- Microbiome specialist Rebiotix reported positive topline data from its Phase 2 study of two doses of RBX2660, a broad-spectrum microbiota suspension, in patients with recurrent Clostridium difficile infection.
- In the PUNCH Open Label study, RBX2660 met its primary efficacy endpoint — preventing C. diff. recurrence — with a success rate of 78.8% compared with 51.8% historical controls treated with antibiotics alone. RBX2660 was well tolerated, with gastrointestinal effects the most commonly reported adverse event.
- RBX2660 has been granted Orphan Drug status, Fast Track status and Breakthrough Therapy Designation from the Food and Drug Administration for its potential to prevent recurrent C. diff. infection.
The human microbiome is made up of over 100 trillion microorganisms in our gut, mouth, skin and elsewhere, with around a hundred microbiome genes for every human gene. Each person carries between two and six pounds of bacteria, and most of these are essential to health. Clostridium difficile are normally found in the gut of up to one in 20 people, and the gut microbiome normally keeps them in balance.
But if this balance is knocked off kilter, for example by antibiotic treatment or long stays in the hospital, a C. diff. infection can lead to painful diarrhea.. This can be life-threatening in vulnerable patient populations. C. diff. infections are usually treated with more antibiotics, but in around a quarter of people the infection recurs, and after two or more episodes of recurrence, the risk rises to 65%.
Rebiotix' Microbiota Restoration Therapy (MRT) candidate RBX2660 aims to reset the balance by delivering a suspension of 'good' bacteria via an enema.
"The 78.8% treatment success achieved in this open label Phase 2 trial demonstrates the potential of RBX2660, a broad spectrum microbiota drug product, to rehabilitate the gut microbiome and break the cycle of C. diff. recurrence. These results, coupled with the safety and efficacy data observed in our prior Phase 2b and Phase 2 clinical trials, position Rebiotix to advance RBX2660 into Phase 3 clinical development," said Lee Jones, president and CEO of Rebiotix.
Rebiotix is also developing RBX7455, an oral formulation of RBX2660, as a more convenient dosage form for the prevention of C. diff. infection. An open-label, dose-ranging Phase 1 trial is currently recruiting.
The microbiome has become an exciting area of research, and Rebiotix faces some rekindled competition. In mid-2016, Seres Therapeutics' stock fell by 50% with the failure of its Phase 2 trial of SER-109, an oral therapeutic containing a variety of bacterial spores in multiple recurrent Clostridium difficile infection. The company is approved to begin a new ECOSPOR III study, with tighter diagnoses and optimized dosing.