Rubius Therapeutics to Highlight the Power of its RED PLATFORM®, Significant Advances Across Red Cell Therapeutic Oncology Pipeline and New Type 1 Diabetes Program at Platform and Pipeline Day

Highly Versatile and Programmable RED PLATFORM Enables Multiple Modalities to Target Different Immune Pathways Across a Range of Diseases

Demonstrated Tolerance Induction with Bystander Suppression in Type 1 Diabetes Preclinical Program with Findings Translatable to Multiple T Cell-Mediated Autoimmune Diseases

Advancing Next-Gen Artificial-Antigen Presenting Cells (aAPCs) with Loadable MHC Class 1 Platform, Enabling Presentation of Multiple Antigens on a Single Red Cell Therapeutic

Continuing Dose Escalation in Single-Agent Phase 1 RTX-240 Clinical Trial in Advanced Solid Tumors with No Dose-Limiting Toxicities Observed to Date and an NK Cell Dose Response with Clinical Results Expected in Q1’22

Scaling Manufacturing to Support a Potential Pivotal Trial and Eventual Commercialization

Live Webcast Today at 11:00 a.m. ET with Rubius Management Team and Dr. Gerald T. Nepom, M.D., Ph.D., Expert in Autoimmunity and Type 1 Diabetes

CAMBRIDGE, Mass., Dec. 16, 2021 (GLOBE NEWSWIRE) — Rubius Therapeutics, Inc. (Nasdaq: RUBY), a clinical-stage biopharmaceutical company that is biologically engineering red blood cells to create an entirely new class of cellular medicines called Red Cell Therapeutics™ for the treatment of cancer and autoimmune diseases, today announced significant advances from its RED PLATFORM and across its pipeline of Red Cell Therapeutics (RCTs) at the Company’s first Pipeline and Platform Day.

“Over the course of our presentations, we will highlight the incredible scope and versatility of the programmable RED PLATFORM, enabling targeting of multiple immune pathways via several different modalities, as well as the progress Rubius Therapeutics is making in advancing our clinical-stage cancer therapies, autoimmune programs and manufacturing capabilities,” said Pablo J. Cagnoni, M.D., “Today, for the first time, we will be unveiling preclinical proof of concept data demonstrating tolerance induction with bystander suppression of type 1 diabetes, a T cell-mediated disease. We expect next year to be data rich with several important clinical milestones from our oncology pipeline, including additional clinical results from the single-agent RTX-240 Phase 1 clinical trial in advanced solid tumors and acute myeloid leukemia and initial clinical results from our RTX-321 Phase 1 clinical trial in advanced HPV 16-positive cancers, which we anticipate occurring during the first quarter of 2022.”

Highlights and Progress

RED PLATFORM

• Achieved clinical validation of the RED PLATFORM with initial clinical results from the single-agent RTX-240 Phase 1 clinical trial in advanced solid tumors, reported in March 2021
  • RCTs are well tolerated, induce the desired biological effect and generate clinical benefit in certain patients with advanced solid tumors
• Advancing next generation aAPCs with loadable MHC Class I, enabling the presentation of multiple antigens on a single RCT and broadening the potential patient population with a library of HLA types
• Enabling rapid and repeatable parallel generation of therapeutic candidates with the programmable RED PLATFORM
  • The platform creates multiple modalities for the treatment of cancer and autoimmune disease and the ability to express hundreds of thousands of copies of therapeutic proteins on or within the cell to access numerous immune pathways

Oncology

Broad Immune Stimulation Approach

RTX-240

• Established clinical proof of concept of RTX-240 in advanced solid tumors, based on initial results reported in March 2021, potentially increasing the likelihood of clinical success across the oncology pipeline
• Escalating the dose of single-agent RTX-240 in the Phase 1 solid tumor clinical trial to three doses of 5e10 followed by one dose 1e10 until disease progression or unacceptable toxicity, based on no dose-limiting toxicities observed to date, a clear dose response in the increase of NK cells and other pharmacodynamic effects
  • Additional clinical results are expected from this trial and the Phase 1 arm in relapsed/refractory AML during the first quarter of 2022.
  • The Company plans to initiate single-agent RTX-240 Phase 2 expansion cohorts in select solid tumor types during the first quarter of 2022.
• Continuing dose escalation in the RTX-240 Phase 1 combination study with pembrolizumab in patients with advanced solid tumors.

RTX-224

• Planning to initiate the Phase 1 clinical trial of RTX-224 in patients with certain advanced solid tumors during the first quarter of 2022
  • Investigational New Drug application cleared

Antigen-Specific Immune Stimulation Approach

RTX-321

• Continuing enrollment in Phase 1 clinical trial of RTX-321 in patients with advanced HPV 16-positive cancers
• Planning to report initial clinical results during the first quarter of 2022

Autoimmune Diseases and Type 1 Diabetes

• Demonstrated tolerance induction and bystander suppression in stringent type 1 diabetes preclinical models
  • Established efficacy in the BDC2.5 adoptive transfer model with data supporting that repeated dosing extended duration of disease protection, reverses established inflammation, which is important for the treatment of existing autoimmunity, and induces two types of regulatory T cells, resulting in protection against re-challenge
  • Showed efficacy in non-obese diabetes (NOD) preclinical model
    • Results at 25 weeks exhibit bystander suppression by delivering only two antigens, indicating the mouse surrogate of RTX-T1D prevented or delayed disease caused by many autoantigens
• These findings are potentially translatable beyond type 1 diabetes to multiple autoimmune diseases, including other Rubius’ high priority target indications, including multiple sclerosis and celiac disease.

