News Release

Prometheus Biosciences Completes Enrollment of the ARTEMIS-UC Cohort 1 Phase 2 Study in Ulcerative Colitis

July 18, 2022

- Global Phase 2 placebo-controlled trial enrolled twice as fast as the industry average, establishing a roadmap for future studies -

- Enrollment initiated in Cohort 2 of CDx+ patients to evaluate the company’s companion diagnostic -

Both APOLLO-CD and ARTEMIS-UC topline results on track for 4Q 2022 -

SAN DIEGO, July 18, 2022 (GLOBE NEWSWIRE) -- Prometheus Biosciences, Inc. (Nasdaq: RXDX), a clinical-stage 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, today announced the completion of enrollment for Cohort 1 of the ARTEMIS-UC global Phase 2 study of PRA023 in ulcerative colitis (UC).   The company previously completed enrollment for APOLLO-CD, a global Phase 2a study of PRA023 in Crohn’s Disease (CD) and topline results from both the APOLLO-CD and ARTEMIS-UC trials are expected in the fourth quarter of this year.

“We are pleased to announce today that we completed enrollment of Cohort 1 of the ARTEMIS-UC trial, which is a major milestone for Prometheus and for people suffering with UC,” said Mark McKenna, Chairman and CEO.  “The pace of enrollment is a testament to the demand for better UC therapies, to investigator excitement around the TL1A target and precision approach, as well as to our team’s flawless execution. We look forward to reporting topline results from both the APOLLO-CD and ARTEMIS-UC studies in the fourth quarter this year.”

“This is a significant achievement in the development path of PRA023 as a potential treatment for both UC and CD, two diseases with extremely high unmet need,” added Allison Luo, MD, Chief Medical Officer. “We are very grateful to all of our investigators and site personnel for their enthusiastic participation and look forward to their continued partnership as we continue to advance this promising therapy with the potential to address both inflammation and fibrosis.”

Prometheus’ Phase 2 ARTEMIS-UC clinical trial has completed enrollment of patients with moderate-to-severe UC who have failed conventional or biological therapy in the initial cohort. The trial is a 12-week, double-blind, placebo-controlled, randomized study to evaluate the efficacy and safety of PRA023 in patients with UC. The initial cohort (Cohort 1) is statistically powered to evaluate the efficacy of PRA023 in 120 patients with UC. The expansion cohort (Cohort 2), which is statistically powered to further evaluate the effectiveness of Prometheus’ companion diagnostic in approximately 40 patients with UC, has begun enrollment and the company will provide an update in the fourth quarter in connection with topline results from the initial cohort of ARTEMIS-UC.

About PRA023: Pipeline in a Product

PRA023 is an IgG1 humanized monoclonal antibody 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 for moderate-to-severe IBD patients predisposed to increased TL1A expression. Prometheus is developing PRA023 for the treatment of immune-mediated diseases including UC, CD, and systemic sclerosis-associated interstitial lung disease (SSc-ILD).

The Company is currently conducting three Phase 2 studies of PRA023: a Phase 2 trial in UC patients, ARTEMIS-UC, a Phase 2a trial in CD patients, APOLLO-CD, and a Phase 2 trial in SSc-ILD, ATHENA-SSc, each utilizing a genetic-based companion diagnostic candidate designed to identify patients who are predisposed to increased expression of TL1A and therefore potentially more likely to respond to PRA023.

About Prometheus Biosciences

Prometheus Biosciences, Inc. is a clinical-stage 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. The company’s precision medicine platform, Prometheus360TM, combines proprietary machine learning-based analytical approaches with one of the world’s largest gastrointestinal bioinformatics databases to identify novel therapeutic targets and develop therapeutic candidates to engage those targets.

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 company’s current beliefs and expectations. Such forward-looking statements include, but are not limited to statements regarding: the timing of topline results of Prometheus’ APOLLO-CD and ARTEMIS-UC trials; and the ability of Prometheus’ genetic-based companion diagnostic candidate to classify patients who are predisposed to increased expression of TL1A or more likely to respond to 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 TM 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; regulatory developments in the United States and foreign countries; 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 company’s prior press releases and filings with the Securities and Exchange Commission (SEC), including under the heading “Risk Factors” in our Form 10-K filed with the SEC on March 9, 2022 and any subsequent filings with the SEC. You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof, and except as required by applicable law, we do not plan to publicly update or revise any forward-looking statements contained herein, whether as a result of any new information, future events, changed circumstances or otherwise. 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 Kurdi
VP Investor Relations and Communications
(646) 241-4400
nkurdi@prometheusbiosciences.com

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