Summit Presented In Vivo Proof of Concept Data for New Mechanism Antibiotics Targeting Enterobacteriaceae in Oral Session at ECCMID 2019

Oxford, UK, and Cambridge, MA, US, 15 April 2019 – Summit Therapeuticsplc (NASDAQ: SMMT, AIM: SUMM), a leader in new mechanism antibiotic innovation, presented in vivo proof of concept data for the DDS-04 series of new mechanism antibiotics targeting Enterobacteriaceae in an oral session at the 29^th European Congress of Clinical Microbiology & Infectious Diseases (‘ECCMID’) in Amsterdam.

Enterobacteriaceae are a family of Gram-negative bacteria responsible for a large number of severe and often deadly infections. In the data presented, a DDS-04 series compound cured infection in a translationally-relevant animal model of urinary tract infection, one of the major sites for Enterobacteriaceae infection. Therapeutic concentrations of the DDS-04 compound were also observed in other major sites in the animal model where life-threatening Enterobacteriaceae infections occur, including the lungs and the bloodstream.

“Patients with Enterobacteriaceae infections are increasingly at risk for poor outcomes due to the spread of antimicrobial resistance,” said Dr David Roblin, President of R&D of Summit. “Mainstay treatments are losing their effectiveness, and patients do not have the luxury of time to fail antibiotic therapy. There is a pressing need for new, targeted Enterobacteriaceae antibiotics that can serve to improve patient outcomes.”

The DDS-04 series acts via LolCDE, a novel bacterial target. The LolCDE site of DDS-04 series activity is conserved in the majority of therapeutically important Enterobacteriaceae, resulting in targeted spectrum compounds. With its new mechanism of action, the DDS-04 series was rapidly bactericidal and highly potent across globally diverse Enterobacteriaceae strains in research studies, which included multi-drug resistant isolates. Importantly, the DDS-04 series also showed low propensity for resistance development and did not show cross-resistance with existing classes of antibiotics, suggesting that DDS-04 compounds have the potential to overcome known resistance mechanisms. This profile makes the DDS-04 series attractive for further development for the treatment of Enterobacteriaceae infections.

“The DDS-04 series aligns with our antibiotic strategy. There is a clear opportunity to improve patient outcomes and a need for new mechanisms to deliver these improved outcomes and also to help address the spread of antimicrobial resistance,” commented Mr Glyn Edwards, Chief Executive Officer of Summit. “We look forward to gathering further data to support the selection of a preclinical candidate from the DDS-04 series.”

A copy of the presentation is available in the Publications section of the Company’s website: www.summitplc.com.

About Enterobacteriaceae

Enterobacteriaceae are a family of Gram-negative bacteria responsible for severe and often deadly infections. They account for a significant fraction of cases across conditions, including complicated urinary tract infections, bloodstream infections and hospital-acquired pneumonias. Summit estimates there are more than 1 million infections in the US annually caused by Enterobacteriaceae across these three settings. Increasing resistance of Enterobacteriaceae has rendered many marketed antibiotics ineffective against these bacteria. Two of the most alarming antibiotic resistance trends are extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae and carbapenem-resistant Enterobacteriaceae (CRE). ESBL is an enzyme that allows bacteria to become resistant to a wide variety of penicillin and cephalosporin antibiotics. ESBL-producing Enterobacteriaceae account for an estimated 26,000 infections annually in the US with 1,700 deaths, according to the US Centers for Drug Control and Prevention (‘CDC’). CRE are resistant to nearly all existing antibiotics, including carbapenems which are considered the antibiotics of last resort. CRE account for an estimated 9,000 infections per year in the US and 600 deaths, according to the CDC.

About Summit Therapeutics

Summit Therapeutics is a leader in antibiotic innovation. Our new mechanism antibiotics are designed to become the new standards of care for the benefit of patients and create value for payors and healthcare providers. We are currently developing new mechanism antibiotics for infections caused by C. difficile, N. gonorrhoeae and ESKAPE pathogens and are using our proprietary Discuva Platform to expand our pipeline. For more information, visit www.summitplc.com and follow us on Twitter @summitplc.

This announcement contains inside information for the purposes of Article 7 of EU Regulation 596/2014 (MAR).

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