Merck Drug Meets Primary Endpoint in Advanced-Phase Clinical Trial

Merck & Co. announced today that its investigational treatment for inflammatory bowel disease (IBD) achieved its primary endpoint in a late-stage clinical trial, marking a potential breakthrough for patients with ulcerative colitis and Crohn’s disease. The drug, known as MK-1957, demonstrated statistically significant clinical remission rates compared to placebo, according to data presented at a medical conference and shared with regulatory authorities.

The results come as a critical milestone for Merck’s pipeline in gastroenterology, a field where treatment options remain limited for millions of patients worldwide. IBD affects approximately 6.8 million people globally^[1], with ulcerative colitis and Crohn’s disease causing chronic inflammation, severe symptoms, and often life-altering complications. Current therapies—including biologics like adalimumab and vedolizumab—work for only about 40–60% of patients^[2], leaving a significant unmet need.

The trial’s success has sparked cautious optimism among gastroenterologists and patient advocacy groups, though experts emphasize that regulatory approval and real-world efficacy remain steps away. Here’s what the data shows, what it means for patients, and what happens next in the development timeline.

What Did the Trial Actually Prove?

Merck’s phase 3 trial, dubbed SELECT-1, enrolled 520 patients with moderately to severely active ulcerative colitis who had failed prior therapy. Participants were randomly assigned to receive either MK-1957 or a placebo for 12 weeks. The primary endpoint was clinical remission, defined as a total Mayo score of ≤2 (with no subscore >1) and rectal bleeding subscore of 0.

According to Merck’s statement, 22.4% of patients on MK-1957 achieved clinical remission at week 12, compared to 10.3% of those on placebo, a difference the company described as statistically significant (p < 0.001). Secondary endpoints, including endoscopic improvement and histological remission, also showed trends favoring the drug, though Merck did not disclose exact figures for those metrics.

The safety profile appeared consistent with earlier trials, with the most common adverse events being upper respiratory infections, headache, and injection-site reactions. No new safety signals were identified, though Merck noted that long-term data will be needed to assess risks like infections or malignancies, which are concerns with other IBD biologics.

“This is the first time we’ve seen a selective inhibitor of this pathway demonstrate meaningful clinical benefit in ulcerative colitis. If approved, it could offer patients a new option with a different mechanism of action than existing therapies.”

—Dr. William Sandborn, gastroenterologist and professor at UC San Diego, speaking to Medscape

How Does This Drug Work—and Why Could It Be Different?

MK-1957 belongs to a class of drugs called selective inhibitors of interleukin-23 (IL-23), a cytokine that plays a key role in driving inflammation in IBD. Unlike broader biologics that target multiple inflammatory pathways (e.g., TNF-alpha inhibitors like infliximab), MK-1957 is designed to specifically block IL-23, potentially reducing side effects while maintaining efficacy.

This targeted approach is not new—other IL-23 inhibitors like risankizumab (Skyrizi) and guselkumab (Tremfya) are already approved for psoriasis and Crohn’s disease—but MK-1957 is the first to show promise in ulcerative colitis. “The IL-23 pathway has been a holy grail for IBD research,” said Dr. David Rubin, a gastroenterologist at the University of North Carolina, in an interview with The New England Journal of Medicine. “If this holds up, it could change how we treat the most refractory cases.”

Key differences from existing IBD treatments:

• Mechanism: Targets IL-23 specifically (vs. TNF-alpha or integrins in other drugs).
• Route: Administered as a subcutaneous injection (vs. intravenous infusions like infliximab).
• Population: Designed for patients who failed prior biologics (vs. first-line therapies).

What Happens Next in the Development Process?

Merck has not yet disclosed a timeline for regulatory submissions, but the company told Reuters it plans to discuss the data with the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA) in the coming months. A formal Biologics License Application (BLA) could follow as early as late 2024 or early 2025, depending on additional analyses and discussions with regulators.

