aibioAptevo reports 87% clinical benefit in frontline AML through Cohort 5
Tickers APVO
Aptevo says mipletamig data from 31 evaluable frontline AML patients show continued activity, and that the RAINIER trial has entered its final dose-optimization stage.
Key facts
- Company
- Aptevo Therapeutics Inc. (NASDAQ: APVO)
- News type
- Company Updates
- Primary source
- Aptevo Therapeutics Inc. SEC filing (Form 8-K)
Aptevo Therapeutics Inc. (Nasdaq: APVO) reported new clinical results from its RAINIER trial of mipletamig in frontline acute myeloid leukemia (AML) on May 6, 2026. In the press release filed on Form 8-K, the company said that mipletamig given with venetoclax and azacitidine produced an 87% clinical benefit rate and an 81% remission rate across 31 evaluable frontline patients treated to date. Aptevo said the results continued to show a consistent profile of clinical activity and favorable safety as the dataset grew.
Dose selection enters its final stage
With Cohort 5 complete, dosing has progressed through all previously evaluated mipletamig dose levels, the company said. The trial has now entered its final stage. That stage includes two final dose-level cohorts, Cohorts 6 and 7, which represent the highest mipletamig dose levels evaluated so far. Enrollment in Cohort 6 is nearing completion. Two groups of six additional patients will be enrolled at select dose levels, and the first of those groups will enroll at the same time as Cohort 6.
Aptevo said these steps will complete the dataset needed to select the recommended Phase 2 dose (RP2D) and to support the planned Phase 2 regulatory interaction. The Phase 2 study will also dose mipletamig with venetoclax and azacitidine. Chief Executive Officer Jeff Lamothe said: "The data is compelling, the remaining work is clearly defined, and the study is on track for completion this year, with the dataset enabling selection of the Phase 2 dose and our advancement into Phase 2."
Efficacy and safety detail
Within the 31 patients, the company reported a 65% complete remission rate. It said 36% of patients with remissions had the TP53 genetic mutation, a high-risk biomarker typically associated with poor prognosis in AML. Six patients treated to date have gone on to allogeneic stem cell transplant. The release reports no cytokine release syndrome. Aptevo said the results outperform the benchmark set by the Phase 3 VIALE-A trial, which reported a composite CR/CRi rate of 66.4% and a CR rate of 37% for venetoclax plus azacitidine in patients ineligible for intensive induction chemotherapy (DiNardo et al., New England Journal of Medicine, 2020). That is a comparison across different trials and patient groups. RAINIER is an early, open-label dose-finding study with no control arm, and the release gives no p-values, survival or duration of response. The clinical benefit rate includes partial responses, and the safety description is favorable without numbers on other adverse events. The tests of the highest doses are still ahead, so safety at those doses is unknown.
Dirk Huebner, M.D., Chief Medical Officer, said: "Our results demonstrate a consistent pattern of clinical activity and favorable safety across patients treated to date." The company says mipletamig has now been evaluated in more than 120 patients over three trials.
Financial position and what comes next
The company's SEC financial data for 2025 show research and development expense of $14.5 million, up from $14.4 million in 2024. Net loss was $26.0 million for 2025 and $24.1 million for 2024. Cash used in operations was $25.6 million for 2025 and $23.8 million for 2024, and year-end cash and cash equivalents for 2024 were $8.7 million.
Aptevo said it expects to complete RAINIER and select the Phase 2 dose this year, and then move into Phase 2. That is a plan, and the Phase 2 trial would still be early in development, with a regulatory interaction ahead. The release gives no cash balance. The 2025 numbers show a company with no product revenue that used $25.6 million of cash in operations against $8.7 million of cash at the end of 2024, so it will need new financing to run Phase 2, and a raise could dilute current holders. The 10-K describes mipletamig as designed to engage both leukemic cells and T cells and bring them together to trigger the destruction of leukemic cells.