Bausch Health's Xifaxan Successor Fails Phase III Trials for Hepatic Encephalopathy Prevention
Key Insights
Bausch Health's new solid soluble dispersion formulation of rifaximin failed to meet primary endpoints in two Phase III trials for preventing hepatic encephalopathy (search) in liver cirrhosis (search) patients.
The RED-C trials enrolled over 1,000 patients across 17 countries but did not demonstrate significant delay in first onset of overt hepatic encephalopathy (search) compared to placebo.
The failure represents a major setback for Bausch Health as analysts had projected the new formulation could generate $2 billion annually, with Xifaxan currently contributing 85% of Salix's $1.89 billion revenue.
Bausch Health suffered a significant pipeline setback after its reformulated version of blockbuster drug Xifaxan failed to demonstrate efficacy in two pivotal Phase III trials for preventing hepatic encephalopathy (search) in patients with advanced liver cirrhosis (search). The failure of both RED-C studies represents a major blow to the company's growth strategy as its flagship product approaches patent expiration.
Trial Results and Market Impact
The two Phase III RED-C clinical trials (RED-C-3131 and RED-C-3132) tested amorphous-rifaximin solid soluble dispersion (SSD) for primary prevention of hepatic encephalopathy (search) in adults with liver cirrhosis (search). The placebo-controlled studies collectively enrolled more than 1,000 patients across 17 countries but failed to meet their primary efficacy objective of lengthening the time to first event of overt hepatic encephalopathy requiring medical intervention in hospital, or death, compared to placebo.
"We are disappointed in the results, as there is currently no approved treatment for these patients," said Thomas Appio, Bausch Health's chief executive. "We are currently reviewing the full dataset to determine potential new development opportunities."
The market reaction was swift and severe, with Bausch Health shares falling approximately 11% after the announcement, dropping from $6.57 at market close on January 22 to $5.91 the following day. This decline reflects the critical importance investors had placed on the SSD rifaximin program for the company's future growth prospects.
Financial Implications and Patent Concerns
The failure carries substantial financial implications for Bausch Health. Analysts had projected SSD rifaximin as a potential $2 billion-a-year product, positioning it as a crucial growth driver as the original Xifaxan approaches patent expiration. The original rifaximin formulation currently dominates Bausch Health's revenue stream, accounting for 85% of Salix's $1.89 billion in revenues in the first nine months of 2025 and representing the largest individual contributor to the company's total pharmaceutical turnover of $3.77 billion in that period.
Xifaxan, originally developed by Salix Pharma (search) before its 2015 acquisition by Bausch Health, has been on the market for more than 20 years. The drug is currently approved for treating traveller's diarrhoea, secondary prevention of hepatic encephalopathy (search), and irritable bowel syndrome. With various lawsuits seeking to overturn its intellectual property ongoing, generics are expected to reach the US market around 2029, following a successful challenge block by Alvogen in 2024.
Therapeutic Rationale and Unmet Need
The SSD formulation was designed to enhance gastrointestinal solubility while minimizing systemic exposure, potentially improving both efficacy and safety of treatment. Bausch Health had hoped to expand rifaximin treatment into the primary prevention category rather than just reducing recurrence risk, which could have tripled the number of eligible patients.
Hepatic encephalopathy (search) represents a significant unmet medical need, occurring as a common and severe neurological complication of liver cirrhosis (search). The condition causes symptoms ranging from mild cognitive impairment to confusion and sleep disturbances due to toxin buildup in the brain, and can be fatal if left untreated. Researchers estimate that hepatic encephalopathy occurs in as many as 40% of patients with liver cirrhosis, which affects approximately one in 400 people across the United States. Currently, no preventative therapies have gained approval for hepatic encephalopathy triggered by liver cirrhosis.
Pipeline and Future Prospects
While the SSD rifaximin setback creates a significant gap in Bausch Health's late-stage pipeline, the company maintains other development programs. Its current pipeline includes epigenetic modulator larsucosterol for treating alcohol-associated hepatitis, S1P modulator amiselimod for ulcerative colitis (currently under internal review), and Thermage FLX, a radiofrequency treatment for skin tightening.
The broader hepatic encephalopathy (search) treatment landscape includes various investigational approaches. Massachusetts General Hospital and Schulan (Hangzhou) Hospital are evaluating faecal microbiota transplantation through Phase II trials, while other institutions are exploring mesenchymal stem cell therapies. Swedish company Umecrine Cognition previously reported promising results with its GABA-A receptor (search)-modulating steroid antagonist golexanolone, though development was paused to prioritize primary biliary cholangitis. Additionally, eGenesis is testing genetically engineered pig liver technology combined with OrganOx's extracorporeal liver cross-circulation system for patients with acute-on-chronic liver failure and hepatic encephalopathy.