Forward-Looking Statements and Risk Factors This presentation and the accompanying oral commentary contain forward-looking statements that involve risks, uncertainties and assumptions. If the risks or uncertainties ever

Unum Therapeutics Inc. January 2019

Forward-Looking Statements and Risk

Factors This presentation and the accompanying oral commentary contain forward-looking statements that involve risks, uncertainties and assumptions. If the risks or uncertainties ever materialize or the assumptions prove incorrect, our results may

differ materially from those expressed or implied by such forward looking statements. All statements other than statements of historical fact could be deemed forward-looking, including, but not limited to, any statements of the plans, strategies,

and objectives of management for future operations, including our clinical development and commercialization plans; any projections of financial information; any statement about historical results that may suggest trends for our business; any

statement of expectation or belief regarding future events; potential markets or market size, technology developments, our clinical product pipeline, clinical data or the implications thereof, enforceability of our intellectual property rights,

competitive strengths or our position within the industry; any statements regarding the anticipated benefits of our collaborations or other strategic transactions; and any statements of assumptions underlying any of the items mentioned. These

statement are based on estimates and information available to us at the time of this presentation and are not guarantees of future performance. Actual results could differ materially from our current expectations as a result of many risks and

uncertainties, including but not limited to, risks associated with: the success, cost and timing of our product development activities and clinical trials; our ability to obtain regulatory approval for and to commercialize our product candidates;

our ability to establish a commercially-viable manufacturing process and manufacturing infrastructure; regulatory requirements and regulatory developments; the effects of competition and technological advances; our dependence on third-party

collaborators and other contractors in our research and development activities, including for the conduct of clinical trials and the manufacture of our product candidates; our ability to obtain, maintain, or protect intellectual property rights

related to our product candidates; among others. For a further description of the risks and uncertainties that could cause actual results to differ from those expressed in these forward-looking statements, as well as risks relating to our business

in general, see our periodic filings filed from time to time with the Securities and Exchange Commission. Unless as required by law, we assume no obligation and do not intend to update these forward looking statements or to conform these statements

to actual results or to changes in our expectations. All of Unum Therapeutics ("Unum") product candidates are investigational product candidates and their safety and efficacy have not yet been established. Unum has not obtained marketing

approval for any product, and there is no certainty that any marketing approvals will be obtained or as to the timelines on which they will be obtained. Any data pertaining to Unum product candidates is interim data, and may include

investigator-reported interim data for which Unum has not yet independently reviewed the source data. The interim data may not be representative of the final results that may be obtained in the corresponding trials and results from earlier trials

may not be representative of results obtained in later trial or pivotal trials.

Key Company Highlights NOVEL T CELL

THERAPY platforms for cancer Promising ANTI-TUMOR ACTIVITY + FAVORABLE TOLERABILITY PROFILE BROAD PIPELINE with three clinical-stage programs, continuing to grow

ACTR Addressing the Challenges for T

Cell Therapies Overcoming immunosuppression improving engineered T cell functionality in the solid tumor environment Expanding the universe of T cell therapy targets universal antibody-targeted T cells for hematologic and solid tumor applications

Product Pipeline Product Candidate

Indication Pre-Clinical Phase I Phase II Hematologic Cancers ACTR707 + rituximab r/r B cell NHL ACTR087 + rituximab r/r B cell NHL ACTR087 + SEA-BCMA r/r Multiple Myeloma Solid Tumor Cancers ACTR707 + trastuzumab HER2+ cancers BOXR1030 GPC3+ cancers

ATTCK-20-03 ATTCK-17-01 ATTCK-20-2 ATTCK-34-01

ACTR: Antibody-Targeted T-Cells ACTR

components Costimulatory + TCR domains: provide signals driving T cell response to tumor cell recognition CD16: naturally occurring Fc receptor responsible for antibody-dependent cellular cytotoxicity (ADCC) Tumor-specific antibodies enable ACTR

T-cells to target cancer cells Fab: binds tumor antigen Fc: binds ACTR receptor ACTR = Antibody-Coupled T cell Receptor

