8-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): September 13, 2021

SQZ BIOTECHNOLOGIES COMPANY

(Exact name of Registrant as Specified in Its Charter)

Delaware	001-39662	46-2431115
(State or Other Jurisdiction of Incorporation)	(Commission File Number)	(IRS Employer Identification No.)

200 Arsenal Yards Blvd Suite 210
Watertown, Massachusetts	02472
(Address of Principal Executive Offices)	(Zip Code)

Registrant’s Telephone Number, Including Area Code: 617 758-8672

N/A

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class	Trading Symbol(s)	Name of each exchange on which registered
Common Stock, $0.001 par value per share	SQZ	The New York Stock Exchange

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 7.01 Regulation FD Disclosure.

On September 13, 2021, SQZ Biotechnologies Company (the “Company”) issued a press release titled “SQZ Biotechnologies Announces First Autoimmune Disease Indication for Tolerizing Antigen Carrier (TAC) Platform.” A copy of the press release is attached hereto as Exhibit 99.1.

The Company is also furnishing a corporate presentation, attached as Exhibit 99.2 to this Current Report on Form 8-K, which the Company intends to use from time to time in meetings with investors and others beginning on September 13, 2021. The corporate presentation will also be available in the investor relations section of the Company’s website at http://sqzbiotech.com.

The information in this Item 7.01 and Exhibits 99.1 and 99.2 attached hereto shall not be deemed “filed” for purposes of Section 18 of the Securities and Exchange Act of 1934, as amended, or otherwise subject to the liabilities of that section, nor shall they be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, except as expressly set forth by specific reference in such filing.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits

Exhibit No.	Description
99.1	Press release issued by SQZ Biotechnologies Company on September 13, 2021.
99.2	SQZ Biotechnologies Company Corporate Presentation.
104	Cover Page Interactive Data File (embedded with the Inline XBRL document)

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

		SQZ BIOTECHNOLOGIES COMPANY
Date: September 13, 2021	By:	/s/ Lawrence Knopf
		Lawrence Knopf
		General Counsel

EX-99.1

Exhibit 99.1

 

SQZ Biotechnologies Announces First Autoimmune Disease Indication

for Tolerizing Antigen Carrier (TAC) Platform

IND filing for Celiac Disease Anticipated in Third Quarter 2022

Clinical Translation Supported by Existing Red Blood Cell-Based Manufacturing

Capabilities and Preclinical Models Demonstrating Treg Mediated Tolerance

WATERTOWN, Mass., September 13, 2021 – SQZ Biotechnologies (NYSE: SQZ), focused on unlocking the full potential of cell therapies for multiple therapeutic areas, today announced that the first clinical translation of the company’s Tolerizing Antigen Carrier (TAC) platform in autoimmune diseases will be for celiac disease, a chronic autoimmune disorder that afflicts millions of patients and has no approved drug treatment. The company anticipates an IND filing in the third quarter of 2022. In preclinical models, SQZ^™ TACs have demonstrated the ability to induce multi-mechanism antigen-specific tolerance relevant to many immune mediated disorders. The company’s celiac disease program may support expansion into additional autoimmune diseases.

“There is significant unmet need for patients with celiac disease. Its acute symptoms, potential for long-term complications, and necessity for a strict gluten free diet can all be extremely difficult,” said Armon Sharei, Ph.D., Chief Executive Officer at SQZ Biotechnologies. “We are excited to apply our TAC platform’s broad potential in immune tolerance, coupled with our existing rapid red blood cell-based manufacturing capabilities, to create a therapeutic that could provide a meaningful benefit to patients with celiac disease. In addition to our existing oncology clinical trials, implementation of our first immune tolerance clinical program will be an important step towards expanding our potential to impact patient lives.”

SQZ TACs leverage the body’s natural mechanisms of red blood cell (RBC) clearance and antigen presentation to induce immune tolerance. TACs are derived from patient RBCs and are designed to carry disease-specific antigen cargos to specialized immune cells that are capable of inducing tolerance through multiple mechanisms.

