RALEIGH – November 02, 2026 -- RedHill Biopharma (NASDAQ: RDHL) said two independent in vitro studies confirmed that its Crohn's disease candidate RHB-204 kills Mycobacterium avium subspecies paratuberculosis (MAP) at a level comparable to RHB-104, which posted a 64% efficacy gain in a Phase 3 trial.
Two microbiology centers confirm MAP-killing in culture and phage assays
The studies used long-term intracellular culture and spot and phage assays. One was led by Professor Tim Bull of City St George's University of London. The other was led by Professor Irene Grant of Queen's University Belfast and Dr Hannah Dane, working with Rapid-myco Technologies.
Bull's work showed positive results across MAP strains from human Crohn's patients and from animal carriers of Johne's disease, which RedHill said suggests both human and veterinary utility. RHB-204 did not induce tolerance during exposure periods of up to 6 days. Bull said "MAP is remarkably difficult to kill and test against" because of its intracellular lifestyle and slow growth.
RHB-204 matched RHB-104 with lower doses of two active ingredients
The Belfast-led work found comparable MAP killing to RHB-104 in both assay types. Efficacy was reached with lower doses of two of the active ingredients, which RedHill said points to potential for reduced toxicity and side effects.
RHB-204 is a fixed-dose oral capsule of clarithromycin, rifabutin and clofazimine. RedHill cites a 40% pill burden reduction versus RHB-104.
RHB-104 Phase 3 showed 64% greater efficacy than standard of care alone
In its Phase 3 trial, RHB-104 plus standard of care was 64% more effective than standard of care alone in Crohn's disease (p = 0.0048). RedHill says this clinical data supports RHB-204.
Reza Fathi, PhD, Senior VP of R&D at RedHill, said Phase 2-ready RHB-204 could be among the first treatments tested in an adequately controlled study of a defined MAP-positive Crohn's population. RedHill pointed to existing collaborations with two European research organizations for MAP detection diagnostics. It said rapid and accurate MAP detection has been a major hurdle in earlier clinical studies of MAP-directed therapies.
Anti-TNF failure in up to 40% of patients frames the market opportunity
Up to 40% of Crohn's patients fail to respond to anti-TNF treatment, and a similar proportion of responders lose response over time, according to the company. It noted that many existing therapies are expensive and intravenously administered, and that several carry Black Box Warnings.
Sales of Crohn's therapies in the United States, Japan and five major European markets are expected to grow at a 3.87% CAGR to $19.1 billion by 2033.
Patent runs to 2041 and regulatory designations extend exclusivity
RHB-204 is patent protected through 2041. It holds FDA Fast Track, Orphan Drug and QIDP designations, plus EU Orphan designation. QIDP status under the GAIN Act extends potential U.S. post-approval exclusivity to 12 years, while EU Orphan status provides eligibility for 10 years.
RedHill intends to explore FDA breakthrough therapy and pediatric orphan drug designations, which could open a route to a priority review voucher. The company is also pursuing partnerships and innovation development grant applications for the program.