As filed with the Securities and Exchange Commission on January 28, 2026 Registration No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 APTEVO THERAPEUTICS INC. (Exact Name of Registrant as Specified in Its Charter) (State or Other Jurisdiction of Incorporation or Organization) (Primary Standard Industrial Classification Code Number) Delaware 2834 81-1567056 (I.R.S. Employer Identification Number) 2401 4th Avenue ...

Core Insights - Aptevo Therapeutics has entered into a $60 million equity line of credit (ELOC) agreement with Yorkville Advisors Global, LP, enhancing its financial flexibility and extending its funding runway into 2029 [1][2][3] Financial Flexibility - The ELOC allows Aptevo to raise funds incrementally at its discretion under market-based conditions, providing affordable capital financing with minimal fees and no warrants [2][3] - The combination of the ELOC and cash on hand is projected to fund the company for three years, allowing for the achievement of key clinical and preclinical milestones [1][3] Clinical Development - Aptevo's portfolio includes five CD3-engaging assets, with mipletamig being a first-in-class CD123 x CD3 bispecific currently evaluated in a Phase 1b/2 trial for frontline acute myeloid leukemia (AML) [5][7] - Mipletamig has shown high remission rates and a favorable safety profile in over 100 patients across three trials, with no observed cytokine release syndrome events [5][6] Pipeline and Innovation - The company is advancing a portfolio of tumor-directed CD3 programs, including bispecific candidates for prostate cancer and solid tumors, utilizing proprietary CRIS-7-derived CD3 binding domains [6][7] - Aptevo has two clinical candidates and six preclinical candidates targeting various solid tumors, all developed from its ADAPTIR and ADAPTIR-FLEX platforms [7]

As filed with the Securities and Exchange Commission on October 1, 2025 Registration No. 333- UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM S-1 REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 APTEVO THERAPEUTICS INC. (Exact Name of Registrant as Specified in Its Charter) Delaware 2834 81-1567056 (State or Other Jurisdiction of Incorporation or Organization) (Primary Standard Industrial Classification Code Number) (I.R.S. Employer Identification Number) 2401 4th Avenue, ...