SQZ Biotechnologies Announces Integrated Point-of-Care Cell Therapy Manufacturing System Demonstrated Comparable or Better Performance Than a More Conventional Clean Room-Based Process

Average Processing Time Per Batch Less Than 6 Hours – a 55% Reduction with Comparable or Improved Product Metrics

First Clinical Use Planned for SQZ^® TACs in Celiac Disease with IND Submission Anticipated in 1H 2023

Preclinical Data on Hematopoietic Stem Cell Engineering and Planned Commercial Research-Use-Only System Presented at ASGCT 2022 Support Potential for Broad Future Point-of-Care Manufacturing Implementation

R&D Investor Event Featuring Point-of-Care Manufacturing Platform and Research-Use-Only System, Tomorrow, May 19, 2022

SQZ Biotechnologies (NYSE: SQZ) announced today that the company’s first generation, integrated point-of-care (POC) cell therapy manufacturing system demonstrated superior process performance and comparable or improved product specifications relative to current clean room-based processes used in clinical development. The non-clinical studies showed that the SQZ^® POC system could produce the company’s red blood cell derived SQZ^® Activating Antigen Carrier (AAC) therapeutic candidate for the treatment of HPV16 positive solid tumors in half the time (under 6 hours), with 90 percent fewer operator hours, while producing comparable drug product. The system is also compatible with hematopoietic stem cells and peripheral immune cells, including B cells, T cells, NK cells, and Monocytes. Data was presented today at the 2022 American Society for Gene and Cell Therapy (ASGCT) annual meeting.

“We are tremendously excited with the cell therapy production data from our prototype point-of-care manufacturing system, which has the potential to produce cell therapies using a range of cell types,” said Howard Bernstein, M.D., Ph.D., Chief Scientific Officer at SQZ Biotechnologies. “Our current clinical manufacturing process is under 24 hours - comparatively faster than other cell therapy manufacturing approaches. Our integrated point-of-care platform represents a further leap with faster production in a closed system that could eliminate the need for an ISO 7 clean room. We look forward to its planned first clinical use in our red blood cell derived SQZ TAC program for celiac disease.”

The company anticipates a SQZ^® TAC IND submission for celiac disease in the first half of 2023. Celiac disease impacts a large patient population globally and it, like many other diseases, could benefit from a scalable, decentralized cell therapy manufacturing model. Manufacturing the first SQZ^® TAC clinical candidate on the SQZ^® POC system will further the development of this decentralized model and support potential future use of the POC system across disease areas.

The SQZ^® POC manufacturing system integrates and automates, among other things, cell isolation, cell washing, Cell Squeeze^® intracellular delivery technology, and product filling. The system is designed to process patient material within a closed, single-use sterile disposable kit. The system architecture offers the potential to be operated outside of an ISO 7 clean room typically required of cell therapies—which could ultimately allow cell therapy manufacturing by SQZ^® POC systems in a variety of care settings.

In addition to the SQZ^® POC presentation at ASGCT, preclinical data were presented on the first study findings of the planned commercial research-use-only (RUO) microfluidic delivery system. The RUO presentation highlighted the gentle, yet efficient, nature of the intracellular delivery system. Data demonstrated the ability to effectively deliver and express mRNA in unactivated T and NK cells as well as to gene edit unactivated T cells with limited impact to viability and downstream function.

Cell Squeeze^® gene editing of autologous hematopoietic stem cells (HSCs) was also presented at the conference. The HSC editing preclinical data demonstrated that the Cell Squeeze^® platform could efficiently deliver mRNA and RNPs into HSCs, a sensitive cell type that has been limited previously by toxicity, cargo restrictions, and scalability using other cell engineering approaches. Analysis of the Cell Squeeze^® processed HSCs determined that their phenotype was maintained in vitro and in vivo illustrating its broad potential for use in certain rare and genetic disease indications.

ASGCT POINT-OF-CARE MANUFACTURING DATA HIGHLIGHTS

• Average processing time per batch run reduced by 55 percent, from 12 hours 45 minutes to 5 hours 45 minutes
• Required person-hours reduced by 90 percent, from 150 hours to 15 hours
• Batches showed comparable attributes, including drug and adjuvant content, cell purity, and interferon gamma secretion (a measure of T cell activation)

ASGCT RESEARCH-USE-ONLY (RUO) SYSTEM DATA HIGHLIGHTS

• RUO system demonstrated robust CRISPR-Cas9 editing in unactivated human T cells, and efficient delivery and expression of mRNA to unactivated T and NK cells
• The gentle nature of the RUO system’s intracellular delivery mechanism resulted in limited impact to T cells. Unactivated T cells retained their unactivated phenotype and demonstrated similar activation and expansion compared to untreated samples
• In contrast, electroporation of unactivated T cells resulted in spontaneous increases in pro-inflammatory cytokine transcripts and secretion, independent of TCR engagement