Earlier this year, the company presented preclinical findings at the Antigen-Specific Immune Tolerance Digital Summit and the Federation of Clinical Immunology Societies demonstrating that its engineered TACs can drive antigen-specific immune tolerance in complex models of autoimmune disease. SQZ TACs were shown to delete antigen-specific T cells, without causing broad immune suppression. Importantly, SQZ TACs also increased antigen-specific regulatory T cells (Tregs) that exerted potent bystander suppression, showing the ability to suppress pathogenic T cells with different autoantigen specificities.

“Our preclinical research has found that SQZ TACs can leverage physiological processes to induce T cell tolerance to disease-driving antigens through multiple

 

mechanisms,” said Howard Bernstein, M.D., Ph.D., Chief Scientific Officer at SQZ Biotechnologies. “We look forward to advancing this promising immune tolerance platform into the clinic for the treatment of celiac disease while in parallel continuing preclinical development for additional autoimmune indications, such as Type 1 diabetes.”

The company will leverage its rapid manufacturing system for the development of SQZ TACs. Earlier this year, the company presented clinical trial findings at the American Society of Clinical Oncology demonstrating the clinical feasibility of its manufacturing system. In the Phase 1 trial of the company’s APC therapeutic candidate for HPV positive tumors, patient batches of the investigational cell therapy were produced in less than 24 hours. The flexibility and scalability of the company’s manufacturing system allows it to be used for both the TAC and Oncology platforms despite different cell types and antigen cargos. SQZ TAC therapeutic candidates are also expected to be compatible with potential future point of care implementations.

About Celiac Disease

Celiac disease is a chronic autoimmune disorder that occurs in genetically predisposed people.^{1 2} The disease is triggered by eating foods containing gluten, which is found in wheat, barley, and rye. Disease symptoms can include abdominal pain, diarrhea, nausea, vomiting, and other common signs. When gluten is ingested the body mounts an immune response that attacks and damages the villi that line the small intestine, which can impact nutrient absorption.³ Many people who have celiac disease have not been diagnosed,⁴ however population-based studies indicate that the disease affects about 2 million people in the United States and approximately 1% of the population worldwide, with regional differences.^{5 6} There is currently no approved drug treatment and patients must therefore maintain a gluten-free diet, which involves strict, lifelong avoidance of exposure to gluten proteins. Long-term complications of celiac disease may include malnutrition, accelerated osteoporosis, nervous system problems and issues related to reproduction. Rare complications can include cancer of the small intestine, cirrhosis, and non-Hodgkin lymphoma.

About SQZ TACs

SQZ TACs are a red blood cell-derived cell therapy platform being developed as an antigen-specific immune tolerance approach for autoimmune diseases. The platform is designed to leverage the natural process of RBC clearance by professional antigen presenting cells (APCs) in the lymphoid organs. This physiological mechanism is tolerogenic by default, instructing the immune system not to mount an attack. SQZ TACs are generated by squeezing RBCs with disease-specific antigens and are made to appear aged. SQZ TACs are designed to be rapidly engulfed by professional APCs and to act as a “Trojan horse” to present antigens in a non-inflammatory context, inducing tolerization of the patient’s T cells against the specific target. Preclinical data has demonstrated deletion and anergy of antigen-specific T cells as well as induction of disease specific Tregs capable of bystander suppression.

 

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 unwanted immune reactions and autoimmune diseases. 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 our platform development, manufacturing capabilities, product candidates, preclinical and clinical activities and outcomes, development plans and progress, clinical efficacy, regulatory submissions, therapeutic impact and market opportunities. 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 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 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 SQZ 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.

Certain information contained in this press release relates to or is based on studies, publications, surveys and other data obtained from third-party sources and our own internal estimates and research. While we believe these third-party sources to be reliable as of the date of this press release, we have not independently verified, and we make no representation as to the adequacy, fairness, accuracy or completeness of any information obtained from third-party sources.

