GlobeNewswire Inc | Jul 19, 2021 08:00AM EDT

July 19, 2021

-First precision approach to IBD by utilizing a companion diagnostic to identify patients-

-Phase 2a initiation in Crohns Disease on track for 3rd Quarter 2021-

- Further details to be provided at R&D Day on July 28th-

SAN DIEGO, July 19, 2021 (GLOBE NEWSWIRE) -- Prometheus Biosciences, Inc. (Nasdaq: RXDX), a biotechnology company pioneering a precision medicine approach for the discovery, development, and commercialization of novel therapeutic and companion diagnostic products for the treatment of immune-mediated diseases, starting first with inflammatory bowel disease (IBD), today announced the initiation of the Phase 2 ARTEMIS-UC clinical trial evaluating PRA023 for moderate-to-severe ulcerative colitis (UC), with first patient enrollment. The study is placebo-controlled and statistically powered to evaluate the efficacy and safety of PRA023 in UC patients. The company plans to provide more details of the Phase 2 ARTEMIS-UC study at R&D Day on July 28th.

The majority of patients with UC cannot achieve clinical remission through the use of currently available therapies, said Allison Luo, MD, Chief Medical Officer of Prometheus. This gives Prometheus compelling motivation to rapidly advance PRA023, addressing both inflammation and fibrosis and leading the precision medicine approach in the IBD space, starting first with the ARTEMIS-UC study.

Prometheus has recently completed the dosing phase of the Phase 1a clinical trial of PRA023, a single center, double-blind, placebo-controlled trial to determine the safety, tolerability, pharmacokinetics, and pharmacodynamics of PRA023 in normal healthy volunteers. Safety and tolerability observed to date supports the initiation of a Phase 2 trial. Final Phase 1a results of PRA023 in UC and CD are expected in the fourth quarter of 2021. Further details will be provided at the companys R&D Day on July 28, 2021. Register here: Prometheus R&D Day

About PRA023

PRA023 is an IgG1 humanized monoclonal antibody (mAb) that has been shown to block tumor necrosis factor (TNF)-like ligand 1A (TL1A). PRA023 binds both soluble and membrane-associated human TL1A with high affinity and specificity and has the potential to substantially improve outcomes formoderate-to-severeIBD patients predisposed to increased TL1A expression. Prometheus is developing PRA023 for the treatment of the two most common forms of IBD, Ulcerative Colitis (UC) and Crohns Disease (CD). The Company has initiated enrollment in a Phase 2 trial in UC patients. The Company is also developing a genetic-based companion diagnostic to identify patients who are predisposed to increased expression of TL1A and therefore potentially more likely to respond to PRA023.

AboutPrometheus Biosciences

Prometheus Biosciences, Inc. is a biotechnology company pioneering a precision medicine approach for the discovery, development, and commercialization of novel therapeutic and companion diagnostic products for the treatment and diagnosis of immune-mediated diseases, starting first with IBD. The Companysprecision medicine platform, Prometheus360, combines proprietary bioinformatics discovery methods with one of the worlds largest gastrointestinal bioinformatics databases to identify novel therapeutic targets and develop therapeutic candidates to engage those targets. Prometheus is headquartered in San Diego, CA.

Forward Looking Statements

Prometheus cautions readers that statements contained in this press release regarding matters that are not historical facts are forward-looking statements. These statements are based on the companys current beliefs and expectations. Such forward-looking statements include, but are not limited to statements regarding: the timing of commencement of Prometheus Phase 2 clinical trial in UC and its Phase 2a clinical trial in CD; Prometheus Enroll360 program and the companys ability to accelerate enrollment in its planned and other future clinical trials; and the timing of Prometheus obtaining the final study results from its Phase 1a clinical trial of PRA023. The inclusion of forward-looking statements should not be regarded as a representation by Prometheus that any of our plans will be achieved. Actual results may differ from those set forth in this press release due to the risks and uncertainties inherent in our business, including, without limitation: Prometheus approach to the discovery and development of precision medicines based on Prometheus360 is unproven; potential delays in the commencement, enrollment and completion of clinical trials and preclinical studies; Prometheus dependence on third parties in connection with product manufacturing, research and preclinical and clinical testing; Prometheus ability to develop companion diagnostics for our therapeutic product candidates; unexpected adverse side effects or inadequate efficacy of our product candidates that may limit their development, regulatory approval and/or commercialization, or may result in recalls or product liability claims; the results of preclinical studies and early clinical trials are not necessarily predictive of future results; Prometheus may not realize any benefits from our current and any future collaborations; regulatory developments inthe United Statesand foreign countries; Prometheus ability to obtain and maintain intellectual property protection for our product candidates and maintain our rights under intellectual property licenses; Prometheus ability to maintain undisrupted business operations due to the COVID-19 pandemic, including delaying or otherwise disrupting its clinical trials, manufacturing and supply chain;and other risks described in the companys prior press releases and filings with theSecurities and Exchange Commission(SEC), including under the heading Risk Factors in Prometheus most recent quarterly report on Form 10-Q and any subsequent filings with theSEC. You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof, and Prometheus undertakes no obligation to update such statements to reflect events that occur or circumstances that exist after the date hereof. All forward-looking statements are qualified in their entirety by this cautionary statement, which is made under the safe harbor provisions of the Private Securities Litigation Reform Act of 1995.

Contacts:Noel KurdiVP Investor Relations and Communications(646) 241-4400nkurdi@prometheusbiosciences.com

Media contact:Juniper PointAmy Conrad(858) 914-1962media@prometheusbiosciences.com