Aptevo Therapeutics Announces 93% Clinical Benefit Rate in TP53 AML

What Happened

• On September 3, 2026, Aptevo Therapeutics Inc. filed a Form 8‑K (Item 8.01) and issued a press release announcing a 93% clinical benefit rate observed with its mipletamig triplet in evaluable frontline acute myeloid leukemia (AML) patients who have TP53 mutations, a patient population historically difficult to treat. The press release is attached as Exhibit 99.1 to the 8‑K.

Key Details

• Filing date: September 3, 2026 (Form 8‑K, Item 8.01).
• Reported result: 93% clinical benefit rate for mipletamig triplet in evaluable frontline AML patients with TP53 mutations.
• Press release included as Exhibit 99.1 per Item 9.01(d).
• 8‑K was signed by Daphne Taylor, Senior Vice President and Chief Financial Officer.

Why It Matters

• A 93% clinical benefit rate in TP53‑mutant frontline AML, if confirmed in full trial data, represents encouraging clinical activity in a subgroup that historically responds poorly to therapy.
• The filing provides a headline clinical update but does not include enrollment numbers, detailed efficacy endpoints, statistical analysis, safety data, or financial impact. Investors should look for the full data release or follow‑up disclosures for context before drawing conclusions about clinical or commercial implications.