A Universal Approach A single

engineered T-cell product used across many different targets and cancer types Opportunity to leverage a broad set of previously manufactured and clinically tested antibodies Control and Tunability Potential to optimize therapeutic index by adjusting

antibody dosing Potential in Solid Tumor Cancers ACTR can discriminate attack between tumor and normal cells based on antigen expression Minimal signaling in the absence of tumor antigen preserves ACTR T cells for sustained attack Key

Differentiating Characteristics of ACTR

A Universal Approach for Tumor Cell

Killing Preclinical data show that the same ACTR T cell has the potential to kill different types of cancer cells in the presence of the right targeting antibody Kudo et al., "T lymphocytes expressing a CD16 signaling receptor exert

antibody-dependent cancer cell killing," Cancer Res. 74:93-103 (2014) In vitro: cancer cell lines In vivo: mice treated (+/-) rituximab, (+/-) ACTR T cells Lymphoma Breast cancer Neuroblastoma Targeting Antibody (anti-CD20) (anti-HER2)

(anti-GD2) ACTR + rituximab ACTR rituximab

ACTR construct only needs to be

engineered, manufactured, and pre-clinically validated once, allowing accelerated development Ability to leverage prior investment in antibody discovery and development, and available safety data Potential for strategic collaborations with antibody

innovators Ability to target T cell antigens not readily amenable to CAR-T approaches 5T4 BCMA CanAg CAIX CD138 CD27L CD56 CD6 CD79b cG250 cytokeratin EGP ETBR FAP fibronectin FOLR1 GPNMB AFP GCC LIV melanin MUC16 NaPi2b nectin PEM STEAP1 SLC44A4

SLITRK6 tenascin TF HLA a5b1 a5b3 CA125 CD200 CD40 CD55 CD80 CTLA4 CXCR4 EGFL7 (and many more ) CEA CEACAM5 EGFr EpCAM HER2 Lewis Y mesothelin MUC1 PSMA TAG 72 CD20 CD22 CD30 CD33 CD38 CD44 CD70 CD74 naked antibodies antibody-drug conjugates

Breadth of Targeting Tumor-targeting antibodies provide opportunities to target a broad range of cancers rapidly and cost effectively

ACTR Control and Tunability

Preclinical data indicate ACTR T cell killing may be adjusted by modulating antibody dose. No similar control exists for current T-cell therapies. In vivo (xenograft) In vitro (tumor cell-line killing) rituximab dose ( g/ml) %

ACTR Clinical Pipeline Rapidly

expanding pipeline spanning three clinical programs Product Candidate Indication Pre-Clinical Phase I Phase II Hematologic Cancers ACTR707 + rituximab r/r B cell NHL ACTR087 + rituximab r/r B cell NHL ACTR087 + SEA-BCMA r/r Multiple Myeloma Solid

Tumor Cancers ACTR707 + trastuzumab HER2+ cancers ATTCK-20-03 ATTCK-17-01 ATTCK-20-2 ATTCK-34-01

Clinical Validation: ACTR in

Lymphoma Potent activity demonstrated in two multi-center trials with r/r NHL patients ATTCK-20-03: ACTR707 (CD28) + rituximab ATTCK-20-2: ACTR087 (41BB) + rituximab Clear dose-dependent ACTR cell expansion observed Persistence of ACTR cells in all

patients while on study Compelling activity and safety profile Anti-tumor activity comparable to NHL CAR-T therapies Favorable safety demonstrated at the correct dose level ACTR707 selected for further development in NHL CD16 CD28 CD3 CD16

4-1BB CD3 ACTR087 ACTR707 ACTR technology proof-of-concept established with potential best-in-class product profile

ACTR + Rituximab Trial Design Cycles

4+ Rituximab q21 days Response Assessments q42 days Cycle 3 Rituximab 1st Response Assessment DLT Assessment Cycle 2 Rituximab Infuse ACTR Cycle 1 Rituximab Lymphodepleting Chemotherapy Leukapheresis Screening/Eligibility ACTR Manufacturing Optional

bridging therapy Phase I, dose escalation Open-label, single-arm Rituximab-treated CD20+ NHL: primary refractory, >2 prior lines of therapy, or post auto-HSCT Lymphodepleting therapy Rituximab (375 mg/m2) administered on a 3-week cycle

