FDA clearance of a new IND for GTB-5550 in multiple myeloma (MM) under an investigator sponsored trial (IST) protocol Initiation of Phase 1 trial in MM patients contingent upon timing and receipt of non-dilutive grant funding Phase 1 dose escalation basket trial with GTB-5550 in solid tumor patients continues to actively enroll, with an update anticipated in Q4 2026 Unaudited proforma cash balance as of September 15, 2026 of approximately $11 million anticipated to provide sufficient cash runway into Q3 2027 SAN FRANCISCO, CALIFORNIA, Sept. 15, 2026 (GLOBE NEWSWIRE) -- GT Biopharma, Inc. (the “Company”) (NASDAQ: GTBP), a clinical stage immuno-oncology company focused on developing innovative therapeutics based on the Company's proprietary TriKE® natural killer (NK) cell engager platform, today announced IND clearance from the FDA for GTB-5550 in multiple myeloma.