Unum Therapeutics Reports First Quarter 2018 Financial Results and Provides Business Update Successfully Completed IPO and Concurrent Private Placement Raising $77 Million in Gross Proceeds Initiated Cohort Expansion of

Unum Therapeutics Reports First Quarter 2018 Financial Results and Provides Business Update

Successfully Completed IPO and Concurrent Private Placement Raising $77 Million in Gross Proceeds

Initiated Cohort Expansion of ATTCK-20-2 Phase I

Trial of ACTR087 in Combination with Rituximab in Patients with CD20+ r/r Non-Hodgkin Lymphoma; Updated Data Expected in 4Q 2018

Phase I Trials of ACTR087 in Combination with SEA-BCMA in Patients with r/r Multiple Myeloma

and ACTR707 in Combination with Rituximab in Patients with CD20+ r/r Non-Hodgkin Lymphoma Ongoing; Preliminary Data from Both Trials Expected in 4Q 2018

On Track to File IND for First Solid Tumor Program, ACTR707 in Combination with Trastuzumab in Patients with HER2+ Advanced

Malignancies, in 2H 2018

CAMBRIDGE, MA, May 14, 2018 Unum Therapeutics Inc. (NASDAQ: UMRX), a clinical-stage biopharmaceutical

company focused on the development of cellular immunotherapies based on its novel, universal Antibody-Coupled T-cell Receptor (ACTR) technology platform, today reported financial results and provided a

corporate update for the first quarter ended March 31, 2018 and recent activities.

Following our successful initial public offering in April

2018 and concurrent private placement, we are in a strong financial position to continue developing our proprietary, universal ACTR technology platform and rapidly advancing our pipeline of cellular immunotherapies through clinical

development, said Chuck Wilson, CEO of Unum. We are currently evaluating the potential of ACTR in combination with different tumor-targeting antibodies, in three ongoing multi-center Phase I trials, ATTCK-20-2 and ATTCK-20-03 evaluating ACTR087 and ACTR707, respectively, in combination with rituximab in

patients with CD20+ r/r Non-Hodgkin Lymphoma (NHL), and ATTCK-17-01 evaluating ACTR087 in combination with SEA-BCMA in patients with r/r multiple myeloma. We expect to report preliminary data from these three trials late this year. In the second half of 2018 we also look forward to filing an IND and initiating

clinical development of ACTR707 in combination with trastuzumab for the treatment of patients with HER2+ advanced cancers, our first solid tumor product candidate.

Recent Business Highlights and Outlook

First Quarter 2018 Financial Results

About Unum Therapeutics

Unum Therapeutics is a clinical-stage biopharmaceutical company focused on the development and commercialization of novel immunotherapy products designed

to harness the power of a patient s immune system to cure cancer. Unum s novel proprietary technology, antibody-coupled T cell receptor (ACTR), is a universal, engineered cell therapy intended to be used in combination with a wide range of

tumor-specific antibodies to target different tumor types. Unum is actively building a pipeline of product candidates composed of ACTR T cells co-administered with antibodies for use in both hematologic and

solid tumor cancers. The Company is headquartered in Cambridge, MA.

Forward looking Statements

This press release contains forward-looking statements. Statements in this press release about our future expectations, plans and prospects, including

projections regarding future revenues and financing performance, our long-term growth, the anticipated timing of our clinical trials and regulatory filings, the development of our product candidates, including the four lead ACTR product candidates,

as well as other statements containing the words anticipate, believe, continue, could, estimate, expect, intend, may, might,

plan, potential, predict, project, should, target, will, or would and similar expressions, constitute

forward-looking statements within the meaning of the safe harbor provisions of The Private Securities Litigation Reform Act of 1995. We may not actually achieve the forecasts disclosed in our forward-looking

statements, and you should not place undue reliance on our forward-looking statements. Actual results could differ materially from the projections disclosed in the forward-looking statements we make as a result of a variety of risks and

uncertainties, including risks related to the accuracy of our estimates regarding expenses, future revenues, capital requirements, and the need for additional financing, the success, cost and timing of our product development activities and clinical

trials, our ability to obtain and maintain regulatory approval for our product candidates, and the other risks and uncertainties described in the Risk Factors sections of our public filings with the Securities and Exchange Commission. In

addition, the forward-looking statements included in this press release represent our views as of the date hereof. We anticipate that subsequent events and developments may cause our views to

change. However, while we may elect to update these forward-looking statements at some point in the future, we specifically disclaim any obligation to do so. These forward-looking statements

should not be relied upon as representing our views as of any date subsequent to the date hereof.

Stern Investor Relations, Inc.

Stephanie Ascher, 212-362-1200

Paul Kidwell, 617-680-1088

UNUM THERAPEUTICS INC.

CONSOLIDATED STATEMENTS OF OPERATIONS

thousands, except share and per share data)

UNUM THERAPEUTICS INC.

CONSOLIDATED BALANCE SHEET DATA