Manufacturing

• Increased cells produced per batch by four times in 50L bioreactors from 2020 to 2021, enabling uninterrupted clinical supply for three Phase 1 arms of the RTX-240 clinical trial and Phase 1 RTX-321 trial
• Additional accomplishments include:
  • High success rate: greater than 90% lot success rate for RTX-240 and RTX-321 clinical supply in 2021
  • Greater than 200 doses administered across three arms of RTX-240 Phase 1 and RTX-321 Phase 1 trials
  • High transduction efficiency: greater than 90% of cells are transduced with therapeutic proteins
  • Highly consistent protein expression (dual or triple)
• Introduced frozen drug substance for RTX-321 and RTX-224, enabling inventory storage of greater than two years
• Developing frozen drug product to further simplify supply chain with the goal of making our therapies available around the world
• Bringing all product testing in-house to strengthen supply chain and reduce time-to-product release
• Continuing to invest in the platform to improve productivity and efficiency
• Scaling to 200L bioreactors by mid-2022 to support potential pivotal trial and eventual commercialization

Video Webcast Information
A live video webcast is scheduled for today from 11:00 a.m. to 2:00 p.m. ET and can be accessed via the Events and Presentations page within the Investor and Media section of the Rubius Therapeutics website. The Rubius management team and Dr. Nepom will host a Q&A session following the presentations.

About Rubius Therapeutics
Rubius Therapeutics is a clinical-stage biopharmaceutical company developing a new class of medicines called Red Cell Therapeutics™. The Company’s proprietary RED PLATFORM® was designed to biologically engineer and culture Red Cell Therapeutics™ that are selective, potent and off-the-shelf allogeneic cellular therapies for the potential treatment of several diseases across multiple therapeutic areas. Rubius’ initial focus is to advance RCT™ product candidates for the treatment of cancer and autoimmune diseases by leveraging two distinct therapeutic modalities — potent cell-cell interaction and tolerance induction. Rubius Therapeutics was recently named among the 2021 Top Places to Work in Massachusetts by the Boston Globe, and its manufacturing site was recently named 2021 Best Places to Work in Rhode Island by Providence Business News. For more information, visit www.rubiustx.com, follow us on Twitter or LinkedIn or like us on Facebook.

Forward-Looking Statements
This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, as amended, including, without limitation, statements regarding beliefs about Rubius’ execution across preclinical and clinical development, Rubius’ plans and expected timing to present clinical results for RTX-240 and RTX-321, beliefs that findings from preclinical models will be translatable to multiple T cell-mediated autoimmune diseases, plans to advance and expectations for aAPCs, plans and timing to scale manufacturing, beliefs about the scope and versatility of the programmable RED PLATFORM and the generation of therapeutic candidates, expectations regarding the timing for initiating the RTX-224 trial, expectations regarding the therapeutic potential and safety profile of our pipeline of Red Cell Therapeutics, our interpretations of data, including as to the efficacy of our product candidates with respect to autoimmune diseases and Type 1 diabetes, as well as beliefs about our manufacturing accomplishments and goals and expectations for further manufacturing activities. The words “may,” “will,” “could,” “would,” “should,” “expect,” “plan,” “anticipate,” “intend,” “believe,” “estimate,” “predict,” “project,” “potential,” “continue,” “target” and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Any forward-looking statements in this press release are based on management’s current expectations and beliefs and are subject to a number of risks, uncertainties and important factors that may cause actual events or results to differ materially from those expressed or implied by any forward-looking statements contained in this press release, including, without limitation, those risks and uncertainties related to the development of our Red Cell Therapeutic product candidates and their therapeutic potential, our ability to execute on our plans and expectations, our analyses of clinical and preclinical data and other risks identified in our  filings with the U.S. Securities and Exchange Commission (SEC), including our Annual Report on Form 10-K for the year ended December 31, 2020 and our subsequent filings with the SEC, including our Quarterly Report on Form 10-Q for the quarter ended September 30, 2021, and risks and uncertainties related to the severity and duration of the impact of COVID-19 on our business and operations. We caution you not to place undue reliance on any forward-looking statements, which speak only as of the date they are made. We disclaim any obligation to publicly update or revise any such statements to reflect any change in expectations or in events, conditions or circumstances on which any such statements may be based, or that may affect the likelihood that actual results will differ from those set forth in the forward-looking statements. Any forward-looking statements contained in this press release represent our views only as of the date hereof and should not be relied upon as representing its views as of any subsequent date.

Contacts:
Investors
Elhan Webb, CFA, VP Investor Relations
elhan.webb@rubiustx.com

Media
Marissa Hanify, Director, Corporate Communications
marissa.hanify@rubiustx.com