Axcella Presents Data at ASH Annual Meeting

Axcella Health Inc. (Nasdaq: AXLA), a biotechnology company pioneering the research and development of novel multifactorial interventions to address dysregulated metabolism and support health, today announced mechanistic data for AXA4010 that are being presented today at the American Society of Hematology's (ASH) 2019 Annual Meeting.

AXA4010, Axcella's first investigational hematology product candidate, is a novel EMM composition designed to target and impact multiple pathways related to red blood cell (RBC) membrane biology, hemolysis, endothelial cell and vascular function, and inflammation. The data being presented at the ASH Annual Meeting are from preclinical studies of constituents of AXA4010.

"Sickle cell disease (SCD) is a chronic hemolytic anemia that is associated with inflammation and metabolic derangements that include nitric oxide depletion and oxidative stress," explains Dr. Shreeram Aradhye, M.D., Axcella's Executive Vice President and Chief Development Officer. "As a result, SCD is an ideal setting in which to study AXA4010's potential impact on multiple aspects of blood health. We are looking forward to leveraging these mechanistic data and findings from our ongoing non-IND clinical study of AXA4010 in subjects with SCD to inform our development plans for this candidate."

Poster 978 presents the findings of the preclinical study, the highlights of which include:

• Plasma amino profiles of adults with SCD were significantly different from adults in the control group, with a 50 percent reduction in Arginine and more than a 30 percent reduction in total essential amino acids, which include Leucine, Valine, Lysine, and Histidine.

• Endothelial cell cultures treated with TNF? and constituents of AXA4010 saw reduction in markers of vascular adhesion, inflammation and cell migration. This was compared to cell cultures that were treated with glutamine and TNF?, which saw an increase in adhesion, no change in inflammation and a reduction in cell migration.

• Compared against individual amino acids, AXA4010 constituents were better at improving overall RBC deformability by improving membrane flexibility, surface-to-volume ratio and intracellular viscosity.

"These data again demonstrate the potential of EMMs to impact multiple dysregulated metabolic pathways," said Bill Hinshaw, president and CEO of Axcella. "We are excited about the continued expansion of Axcella's portfolio beyond our liver- and muscle-related programs, into hematology."

Further information is contained in the following presentation at ASH:
Abstract Number: #124224
Title: A Novel Composition of Endogenous Metabolic Modulators, AXA4010, Impacts Adhesion, Inflammation and RBC Membrane Deformability in Preclinical Models of Sickle Cell Disease
Presentation Type: Poster
Session Date/Time: December 7 from 5:30-7:30 p.m. ET
Location: Orange County Convention Center, Hall B

About Endogenous Metabolic Modulators

Endogenous metabolic modulators (EMMs) are a broad family of molecules, including amino acids, which fundamentally impact and regulate human metabolism. Our AXA Candidates are comprised of EMMs that individually have a history of safe use as food. We believe that, unlike conventional targeted interventions currently used to address dysregulated metabolism, EMM compositions have the potential to directly and simultaneously modulate multiple metabolic pathways implicated both in complex diseases and overall health.

Internet Posting of Information

Axcella uses its website, www.axcellahealth.com, as a means of disclosing material nonpublic information and for complying with its disclosure obligations under Regulation FD. Such disclosures will be included on the company's website in the "Investors and News" section. Accordingly, investors should monitor such portions of the company's website, in addition to following its press releases, SEC filings and public conference calls and webcasts.

About Axcella

Axcella is designing and developing AXA Candidates, compositions of endogenous metabolic modulators, or EMMs, engineered in distinct ratios, designed to target and maximize the fundamental role that EMMs play in regulating multiple metabolic functions. Axcella's AXA Candidates are generated from its proprietary, human-focused AXA Development Platform. Axcella believes its expertise and capabilities in EMMs position it to become a preeminent biotechnology company reprogramming metabolism to address a diverse set of complex diseases and support health. Axcella's AXA Development Platform has already produced a pipeline of product candidates in programs targeting liver, muscle and blood. Axcella was founded by Flagship Pioneering. For more information, visit www.axcellahealth.com.

Forward Looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, as amended, including, without limitation, statements regarding the characteristics and development potential of product candidates, including AXA4010, potential expansion into new non-therapeutic and therapeutic fields, the ability of endogenous metabolic modulators to impact dysregulated metabolism and health and the timing of the company's preclinical and clinical studies and the timing of receipt of data from the same. The words "may," "will," "could," "would," "should," "expect," "plan," "anticipate," "intend," "believe," "estimate," "predict," "project," "potential," "continue," "target" and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Any forward-looking statements in this press release are based on management's current expectations and beliefs and are subject to a number of risks, uncertainties and important factors that may cause actual events or results to differ materially from those expressed or implied by any forward-looking statements contained in this press release, including, without limitation, those related to the breadth of the company's pipeline of product candidates, the strength of the AXA Development Platform, the efficiency of the company's discovery and development approach, the clinical development and safety profile of the company's product candidates and their health or therapeutic potential, whether and when, if at all, the company's product candidates will receive approval from the U.S. Food and Drug Administration and for which, if any, indications, competition from other biotechnology companies, the company's liquidity, its ability to successfully develop product candidates through current and future milestones on the anticipated timeline, if at all, past results from preclinical studies and non-IND clinical studies not being representative of future results, and other risks identified in the company's SEC filings, including Axcella's Quarterly Report on Form 10-Q and subsequent filings with the SEC. The company cautions you not to place undue reliance on any forward-looking statements, which speak only as of the date they are made. Axcella disclaims any obligation to publicly update or revise any such statements to reflect any change in expectations or in events, conditions or circumstances on which any such statements may be based, or that may affect the likelihood that actual results will differ from those set forth in the forward-looking statements. Any forward-looking statements contained in this press release represent the company's views only as of the date hereof and should not be relied upon as representing its views as of any subsequent date. The company explicitly disclaims any obligation to update any forward-looking statements.