Rheos Medicines Forms Research Collaboration With CRYOSTEM to Evaluate MALT1?Targeted Therapeutics for Graft-versus-Host-Disease

Rheos Medicines, a biopharmaceutical company bringing molecular targeting and precision treatment to autoimmune and inflammatory disease, today announced a research collaboration with the French non-profit research organization CRYOSTEM. The goal of the research collaboration is to provide biological resources from HSCT (Hematopoietic Stem Cell Transplantation) patients in order to evaluate MALT1-targeted therapeutics, including Rheos's lead product candidate, RHX-317, for Graft-versus-Host Disease (GvHD), based on functional immunologic profiling of patients and identification of molecular signatures for MALT1 activity. This collaboration supports a precision medicine approach to enable the treatment of GvHD, by defining the predominant metabolic pathways in the anabolic hub that drive key pathogenic pathways in GvHD patient subsets.

"CRYOSTEM chose to establish this collaborative research program with Rheos because it aligns with our mission to promote our collection of biological resources to help scientists accelerate innovation and extract new knowledge to allow better prevention, diagnosis and treatment of GvHD as one of the HSCT major complications that is a barrier to effective stem cell transplants for patients," said Professor Régis PEFFAULT de LATOUR, co-founder and scientific coordinator of CRYOSTEM.

The research program brings together the collaborators' two domains of expertise to address the challenge of treating GvHD, a major cause of post-transplant morbidity and mortality in patients who undergo allogeneic HSCT. With its proprietary technology platform, Rheos brings insights from studies showing that MALT1 activity underpins the activation of multiple cell types and signaling pathways within a metabolic hub that is dysregulated in GvHD, as well as approaches to predict and stratify patient response to treatment. CRYOSTEM operates through a national biobanking network bringing together transplant units and Biological Resources Centers to accelerate research in the area of complications of HSCT, housing the first and unique collection in Europe dedicated to HSCT complications. This collection of approximately 200,000 biological samples, taken from patients before and after transplant, support research projects that meet rigorous selection criteria by a world-renowned scientific committee.

"This research collaboration with the world-class experts at CRYOSTEM will enable us to significantly build on our existing work in immune cells from healthy donors, and now study GvHD patient samples to evaluate the effect of inhibiting a key drug target on the activation state of multiple immune cells and the specific pathways that are dysregulated in GvHD," said Dania Rabah, Ph.D., Chief Scientific Officer of Rheos Medicines. "We believe the data generated under this collaboration can validate our precision medicine approach to identify novel patient subsets in autoimmune and inflammatory diseases, while also informing the clinical development plan for RHX-317, our novel MALT1 inhibitor drug candidate to treat GvHD."

Under the terms of the research collaboration, CRYOSTEM will provide Rheos with biological resources for post-transplant patients in three categories: those who developed acute GvHD, those who developed chronic GVHD, and those who did not develop GvHD. Rheos will evaluate therapeutic targets for GvHD through these study methods:

• Measure the effectiveness of MALT1 inhibition against disease-relevant functions of immune cells, comparing results across the three different categories of patient samples to determine sensitivity of MALT1 inhibitor drug response and target validation in chronic GvHD.
• Perform multi-omic analyses of patient samples to define signatures reflecting MALT1 therapeutic activity.

Upon successful completion of these initial studies, both parties may agree to expand the research to include larger GvHD patient cohorts and additional evaluation of patient subsets to predict therapeutic response for a potential precision medicine approach to GvHD.

"As with many diseases that have an aberrant immune response, today's treatments for GvHD involve broad immunosuppression, and we lack molecularly-targeted medicines that target disease pathways," said Robert Zeiser, M.D., Head of Tumor Immunology and Immune Modulation and professor at the University of Freiburg Medical Center in Germany. "Rheos's therapeutic approach to target MALT1 for the treatment of GvHD is built on compelling findings that MALT1 activates cellular activity and signaling pathways that are dysregulated in GvHD. I look forward to continued progress with this MALT1 inhibitor that offers a promising new approach for patients with GvHD."

About MALT1

MALT1 (mucosa-associated lymphoid tissue lymphoma translocation protein 1) is a dual-function scaffolding molecule and paracaspase that is expressed preferentially in immune cells. In addition to its role in NF-?B mediated lymphocyte activation and proliferation, Rheos has shown that MALT1 activity is central to the anabolic shift that fuels pathogenic functions of immune cells. Inhibiting MALT1 attenuates the activity of multiple immune cell types simultaneously to dampen the inflammatory response in the activated immune system. Because of its role in cellular metabolism, the effects of MALT1 inhibition can be monitored by metabolite signatures, opening an opportunity to monitor disease and evaluate activity of therapeutics in patients and patient subsets.

About CRYOSTEM

CRYOSTEM was initiated in 2010, under the aegis of the SFGM-TC (Société Francophone de Greffe de Moelle et de Thérapie Cellulaire (https://www.sfgm-tc.com/) to create a multicenter biobank in the field of HSCT. After initially concentrating on Graft-versus-Host Disease (GvHD), CRYOSTEM has broadened its focus to all HSCT complications. Thanks to its network of all the transplant units in France and 28 Biological Resources Centers, CRYOSTEM has established a standardized collection of high-quality biological samples associated with well-annotated clinical data from donors and patients pre- and post-HSCT. Currently, the collection has reached approximately 200,000 available samples coming from nearly 5,900 patients. Since 2015, CRYOSTEM has provided the national and international scientific community with these samples for large-scale research to improve the knowledge of HSCT complications. CRYOSTEM has been funded by the French government's "National Investment Program" and has also received financial support from the French National Cancer Institute (INCa) and patient associations. For more information, please visit www.cryostem.org.

About Rheos Medicines

Rheos Medicines is a biopharmaceutical company developing novel, small molecule medicines to treat autoimmune and inflammatory diseases with greater precision by targeting the metabolic hubs of the immune system. Using our proprietary MetPMtm platform, the Rheos team integrates an unmatched knowledge base of immunometabolism networks based on bioinformatic integration of genetic, transcriptomic, epigenomic and metabolomic datasets, including from patient data and samples. We have built a pipeline of novel, differentiated drug programs to address autoimmune and inflammatory diseases by targeting fundamental underpinnings of immune system dysfunction while, at the same time, identifying the molecular signatures for patient stratification and selection. Rheos has assembled leading scientists whose discoveries opened the field of immunometabolism, clinicians with a deep understanding of immune-mediated diseases, and an experienced biotech leadership team. Rheos was founded by Third Rock Ventures and is located in Cambridge, MA. For more information, please visit www.rheosrx.com. We invite you to follow us on LinkedIn and @Rheosrx.