Ad hoc announcement pursuant to Art. 53 LR

• Comparable long-term effectiveness to standard of care corticosteroids over 5 years
• Normal growth maintained, in contrast to growth suppression commonly seen with standard of care corticosteroids
• Significantly lower rate of vertebral fractures reported with AGAMREE
• Lower incidence of cataracts than normally seen for DMD patients on corticosteroids

Pratteln, Switzerland, November 4, 2025 – Santhera Pharmaceuticals (SIX: SANN) today reported positive topline results from an analysis of long-term data, including first assessments from the ongoing, open-label, multicenter GUARDIAN study evaluating AGAMREE® (vamorolone) in patients with Duchenne muscular dystrophy (DMD).

The long-term analysis included corticosteroid-naïve patients who began AGAMREE treatment between four and seven years of age in clinical studies and continued through various access programs, including the GUARDIAN study. Data from up to 110 patients were analyzed, with patient numbers varying by analysis depending on data availability. In this long-term analysis, patients had received AGAMREE for up to eight years, with a median follow-up of about five years. Most patients remained on higher doses (4–6 mg/kg/day) in real-world clinical settings over the observation period.

Patients treated with AGAMREE maintained motor function over extended follow-up, demonstrating durable efficacy as measured by time to loss of ambulation comparable to standard of care corticosteroids (p=0.91). In pre-specified subgroup analyses, no differences were observed compared with either daily deflazacort or prednisone.

Importantly, the data continue to support a differentiated safety and tolerability profile versus traditional corticosteroids. Patients treated with AGAMREE experienced a significantly lower rate of vertebral fractures (p=0.0061), maintained normal growth without the stunting seen with standard of care corticosteroids (p<0.0001), and showed fewer cases of cataracts than those treated with glucocorticoids, including a notably lower incidence versus deflazacort (p<0.015). Additionally, to date, no cases of glaucoma were observed. On average, changes in BMI or weight, when matched for height, did not differ, and no new safety signals were observed.

Detailed results are being submitted for presentation at a major international scientific conference in Q1 2026. In line with standard scientific practice, the complete data will be shared publicly following the conference presentation, once the organizers have completed their review and presentation process. In addition, further readouts from the GUARDIAN study are planned over the next three years, focusing on a broader set of efficacy and safety outcomes, including assessments of upper limb function, pubertal development, eye health, and cardiac function, as well as other relevant parameters.

Having shared the data with members of our scientific steering committee, all KOLs in the DMD field, we are very encouraged by their response.

Prof Eugenio Mercuri, Professor of Pediatrics and Child Neuropsychiatry, Universita Cattolica del Sacro Cuore, commented: “These data provide important evidence that long term treatment with vamorolone provides durable efficacy, with a substantial reduction in the risk of spine fractures and of improvement in height, in contrast to what is observed with conventional steroids.”

Prof Francesco Muntoni, Professor of Neurology, University College London, said: “These preliminary data are encouraging. In particular, it is reassuring to see that children continue to grow in height without an apparent impact on treatment efficacy. Children treated with other corticosteroids often experience significant growth stunting, which has a considerable impact on their quality of life.”

Prof Craig McDonald, Professor of Physical Medicine & Rehabilitation and Pediatrics at UC Davis, added: “It is good to see long-term efficacy comparable to other corticosteroids, and the data on height and bone health are consistent with other vamorolone studies. These data now clearly show the benefits of treating early and maintaining treatment at effective doses with vamorolone. Interestingly, the benefits we see in preservation of muscle function, height, and better bone health may also have important implications for older DMD patients, for example, for upper-limb and respiratory function. I look forward to the ongoing data collection in the GUARDIAN study.”

Shabir Hasham, Chief Medical Officer of Santhera, said: “We are truly delighted to offer the DMD community a corticosteroid treatment option that can provide long-term benefit and significantly reduce the occurrence of some of the most debilitating side effects that often lead to dose down-titration or discontinuation. Having a treatment better suited to long-term use becomes even more important as other DMD therapies used in combination with corticosteroids become available. Furthermore, the GUARDIAN study will continue to collect important efficacy and safety data across a wider range of outcomes as patients grow older and remain on treatment longer, and we look forward to communicating these findings to the Duchenne clinical community.”