ATTCK-20-03 Patient Characteristics

Characteristic Dose Level 1 (n=6) Dose Level 2 (n=3) Diagnosis: DLBCL, n (%) 5 (83) 3 (100) Diagnosis: Gr3b FL, n (%) 1 (17) 0 Median age, years (range) 61 (57-76) 58 (47-77) Age 65 years, n (%) 2 (33) 1 (33) Men, n (%) 5 (83) 2 (67)

3 prior therapies, n (%) 3 (50) 2 (67) Refractory to prior therapy*, n (%) 5 (83) 3 (100) Received autologous stem cell transplant, n (%) 2 (33) 3 (100) Received optional bridging therapy, n (%) 5 (83) 1 (33) Mean baseline SPD of target lesion, cm2

(range) 24 (6-112) 14 (12-134) *Refractory defined as PD as best response to any line of chemotherapy or relapse 12 months post ASCT SPD = sum of product diameters Database snapshot: 01November18

Expansion and Persistence The median

peak expansion in Dose Level 2 > 6x Dose Level 1, suggesting dose-dependent ACTR expansion Persistence observed through 233 days (C12D1) post ACTR administration ACTR T cells demonstrate expansion post-infusion and durable persistence Data

snapshot: 02 November 2018 Peak ACTR expansion ACTR expansion and persistence by qPCR

ATTCK-20-03 Adverse Events Adverse

Events of Special Interest (AESI) Subjects with AESI, n Dose Level 1 (n=6) Dose Level 2 (n=3) New malignancy 0 0 Cytokine release syndrome 0 0 Use of therapeutic plasma exchange for any non-disease related AE 0 0 Clinically significant neurologic

disorder 0 0 Clinically significant rheumatologic/autoimmune disorder 0 0 Clinically significant hematologic disorder (excluding cytopenias related to LD chemo) 0 0 Clinically significant = in the opinion of the investigator, clinically meaningful

Database snapshot: 01November18 Preferred Term, n (%) Subjects with Serious Adverse Events (SAEs) Related to ACTR707 Dose Level 1 (n=6) Dose Level 2 (n=3) Febrile neutropenia 1 (17) 1 (33) Pancytopenia 0 (0) 1 (33)

ATTCK-20-03 Anti-Tumor Activity Dose

Level Response Duration of Response (days) Optional Bridging therapy # prior therapies^ ASCT Refractory* to prior therapy Diagnosis Baseline SPD (cm2) 1 Complete 207+ No 2 no no Gr3b FL 24 1 Complete 180+ Yes 5 yes yes DLBCL 23.4 1 Complete 85 Yes 3

no yes DLBCL 11.9 2 Complete 71+ Yes 3 yes yes DLBCL 14 *Refractory defined as PD as best response to any line of chemotherapy or relapse 12 months post ASCT ^All subjects received rituximab as prior therapy Database snapshot: 01November18

Dose Level 1 Six enrolled and treated subjects Three subjects with complete responses; three subjects with disease progression Dose Level 2 Three enrolled and treated subjects One subject with complete response; two subjects with disease progression

Summary of complete responses

Lymphoma Summary & Next Steps

Summary Clinical testing in two independent trials demonstrates anti-tumor activity with a favorable dose-dependent safety profile in relapsed/refractory aggressive NHL patients ACTR707 selected for further development based on best-in-class

potential Next Steps ACTR707 + rituximab (ATTCK-20-03, Phase 1) Complete Dose Level 3 safety evaluation and assessment Cohort expansion at recommended phase 2 dose (RP2D) ACTR087 + rituximab (ATTCK-20-2, Phase 1) Complete ATTCK-20-2 dose

confirmation of ACTR087 at RP2D

ACTR + SEA-BCMA (ATTCK-17-01)

Collaborating with Seattle Genetics to co-develop and co-commercialize novel ACTR + SGI mAb Potential differentiating characteristics Despite high response rates, durability remains a question for many BCMA targeting assets in development Multiple

mechanisms of action exerted by ACTR+SEA-BCMA combination may deepen responses and enhance durability Improved ACTR T cell persistence may translate into enhanced response duration compared to CAR-T Study Design & Objectives Open label Phase I

adaptive dose-escalating study (exploring both ACTR cell dose and antibody dose) Define safety and tolerability of ACTR087 in combination with SEA-BCMA Determine recommended Phase II dose of the combination

