Unum Therapeutics Reports Second Quarter 2020 Financial Results and Provides Corporate Updates Completed acquisition of Kiq, including lead clinical-stage compound PLX9486, a potent and selective KIT D816V inhibitor Comp

Unum Therapeutics Reports Second Quarter 2020

Financial Results and Provides Corporate Updates

Completed acquisition of Kiq, including lead clinical-stage compound PLX9486,

a potent and selective KIT D816V inhibitor

Company positioned to advance best-in-class precision kinase

Advancing clinical trials in Systemic Mastocytosis and Gastrointestinal Stromal Tumors ( GIST )

CAMBRIDGE, Mass., August 11, 2020 Unum Therapeutics Inc. (Nasdaq: UMRX), a biopharmaceutical company focused on developing novel, best-in-class precision kinase inhibitors for a range of patients living with cancer and other unmet medical needs, today announced financial results for the second quarter

ended June 30, 2020 and provided corporate updates.

With the recent acquisition of Kiq, Unum s focus on PLX9486 creates an exciting

opportunity as we advance development of novel precision kinase inhibitors to treat patients with cancer and a range of other diseases with limited safe and effective treatment options, said Chuck Wilson, Ph.D., President and CEO of Unum.

PLX9486 is a highly potent and selective KIT D816V inhibitor that has demonstrated promising clinical data, and we believe has significant potential to transform the management of serious diseases in many individuals. With PLX9486 as a

cornerstone, we believe our team at Unum is poised to build a pipeline of best-in-class, precision kinase inhibitors.

Recent Program and Corporate Highlights

Unum plans to initiate clinical development of PLX9486 as a monotherapy for patients with Advanced Systemic Mastocytosis (ASM) and Indolent

Systemic Mastocytosis (ISM) with the goal of demonstrating a best-in-class clinical profile. Patients living with systemic mastocytosis experience a range of symptoms,

including reduced life span and chronic conditions, and there are limited treatment options available. Unum expects to initiate clinical testing in ASM patients in the first half of 2021, followed by trials in ISM patients in the second half of

In addition, PLX9486 has demonstrated promising clinical activity in a Phase 1/2 trial in patients with GIST demonstrating 11 months

median progression free survival in 18 GIST patients treated in a second line or later setting. Safety data from both single agent and combination trials in more than 50 patients supports further clinical development. PLX9486 is currently in Phase 2

clinical development in GIST, and Unum plans to advance the compound into additional clinical trials in the second half of 2021. Unum plans to present further details from PLX9486 studies at an upcoming medical meeting.

Second Quarter 2020 Financial Results

About Unum Therapeutics

Unum Therapeutics is a biopharmaceutical company focused on developing a pipeline of novel, best-in-class precision kinase inhibitors for a range of patients living with cancer and other unmet medical needs. Unum s most advanced program, PLX9486, is a highly potent and selective KIT D816V

inhibitor in development to treat systemic mastocytosis and GIST patients.

Unum s legacy cell therapy programs utilize proprietary BOXR technology 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 is headquartered in Cambridge, MA.

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

Forward Looking Statements

This press release contains

forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, including, but not limited to, statements regarding: uses of proceeds; projected cash runways; and future product development plans. The use of

words such as, but not limited to, anticipate, believe, continue, could, estimate, expect, intend, may, might, plan,

potential, predict, project, should, target, will, or would and similar words expressions are intended to identify forward-looking statements. Forward-looking

statements are neither historical facts nor assurances of future performance. Instead, they are based on our current beliefs, expectations and assumptions regarding the future of our business, future plans and strategies, our clinical results and

other future conditions. New risks and uncertainties may emerge from time to time, and it is not possible to predict all risks and uncertainties. No representations or warranties (expressed or implied) are made about the accuracy of any such

forward-looking statements. 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. Such forward-looking statements are subject to a number of

material risks and uncertainties including but not limited to those set forth under the caption Risk Factors in Unum s most recent Annual Report on Form 10-K filed with the SEC, as well as

discussions of potential risks, uncertainties, and other important factors in our subsequent filings with the SEC. Any forward-looking statement speaks only as of the date on

which it was made. Neither we, nor our affiliates, advisors or representatives, undertake any obligation to publicly update or revise any forward-looking statement, whether as result of new

information, future events or otherwise, except as required by law. These forward-looking statements should not be relied upon as representing our views as of any date subsequent to the date hereof.

UNUM THERAPEUTICS INC.

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

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

UNUM THERAPEUTICS INC.

CONDENSED CONSOLIDATED SELECTED BALANCE SHEET DATA

(unaudited, in thousands)