 

SQZ Biotechnologies IR Contact:

investors@sqzbiotech.com

SQZ Biotechnologies Media Contact:

John Lacey

Corporate Communications

john.lacey@sqzbiotech.com

781-392-5514

¹  Leonard MM, Sapone A, Catassi C, et al. Celiac Disease and Nonceliac Gluten Sensitivity: A Review. JAMA 2017;318:647-656

²  Celiac Disease Foundation website (as of Sept 13,2021)

³  Beyond Celiac website (as of Sept 13, 2021)

⁴  National Institute of Diabetes and Digestive and Kidney Diseases website (as of Sept 13, 2021)

⁵  Lionetti E, Gatti S, Pulvirenti A, et al. Celiac disease from a global perspective. Best Pract Res Clin Gastroenterol 2015;29:365-79.

⁶  Leonard MM, Sapone A, Catassi C, et al. Celiac Disease and Nonceliac Gluten Sensitivity: A Review. JAMA 2017;318:647-656

EX-99.2

Exhibit 99.2 Empower Cells to Change Lives® September 2021

Forward Looking Statements and Legal Disclaimers This presentation contains forward‐looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. All statements contained in this presentation that do not relate to matters of historical fact should be considered forward‐looking statements, including statements relating to our development of our product candidates, the promise and potential impact of our preclinical or clinical trial data, the timing of and plans to continue or initiate preclinical studies and clinical trials of our product candidates, the timing and results of any preclinical studies, clinical trials or readouts and the sufficiency of cash to fund operations. These forward‐looking statements are based on management's current expectations. The words ”may,” “will,” “should,” “expect,” “plan,” “anticipate,” “could,” “intend,” “target,” “project,” “estimate,” “believe,” “predict,” “potential” or “continue” or the negative of these terms or other similar expressions are intended to identify forward‐looking statements, although not all forward‐ looking statements contain these identifying words. These statements are neither promises nor guarantees, but involve known and unknown risks, uncertainties and other important factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward‐looking statements, including, but not limited to, the following: the impact of the COVID‐19 pandemic on our operations, including our preclinical studies and clinical trials, and the continuity of our business; we have incurred significant losses, are not currently profitable and may never become profitable; our need for additional funding; our cash runway; our limited operating history and the prospects for our future viability; the lengthy, expensive, and uncertain process of clinical drug development, including potential delays in regulatory approval; the continued relationship with our collaboration partners in our development of products, including in our SQZ™ APC oncology pipeline; the approach we are taking to discover and develop product candidates and whether it will lead to marketable products; the expense, time‐consuming nature and uncertainty of clinical trials; enrollment and retention of patients; potential side effects of our product candidates; our ability to maintain our relationships with our suppliers; protection of our proprietary technology and the confidentiality of our trade secrets; potential lawsuits for, or claims of, infringement of third‐party intellectual property or challenges to the ownership of our intellectual property; our ability to retain key personnel and to manage our growth; the potential volatility of our common stock; costs and resources of operating as a public company; unfavorable or no analyst research or reports; and securities class action litigation against us. These and other important factors discussed in our filings with the US Securities and Exchange Commission could cause actual results to differ materially from those indicated by the forward‐looking statements made in this presentation. Any such forward‐looking statements represent management's estimates as of the date of this presentation. New risk factors and uncertainties may emerge from time to time, and it is not possible to predict all risk factors and uncertainties. While we may elect to update such forward‐ looking statements at some point in the future, except as required by law, we disclaim any obligation to do so, even if subsequent events cause our views to change. Although we believe the expectations reflected in such forward‐looking statements are reasonable, we can give no assurance that such expectations will prove to be correct. These forward‐looking statements should not be relied upon as representing our views as of any date subsequent to the date of this presentation. Certain information contained in this presentation relates to or is based on studies, publications, surveys and other data obtained from third‐party sources and our own internal estimates and research. While we believe these third‐party sources to be reliable as of the date of this presentation, we have not independently verified, and we make no representation as to the adequacy, fairness, accuracy or completeness of any information obtained from third‐party sources. In addition, all of the market data included in this presentation involves a number of assumptions and limitations, and there can be no guarantee as to the accuracy or reliability of such assumptions. Neither we nor our affiliates, advisors or representatives makes any representation as to the accuracy or completeness of the data included in this presentation or undertake to update such data after the date of this presentation. Finally, while we believe our own internal research is reliable, such research has not been verified by any independent source. 2

