GlobeNewswire Inc | Aug 2, 2021 08:00AM EDT

August 02, 2021

- First Anti-TL1A trial in Crohns Disease -

- APOLLO-CD Phase 2a along with ARTEMIS-UC Phase 2 topline results expected in fourth quarter 2022 -

- Final Phase 1a results for PRA023 in normal healthy volunteers expected in fourth quarter 2021-

SAN DIEGO, Aug. 02, 2021 (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, starting first with inflammatory bowel disease (IBD), today announced the initiation of the APOLLO-CD Phase 2a clinical trial evaluating PRA023 for moderate-to-severe Crohns disease (CD), with first patient enrollment.

We are excited to advance PRA023 into the APOLLO-CD Phase 2a study as we believe its novel mechanism of action, designed to address both inflammation and fibrosis, can have a significant impact on patients suffering with Crohns disease, said Allison Luo, MD, Chief Medical Officer of Prometheus. We believe PRA023 has the potential to address the highest unmet need of fibrostenotic disease in this patient population.

The APOLLO-CD Phase 2a trial is an open-label study designed to evaluate the proof-of-concept efficacy and safety of PRA023 in moderate-to-severe Crohns disease with centrally read endoscopy as the primary endpoint. Dosing regimen of the 50 subjects in the study will consist of 1,000 mg on day 1, followed by 500 mg on weeks 2, 6, and 10 for a total of 12 weeks on therapy. The primary endpoint at week 12 will evaluate the proportion of patients achieving endoscopic improvement as defined by 50% decrease in Simple Endoscopic Score for Crohns Disease (SES-CD), which assesses the size of mucosal ulcers, the ulcerated surface, the endoscopic extension and the presence of stenosis. Each subject will also be assessed for the status of companion diagnostic (CDx) assay we are developing and subgroup analyses for all endpoints will be conducted based on CDx results.

Clinicians and patients are excited about Prometheus precision approach coupled with the anti-fibrotic mechanistic approach of the anti-TL1A therapy, said Dr. G. Aaron Duvall, gastroenterologist and investigator at Tyler Research Institute. I am thrilled to participate in both the ulcerative colitis and Crohns disease studies to help bring this novel therapeutic approach, with the use of a companion diagnostic, to patients.

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 this Phase 2a trial. Final Phase 1a results of PRA023 are expected in the fourth quarter of 2021. Separately, Prometheus recently initiated and dosed the first patient in the ARTEMIS-UC Phase 2 trial to evaluate the efficacy and safety of PRA023 in moderate-to-severe ulcerative colitis (UC) patients.

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, UC and CD. The Company has initiated enrollment in a Phase 2 trial in UC patients and a Phase 2a trial in CD patients, each utilizing a genetic-based companion diagnostic designed 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 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 and diagnosis of immune-mediated diseases, starting first with IBD. The Companysprecision medicine platform, Prometheus360TM, 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 potential of PRA023 and a companion diagnostic to address a high unmet need for patients; and the timing of Prometheus reporting 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 Prometheus360TM is unproven, and the Company may not be able to develop any therapeutics or companion diagnostic products of commercial value; 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 a companion diagnostic for PRA023; the success of clinical trials and preclinical studies for its product candidates and companion diagnostic; 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 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