Cosmo Announces Positive Phase 2 Study of Rifamycin 1% Topically Acting Gel, Meeting the Primary Endpoint in Distal Ulcerative Colitis and Ulcerative Proctitis

Week-6 remission was 46.2% versus 14.3% with placebo; Phase 3 planning will be informed by FDA and EMA discussions.

Rhea-AI Summary

Cosmo (CMOPF) reported that rifamycin 1% topically acting gel met its Phase 2 primary endpoint in distal ulcerative colitis and ulcerative proctitis. At week 6, 46.2% achieved clinical remission versus 14.3% with placebo (p=0.0190). The randomized, double-blind trial enrolled 76 patients with mildly to moderately active disease; 60 completed the study and formed the primary analysis population, excluding major eligibility violations affecting results.

Eight drug-related adverse events were reported, with no unexpected safety findings. Three serious adverse events were considered unrelated to treatment. Patients reported treatment satisfaction of 74.3% and willingness to repeat treatment of 82.1%. Secondary and exploratory endpoint analyses remain ongoing. Cosmo plans FDA and EMA discussions to inform further development and Phase 3 planning.

4 points · 1 major

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Positive

• Major pointWeek-6 clinical remission reached 46.2% versus 14.3% with placebo, meeting the primary endpoint (p=0.0190).
• Minor pointNo unexpected safety findings emerged during the six-week study.
• Minor pointPatient treatment satisfaction was 74.3%, with 82.1% expressing willingness to repeat treatment.
• Minor point. Forward-looking: it has not happened yet and may not happen.Cosmo plans FDA and EMA discussions to inform further clinical development.

Negative

• Minor pointEight drug-related adverse events and three serious adverse events occurred; none of the serious events were considered treatment-related.
• Minor pointPrimary analysis included 60 patients completing the study without major eligibility violations affecting results, versus 76 enrolled.
• Minor point. Forward-looking: it has not happened yet and may not happen.Secondary and exploratory endpoint analyses remain ongoing.
• Minor point. Forward-looking: it has not happened yet and may not happen.Phase 3 planning will be informed by FDA and EMA discussions.

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Ad hoc announcement pursuant to Art. 53 LR

• 46.2% clinical remission with rifamycin 1% topically acting gel vs 14.3% with placebo (p=0.0190).
• The therapy represents a new non-immune suppressive treatment modality, designed to achieve delivery to the distal colon with a novel liquid to gel delivery system, and a neutral pH.
• The results suggest that the anti-microbial properties of rifamycin may be positively affecting the gut microbiome and affecting host immune responses.
• Phase 3 planning will be informed by FDA and EMA discussions
• Investor call today at 4 pm CEST

Dublin, Ireland--(Newsfile Corp. - October 19, 2026) - Cosmo N.V. (SIX: CMHC) (FSE: C43) (“Cosmo”) today announced topline results from its Phase 2 study (EUCT number: 2023-506917-23-00) of rifamycin 1% topically acting gel in patients with mildly to moderately active distal ulcerative colitis (DUC) and ulcerative proctitis. The study was designed in line with the US Food and Drug Administration (FDA) guidance on the development of drug products for ulcerative colitis.¹ The study met its primary endpoint, with a significantly greater proportion of patients treated with rifamycin 1% topically acting gel achieving clinical remission than with placebo.

Study Design

The study was a randomized, double-blind, placebo-controlled, 6-week trial in 76 patients with a diagnosis, established for at least one month, of mildly to moderately active DUC or ulcerative proctitis. All patients had a full colonoscopy with biopsy at study entry to confirm active inflammation and to exclude patients with quiescent disease, who could inflate response rates in this indication.

Patients meeting inclusion and exclusion criteria were randomized (2:1) to rifamycin 1% topically acting gel or placebo and were treated once daily for 6 consecutive weeks. The primary endpoint, defined in line with FDA guidance,¹ was the proportion of patients in clinical remission at week 6, defined as a total Mayo score of 2 or lower, rectal bleeding subscore of 0, stool frequency subscore of 0 or 1, and endoscopic subscore of 0 or 1. Clinical remission is the gold standard endpoint in ulcerative colitis and the benchmark the FDA uses to approve new treatments. It is a demanding bar to reach: patients must be free of symptoms and show a colon free of major UC lesions on examination. Achieving remission is a meaningful outcome for patients and a strong signal of a drug's potential.

Key Findings

60 patients completed the study and comprised the primary analysis population (these were patients completing the study without major eligibility violations impacting the study results). 46.2% of patients treated with rifamycin 1% topically acting gel achieved clinical remission, compared with 14.3% in the placebo arm (a 3.2-fold increase), with the difference between the two arms reaching statistical significance (p = 0.0190).

