--- title: "Aptevo reports 93% clinical benefit rate" url: "https://aibio.space/news/aptevo-reports-93-percent-clinical-benefit-rate-mipletamig-tp53/" publisher: "aibio.space (Biotech Investor Relations News)" date: "2026-09-03" section: "Company Updates" tickers: "NASDAQ:APVO" source: "https://www.sec.gov/Archives/edgar/data/1671584/000119312526381098/apvo-ex99_1.htm" summary: "Thirteen of 14 evaluable TP53-mutated frontline AML patients treated with mipletamig, venetoclax and azacitidine had clinical benefit, according to Aptevo'" --- By the aibio.space news desk. Sources - [Aptevo Therapeutics Inc. 8-K (2026-09-03)](https://www.sec.gov/Archives/edgar/data/1671584/000119312526381098/apvo-ex99_1.htm) - [Aptevo Therapeutics Inc. 10-K (2026-03-26): business](https://www.sec.gov/Archives/edgar/data/1671584/000119312526126278/apvo-20251231.htm) - [Aptevo Therapeutics Inc. financial data (SEC XBRL)](https://www.sec.gov/Archives/edgar/data/1671584/000119312526126278/) [APVO](https://aibio.space/companies/aptevo-therapeutics/) 2026-09-03 # Aptevo reports 93% clinical benefit rate with mipletamig in TP53-mutated AML Tickers [APVO](https://aibio.space/companies/aptevo-therapeutics/) Thirteen of 14 evaluable TP53-mutated frontline AML patients treated with mipletamig, venetoclax and azacitidine had clinical benefit, according to Aptevo's September 3, 2026 release. ## Key facts - **Company**: Aptevo Therapeutics Inc. (NASDAQ: APVO) - **News type**: Company Updates - **Primary source**: [Aptevo Therapeutics Inc. 8-K (2026-09-03)](https://www.sec.gov/Archives/edgar/data/1671584/000119312526381098/apvo-ex99_1.htm) *An optical research setup with lenses and lasers. CC0, via rawpixel. The picture shows the field, not the companies named.* Aptevo Therapeutics Inc. said on September 3, 2026 that it observed a 93% clinical benefit rate with its mipletamig triplet in evaluable frontline acute myeloid leukemia (AML) patients with TP53 mutations. The release is an [exhibit to an 8-K](https://www.sec.gov/Archives/edgar/data/1671584/000119312526381098/apvo-ex99_1.htm). The company describes TP53-mutated AML as one of the most difficult forms of the disease to treat, with patients who have historically responded poorly to treatment. ## The results Of 14 evaluable TP53-mutated patients treated with mipletamig in combination with venetoclax and azacitidine, two came from the previously completed dose expansion trial. Thirteen of them, or 93%, experienced clinical benefit. Clinical benefit in the release includes complete remission (CR), complete remission with incomplete hematologic recovery (CRi), partial response (PR), and morphologic leukemia-free state (MLFS). Eleven patients achieved CR or CRi, a rate of 79%, and nine of them reached complete remission. The release compares the 79% CR/CRi rate with a published 41% composite remission rate for venetoclax plus azacitidine in treatment-naive patients with poor-risk cytogenetics and TP53-mutated AML. The source of that benchmark is a 2022 article by Pollyea and colleagues in Clinical Cancer Research. Aptevo notes that the benchmark is a comparison across different trials and patient populations. Dirk Huebner, M.D., Chief Medical Officer of Aptevo, said: "TP53-mutated AML remains one of the most challenging AML subpopulations to treat." The release says TP53 mutations can make leukemia cells more resistant to treatment, which makes deep and durable responses in this group particularly difficult to achieve. ## What the numbers do not show The 93% headline rests on 14 patients, two of them from a different, earlier trial. It uses the broadest definition of benefit, which counts partial responses and a morphologic leukemia-free state alongside remissions. The stricter result is nine complete remissions, and 11 of 14 with CR or CRi. The release gives no data on how long the responses lasted, survival, or how many patients went on to transplant in this subgroup. It reports no p-value, and the study is open-label with no control arm, so the comparison with the 41% benchmark is across different trials and populations, as the company concedes. It also says nothing on safety in this subgroup, and it leaves out how many TP53-mutated patients were not evaluable. ## The trial and next steps The release says the RAINIER study is evaluating mipletamig in combination with venetoclax and azacitidine in frontline AML patients who are unfit to receive standard high-intensity chemotherapy. RAINIER is a Phase 1b/2 dose optimization, multi-center, multi-cohort, open-label study. It enrolls adults aged 18 or older who are newly diagnosed with AML and not eligible for intensive induction chemotherapy. The Phase 1b part uses 28-day cycles of treatment across multiple, sequential cohorts, and it is followed by a Phase 2 study. The dose optimization phase is expected to be completed by year-end 2026, and the company plans regulatory interaction in the first half of 2027 to determine next steps. ## The drug and the company According to the release, mipletamig is designed to redirect the patient's immune system to destroy leukemic cells and leukemic stem cells that express CD123. It is designed to engage both leukemic cells and T cells and bring them together to trigger the destruction of leukemic cells. The release says it uses a CRIS-7-derived CD3 binding pathway that is purposefully designed to reduce the likelihood and severity of cytokine release syndrome. Mipletamig has orphan drug designation for AML. The 10-K describes Aptevo as a clinical-stage biotechnology company with two clinical candidates and six preclinical candidates. The XBRL data show research and development expense of $14.5 million for 2025, compared with $14.4 million for 2024. The net loss was $26.0 million in 2025 and $24.1 million in 2024. Operations used $25.6 million of cash in 2025 and $23.8 million in 2024. Year-end 2025 cash and cash equivalents were $21.6 million, according to a 10-Q filed August 14, 2026, and the XBRL data show $9.8 million at June 30, 2026. That is well short of a year of operating cash use, so more financing, with possible dilution, is likely before Phase 2. [Report an error](https://aibio.space/reputation/#correction) ## Companies in this story APVO Aptevo Therapeutics Inc. 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Cite as: aibio.space, "Aptevo reports 93% clinical benefit rate", 2026-09-03, https://aibio.space/news/aptevo-reports-93-percent-clinical-benefit-rate-mipletamig-tp53/