• Phase 1 SQZ-AAC-HPV-101 Clinical Trial Resumed Following the Observation of a Confirmed Complete Response in the First Patient in the Lowest-Dose Cohort; Anticipate Data for the Highest-Dose Cohort in the Fourth Quarter of 2023
• SQZ^® eAPC Phase 1/2 Trial Enrollment on Track; Anticipate Data for the Highest-Dose Monotherapy Cohort in Mid-2023

SQZ Biotechnologies Company (NYSE: SQZ), focused on unlocking the full potential of cell therapies, today reported first quarter 2023 financial results and recent portfolio updates.

“The confirmed complete response in our first patient in the AAC trial has brought enthusiasm to our trial sites, and we are encouraged by the positive momentum for enrollment in both the AAC and eAPC clinical trials,” said Howard Bernstein, M.D., Ph.D., Interim Chief Executive Officer and Member of the Board of Directors. “This is a crucial period for SQZ, and I am proud of our team’s unrelenting commitment to help our patients. We are excited to gather more data in our trials and look forward to sharing our findings later this year.”

First Quarter 2023 and Recent Portfolio Updates

Clinical Programs:

SQZ® Enhanced Antigen Presenting Cell (“eAPC”) Platform in Oncology

• Enrolling highest-dose cohort of monotherapy dose escalation trial
• On track to report initial clinical data for the middle- and highest-dose monotherapy cohorts in the middle of 2023

SQZ® Activating Antigen Carriers (“AAC”) Platform in Oncology

• A confirmed complete response (CR), by RECIST 1.1 criteria, was observed in the first patient in the lowest-dose cohort of the SQZ-AAC-HPV-101 Phase 1 clinical trial for HPV16+ solid tumors
  • In light of the response, the Company resumed patient enrollment in the SQZ-AAC-HPV-101 clinical trial
• The Study Safety Committee recommended the Company move directly to the highest-dose cohort
• Currently enrolling patients for the highest-dose cohort
• Initial clinical data from the highest-dose cohort is anticipated in the fourth quarter of 2023

Earlier Stage Programs:

• The Company will continue to explore partnerships and collaborations for its earlier stage assets and programs, including SQZ® Tolerizing Antigen Carriers (“TAC”) Platform in Immune Tolerance

First Quarter 2023 Financial Highlights

• Revenue for the quarter ended March 31, 2023, was $0.0 compared to $2.9 million for the same period in 2022
• Research and development expenses for the quarter ended March 31, 2023, were $13.0 million compared to $17.0 million for the same period in 2022
• General and administrative expenses for the quarter ended March 31, 2023, were $5.3 million compared to $6.9 million for the same period in 2022
• Net loss for the quarter ended March 31, 2023, was $17.7 million, compared to $21.0 million for the same period in 2022
• As of March 31, 2023, the Company had cash and cash equivalents of $39.9 million and anticipates this will be sufficient to fund operating expenses and capital expenditure requirements into 2024

About SQZ Biotechnologies

SQZ Biotechnologies is a clinical-stage biotechnology company focused on unlocking the full potential of cell therapies. The Company’s proprietary Cell Squeeze® technology offers the unique ability to deliver multiple biological materials into many patient cell types to engineer what the Company believes can be a broad range of potential therapeutics. The Company’s goal is to create well-tolerated cell therapies that can provide therapeutic benefit for patients and improve the patient experience over existing cell therapy approaches. With production timelines under 24 hours and the opportunity to eliminate preconditioning and lengthy hospital stays, the Company believes its approach could change the way people think about cell therapies. For more information, please visit www.sqzbiotech.com.

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 the timing and outcome of the Company’s clinical trials, clinical safety and efficacy of its therapeutic candidates, the potential addressable market for the Company’s therapeutic candidates and cash availability. 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 the Company’s significant losses incurred since inception and expectation to incur significant additional losses for the foreseeable future; the Company’s need for additional funding; our ability to continue as a going concern; our ability to successfully execute and achieve the anticipated benefits of our restructuring plan; the development of the Company’s initial product candidates, upon which its business is highly dependent; the impact of the COVID-19 pandemic on the Company’s operations and clinical activities; the lengthy, expensive, and uncertain process of clinical drug development, including uncertain outcomes of clinical trials and potential delays in regulatory approval; and protection of the Company’s proprietary technology, intellectual property portfolio and the confidentiality of its trade secrets. These and other important factors discussed under the caption "Risk Factors" in the Company’s Quarterly Report on Form 10-Q, the company’s 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 the Company undertakes 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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