SQZ Biotech: Unlocking the Full Potential of Cell Therapies üSQZ Technology addresses fundamental challenge of engineering diverse cell functions • Multiple cell therapy platforms with expansive potential across oncology, autoimmune and infectious diseases • Partnership with Roche and potential for additional BD opportunities across portfolio üThree clinical programs expected to have data readouts throughout 2022 • Lead APC program demonstrated safety, manufacturability and immune activation in solid tumors • Additional INDs targeted over the next 18 months üDemonstrated scalable cell therapy manufacturing • Fast, reliable and cost‐efficient with production times < 24hr • Path to potential point‐of‐care implementation 3

® Unique Cell Squeeze Technology Enables Differentiated Capabilities Cells and target cargo Cell membranes are Membranes 1 3 5 together in suspension temporarily disrupted reseal Cells are squeezed through SQZ Target cargo enters the 2 4 chip at high speeds cytosol of the cells Applicable to diverse Robust across material Preservation of cell ++ cell types classes function EP SQZ Proteins and peptides PBMCs Gene editing complexes RBCs Nanomaterials Nucleic Acids HSC/iPSCs Small molecules Electroporation (EP) results in substantial gene misregulation vs. Squeezing 4

Manufacturing: Fast, Reliable and Potential to Expand Cell Therapy Access Manufacturing Process and Patient Experience Approach Strengths and Considerations ~24‐113 days vein‐to‐vein • High cost • Lymphodepletion Autologous • Bridging chemotherapy• Long turn‐around times ~10‐12 days enrollment to infusion • Off‐the‐shelf • Potential Efficacy/Safety limitations due to Allogeneic • Lymphodepletion mismatch ~1 week vein to vein SQZ • No preconditioning • Rapid production, potential cost‐efficiency Cell Therapy • No planned • Many doses available from single production run hospitalizations Today Possible same day treatment SQZ • On‐site production without a clean room Point‐of‐Care • Could enable much broader accessibility Vision 5

Addressing Challenges That Could Unlock Broader Cell Therapy Universe Universe of Possible Cell Therapies Hematology Oncology Viral Cell Squeeze Solid Tumors Electroporation Transduction Technology Ability to retain cell ++ +++ health and function Flexibility in cell Autoimmune ++ + +++ types and cargo Breadth of disease ++ +++ applicability Infectious Manufacturing speed Disease ++ +++ and reliability Almost all cell therapies today are produced with Regenerative electroporation or viral transduction techniques Medicine 6

Directing Immune System to Drive Antigen Specific Activation and Tolerization 1. Antigen (What to target) 2. Context (Activation vs. Tolerance) Determinants Antigen presenting cells (APCs) Once a T cell’s TCR is engaged, it looks for show peptide antigen on MHC‐I clues via APC surface receptors and of an Immune and MHC‐II that T cells look at cytokines for whether to become activated Reaction using their T cell receptors (TCR) or tolerized Immune Activation Immune Tolerance Antigen: T Cells T Cells APC Context …activation against the target …tolerization against the target Indications: Outcome: CD8 Killer T cells CD4 Helper T cells CD8 Killer T cells Regulatory T cells CD8 Killer T cells are activated to attack desired target Activating cells (e.g., CD8, CD4) are deleted or and CD4 T cells are activated to support a broader anergized and Tregs are upregulated, blocking reaction (e.g., antibodies) unwanted immune response against the target 7 T Cell APC Surface receptors + Cytokines

Strategy: Leverage Flexible Technology To Quickly Expand Indications From Each Platform Autoimmune Disease Chronic Infectious Disease Oncology Annual incidence (‘000s) Prevalence (M) Prevalence (M) 3 3 400 KRAS 300 2 2 Potential Patient 200 Impact: HPV 1 1 (Patient numbers, US) 100 0 0 0 HBV HIV Other Celiac T1D Other SQZ Cell Therapy Platform: SQZ APCs SQZ eAPCs SQZ AACs SQZ TAC SQZ eAPCs Initial proof of concept in HPV Initial proof of concept in Celiac Initial proof of concept in HBV Strategy: Leverage SQZ Identify benefits of each platform Expand into additional indications Expand into additional indications cargo flexibility (e.g., HIV) (e.g., T1D) Expand into additional indications (e.g., KRAS G12D and G12V) 8

