Bayer and Systems Oncology sign exclusive license agreement on innovative breast cancer treatment approach ERSO™

Bayer has entered into an exclusive global license agreement with Systems Oncology, LLC, for ERSO™, a compound in pre-clinical development for the treatment of metastatic Estrogen Receptor-positive (ER+) breast cancer.

ERSO is a small molecule activator of the Unfolded Protein Response (UPR) in ER+ breast cancer cells. ERSO’s differentiated mechanism of action offers significant potential to provide a meaningful novel treatment option for women with metastatic ER+ breast cancer, an area where new therapies are urgently required.

“Despite the overall progress we see in the treatment of breast cancer, there are only limited treatment options for patients whose disease progressed, in particular in the metastatic setting,” said Robert LaCaze, Member of the Executive Committee of the Pharmaceuticals Division and Head of the Oncology Strategic Business Unit at Bayer.

“In line with our Oncology strategy to focus on areas with a high medical need and innovative approaches with the potential to make a meaningful impact, we are excited to partner with Systems Oncology in developing ERSO. ERSO offers a promising transformational approach to treating a large proportion of women with ER-positive breast cancer, and enhances our portfolio enabling us to deliver new therapies for patients who are waiting for them.”

With over 2 million new cases worldwide in 2018, breast cancer is the most common tumor type in women and the second leading tumor type overall. The prognosis as well as available treatment options depend highly on the subtype and stage of breast cancer. Around 70% of all women with breast cancer have ER+ disease, with the survival rate for metastatic ER+ breast cancer being only 20%.

Thus, the need for additional treatment options beyond established anti-hormonal treatment approaches remains high. In preclinical studies, ERSO showed activity in ER+ breast cancer cells as well as activity on ER mutations conferring a resistance to standard treatments.

ERSO’s mode of action of activating the Unfolded Protein Response (UPR) in ER+ breast cancer cells offers a significant differentiation from current and potential upcoming anti-hormonal agents. In addition, the therapeutic potential of this novel mode of action in other tumor types is currently being investigated.

“Given ERSO’s unique mechanism and potential to transform cancer care, it was important for us to align with a sophisticated group that understands innovation. Bayer is a proven innovator who shares our vision for ERSO, and they have the clinical, scientific, and business leadership to succeed”, said Dr. Spyro Mousses, CEO and Co-Founder of Systems Oncology.

“With the experienced team at Bayer leading the development effort, I fully expect that this exciting new therapy has the potential to create a real paradigm-shift for breast cancer care”, said Dr. Joyce O’Shaughnessy, Baylor University Medical Center, Texas Oncology, US Oncology.

“The collaboration with Systems Oncology combines their deep experience in identifying novel treatment pathways with our global footprint and established profile in order to deliver new treatment options that can improve patient outcomes”, said Marianne De Backer, PhD, MBA, Member of the Executive Committee and EVP, Head Strategy and Business Development & Licensing, Pharmaceuticals Division of Bayer AG. “It underlines our commitment to explore partnerships on innovative treatment approaches at all levels.”

Under the terms of the agreement, Bayer will be responsible for developing and commercializing ERSO globally. Systems Oncology will receive an upfront payment of 25 million US dollars and is eligible to receive payments from Bayer upon achievement of certain development, and commercialization milestones totaling 345 million US dollars, as well as royalties on future global net sales.

The Pharmaceuticals Business Development & Licensing team of Bayer facilitated this collaboration.

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This release may contain forward-looking statements based on current assumptions and forecasts made by Bayer management. Various known and unknown risks, uncertainties and other factors could lead to material differences between the actual future results, financial situation, development or performance of the company and the estimates given here. These factors include those discussed in Bayer’s public reports which are available on the Bayer website at The company assumes no liability whatsoever to update these forward-looking statements or to conform them to future events or developments.

Bayer AG Leverkusen,