About AGAMREE® (vamorolone)
AGAMREE is a novel drug with a mode of action based on binding to the same receptor as glucocorticoids but modifying its downstream activity. Moreover, it is not a substrate for the 11-β-hydroxysteroid dehydrogenase (11β-HSD) enzymes that may be responsible for local drug amplification and corticosteroid-associated toxicity in local tissues [2-5]. This mechanism has shown the potential to ‘dissociate’ efficacy from steroid safety concerns and therefore AGAMREE is positioned as a dissociative anti-inflammatory drug and an alternative to existing corticosteroids, the current standard of care in children and adolescent patients with DMD [2-5].

In the pivotal VISION-DMD study, AGAMREE met the primary endpoint Time to Stand (TTSTAND) velocity versus placebo (p=0.002) at 24 weeks of treatment and showed a good safety and tolerability profile [2, 5]. The most commonly reported side effects were cushingoid features, vomiting, weight increase and irritability. Side effects were generally of mild to moderate severity.

Currently available data show that AGAMREE, unlike corticosteroids, has no restriction of growth [6] and no negative effects on bone metabolism as demonstrated by normal bone formation and bone resorption serum markers [7].

▼ This medicinal product is subject to additional monitoring. This will allow quick identification of new safety information. Healthcare professionals are asked to report any suspected adverse reactions.

References:
[1]        Dang UJ et al. (2024) Neurology 2024;102:e208112. doi.org/10.1212/WNL.0000000000208112. Link.
[2]         Guglieri M et al (2022). JAMA Neurol. 2022;79(10):1005-1014. doi:10.1001/jamaneurol.2022.2480. Link.

[3]         Liu X et al (2020). Proc Natl Acad Sci USA 117:24285-24293
[4]         Heier CR et al (2019). Life Science Alliance DOI: 10.26508
[5]         Ward et al., WMS 2022, FP.27 - Poster 71. Link.
[6]        Hasham et al., MDA 2022 Poster presentation. Link.

About Santhera
Santhera Pharmaceuticals (SIX: SANN) is a Swiss specialty pharmaceutical company focused on the development and commercialization of innovative medicines for rare neuromuscular diseases with high unmet medical need. The Company has an exclusive license from ReveraGen for all indications worldwide to AGAMREE® (vamorolone), a dissociative steroid with novel mode of action, which was investigated in a pivotal study in patients with Duchenne muscular dystrophy (DMD) as an alternative to standard corticosteroids. AGAMREE for the treatment of DMD is approved in the U.S. by the Food and Drug Administration (FDA), in the EU by the European Commission (EC), in the UK by the Medicines and Healthcare products Regulatory Agency (MHRA), in China by the National Medical Products Administration (NMPA), in Hong Kong by the Department of Health (DoH) and in Canada by Health Canada. Santhera has out-licensed rights to AGAMREE for North America to Catalyst Pharmaceuticals and for China and certain countries in Southeast Asia to Sperogenix Therapeutics. For further information, please visit www.santhera.com.

AGAMREE® is a trademark of Santhera Pharmaceuticals.

For further information please contact:

Santhera
Catherine Isted, Chief Financial Officer: IR@santhera.com

ICR Healthcare: Santhera@icrhealthcare.com

Disclaimer / Forward-looking statements
This communication does not constitute an offer or invitation to subscribe for or purchase any securities of Santhera Pharmaceuticals Holding AG. This publication may contain certain forward-looking statements concerning the Company and its business. Such statements involve certain risks, uncertainties and other factors which could cause the actual results, financial condition, performance or achievements of the Company to be materially different from those expressed or implied by such statements. Readers should therefore not place undue reliance on these statements, particularly not in connection with any contract or investment decision. The Company disclaims any obligation to update these forward-looking statements.

# # #

Attachment

• Santhera Guardian Topline Data_04_11_25 FINAL 4pm