Beam Therapeutics Reports Additional Data at ASGCT Annual Meeting and First Quarter 2020 Financial Results Alpha-1 Antitrypsin Deficiency Program Demonstrates More than Four-Fold Increase in Circulating Levels of Functio

Beam Therapeutics Reports Additional Data at ASGCT Annual Meeting and First Quarter 2020 Financial Results

Alpha-1 Antitrypsin Deficiency Program Demonstrates More than Four-Fold Increase in Circulating Levels of Functional Protein Following Durable Direct Correction In Vivo

Novel HbG-Makassar Program for Sickle Cell Disease Demonstrates Direct Correction Levels Greater than 80% with Corresponding HbS Globin Reduction to Less than 20%

Base Editing Program to Recreate Hereditary Persistence of Fetal Hemoglobin Shows Greater than 90% Editing and 65% Increase in Gamma Globin Protein after 16 weeks Engraftment

CAMBRIDGE, Mass., May 12, 2020 - Beam Therapeutics Inc. (Nasdaq: BEAM), a biotechnology company developing precision genetic medicines through base editing, today reported additional data from multiple oral and poster presentations during the ongoing 23rd American Society of Gene and Cell Therapy (ASGCT) Annual Meeting as well as its first quarter 2020 financial results.

"The start to 2020 has been one of focused execution across our business and continued advancement of our proprietary base editing platform and portfolio, even with the uncertainty around the COVID-19 pandemic," said John Evans, chief executive officer of Beam. "We are pleased to have a strong showing during ASGCT, in which we are presenting our first in vivo proof of concept for base editing in alpha-1 antitrypsin deficiency as well as two potentially best-in-class approaches for base editing in sickle cell disease, including the direct correction of the HbS point mutation. These data are a testament to the compelling therapeutic potential of base editors and, coupled with our financial strength following our initial public offering, position us to continue our comprehensive investment to develop base editors as a new class of precision genetic medicines for patients."

Updated Data Presented at ASGCT

Business Continuity Plans

First Quarter 2020 Financial Results

About Beam Therapeutics

Beam Therapeutics (Nasdaq: BEAM) is a biotechnology company developing precision genetic medicines through the use of base editing. Beam's proprietary base editors create precise, predictable and efficient single base changes, at targeted genomic sequences, without making double-stranded breaks in the DNA. This enables a wide range of potential therapeutic editing strategies that Beam is using to advance a diversified portfolio of base editing programs. Beam is a values-driven organization committed to its people, cutting-edge science, and a vision of providing life-long cures to patients suffering from serious diseases. For more information, visit www.beamtx.com.

Forward-Looking Statements

This press release contains forward-looking statements. Investors are cautioned not to place undue reliance on these forward-looking statements, including statements about our plans for scientific publications, the expected timing of filing INDs applications, the therapeutic applications of our technology and our ability to develop base editors as a new class of precision genetic medicines for patients. Each forward-looking statement is subject to risks and uncertainties that could cause actual results to differ materially from those expressed or implied in such statement. Applicable risks and uncertainties include the risks and uncertainties, among other things, regarding: the success in development and potential commercialization of our product candidates; our ability to obtain, maintain and enforce patent and other intellectual property protection for our product candidates; whether preclinical testing of our product candidates and preliminary or interim data from preclinical and clinical trials will be predictive of the results or success of ongoing or later clinical trials; that enrollment of clinical trials may take longer than expected; that our product candidates will experience manufacturing or supply interruptions or failures; that we will be unable to successfully initiate or complete the preclinical and clinical development and eventual commercialization of our product candidates; that the development and commercialization of our product candidates will take longer or cost more than planned; and the other risks and uncertainties identified under the heading "Risk Factors" in our Annual Report on Form 10-K for the year ended December 31, 2019 and in any subsequent filings with the Securities and Exchange Commission. These forward-looking statements (except as otherwise noted) speak only as of the date of this press release. Factors or events that could

cause our actual results to differ may emerge from time to time, and it is not possible for us to predict all of them. We undertake no obligation to update any forward-looking statement, whether as a result of new information, future developments or otherwise, except as may be required by applicable law.

THRUST Strategic Communications