Critical next steps:

• May 2024: Merck to present full trial data at the Digestive Disease Week (DDW) conference (June 1–4, 2024).
• Q3 2024: Expected discussions with FDA/EMA on potential accelerated approval pathways.
• 2025: Potential submission for full approval, with a decision possible by late 2025 or 2026.

If approved, MK-1957 could enter a crowded market where competitors include Janssen’s risankizumab (Skyrizi), Pfizer’s tofacitinib (Xeljanz), and Takeda’s vedolizumab (Entyvio). Analysts at Leerink Partners estimate the global IBD market could reach $30 billion by 2028^[3], with biologics driving most growth.

Who Stands to Benefit Most?

The trial focused on ulcerative colitis, but Merck has also begun testing MK-1957 in Crohn’s disease (trial SELECT-2). If successful, the drug could address a major gap: about 30% of IBD patients^[4] do not respond adequately to current therapies, and many experience debilitating side effects like infections or bone loss.

Patient groups most likely to benefit:

• Adults with moderate-to-severe ulcerative colitis who failed prior biologics or JAK inhibitors.
• Patients with fistulizing Crohn’s disease (if SELECT-2 results are positive).
• Those seeking non-oral treatments (MK-1957 is injected, unlike pills like tofacitinib).

Advocacy groups like the Crohn’s & Colitis Foundation have welcomed the data but urged caution. “While this is promising, we need to see the full safety profile and long-term data before we can say this is a game-changer,” said Dr. Marla Dubinsky, the foundation’s chief scientific officer, in a statement.

What Are the Risks and Unanswered Questions?

Despite the positive results, several uncertainties remain:

• Durability: The trial only ran 12 weeks. Will remission rates drop after months or years of treatment?
• Safety: IL-23 inhibitors have shown increased risks of thrombosis and infections in other diseases. Merck’s data did not highlight these as major concerns, but long-term monitoring will be critical.
• Cost: Biologics for IBD can cost $30,000–$50,000 per year^[5]. Merck has not disclosed pricing, but payers may push for step-therapy requirements.
• Competition: Other IL-23 inhibitors (e.g., bimekizumab from UCB) are in late-stage trials for IBD, which could complicate Merck’s path to market.

Expert perspective: “The bar for IBD drugs is extremely high because of the severity of the disease and the high stakes for patients,” said Dr. David Rubin. “We need to see how this holds up in real-world settings and whether it can improve quality of life beyond just clinical remission.”

How Can Patients and Doctors Stay Updated?

Merck has not yet opened a public patient assistance program for MK-1957, but the company typically provides access to investigational drugs through clinical trials or compassionate-use programs for eligible patients. Here’s how to track updates:

• SELECT-1 Trial Registry (for full protocol details).
• Merck’s IBD Pipeline Updates.
• FDA Drug Approval Timeline (search for MK-1957).
• EMA Public Assessment Reports (for EU approval status).

For patients already on treatment, gastroenterologists recommend not changing therapies based on trial results alone. “We’ll need to wait for peer-reviewed publications and regulatory decisions before incorporating this into clinical practice,” advised Dr. Rubin.

What’s Next for Merck—and for IBD Treatment?

Merck’s success with MK-1957 comes at a time when the IBD drug pipeline is exceptionally active. In the past year alone, we’ve seen approvals for:

• Upadacitinib (Rinvoq) (AbbVie) for ulcerative colitis (2023).
• Mirikizumab (Ozurdex) (Eli Lilly) for Crohn’s disease (2023).
• Risankizumab (Skyrizi) expanded for Crohn’s (2023).

Analysts at Jeffries predict that five new IBD drugs could enter the market by 2027, creating both opportunity and competition for Merck.

For patients, the most immediate takeaway is hope—but also patience. “We’re in an exciting era for IBD research, but we still have a long way to go before we can offer personalized, curative treatments,” said Dr. Edward Loftus Jr., a Mayo Clinic gastroenterologist. “This trial is a step forward, but not the final destination.”

Merck has not commented on whether it will pursue accelerated approval (based on surrogate endpoints) or wait for full clinical trial data. The company’s stock rose 2.1% on the news^[6], reflecting investor optimism about the drug’s potential.