Aptevo Therapeutics Plans a Phase 2 Trial in 2H23 in Frontline and Relapsed/Refractory Patients who are Venetoclax Treatment Naïve

Data Demonstrating APVO436 to be Safe and Well-Tolerated and Clinically Active Among AML Patients in Both Combination and Monotherapy Regimens Presented at the 64^th American Society of Hematology (ASH) Annual Meeting and Exposition

SEATTLE, WA, December 12, 2022 -- Aptevo Therapeutics Inc. ("Aptevo" or the "Company") (NASDAQ:APVO), a clinical-stage biotechnology company focused on developing novel immuno-oncology therapeutics based on its proprietary ADAPTIR™ and ADAPTIR-FLEX™ platform technologies, today announced that APVO436, in combination with venetoclax and azacitidine, achieved a 100% clinical benefit rate (CBR) in venetoclax treatment naïve AML patients. The data, which was presented in a poster session at the 64^th American Society of Hematology (ASH) Annual Meeting and Exposition in New Orleans, also showed that APVO436, when given in combination with this standard-of-care regimen, was observed to be generally safe and well tolerated.

Aptevo plans to initiate a Phase 2 trial in the second half of 2023 to further evaluate APVO436 in combination with venetoclax and azacitidine among frontline and relapsed/refractory AML patients who are venetoclax treatment naïve.

"The results of this APVO436 study are encouraging. More specifically, the combination of APVO436 with venetoclax and azacitidine (triple therapy) shows exciting potential, particularly in the venetoclax-naïve patient population," said Justin M. Watts, MD, Associate Professor of Medicine, Chief, Leukemia Section at the University of Miami Sylvester Comprehensive Cancer Center and lead author of the poster. "A larger Phase 2 trial of APVO436 in combination with venetoclax and azacitidine will be important to further explore its potential to improve outcomes in this AML patient population with high unmet need."

In the Phase 1b trial cohort 2, a total of 16 response-evaluable patients received the combination therapy of venetoclax and azacitidine with APVO436 and 75% experienced clinical benefit. 100% of patients in this cohort who had not received venetoclax previously, experienced clinical benefit; a favorable outcome with respect to a variety of response categories including CR, CRi and MLFS.

The combination of venetoclax and azacitidine with APVO436 in venetoclax treatment naïve response-evaluable patients in cohort 2 outperformed a composite benchmark across all clinical benefit categories as shown below.

"Based on these positive outcomes we will prepare for a Phase 2 trial initiation in the second half of 2023, focused on evaluating frontline and relapsed/refractory AML patients who are venetoclax treatment naïve and who will be treated with the combination of APVO436 plus standard-of-care venetoclax and azacitidine, where the clinical benefit in a subset of cohort 2 patients in the current trial is 100%," said Dirk Huebner, MD, Chief Medical Officer of Aptevo Therapeutics. "The results we observed in this study inform and support advancing APVO436 in the clinic, while also validating our platform technology. The data also show clinical activity, safety and tolerability in both combination and monotherapy settings."

Additional Results

Aptevo's ongoing Phase 1b expansion trial in both combination and monotherapy, will enroll adult patients (aged ≥18 years) with AML, at different disease stages, into five different cohorts of up to approximately 18 patients each. Current results are being reported for combination cohorts 1 and 2, and monotherapy cohorts 3 and 5. Trial enrollment for cohort 3 is ongoing while enrollment for cohorts 1 and 2 has finished. Additional data and observations include the following:

• Clinical activity was observed in both monotherapy and combination cohorts
  • Monotherapy activity observed in cohort 3
  • APVO436 Safety: APVO436 has been observed to be generally well tolerated in both combination therapy and monotherapy
    • CRS was observed in fewer than one-quarter of patients within the safety population and in most cases was mild or moderate (grade 1 or 2) and was manageable in the clinic
    • Side effects were generally manageable and resolved while patients remained on treatment

"We are very excited about the data reporting out today because it shows that our lead candidate, APVO436, has the potential to impact the AML treatment paradigm in a meaningful way that could truly benefit patients. The data also provide additional evidence for safety and tolerability in both combination therapy and monotherapy. Further, we observed a 100% clinical benefit in a patient population that supports advancement of APVO436 into Phase 2 evaluation," said Marvin L. White, President and CEO of Aptevo Therapeutics. "From a business perspective, this represents a win because first, we have positive data to report from the trial and second, we will use the data to inform the Phase 2 protocol and implement a trial with the highest probability of success."

To view the abstract, click here.

About Aptevo Therapeutics Inc.

Aptevo Therapeutics Inc. is a clinical-stage biotechnology company focused on developing novel immunotherapies for the treatment of cancer. Aptevo is seeking to improve treatment outcomes of cancer patients. For more information, please visit www.aptevotherapeutics.com.

About APVO436

APVO436 is a bispecific CD3xCD123 ADAPTIR currently in Phase 1b development in a multi-center, multi-cohort trial designed to evaluate safety, tolerability and efficacy in combination therapy and monotherapy for patients with AML. The Company plans to initiate a Phase 2 trial, evaluating APVO436 in combination with venetoclax and azacitidine in patients with AML who are venetoclax treatment naïve, in 2H23.

Overexpression of CD123 is the hallmark of many forms of leukemia. Aptevo's lead proprietary drug candidate, APVO436 is a bispecific CD3xCD123 ADAPTIR that is designed to redirect the immune system of the patient to destroy leukemia cells expressing the target CD123 molecule on their surface. This antibody-like recombinant protein therapeutic is designed to engage both leukemia cells and T-cells of the immune system and bring them closely together to trigger the destruction of leukemia cells. APVO436 has been engineered using Aptevo's proprietary and enabling bioengineering methods and is designed to reduce the likelihood and severity of cytokine release syndrome (CRS). APVO436 has received orphan drug designation ("orphan status") for AML according to the Orphan Drug Act.