Cadazolid, a novel antibiotic, is a strong inhibitor of Clostridium difficile protein synthesis, leading to potent suppression of toxin and spore formation.

In preclinical studies cadazolid showed potent in vitro activity against Clostridium difficile isolates and a low propensity for resistance development. In a human gut model of Clostridium difficile-associated diarrhea (CDAD), cadazolid had a very limited impact on the normal gut microflora.

Cadazolid absorption is negligible resulting in high gut lumen concentrations and low systemic exposure, even in severe cases of CDAD where the gut wall can be more damaged and drug absorption potentially increased.

The US FDA has designated cadazolid as both a Qualified Infectious Disease Product (QIDP) and a Fast Track development program for the treatment of CDAD.


Cadazolid is evaluated in the IMPACT program (International Multi-center Program Assessing Cadazolid Treatment in patients suffering from Clostridium difficile-associated diarrhea). The program comprises two Phase III studies comparing the efficacy and safety of cadazolid (250 mg administered orally twice daily for 10 days) versus vancomycin (125 mg administered orally four times daily for 10 days).

The IMPACT program is designed to determine whether the clinical response after administration of cadazolid is non-inferior to vancomycin in subjects with CDAD, and whether administration of cadazolid is superior to vancomycin in the sustained clinical response. The program commenced enrollment in the fourth quarter 2013 with a target of approximately 1’260 subjects worldwide, and results are expected in mid-2017.


Cadazolid was studied in a Phase II multi-center, double-blind, randomized, active reference, parallel group, therapeutic exploratory study. The study evaluated the efficacy, safety and tolerability of a 10-day, twice daily oral administration of 3 doses (250 mg, 500 mg or 1,000 mg b.i.d.) of cadazolid in subjects with CDAD. As the current standard of care for CDAD, oral vancomycin (125 mg qid for 10 days) was used as the active reference. The study was completed in December of 2012, after having enrolled 84 subjects with CDAD.

The results of the Phase II study indicate that the effect of all doses of cadazolid were numerically similar to, or better than vancomycin on key endpoints including CDAD clinical cure rates as well as sustained cure rates. Clinical cure rate was defined as the resolution of diarrhea and no further need for CDAD therapy at test-of-cure 24 to 72 hours after the last dose of treatment, while sustained cure rate was defined as clinical cure with no recurrence of CDAD up to 4 weeks post-treatment. Recurrence rates were numerically lower for all doses of cadazolid as compared to vancomycin. Cadazolid was safe and well tolerated.


2014 – Cadazolid receives US FDA QIDP & Fast Track designation for development in CDAD
2013 – Initiation of Phase III development
2012 – Completion of Phase II development


T. Louie et al., A Multicenter, Double-Blind, Randomized,Phase 2 Study Evaluating the Novel Antibiotic, Cadazolid, in Patients with Clostridium difficile Infection. Antimicrob.Agents Chemother. 2015;59(10):6266-73

D.N. Gerding et al., Susceptibility of Clostridium difficile Isolates from a Phase 2 Clinical Trial of  Cadazolid and Vancomycin in C. difficile infection. J. Antimicrob. Chemother., available online doi:10.1093/jac/dkv300



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