RHB-104 is a investigative treatment for inflammatory disorders that include Crohn’s disease and rheumatoid arthritis (RA) but also multiple sclerosis (MS). It is being developed by RedHill Biopharma.
An oral capsule, the drug has been tested in combination with Rebif (interferon beta-1a) to treat symptoms of relapsing-remitting multiple sclerosis (RRMS).
RHB-104 was originally developed by Giaconda (under the name Myoconda) and was sold to RedHill in 2010.
How RHB-104 works
RHB-104 is a mixture of three antibiotics, a class of drugs normally used to treat infections due to their ability to block the growth of or kill bacteria. RHB-104 consists of clarithromycin (63 percent), rifabutin (30 percent), and clofazimine (7 percent). Its initial treatment target was Crohn’s disease based on evidence the disease can be caused by Mycobacterium avium paratuberculosis (MAP) infections.
However, RHB-104 is thought to have mechanisms of action beyond that of fighting infections and, specifically, to have neuroprotective and anti-inflammatory properties. As MS symptoms can be due to inflammation that damages the myelin sheath (the protective layer surrounding the nerve fibers), the drug candidate may help RRMS patients to combat disease flares.
Evidence also suggests that infections, such as by MAP, may have a causal role in the development of MS in some people. These patients may experience a greater benefit taking RHB-104 in combination with MS treatments such as Rebif.
RHB-104 in clinical trials
RHB-104 was tested in four preclinical studies, three using an MS mouse model. These demonstrated that RHB-104 had the ability to reduce levels of inflammation and demyelination as well as the frequency of relapses in the mice.
RedHill next undertook a Phase 2 proof-of-concept study (NCT01717664) of RHB-104 as an add-on therapy to interferon beta-1a in 18 RRMS patients. The trial, called CEASE-MS, assessed the patients’ response to 24 weeks of Rebif with RHB-104, followed by a 24-week treatment period with Rebif only. All patients had previously been treated with Rebif for an average of five years.
The trial’s final results were announced in December 2016, and were consistent with the previously announced interim results after 24 weeks. Overall, they suggested that RHB-104 was well-tolerated and safe in RRMS patients. The beneficial effects of RHB-104 appeared to be maintained after discontinuing it.
No serious adverse events were observed during the treatment, supporting further clinical trials for RHB-104 in MS.
Two Phase 3 clinical trials, called MAPUS (NCT01951326) and MAPUS2 (NCT03009396), are currently assessing RHB-104 to treat Crohn’s disease.
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