ASGCT HEMATOPOIETIC STEM CELL (HSC) DATA HIGHLIGHTS

• Cell Squeeze^® technology efficiently delivered mRNA and RNPs into HSCs; 90 percent of HSCs expressed transferred mRNA, and high editing rates were achieved using B2M and CCR5 targeting RNPs
• HSC phenotype was maintained following Cell Squeeze^® treatment compared to controls as determined by microarray analysis, CFC assay, and NBSGW mouse engraftment study
• Cell Squeeze^® treated HSCs could be transferred immediately following treatment, and demonstrated superior engraftment versus electroporation

R&D INVESTOR EVENT DETAILS

The company will host a live R&D Investor event with optional virtual participation on Thursday, May 19, 2022, beginning at 4:05 p.m. ET. Onsite and virtual participants can register in advance by completing the registration form on the event website: https://investorday.sqzbiotech.com/. Following the event, a webcast replay will be made available on the company’s investor website: investors.sqzbiotech.com.

ASGCT PRESENTATION TITLES AND TIMING

SQZ Point-of-Care Manufacturing Presentation

Title: A Decentralized and Integrated Manufacturing System for the Rapid and Cost-Effective Production of Cell Therapy Drug Products

SQZ Presenter: Maisam Dadgar

Session Title: Cell Therapy Product Engineering, Development or Manufacturing

Abstract Number: 1171

Date & Time: Wednesday, May 18, 2022, from 5:30-6:30 PM

STEMCELL TECHNOLOGIES Immune Cell Engineering Poster Presentation

Title: A New Benchtop System for Simple and Versatile Introduction of Macromolecules into Human Lymphocytes by Microfluidic Squeezing

STEMCELL Presenter: Eric Ouellet, Ph.D.

Session Title: Synthetic/Molecular Conjugates and Physical Methods for Delivery II

Abstract Number: 997

Date & Time: Wednesday, May 18, 2022, from 5:30-6:30 PM

SQZ Hematopoietic Stem Cell Research Presentation

Title: Rapid, Gentle, and Scalable Engineering of Hematopoietic Stem Cells Using Vector-Free Microfluidic Cell Squeeze® Technology

SQZ Presenter: Murillo Silva, Ph.D.

Session Title: Cell Therapy Product Engineering, Development or Manufacturing

Abstract Number: 1176

Date & Time: Wednesday, May 18, 2022, from 5:30-6:30 PM

About SQZ Biotechnologies

SQZ Biotechnologies Company is a clinical-stage biotechnology company focused on unlocking the full potential of cell therapies for patients around the world and has active programs in oncology, autoimmune and infectious diseases, as well as additional exploratory initiatives to support future pipeline growth. The company’s proprietary Cell Squeeze® technology offers the unique ability to deliver multiple biological materials into many cell types to engineer what we believe can be a broad range of potential therapeutics. With demonstrated production timelines under 24 hours and the opportunity to eliminate preconditioning and lengthy hospital stays, our approach could significantly broaden the therapeutic range and accessibility of cell therapies. The company’s first therapeutic applications seek to generate target-specific immune responses, both in activation for the treatment of solid tumors and infectious diseases, and in immune tolerance for the treatment of autoimmune diseases. For more information, please visit www.sqzbiotech.com.

About STEMCELL Technologies

STEMCELL Technologies supports life sciences research with more than 2,500 specialized reagents, tools, and services. STEMCELL offers high-quality cell culture media, cell separation technologies, instruments, accessory products, educational resources, and contract assay services that are used by scientists performing stem cell, immunology, cancer, regenerative medicine, and cellular therapy research globally. To learn more and receive future announcements about the RUO system in development, visit www.stemcell.com/RUOsystem.

Forward Looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. All statements contained that do not relate to matters of historical fact should be considered forward-looking statements, including without limitation statements relating to events and presentations, regulatory submissions, platform development, product candidates, preclinical and clinical activities, progress and outcomes, development plans, manufacturing capabilities, clinical safety and efficacy results, therapeutic potential, market opportunities and disease prevalence. These forward-looking statements are based on management's current expectations. Actual results could differ from those projected in any forward-looking statements due to several risk factors. Such factors include, among others, risks and uncertainties related to our limited operating history; our significant losses incurred since inception and expectation to incur significant additional losses for the foreseeable future; the development of our initial product candidates, upon which our business is highly dependent; the impact of the COVID-19 pandemic on our operations and clinical activities; our need for additional funding and our cash runway; the lengthy, expensive, and uncertain process of clinical drug development, including uncertain outcomes of clinical trials and potential delays in regulatory approval; our ability to maintain our relationships with our third party vendors and strategic collaborators; and protection of our proprietary technology, intellectual property portfolio and the confidentiality of our trade secrets. These and other important factors discussed under the caption "Risk Factors" in our most recent Annual Report on Form 10-K and other filings with the U.S. Securities and Exchange Commission could cause actual results to differ materially from those indicated by the forward-looking statements. Any forward-looking statements represent management's estimates as of this date and we undertake no duty to update these forward-looking statements, whether as a result of new information, the occurrence of current events, or otherwise, unless required by law.

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