Diverse Pipeline: Synergistic in Execution yet Independent in Mechanism CELL SOURCE/ PLATFORM INDICATION PRE‐CLINICAL PHASE 1/2 CARGO H&N, Cervical, Anal PBMC + Peptide Other Solid Tumors SQZ APCs RBC H&N, Cervical, Anal + Peptide KRAS mut Solid Tumors + SQZ AACs Adjuvant Other Solid Tumors PBMC + Solid Tumors mRNA SQZ eAPCs Celiac disease RBC + Protein SQZ TACs Type 1 Diabetes Chronic Hepatitis B Virus PBMC + mRNA Rapid Response Vaccines SQZ eAPCs 9 INFECTIOUS AUTO‐ ONCOLOGY DISEASE IMMUNITY

Oncology SQZ™ Approach SQZ eAPCs SQZ APCs SQZ AACs 10

Importance of Engineering Antigen Presentation for Powerful CD8 Activation Strong Correlation of CD8 TILs with Clinical Response CD8 T Cell Infiltration as a Prognostic Indicator in Solid Tumors PC Tumeh et. al. Nature. 2014 Responders Progressors Balermpas, et. Al. British Journal of Cancer. October 2013. “Positive prognostic value of CD8 T cells was confirmed in more than 18,700 patients across ‐Bruni et al, Nature Reviews 2020 17 solid cancer types” 11

Oncology SQZ™ Approach SQZ AACs SQZ APCs SQZ eAPCs 12

Overcoming the Challenge of Cancer Vaccines TM Typical Cancer Vaccine Mechanism: SQZ APC Mechanism: Cross‐Presentation Direct Presentation MHC‐I = CD8 T Cell MHC‐I = CD8 Activation Endocytosis Squeezed Antigen MHC‐II = CD4 + antibodies • Primarily generates MHC‐II presentation for CD4 and • Primarily generates MHC‐I presentation to CD8 T cells antibody responses• CD8 T cell responses in the tumor are highly correlated • Suited for prophylactic vaccines with patient outcomes Prioritizes creation of Prioritizes creation of CD4 helper cells Antibodies CD8 Killer T cells 13

Ongoing Phase 1/2 Trial: Flexible Design, Combination Data in 2022 Monotherapy Enrollment Complete Open for Enrollment 0.5M cells 2.5M cells 2.5M cells 5M cells per kg per kg per kg (DP) per kg (DP) Cohort 1 Cohort 2 Cohort 3 Cohort 3a Combination Therapy Atezo Ipi/Nivo Other I/O SQZ‐APC‐HPV Combo Combos Combos Phase 1/2 Trial Information • Basket trial across HPV+ tumors: H&N, Cervical, Anal, Penile, Vulvar/Vaginal • Potential to enroll up to 200 patients in Phase 1/2 trial • Several dosing and boosting schedules being explored Earlier Line • Initial monotherapy data presented in June 2021 at ASCO Expansion Cohorts • High monotherapy cohort enrolling • Combination expected to begin in 2021 with data in 2022 Trial ID: NCT04084951 14

