SELLAS Life Sciences’ CDK9 Inhibitor GFH009 Selected for Pediatric Preclinical in Vivo Testing (PIVOT) Program in Pediatric Cancers by the National Cancer Institute

Studies are Supported and Funded Through Cooperative Agreement Grants from the National Cancer Institute

GFH009 to be Evaluated Against Pediatric Solid Tumors and Leukemia Models at Eight Participating Research Institutions

NEW YORK, Dec. 06, 2022 (GLOBE NEWSWIRE) — 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 announced that SELLAS’ highly selective CDK9 inhibitor, GFH009, will be evaluated in pediatric solid tumors and leukemia models through the National Cancer Institute (NCI) Pediatric Preclinical in Vivo Testing (PIVOT) Program.

GFH009 testing through the program involves a two-phase research plan for pharmacokinetics (PK) and efficacy in pediatric tumors. In the first phase, PIVOT principal investigators will conduct PK experiments to confirm the appropriate dose and route administration for GFH009. In the second phase, monotherapy in vivo efficacy testing for GFH009 will be performed by PIVOT investigators. Studies will be supported through cooperative agreement grants from the NCI to the seven PIVOT research programs performing the testing and a centralized coordinating center.

“Participation in the NCI PIVOT Program provides an extensive and invaluable level of expertise in preclinical pediatric cancer testing and we are excited that we were granted this program after a diligent review process. In addition to being a source of non-dilutive funding for our GFH009 program, we also believe this discovery work could ultimately support a path to a rare disease pediatric voucher,” said Angelos Stergiou, MD, ScD h.c., President and Chief Executive Officer of SELLAS. “We are optimistic that the significant anti-tumor activity of GFH009 recently demonstrated in in vitro and in vivo models will be mirrored in PIVOT’s pediatric studies, allowing us to further expand our GFH009 clinical development program to include pediatric tumor types,” continued Dr. Stergiou.

The NCI-supported PIVOT program is a comprehensive program to systematically evaluate novel agents against genomically characterized pediatric solid tumor and leukemia models at eight participating research institutions. By supporting a more reliable agent prioritization process, the PIVOT program contributes to the goal of accelerating discovery of more effective treatments for children with cancer.

Each PIVOT principal investigator has expertise in preclinical testing of childhood cancer in vivo models. These models utilize patient derived xenografts, many of which are refractory to current standard of care treatments, from high-risk childhood cancers and have undergone comprehensive genomic characterization to demonstrate close resemblance to genetic alterations seen in the respective human cancers. Research strategies are based on a substantial body of data showing that preclinical testing in the appropriate pediatric cancer models, combined with expertise on relative drug exposures tolerated in mice and humans, provides powerful insights into likely clinical utility of investigational agents.

PIVOT Program participating institutions and relevant pediatric cancer models are as follows:

• Jackson Laboratory which serves as PIVOT Coordinating Center
• St. Jude Children’s Research Hospital for soft tissue sarcomas including rhabdomyosarcoma
• MD Anderson Cancer Center for osteosarcoma
• University of Texas Health Science Center San Antonio for Ewing sarcoma rhabdomyosarcoma, kidney, and liver cancers
• Memorial Sloan Kettering Cancer Center for pediatric sarcomas and other solid tumors
• Children’s Hospital of Chicago for orthotopic CNS tumors
• Children’s Cancer Inst Australia for acute lymphoblastic leukemia
• Children’s Hospital of Philadelphia for neuroblastoma

About SELLAS Life Sciences Group, Inc.
SELLAS is a late-stage clinical biopharmaceutical company focused on the development of novel therapeutics for a broad range of cancer indications. SELLAS’ lead product candidate, galinpepimut-S (GPS), is licensed from Memorial Sloan Kettering Cancer Center and targets the WT1 protein, which is present in an array of tumor types. GPS has potential as a monotherapy and combination with other therapies to address a broad spectrum of hematologic malignancies and solid tumor indications. The Company is also developing GFH009, a small molecule, highly selective CDK9 inhibitor, which is licensed from GenFleet Therapeutics (Shanghai), Inc., for all therapeutic and diagnostic uses in the world outside of Greater China. For more information on SELLAS, please visit www.sellaslifesciences.com.

Forward-Looking Statements
This press release contains forward-looking statements. All statements other than statements of historical facts are “forward-looking statements,” including those relating to future events. In some cases, forward-looking statements can be identified by terminology such as “plan,” “expect,” “anticipate,” “may,” “might,” “will,” “should,” “project,” “believe,” “estimate,” “predict,” “potential,” “intend,” or “continue” and other words or terms of similar meaning. These statements include, without limitation, statements related to the pre-clinical development of GFH009 and the potential for GFH009 as a drug development candidate. These forward-looking statements are based on current plans, objectives, estimates, expectations and intentions, and inherently involve significant risks and uncertainties. Actual results and the timing of events could differ materially from those anticipated in such forward-looking statements as a result of these risks and uncertainties, which include, without limitation, risks and uncertainties associated with the COVID-19 pandemic and its impact on the Company’s clinical plans and business strategy, risks and uncertainties associated with oncology product development and clinical success thereof, the uncertainty of regulatory approval, and other risks and uncertainties affecting SELLAS and its development programs as set forth under the caption “Risk Factors” in SELLAS’ Annual Report on Form 10-K filed on March 31, 2022 and in its other SEC filings. Other risks and uncertainties of which SELLAS is not currently aware may also affect SELLAS’ forward-looking statements and may cause actual results and the timing of events to differ materially from those anticipated. The forward-looking statements herein are made only as of the date hereof. SELLAS undertakes no obligation to update or supplement any forward-looking statements to reflect actual results, new information, future events, changes in its expectations or other circumstances that exist after the date as of which the forward-looking statements were made.

Investor Contact
Bruce Mackle
Managing Director
LifeSci Advisors, LLC
SELLAS@lifesciadvisors.com