Endpoint	Rifamycin 1% topically acting gel (N=39)	Placebo (N=21)	p-value
Proportion of patients achieving clinical remission at week 6	46.2%	14.3%	0.0190

 

Rifamycin 1% topically acting gel was well tolerated. Drug-related adverse events were low (8), and no unexpected safety findings emerged during the study. Three serious AEs were reported during the study, none of which considered to be treatment-related.

Patients reported very high treatment satisfaction (74.3%) and expressed willingness to repeat the treatment in future (82.1%).

Analyses of secondary and exploratory endpoints are ongoing, and full results will be presented at upcoming major medical meetings or congresses.

Next Steps

Cosmo plans to discuss the results with both the FDA and EMA to inform the next stages of clinical development.

Unmet Need in DUC and Ulcerative Proctitis

Ulcerative colitis (UC) is a chronic inflammatory bowel disease characterized by a relapsing disease course and significant patient burden. Distal disease involvement, including proctitis, is reported in approximately 70% of patients with UC at the time of diagnosis.² With nearly two million people living with UC in the US³ and 1.5 million in Europe,^4,5 DUC and ulcerative proctitis represent a substantial proportion of the UC population, potentially affecting approximately 2.4 million patients across these regions. Rectal inflammation is a major driver of symptoms and reduced quality of life in UC, yet remains inadequately controlled in many patients. Although both US and European guidelines place rectal therapy at the center of induction treatment for mild-to-moderate distal disease and proctitis, there have been no meaningful therapeutic advances in these indications in decades. This has led to both near- and long-term treatment gaps, as achieving early remission in left-sided disease prevents the spread of inflammation to the whole colon (pancolitis).

Ulcerative proctitis represents a significant unmet medical need. Historically excluded from most advanced-therapy development programs, patients with isolated disease have limited evidence-based treatment options for their condition.

Moreover, despite a growing body of evidence demonstrating the importance of the microbiome in UC pathogenesis, prior studies have not shown a clear benefit of antibiotic therapy in resolving UC symptoms and inflammation.⁶ As a result, there remains a significant need for safe, effective, and topically acting therapies designed to address the unique biology and symptom burden of DUC and ulcerative proctitis.

Rifamycin 1% topically acting gel targets the intestinal microbial environment believed to drive and sustain mucosal inflammation in the disease. Moreover, it has anti-inflammatory properties, as demonstrated by several pharmacological studies.^6-10 These attributes are combined with precision local delivery, strong mucosal adherence, and a neutral pH formulation, enabled by Cosmo’s proprietary technology, which transforms a liquid enema into a bio-adhesive gel upon administration. This allows targeted delivery of the active drug directly to the distal colon and rectum, where inflammation occurs, while minimizing systemic exposure and side effects.

Physician Commentary

Professor David Rubin, Joseph B. Kirsner Professor of Medicine and Director of the Inflammatory Bowel Disease Center at the University of Chicago Medicine, said: “Previously available topical therapies for distal UC or isolated proctitis have been inadequate due to limited efficacy and poor tolerability. The results of this rifamycin formulation are very positive, and combine both the novel treatment effect of rifamycin as well as a unique and attractive delivery system that I believe will be greatly appreciated by patients. The results of this anti-microbial treatment are also provocative and warrant further study of the potential for targeting the gut microbiome effectively in UC.”

Professor Simon Travis, Professor of Clinical Gastroenterology, University of Oxford, and former President of the European Crohn’s and Colitis Organization (ECCO), who contributed to the study design, said: “The Phase 2 results are particularly encouraging and demonstrate a clear benefit using the same rigorous efficacy criteria typically applied in the Phase 3 trials that support approval. Beyond the efficacy findings, the programme is notable for evaluating a novel gel formulation designed for target delivery and retention in the distal colon. If approved, rifamycin 1% could become the first antibiotic approved for ulcerative colitis, an advance that could redefine how we manage patients with distal disease and proctitis.”

Management Commentary

Giovanni Di Napoli, Chief Executive Officer of Cosmo, said: “These results validate our patient-centric approach to solving day-to-day clinical challenges. Rifamycin 1% topically acting gel is our answer to the question the UC community has been asking for forty years: how do we treat local disease without suppressing the immune system? It embodies what defines Cosmo: innovative formulation, end-to-end in-house development, and the rapid translation of science from preclinical models. For the approximately 2.4 million patients in the US and Europe affected by DUC and ulcerative proctitis, rifamycin 1% topically acting gel has the potential to establish a new treatment paradigm. Patients don’t want to wait, and neither do we: we will discuss these data regulatory agencies and move into Phase 3 as fast as regulators allow.”

