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- Exhibit 99.1 SELLAS Life Sciences Reports Second Quarter 2026 Financial Results and Provides Corporate Update Final Analysis of Phase 3 REGAL Trial of Galinpepimut - S ( GPS ) in Acute Myeloid Leukemia to be Conducted Following the 80th Event - - 28 Patients Enrolled in Phase 2 Trial of SLS009 in Newly Diagnosed First - Line AML ; Topline Data Expected in Q4 2026 - Strong Preclinical Indications of Efficacy of SLS009 in Advanced Pancreatic Cancer Resistant to RAS inhibitors , Clinical Development Preparations Ongoing - - $ 138.3 Million in Cash and Cash Equivalents as of June 30 , 2026 - NEW YORK , NY , August 11 , 2026 -- SELLAS Life Sciences Group , Inc. ( NASDAQ : SLS ) ( “ SELLAS " or the " Company " ) , a late - stage clinical biopharmaceutical company focused on the development of novel therapies for a broad range of cancer indications , today reported financial results for the second quarter ended June 30 , 2026 , and provided a corporate update . " The second quarter was an important period of execution for SELLAS as we continued to advance both of our lead clinical programs , GPS and SLS009 , " said Angelos Stergiou , MD , SCD h.c. , President and Chief Executive Officer of SELLAS . " For GPS , we are approaching the pre - specified 80 th event in the Phase 3 REGAL trial marking a critical step toward the final efficacy analysis and , if successful , a potential BLA submission to the FDA . At the same time , we are making meaningful progress with SLS009 in our ongoing Phase 2 frontline AML study , where dosing continues and enrollment is tracking ahead of industry standards , with topline data expected in the fourth quarter of 2026. In addition , we have obtained promising results from preclinical studies in pancreatic ductal adenocarcinoma ( PDAC ) and intend to support clinical development at a top - tier academic institution . Together , these programs reflect our commitment to developing differentiated therapies that may address significant unmet needs for patients with AML and support meaningful long - term value creation for SELLAS . ” Recent Corporate Highlights : Phase 3 REGAL Trial of GPS : Ongoing Phase 3 trial in AML patients who have achieved complete remission following second - line salvage therapy . The Company will announce when the required pre - specified 80th event occurs , which will trigger the customary database lock , blinded data review procedures before statistical analysis , unblinding , and disclosure of topline results . Ongoing dosing of SLS009 in earlier - line AML : 28 patients have been enrolled , and enrollment and dosing continue in the ongoing 80 - patient Phase 2 trial in newly diagnosed AML patients , including those who become refractory early to AZA / VEN treatment identified through extensive transcriptomics , genomics , and proteomics models . Topline data expected in Q4 2026. Additional information about the trial can be found at clinicaltrials.gov ( NCT04588922 ) .