SELLAS Life Sciences’ GFH009 Demonstrates Cancer Cell Growth Inhibition in Preclinical In Vitro Studies in Solid Cancer and Acute Myeloid Leukemia Cell Lines

– Results Demonstrate Significant Anti-Tumor Effects on All Selected Cell Lines –

– In Three of the Four Cell Lines, GFH009 Inhibited Cancer Growth by 90 to 100 Percent –

NEW YORK, Aug. 09, 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 results from preclinical in vitro studies for its highly selective CDK9 inhibitor, GFH009, in solid cancer and acute myeloid leukemia (AML) cell lines. The data shows that GFH009 demonstrated significant anti-tumor effects in all four selected cell lines. In three out of the four cell lines, GFH009 inhibited cancer cell growth by 90 to 100 percent.

The in vitro studies were conducted at an independent, third-party contract research organization, Translational Drug Development (TD2), and the following cell lines were selected for the studies based on their unique characteristics, combined with GFH009’s mechanism of action:

• RH30: a pediatric soft tissue sarcoma cell line that is a model for studying high-risk pediatric rhabdomyosarcoma, an indication for which currently available treatments are limited to high-dose chemotherapy with unsatisfactory results. RH30 cells are driven by PAX3-FOXO1, a transcription factor whose expression is strictly needed for tumor cell survival. RH30 is also dependent on MYCN, a major target of CDK9 inhibition. Treatment with GFH009 resulted in 90 percent or more cancer inhibition at dose levels equivalent to those already demonstrated to be safe in patients in the ongoing Phase 1 trial with no viable cancer cells at the highest dose levels.
• NCI-H209: a small cell lung cancer cell line characterized by the loss of function of two major tumor suppressor genes, RB1 and TP53. This cell line also expresses MCL-1, a major target of CDK9 inhibition. Treatment with GFH009 resulted in 90 percent or more cancer inhibition at dose levels equivalent to those already demonstrated to be safe in patients in the ongoing Phase 1 trial with no viable cancer cells at highest dose levels.
• SKOV-3: an ovarian cancer cell line containing the wild type BRCA1 gene and highly expresses CDK9. Treatment with GFH009 resulted in more than 50 percent cancer inhibition at dose levels equivalent to those already demonstrated to be safe in patients in the ongoing Phase 1 trial.
• OCI-AML-2: an AML cell line that develops resistance to the chemotherapy venetoclax on exposure. Treatment with GFH009 resulted in 90 to 100 percent cancer inhibition at dose levels equivalent to those already demonstrated to be safe in patients in the ongoing Phase 1 trial with no viable cancer cells at the highest dose levels.

“The data from preclinical studies that we are reporting today demonstrates that certain cancer cell lines, whose survival depends on specific changes in the cell, can be identified and treated with GFH009,” said Dragan Cicic, MD, Senior Vice President, Clinical Development, of SELLAS. “Through identifying specific genes in cancer cells, GFH009 has shown in these preclinical studies the ability to stop the transcription and expression from gene to protein, inhibiting cancer cell growth altogether. We will utilize this important information as we design our clinical development program for GFH009 in adult and pediatric tumor types.”

About Translational Drug Development (TD2)  
TD2 is an oncology development organization that provides innovative services for oncology-focused companies. Using a dedicated team of professionals with broad experience and understanding in drug development, TD2 is uniquely positioned to support improved and accelerated development of medicines for life-threatening oncology diseases. TD2 applies rigorous and high-throughput translational preclinical development, combined with regulatory affairs expertise, to customize clinical trial design and execution. TD2’s suite of capabilities encourages the timely selection of patient populations who are most likely to benefit from a new agent, and the rapid identification of clinically significant endpoints. TD2 is committed to reducing the risks and uncertainty inherent in the drug development process and to the acceleration of patient access to promising treatments. For more information, visit www.TD2inc.com. 

About SELLAS Life Sciences Group, Inc.
SELLAS Life Sciences Group, Inc. (NASDAQ: SLS) 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 or in 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 preclinical data for GFH009, plans for further 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
Allison Soss
KCSA Strategic Communications
Email: SELLAS@kcsa.com
Phone: 212.896.1267

Media Contacts
Raquel Cona / Michaela Fawcett
KCSA Strategic Communications
Email: SELLAS@kcsa.com
Phone: 212.896.1276