Full Press Release Details
Ten patients initially deemed unfit for intensive chemotherapy proceeded to stem cell transplant
Transplant rate compares favorably with historical standard-of-care experience, adding to growing clinical evidence supporting mipletamig's potential to improve outcomes in frontline AML
Aptevo expects the RAINIER dose optimization trial to conclude by year-end, with FDA interaction and initiation of a Phase 2 clinical trial anticipated in the first half of 2027
SEATTLE, WA / ACCESS Newswire / October 26, 2026 / Aptevo Therapeutics Inc. (Nasdaq:APVO), a clinical-stage biotechnology company developing novel multispecific immuno-oncology therapeutics, today announced that ten patients with newly diagnosed acute myeloid leukemia (AML) have advanced to allogeneic stem cell transplant following treatment with mipletamig in combination with venetoclax and azacitidine. Stem cell transplant uses donor cells to replace a patient's blood-forming stem cells and can offer eligible patients the possibility of long-term remission or cure.
Notably, ten of 47 (21%) evaluable frontline patients treated with mipletamig in combination with venetoclax and azacitidine (VEN+AZA) proceeded to allogeneic stem cell transplantation, a potentially curative treatment option. This includes nine patients from the ongoing Phase 1b RAINIER trial and one patient from the previously completed dose expansion trial. This finding is particularly encouraging in a patient population initially deemed unfit for intensive induction chemotherapy, where advanced age, underlying health conditions and other factors can limit treatment options. The ability of these patients to proceed to transplant provides an additional encouraging indication of mipletamig's clinical activity in combination with the current standard of care.
The finding is also notable in the context of historical clinical experience with VEN+AZA alone. In the pivotal Phase 3 VIALE-A trial, three of 286 patients (0.7%) receiving VEN+AZA subsequently underwent stem cell transplantation* compared with (21%). Although cross-trial comparisons are limited by differences in patient populations, study design and follow-up, these observations add to the growing body of evidence supporting mipletamig's potential to improve treatment outcomes and help patients reach potentially curative treatment options. *Gangat N, et al. Venetoclax and hypomethylating agent therapy in newly diagnosed acute myeloid leukemia: A Mayo Clinic series and comparison with VIALE-A study. American Journal of Hematology. 2024.
"Each subset analysis helps us better understand the potential of mipletamig in frontline AML," said Dirk Huebner, M.D., Chief Medical Officer of Aptevo. "Our previously reported TP53 findings were particularly encouraging given the historically poor outcomes associated with that mutation. Now, we are seeing ten patients advance to stem cell transplant, a treatment that can offer AML patients the possibility of long-term remission or cure. These observations add another important dimension to the clinical activity we have reported and support continued evaluation of the mipletamig triplet."
Reaching transplant matters and achieving a deep remission is a prerequisite for a successful transplant procedure. Remission reflects a reduction in leukemia, while transplant is an optimal outcome that can offer selected patients the possibility of prolonged remission or cure. Reaching transplant requires an adequate response to initial treatment, medical eligibility, and a suitable donor and treatment plan.
Mipletamig is being evaluated with venetoclax and azacitidine in RAINIER, Aptevo's Phase 1b/2 study in newly diagnosed AML patients who are not eligible for intensive induction chemotherapy. The current stage of RAINIER is evaluating mipletamig dosing to guide the next stage of clinical testing. Aptevo expects to complete this work by year-end 2026 and discuss next steps with regulators in the first half of 2027.
Aptevo's wholly owned lead proprietary drug candidate, mipletamig, is being evaluated for the treatment of AML. Mipletamig is designed to redirect the patient's immune system to destroy leukemic cells and leukemic stem cells expressing CD123, which is overexpressed on leukemic stem cells and AML blasts. Mipletamig 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. Mipletamig is purposefully designed to reduce the likelihood and severity of cytokine release syndrome by using the CRIS-7-derived CD3 binding pathway, an approach that differentiates Aptevo from competitors.
Aptevo Therapeutics Inc. (Nasdaq:APVO) is a clinical-stage biotechnology company focused on developing novel bispecific and trispecific immunotherapies for the treatment of cancer. The Company's lead clinical candidate, mipletamig, is currently being evaluated in RAINIER, a two-part Phase 1b/2 trial for the treatment of frontline acute myeloid leukemia in combination with standard-of-care venetoclax and azacitidine. Mipletamig has received orphan drug designation for AML under the Orphan Drug Act.
In the solid tumor space, Aptevo's lead assets are focused on well-established targets to progress novel immunomodulatory platform backbones that are conditionally active only in the tumor.
This work includes advancing APVO451, a targeted trispecific immunotherapy candidate for solid tumors, and a strategic collaboration with Niowave to develop up to three radiopharmaceutical oncology programs. The first radiopharmaceutical program is expected to target nectin-4, a tumor-associated antigen expressed in multiple solid tumor types. Both preclinical molecules are expected to advance into investigational new drug (IND)-enabling studies in 2027.
The Company's eight pipeline candidates are created using its proprietary ADAPTIR™ and ADAPTIR-FLEX™ platforms, which are designed to generate differentiated multispecific therapeutics. For more information, please visit http://www.aptevotherapeutics.com .
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, statements regarding Aptevo's expectations about the activity, efficacy, safety, tolerability and durability of mipletamig, including in combination with venetoclax and azacitidine; statements related to the progress of the RAINIER trial, including statements related to anticipated clinical and regulatory milestones; statements related to a growing number of patients treated with the mipletamig triplet advancing to stem cell transplant and mipletamig's role in offering AML patients the possibility of long-term remission or cure, statements related to the responses observed in patients with TP53-mutated AML and whether further study of mipletamig in combination with venetoclax and azacitidine will continue to show clinical benefit in patients with TP53-mutated AML; whether Aptevo's strategy will translate into an improved overall survival rate in acute myeloid leukemia (AML); whether the mipletamig data in combination therapy will be indicative of later stage clinical trials; whether Aptevo's strategy will translate into improved overall survival in AML, especially among patient subgroups with poor prognosis; its expectations regarding the effectiveness of its ADAPTIR and ADAPTIR-FLEX platform; development and continued development of Aptevo's current and potential future molecules, including Aptevo's trispecific candidates and their future development and efficacy with respect to addressing multiple solid tumor types; whether pre-clinical studies of Aptevo's trispecific candidates will show the desired anti-tumor efficacy, mechanism of action and safety profile and whether Aptevo's trispecific candidates will function with new mechanisms of action compared to our previous candidates and synergistically induce a biological response; the potential benefits, timing, scope and outcomes of the co-development collaboration with Niowave; and any statements containing the words "may," "continue to," "believes," "expects," "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 are 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. Additional risks and factors that may affect results are set forth in Aptevo's filings with the Securities and Exchange Commission, including its Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2026, and its subsequent reports on Form 10-Q and current reports on Form 8-K. 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 Vice President, Investor Relations & Corporate Communications Aptevo Therapeutics Email: [email protected] or [email protected] Phone: 206-859-6628