Investor Call

Cosmo’s management will host a conference call with investors and analysts today at 4:00 pm CEST to discuss the Phase 2 results.

Conference Call Participants may call the following numbers, 10 – 15 minutes before conference start
Switzerland / Europe: United Kingdom: United States: HD Web Phone™:	+41 (0) 58 310 50 00 +44 (0) 203 059 58 63 +1 (1) 631 570 56 13 Click Here	Other international numbers available HERE
Webcast link: https://event.choruscall.com/mediaframe/webcast.html?webcastid=Yi060EX3

 

About Cosmo
Cosmo is a life sciences company focused on MedTech AI, dermatology, gastrointestinal diseases, and contract development and manufacturing (CDMO). We design, develop, and manufacture advanced solutions that address critical medical needs and raise the standard of care. Our technologies are trusted by leading global pharmaceutical and MedTech companies and reach patients and healthcare providers around the world. Guided by our purpose - Building Health Confidence - our mission is to empower patients, healthcare professionals, and partners by innovating at the intersection of science and technology. Founded in 1997, Cosmo is headquartered in Dublin, Ireland, with offices in San Diego (USA), and in Lainate, Rome, and Catania (Italy).
For more information, visit www.cosmohealthconfidence.com.

Financial calendar

Jefferies Global Healthcare Conference, London	November 16-19, 2026
Berenberg European Conference, Windsor	November 30-December 3, 2026

 

For further information, please contact:
investor.relations@cosmohc.com

This press release contains forward-looking statements that reflect Cosmo’s current expectations regarding the clinical development, regulatory assessment, and potential future availability of the investigational product. Such statements are subject to significant known and unknown risks and uncertainties, which may cause actual results, performance or achievements to differ materially from those expressed or implied herein. These risks and uncertainties include, without limitation, the completion and outcomes of additional clinical analyses, interactions with and determinations by regulatory authorities, reliance on third-party partners, the potential impact of external scientific or medical developments, and other factors described in Cosmo’s publicly available filings and reports. All statements other than statements of historical fact are statements that could be deemed forward-looking statements. The reader is cautioned that any such forward-looking statements are not guarantees of future performance and involve risks and uncertainties and is cautioned not to place undue reliance on these forward-looking statements. All forward-looking statements are based on information currently available to Cosmo, and Cosmo assumes no obligation and disclaims any intent to update any such forward-looking statements, except as required by applicable law.

References

1. FDA Guidance for Industry – Development of drug products for the treatment of ulcerative colitis (April 2022)
2. Fumery M. et al. Clin Gastroenterol Hepatol. 2018. 16(3): 343-356.
3. Weisman MH. et al. Prev Med Rep. 2023. 33: 102173.
4. Heydari K. et al. Gastroenterol Hepatol Bed Bench. 2025. 18(2): 132-146.
5. United Nations, Department of Economic and Social Affairs, Population Division. World Population Prospects 2024.
6. Rosette C. et al. J Infectiology. 2019. 2(4): 18-24.
7. Rosette C. et al. Drug Metab. Pharmacokinet. 2019. 34(3): 172-180.
8. Aiello C. et al. Microbiol. Res. 2025. 16, 44.
9. Mangano K. et al. Drug Deliv. Transl. Res. 2025. 15(9): 3296-3306.
10. Mangano K. et al. J Clin Med. 2026 Aug 19;15(16):6409.

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To view the source version of this press release, please visit https://www.newsfilecorp.com/release/319677

FAQ

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What did Cosmo's Phase 2 rifamycin gel trial show?

Rifamycin 1% topically acting gel met the primary endpoint, with 46.2% achieving clinical remission at week 6 versus 14.3% with placebo (p=0.0190). The primary analysis included 39 patients receiving rifamycin and 21 receiving placebo.

What are Cosmo's next steps for rifamycin gel?

Cosmo plans to discuss the results with the FDA and EMA to inform the next stages of clinical development and Phase 3 planning. Analyses of secondary and exploratory endpoints are ongoing, with full results to be presented at upcoming medical meetings or congresses.

How did Cosmo's rifamycin trial define clinical remission?

Clinical remission required a total Mayo score of 2 or lower, a rectal bleeding subscore of 0, a stool frequency subscore of 0 or 1, and an endoscopic subscore of 0 or 1. These measures assess symptoms and inflammation seen during examination of the colon.

How was Cosmo's Phase 2 rifamycin gel trial conducted?

Patients were randomly assigned 2:1 to rifamycin gel or placebo and treated once daily for 6 consecutive weeks. All patients underwent a full colonoscopy with biopsy at entry to confirm active inflammation and exclude inactive disease. Their diagnosis had been established for at least one month.