blasts . This antibody-like recombinant protein therapeutic is designed to engage both leukemic cells and T cells of the immune system and bring them closely together to trigger the destruction of leukemic cells. APVO436 is purposefully designed to reduce the likelihood and severity of CRS by use of a unique CD3 derived from CRIS-7 vs. the CD3 used by other competitors. APVO436 has received orphan drug designation ("orphan status") for AML according to the Orphan Drug Act.

The Phase 1b Dose escalation trial results showed a 91% clinical benefit rate in combination with venetoclax + azacitidine in venetoclax naïve patients, a 27% incidence of CRS across all trial cohorts (the majority were grades 1 & 2) and meaningful duration of remission, including three patients who transitioned to transplant after receiving therapy, the best possible outcome for AML patients.

The Company is planning to commence the first part of the Phase 1b/2 dose optimization program in the first half of 2024.

APVO711
APVO711, a bispecific checkpoint inhibitor with added functionality, targets PD-L1 and CD40, and is designed to function to synergistically induce a biological response. This is achieved by simultaneously engaging in two clinically validated T cell activating mechanisms: 1) blocking of PD-L1/PD-1 inhibitory pathway and 2) CD40 signaling augments APC maturation resulting in enhanced T cell stimulation. APVO711 is designed to activate CD40 only in the presence of PD-L1 binding for an improved safety profile. The Company believes APVO711 has the potential to positively impact the treatment paradigm of multiple solid tumor types for which there is currently significant unmet medical need.

About Aptevo Therapeutics Inc.
Aptevo Therapeutics Inc. is a clinical-stage biotechnology company focused on developing novel immuno-oncology therapies for the treatment of cancer. Aptevo is seeking to improve treatment outcomes for cancer patients. 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. All statements, other than statements of historical fact, including, without limitation, Aptevo's expectations about the activity, efficacy, safety, tolerability and durability of its therapeutic candidates and potential use of any such candidates, including in combination with other drugs, as therapeutics for treatment of disease, its expectations regarding the effectiveness of its ADAPTIR and ADAPTIR-FLEX platforms, statements related to the progress of Aptevo's clinical programs, including statements related to anticipated clinical and regulatory milestones such as Phase 1b/2 trial initiation for APVO436 in frontline, venetoclax naïve AML patients, whether further study of APVO436 in a Phase 1b dose optimization trial focusing on multiple doses of APVO436 in combination with venetoclax + azacitidine on a targeted patient population will continue to show clinical benefit, whether Aptevo's final trial results will vary from its earlier assessment, whether biomarker analyses will continue to confirm biological activity of ALG.APV-527, whether higher dose ranges will result in increased signs of clinical activity, whether further study of ALG.APV-527 across a cross section of multiple tumor types will continue to show clinical benefit, the possibility and timing of interim data readouts for ALG.APV-527, whether Aptevo's final trial results will vary from its preliminary or interim assessments, the possibility and timing of preliminary or interim data readouts for ALG.APV-527, statements related to the progress of and enthusiasm for Aptevo's clinical programs, whether pre-clinical studies of APVO711 will show the desired anti-tumor efficacy, mechanism of action and safety profile, whether APVO711 will demonstrate the ability to fight a range of solid malignancies, statements related to the progress towards an IND filing for APVO711, statements related to Aptevo's ability to generate stockholder value, whether Aptevo will continue to have momentum in its business in the future, and any other statements containing the words "may," "continue to," "believes," "knows," "expects," "optimism," "potential," "designed," "promising," "plans," "will" and similar expressions are intended to identify 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.

There are several 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; further assessment of preliminary or interim data or different results from later clinical trials; adverse events and unanticipated problems, adverse developments in clinical development, including unexpected safety issues observed during a clinical trial; and changes in regulatory, social, macroeconomic and political conditions. For instance, actual results may differ materially from those indicated by such forward-looking statements as a result of various important factors, including the uncertainties inherent in the results of preliminary or interim data and preclinical studies being predictive of the results of later-stage clinical trials, initiation, enrollment and maintenance of patients, and the completion of clinical trials, the availability and timing of data from ongoing clinical trials, the trial design includes combination therapies that may make it difficult to accurately ascertain the benefits of APVO436, expectations for the timing and steps required in the regulatory review process, expectations for regulatory approvals, the impact of competitive products, our ability to enter into agreements with strategic partners or raise funds on acceptable terms or at all and other matters that could affect the availability or commercial potential of Aptevo's product candidates, business or economic disruptions due to catastrophes or other events, including natural disasters or public health crises such as the coronavirus (referred to as COVID-19), geopolitical risks, including the current war between Russia and Ukraine and the rising conflict in the Middle East, and macroeconomic conditions such as economic uncertainty, rising inflation and interest rates, continued market volatility and decreased consumer confidence. These risks are not exhaustive, Aptevo faces known and unknown risks. Additional risks and factors that may affect results are set forth in Aptevo's filings with the Securities and Exchange Commission, including its Annual Report on Form 10-K for the fiscal year ended December 31, 2023, 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. Any forward-looking statement speaks only as of the date of this press release, and, except as required by law, Aptevo does not assume any obligation to update any forward-looking statement to reflect new information, events, or circumstances.

CONTACT:
Miriam Weber Miller
Head, Investor Relations & Corporate Communications
Aptevo Therapeutics
Email: IR@apvo.com or Millerm@apvo.com
Phone: 206-859-6628

SOURCE: Aptevo Therapeutics