* Ph 1 Mono Data: SQZ™ APCs Demonstrated Safety and Reliable Manufacturing Safety • No patient met pre‐specified DLT criteria Total • No related Grade ≥3 SAEs reported: Patient Demographics (N=12) Age, years • Grade 2 (related) – CRS (1 pt) Median (Min, Max) 62.5 (47, 68) • Unrelated SAEs ‐ Grade 3 (7 pts), Grade 4 (1 pt) and Grade 5 (1 pt) Baseline RMH score, n (%) • No dose reduction High (≥2) 6 (50.0) • No treatment‐related deaths Site of primary tumor, n (%) Anus 6 (50.00) Cervix 2 (16.7) Head & Neck 3 (25.0) Manufacturing: Robust, consistent production in <24hrs Site of Metastases, n (%) 12 (100.0) Liver Mets 7 (58.3) Viability End‐to‐End Process Time Lung Mets 5 (41.6) 25 Other sites* 6 (50.0) Prior Systemic Therapy, n (%) 20 100% Chemotherapy 12 (100.0) IFN‐γ secretion 15 Checkpoint Inhibitor 11 (91.7) Refractory to ICI (PD as 9/11 10 BOR) 5 (41.6) 5 Other All manufactured patient APCs induced IFN‐γ secretion by T cells 0 Processing Time 15 * Phase 1 monotherapy data presented at ASCO June 2021 Viability (%)

* Encouraging Increase in Immune Activity in Certain Patients Case Study: Patient 2 (Cohort 1 ‐ 0.5e6/kg q3w) SD SD BOR 345+ 246+ Survival FU* Dose • 65‐year‐old woman – cervical cancer RMH 10 • 3.5 years after diagnosis following treatment with (1) cisplatin/paclitaxel/ bevacizumab [BOR=CR] and (2) Pembrolizumab [BOR=PD] • Low tumor burden, ECOG=0, RMH=1 • On treatment for 10+ months, BOR=SD • 2‐fold increase in CD8 TIL vs. baseline Case Study: Patient 7 Case Study: Patient 7 Cohort 2 (2.5e6/kg q3w) Dose 100 • 67‐year‐old male – H&N cancer 80 • 1 year after diagnosis following 60 treatment with carbo/5FU/pembro (BOR=PR) 40 • High tumor burden, ECOG=1, RMH=0 20 • On treatment for 3 months, BOR=SD • 6‐fold increase in CD8 TIL vs. baseline Patient 27 -50 -19 42 84 250 *Survival Follow Up Study Day 16 * Phase 1 monotherapy data presented at ASCO June 2021 2 CD8 cells/mm in CN (mm) (mm)

Next Step: Combinations ‐ Potential Synergies with Other I/O Compounds Antigen‐Specific Responses could be Preclinical data demonstrated synergistic potential of SQZ APCs in combination with Roche PD1‐IL2v Amplified with Combination TM SQZ APCs drive I/O drugs tumor‐specific T enhance activity cell activation downstream 17 Presented at SITC 2020 in SQZ Poster and Roche Oral Presentation 3 Tumor Volume (mm )

Oncology SQZ™ Approach SQZ eAPCs SQZ AACs SQZ APCs 18

nd 2 Generation APCs: Enhancing with Combination‐like Functionality TM SQZ eAPC Enhanced APCs (eAPC): • Multiple mRNA as cargo SQZ eAPC • Broader antigen repertoire in mRNA potentially Signals 2 3 increases addressable population 2‐3x 1 • Addition of co‐stimulatory factors and cytokines: MHC‐I membrane‐bound IL‐2, IL‐12 and CD86 CD86 IL‐2 o Potential for combination functionality in IL‐12 TCR single cell therapy o Could reduce toxicity normally seen with traditional combinations CD8 T Cell eAPC IND targeted by end of 2021 19

Oncology SQZ™ Approach SQZ APCs SQZ AACs SQZ eAPCs 20

Creating Antigen Carriers from RBCs to Direct Immune Response Antigen Lymphoid Organ Presentation Cargo SQZ™ Antigen Carriers • Antigen Carriers generated by squeezing RBCs deliver antigen to guide a specific immune response • Leverage the natural process by which RBCs are regularly cleared by the body • Professional APCs in lymphoid organs are primarily responsible for RBC clearance • Antigen Carriers Act as “Trojan horses” to deliver antigen to these endogenous professional APCs 21

SQZ™ AACs Demonstrated Robust Activation in Preclinical Studies Lymphoid Organ Activation Antigen + Activating Adjuvant T cell activation SQZ™ AACs 1. High Quantities of CD8+ T Cells 3. High Quality T Cell Responses 2. Specific T Cell Responses As presented at SITC 2020 22 Data in HPV Tumor Model