ATTCK-17-01 Status Completed first

three cohorts in dose escalation, starting at very low antibody doses SEA-BCMA: 0.03 mg/kg (n=1) 0.1 mg/kg (n=1) 0.3 mg/kg (n=5) ACTR087: target = 30 x 106 ACTR+ T cells SEA-BCMA well-tolerated with expected pharmacological profile

ACTR087 expansion observed in the peripheral blood of all subjects Safety profile supports further dose escalation Enrollment in cohort 4 (2 mg/kg SEA-BCMA; 30 x 106 ACTR+ T cells) is ongoing

ACTR expansion and persistence

ATTCK-17-01 Safety and T Cell Expansion AESI n (%) (Cohorts 1-3; n=7) New malignancy 0 Cytokine release syndrome 1 (14)* Use of therapeutic plasma exchange for any non-disease related AE 0 Clinically significant neurologic disorder 1(14)^ Clinically

significant rheumatologic/ autoimmune disorder 0 Clinically significant hematologic disorder (excluding cytopenias related to LD chemo) 0 Clinically significant = in the opinion of the Investigator, clinically meaningful, requires

medical intervention, and medically important within the context of study treatment * Serious event of grade 1 CRS (cohort 2) that resolved without therapeutic intervention ^ Non-serious, grade 1 event of preferred term neurotoxicity (cohort 3) that

resolved without therapeutic intervention. Data cutoff: 01 November 2018 Adverse Events of Special Interest (AESIs) No DLTs and no severe CRS or neurological events reported ACTR087 demonstrates expansion and persistence in Cohorts 1-3 ongoing at up

ACTR + Trastuzumab (ATTCK-34-01)

vehicle ACTR alone ACTR + trastuzumab trastuzumab HER2 CAR Potent xenograft activity First ACTR Solid Tumor Program Combination for the treatment of adult patients with relapsed/refractory HER2+ cancers Intending to enroll patients with HER2+ breast

cancer, gastric cancers, and other HER2+ malignancies >10,000 patients (U.S.) with HER2+ breast or gastric cancers have exhausted current standard of care Antibody-based treatment options have failed to achieve durable complete responses for

metastatic disease Current Status IND in effect Enrolling patients

ATTCK-34-01: Study Design Schema

Example dose escalation schema (n = 12-24 subjects) Design Adaptive Bayesian design Exploring multiple dose levels of ACTR707 and trastuzumab Dose escalation followed by cohort expansion Objectives Assess safety and tolerability of ACTR707

and trastuzumab Assess anti-tumor activity Secondary measures: ACTR707 T cell expansion and persistence trastuzumab PK inflammatory markers cytokines and chemokines Patient population Histologically confirmed, HER2-positive, advanced solid tumor

malignancy (including breast cancer, gastric or gastroesophageal junction adenocarcinoma, or other locally advanced, recurrent or metastatic malignancy) Disease progression during or immediately following the immediate prior therapy, or within 6

months of completing adjuvant therapy for subjects with breast cancer ACTR707 dose trastuzumab dose cohort 1 cohort 2b cohort 3 cohort 2a

ACTR Selectivity in Solid Tumors

Many solid tumor antigens (e.g., HER2) exhibit low level expression on some normal tissues On-target, off-tumor toxicity can result from inappropriate attack by CAR-T ACTR demonstrates a threshold effect for cytotoxic killing - minimal

activity when antigen is below a target threshold tumor cell lines (HER2 high) normal tissue cells (HER2 low) tumor CAR T cell tumor ACTR T cell normal ACTR T cell normal CAR T cell ACTR can differentiate between tumor cell lines and normal tissue

cells while HER2 CAR cannot ACTR + trastuzumab HER2 CAR

Overcoming Solid Tumor

Immunosuppression BOXR components (1) Chimeric Receptor: universal ACTR or antigen-specific CAR drives cancer cell targeting and attack + (2) Bolt-On: independent transgene that re-programs T cell biology to improve functionality in the tumor

microenvironment (TME) BOXR = Bolt-On Chimeric Receptor Tumor microenvironment (TME) inhibits immune function, limiting efficacy of engineered T cells Unum's BOXR technology is designed to target the TME, yielding more effective T cell