Summit Therapeutics plc: Phase 2 CoDIFy Trial Results Published in Lancet Infectious Diseases

Summit Therapeutics plc

('Summit', or the 'Company')


Oxford, UK, 2 May 2017 - Summit Therapeutics plc (AIM: SUMM, NASDAQ: SMMT), the drug discovery and development company advancing therapies for Duchenne muscular dystrophy and C. difficile infection ('CDI'), announces the online publication of results from the Company's Phase 2 clinical trial, called CoDIFy, in The Lancet Infectious Diseases. CoDIFy evaluated the Company's novel antibiotic for the treatment of CDI, ridinilazole, against standard of care, vancomycin. The results showed ridinilazole demonstrated substantial clinical benefit over vancomycin. This included ridinilazole achieving statistical superiority over vancomycin in sustained clinical response ('SCR'), a composite endpoint of cure at the end of treatment and no recurrence 30 days after treatment, a result which was driven by a large numerical reduction in infection recurrence.

"CDI is a serious disease that is a major healthcare challenge due to the high recurrence rates which are believed to be exacerbated by the broad spectrum antibiotics we use to treat CDI today," Professor Mark Wilcox, University of Leeds and Principal Investigator in CoDIFy commented. "A highly selective antibiotic has the potential to transform the current treatment paradigm and keep recurrent CDI at bay. The ability of ridinilazole to provide a significant increase in sustained clinical responses compared with the standard of care in CoDIFy provides evidence that ridinilazole is highly selective and warrants its continued clinical development."

Key results from CoDIFy published in The Lancet Infectious Diseases:

  • Ridinilazole achieved statistical superiority in sustained clinical response ('SCR') with rates of 66.7% compared with 42.4% for vancomycin.
  • Ridinilazole achieved a large numerical reduction in recurrent disease over vancomycin (14.3% recurrence with ridinilazole vs. 34.8% recurrence with vancomycin).
  • Ridinilazole met the pre-specified endpoint of non-inferiority on cure rates at the end of treatment (77.8% for ridinilazole vs. 69.7% for vancomycin).
  • Median time to resolution of diarrhoea favoured ridinilazole (four days on ridinilazole vs. five days on vancomycin) and numerically more subjects on ridinilazole had resolution of diarrhoea compared with vancomycin by day six (77.8% vs. 63.6%).
  • Median time to hospital discharge was five days for ridinilazole-treated subjects versus seven days for vancomycin-treated subjects.
  • Ridinilazole was retained in the gut, the site of infection, with negligible systemic exposure observed.
  • Adverse event profiles were similar between ridinilazole-treated and vancomycin-treated subjects, with no safety signals being identified with ridinilazole.

Mr Glyn Edwards, Chief Executive Officer of Summit, added: "The results of our CoDIFy trial provided further evidence of ridinilazole's ability to address the key clinical issue of recurrence, which could lead to improved patient care and reduced economic burden of CDI. We are therefore planning to progress this novel programme into Phase 3 clinical trials. With ridinilazole, we believe we have a promising potential treatment option for this potentially fatal infectious disease."

Ridinilazole is now being prepared for entry into a Phase 3 clinical programme that is expected to comprise two Phase 3 trials evaluating ridinilazole compared to vancomycin. The primary endpoint of the Phase 3 clinical trials is expected to be testing for superiority on sustained clinical response. The Phase 3 clinical trials are planned to start in the first half of 2018. 

The publication reference is Lancet Infect Dis 2017; published online Apr 28:

About CoDIFy

CoDIFy was a double blind, randomized, active controlled, multi-centre, Phase 2 clinical trial that evaluated the efficacy of ridinilazole against vancomycin in a total of 100 patients. Half of the patients received ridinilazole for ten days (200 mg, twice a day), and the remaining half received vancomycin for ten days (125 mg, four times a day). In addition to the results described above, ridinilazole was found to be highly preserving of the gut microbiome. Ridinilazole treated patients in CoDIFy exhibited no further damage to their microbiome during therapy with a proportion of patients showing initial evidence of recovery of key bacterial groups with roles in protecting from CDI. In contrast, vancomycin treated patients suffered substantial damage to their gut microbiome during treatment and this persisted in many patients during the 30-day post treatment period.

About C. difficile Infection

C. difficile infection is a serious healthcare threat in hospitals, long-term care homes and increasingly the wider community with over one million estimated cases of CDI each year in the United States and Europe. It is caused by an infection of the colon by the bacterium C. difficile, which produces toxins that cause inflammation and severe diarrhoea, and in the most serious cases can be fatal. Patients typically develop CDI following the use of broad-spectrum antibiotics that can cause widespread damage to the natural gastrointestinal (gut) flora and allow overgrowth of C. difficile bacteria. Existing CDI treatments are predominantly broad spectrum antibiotics, and these cause further damage to the gut flora and are associated with high rates of recurrent disease. Recurrent disease is the key clinical issue as repeat episodes are typically more severe and associated with an increase in mortality rates and healthcare costs. The economic impact of CDI is significant with one study estimating annual acute care costs at $4.8 billion in the US. 

About Ridinilazole

Ridinilazole is an orally administered small molecule antibiotic that Summit is developing specifically for the treatment of CDI. In preclinical efficacy studies, ridinilazole exhibited a narrow spectrum of activity and had a potent bactericidal effect against all clinical isolates of C. difficile tested. In a Phase 2 proof of concept trial in CDI patients, ridinilazole showed statistical superiority in sustained clinical response ('SCR') rates compared to the standard of care, vancomycin. In this trial, SCR was defined as clinical cure at end of treatment and no recurrence of CDI within 30 days of the end of therapy. Ridinilazole has received Qualified Infectious Disease Product ('QIDP') designation and has been granted Fast Track designation by the US Food and Drug Administration. The QIDP incentives are provided through the US GAIN Act and include an extension of marketing exclusivity for an additional five years upon FDA approval.

About Summit Therapeutics

Summit is a biopharmaceutical company focused on the discovery, development and commercialization of novel medicines for indications for which there are no existing or only inadequate therapies. Summit is conducting clinical programs focused on the genetic disease Duchenne muscular dystrophy and the infectious disease C. difficile infection. Further information is available at and Summit can be followed on Twitter (@summitplc).