Unum Therapeutics Reports Second Quarter 2019 Financial Results and Provides Corporate Updates - Updated results from Phase 1 trial with ACTR707 in combination with rituximab in adults with relapsed/refractory non-Hodgki

Unum Therapeutics Reports Second Quarter 2019 Financial Results

and Provides Corporate Updates

- Updated results from Phase 1 trial with ACTR707 in combination with rituximab in

adults with relapsed/refractory non-Hodgkin lymphoma confirms the clinical activity

achieved in previous cohorts with no adverse events of cytokine release syndrome

or severe neurotoxicity -

- Phase 1 trial enrollment continuing with ACTR707 in combination with trastuzumab

in HER2+ solid tumor cancers -

- IND-enabling studies underway with BOXR1030 in solid tumor cancers -

CAMBRIDGE, MA, August 12, 2019 Unum Therapeutics Inc. (NASDAQ: UMRX), a clinical-stage biopharmaceutical company focused on developing curative

cell therapies for cancer, today reported financial results and corporate updates for the second quarter ended June 30, 2019, and provided recent activities.

During the quarter, we advanced our preclinical and clinical pipeline programs that are designed to improve the targeting and functionality of T cells

to expand their use in hematologic and solid tumor cancers, said Chuck Wilson, President and Chief Executive Officer of Unum. Today, we reported preliminary results from Cohort 3 of the Phase 1 trial with ACTR707 in patients with

relapsed or refractory non-Hodgkin lymphoma. We are very encouraged by the results from this trial that support our progress towards developing a competitive program with complete responses achieved in five of

the 14 patients treated and no reported adverse events of cytokine release syndrome or severe neurotoxicity. Patient enrollment in Cohort 4 is now complete and we anticipate providing results from this cohort later this year. Our ACTR and BOXR

platform initiatives in solid tumors also continued during the quarter, with Phase 1 trial enrollment activities progressing on our ACTR707 program in patients with HER2+ solid tumors. Our BOXR platform is designed to improve the functionality of

engineered T cells by incorporating a bolt-on transgene to overcome resistance of the solid tumor microenvironment to T cell attack, and we are pleased to advance our first candidate from this

platform, BOXR1030, towards clinical trials.

Recent Program and Corporate Highlights

ACTR707 Hematologic Program Highlights:

As a preliminary update provided today, for the five patients treated in Cohort 3 (55M ACTR707+ T cells), a complete response was achieved in

one of five patients (20%) with overall responses in four of five patients (80%). The overall responses achieved in this cohort included evidence of deepening responses in two patients whose stable disease improved after the initial response

assessment at day 42 to a partial and a complete response, respectively, as of the data cutoff in May 2019 (Table 1).

Durable responses were observed in patients achieving a complete response with the

durability of response ranging from 85-387+ days. In the first three cohorts, ACTR707 was well-tolerated in combination with rituximab. No dose-limiting toxicities (DLTs), no adverse events of cytokine release

syndrome (CRS), and no severe neurological adverse events including neurotoxicity have been reported in Cohorts 1, 2 and 3 as of the May 2019 cutoff. Serious adverse events that were assessed by the investigator as possibly related to ACTR707

include two cases of febrile neutropenia and one case of cytopenia in Cohorts 1 and 2 (Table 2).

ACTR707 Solid Tumor Program Highlights:

Phase 1 trial (ATTCK-34-01) with ACTR707 in HER2+ advanced

solid tumor cancers ongoing: Clinical trial site activation, patient identification, screening and enrollment continues in the first dose cohort of ATTCK-34-01, a

Phase 1, multicenter, open-label, single-arm, dose-escalation trial evaluating ACTR T cells (ACTR707) in combination with trastuzumab for the treatment of patients with HER2+ advanced cancers. Unum plans to

report updates from the ATTCK-34-01 trial including patient enrollment status and preliminary safety data at the end of 2019.

Preclinical data demonstrate that, unlike traditional trastuzumab-based CAR-T cells that target HER2,

ACTR707+ T cells administered with trastuzumab are highly selective for HER2-overexpressing tumor cells and discriminate against cells from normal tissues that express low levels of HER2. The preclinical activity of ACTR707+ T cell has been shown to

be dose-dependent demonstrating control of ACTR707 activity by modulation of trastuzumab concentration. Together, the preclinical data suggest that ACTR cells in combination with trastuzumab may exhibit an improved clinical therapeutic index.

BOXR Solid Tumor Program Highlights:

In early 2019, Unum nominated BOXR1030 as the first product candidate from the BOXR platform. In addition to research to further characterize

its mechanism of action, preclinical studies of BOXR1030 are underway to support the filing of an investigational new drug (IND) application for BOXR1030. Unum plans to present preclinical data regarding BOXR1030 in the second half of 2019.

ACTR087 Hematologic Program Highlights:

Corporate Highlights:

Second Quarter 2019 Financial

Investor Call and Webcast Information

live conference call and webcast today, August 12, 2019, at 4:30 p.m. ET, to discuss these financial results and company updates. To access the call, please dial

866-300-3411 (domestic) or 636-812-6658 (international) and refer to conference ID number

5658375. A webcast will be available at unumrx.com at least 10 minutes before the event begins. The archived webcast will be available at the same location approximately two hours after the event and will be archived for 90 days.

About Unum Therapeutics

Unum Therapeutics is a

clinical-stage biopharmaceutical company focused on developing curative cell therapies to treat a broad range of cancer patients. Unum s novel proprietary technologies include Antibody-Coupled T cell Receptor (ACTR), an autologous engineered T-cell therapy that combines the cell-killing ability of T cells and the tumor-targeting ability of co-administered antibodies to exert potent antitumor immune responses, and Bolt-On Chimeric Receptor (BOXR), designed to improve the functionality of engineered T cells by incorporating a bolt-on transgene to overcome resistance of the

solid tumor microenvironment to T cell attack. Unum has multiple programs in Phase 1 clinical testing, including ACTR707 used in combination with rituximab in adult patients with r/r NHL and used in combination with trastuzumab in adult patients

with HER2+ advanced cancer, and ACTR087 used in combination with the novel antibody SEA-BCMA in r/r multiple myeloma. The Company is headquartered in Cambridge, MA.

Follow Unum Therapeutics on social media: @UnumRx, and LinkedIn.

Forward looking Statements

This press release contains

forward-looking statements including, without limitation, statements regarding our future expectations, plans and prospects, including projections regarding future revenues and financial performance, our long-term growth, enrollment and results for

our preclinical and clinical activities, the development of our product candidates, including the lead ACTR product candidates and the BOXR platform and product candidates, non-clinical or clinical options to

resolve the partial clinical hold on ATTCK-20-2,

and the anticipated timing and success of any of our preclinical studies, clinical trials and regulatory filings, 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,

as amended. 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

UNUM THERAPEUTICS INC.

CONSOLIDATED STATEMENTS OF OPERATIONS

(unaudited, $ in thousands, except share and per share amounts)

UNUM THERAPEUTICS INC.

CONSOLIDATED SELECTED BALANCE SHEET DATA

(unaudited, in thousands)