Flexible AAC Candidate Trial Design | Monotherapy & Combination with ICIs Monotherapy 2022 IND 50 M Dose determined by Additional KRAS‐Mutant AACs/kg Cohort 1 observations Cohorts Tumors Cohort 1 Cohort 2 Combination Therapy SQZ‐AAC‐HPV Multiple I/O Phase 1/2 Trial Information Combo Cohorts • Basket trial across HPV+ tumors: H&N, Cervical, Anal, Penile, Vulvar/Vaginal • Safety‐adjusted dose escalation allowing for data driven Earlier Line escalation Expansion Cohorts • No need for escalation in combo cohorts, starting with the Mono or Combo recommended phase 2 dose • Monotherapy start in 2021 with data in 2022 Trial ID: NCT04892043 23

Autoimmune Diseases SQZ™ Approach SQZ TACs 24

SQZ™ TACs ‐ Directing Tolerogenic Immune Response SQZ™ Tolerizing Antigen Carriers (SQZ TACs) Leveraging antigen carriers from RBCs squeezed with antigen only (no adjuvant) tolerize the immune response to that antigen Activation SQZ Cargo Antigen + Activating Adjuvant Lymphoid Organ T cell activation SQZ AACs (Activating Antigen Carrier) Engulfment by APCs Tolerization Anergy T reg upregulation Antigen SQZ TACs T cell deletion (Tolerizing Antigen Carrier) Bystander Suppression 25

TACs Prevented Onset of Type 1 Diabetes Through Multiple Mechanisms SQZ™ TACs Demonstrate Durable Disease TACs Restore Tolerance Through Multiple Pathways Altering Benefit in T1D Preclinical Models Central to Complex Autoimmune Diseases 1. Decrease Autoreactive T Cells 3. Induce Bystander Suppression Control TACs Disease driving CD8 T cells In a model with multiple reduced by 60x in pancreas of pathogenic T cell specificities, SQZ T1D TACs TAC treatment for 1 antigen certain T1D models caused 10x reduction in T cells of a different autoantigen 2. Increase Antigen‐Specific T Cells reg Antigen‐specific regulatory T cells increased by 5x in pancreas with parallel increase in suppressor cytokine IL‐10 26 As presented at FOCIS 2021

SQZ™ TAC Opportunity in Celiac Disease Celiac Disease: Lead SQZ TAC Indication with High Unmet Need for a Tolerizing Therapy Potential Year Diagnosed CeD, US expansion SQZ‐TAC‐CeD Target Product Profile 2020 1.06M populations Initial target Long‐acting tolerization for release population: 2025 1.55M of dietary gluten restrictions ~60% of total Initial clinical population: well‐ CeD cases No approved treatments controlled and symptomatic patients with Celiac disease TM Compelling Case for SQZ TAC Potential in Celiac Disease: ü Well‐defined exogenous antigen and strong evidence of T cell driven pathology ü Rapid read‐out potential: Phase 1 trial design incorporates gluten challenge to enable early clinical PoC data ü Anticipated CeD IND in Q3 2022 27

Infectious Diseases and beyond 28

Potential for Multiple Clinical Readouts In 2022 Milestones through end of 2022 Investment Highlights • Phase 1/2 Add’l Monotherapy data • Phase 1/2 Combination data SQZ APCs ü Proprietary technology with potential to expand • Phase 1/2 data application of cell therapies • KRAS IND submission SQZ AACs ü Fast, reliable and cost‐efficient manufacturing potential • IND submission ü Unique cell therapy engine applicable across diseases • Phase 1/2 data SQZ eAPCs ü Clinical stage pipeline with multiple platform readouts expected across 2022 • Celiac IND submission SQZ TACs ü Additional INDs leverage de‐risked manufacturing backbone to expand potential patient impact • HBV IND submission ü Existing Roche partnership; potential additional BD SQZ eAPCs opportunities • Point‐of‐care non‐clinical testing data 29 INFECTIOUS AUTO‐ CORPORATE ONCOLOGY DISEASE IMMUNITY

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