International retrospective cohort study published on "molecular mechanisms underlying the effectiveness of tiratricol in patients with resistance to thyroid hormone beta (RTH-beta)" Stockholm, Sweden, October 16, 2026. Egetis Therapeutics AB (publ) ("Egetis" or the "Company") (NASDAQ Stockholm: EGTX), today announced the publication (Liao, Marelli et al. 2026; https://www.thelancet.com/journals/ebiom/article/PIIS2352-3964(26)00396-8/fulltext) of the largest retrospective cohort study to date of patients with resistance to thyroid hormone beta (RTH-beta) treated with tiratricol (triiodothyroacetic acid or Triac), providing an integrated characterization of the effectiveness and molecular mechanisms of tiratricol in RTH-beta. The study, led by Erasmus Medical Center, Rotterdam, The Netherlands, included 28 patients aged 0.4 to 73 years, with 18 different thyroid hormone receptor beta (THRB) mutations, treated at six centres in four countries. Median treatment lasted about four years (50 months). Tiratricol lowered thyroid stimulating hormone (TSH) and free thyroxine (FT4). Mean FT4 decreased 37% (p<0.0001) and mean TSH decreased by 43% (p<0.0001) together with reductions in heart rate of 10 bpm (p=0.014), known to be associated with the lowering of thyrotoxicosis. The authors conclude that the study provides further support to the recommendations for tiratricol treatment in the guidelines by the European Thyroid Association and may support prospective clinical trials. Nicklas Westerholm, CEO of Egetis Therapeutics, said: "We are encouraged to see these important data published in a leading peer-reviewed journal. As the largest retrospective study of tiratricol in patients with RTH-beta conducted to date, the findings provide valuable insights of both the potential clinical effects and underlying mechanism of action of tiratricol across a broad range of THRB mutations. Together with the significant unmet medical need in RTH-beta, these results further strengthen the scientific rationale for continued development of tiratricol in this patient population." As previously communicated, work is ongoing at Egetis to finalize the development plan for tiratricol in RTH-beta where scientific advisory boards have been convened and preparations for regulatory interactions are ongoing. RTH-beta is a distinct indication, with no overlap in patient populations with MCT8 deficiency. Tiratricol is not currently licensed for treatment of RTH-beta. About resistance to thyroid hormone beta Resistance to Thyroid Hormone Beta (RTH-beta) is a rare inherited disorder caused by mutations in the THRB gene, leading to impaired thyroid hormone receptor beta (TR-beta) signalling. RTH-beta occurs equally in males and females. As a result of impaired TR-beta-mediated feedback regulation of the hypothalamic-pituitary-thyroid (HPT) axis, patients present with elevated circulating thyroid hormone levels, leading to clinical manifestations affecting multiple organ systems. Patients with RTH-beta may present with goiter, as well as cardiovascular, metabolic, and neurocognitive manifestations. Recent evidence from independent patient cohort studies suggests increased cardiovascular morbidity in patients with RTH-beta. These studies report reduced life expectancy compared with the general population, with higher free thyroid hormone T4 (FT4) concentrations being associated with mortality and/or major cardiovascular events. The incidence of RTH-beta is estimated to be between 1 per 20,000-40,000 live births. There are currently no approved therapies for RTH-beta, representing a significant unmet medical need. Tiratricol has been granted Orphan Drug Designation for the treatment of RTH-beta in both the United States and the European Union. Reference: W. Liao, F. Marelli, et al. Molecular mechanisms underlying the effectiveness of triiodothyroacetic acid (Triac) in patients with resistance to thyroid hormone β (RTHβ): a multicentre, international, retrospective cohort study, eBioMedicine 2026;133: 106512 Disclaimer: Erasmus Medical Center is Egetis' licensor and receives royalties from Egetis; certain authors have received fees from Egetis. Egetis had no influence on the conduct or analysis of the study. About Egetis Therapeutics Egetis Therapeutics is a commercial-stage pharmaceutical company focused on developing and delivering innovative therapies for patients with rare diseases with significant unmet medical need. Combining scientific and clinical expertise with integrated late-stage development, regulatory and commercial capabilities and manufacturing expertise, Egetis is committed to delivering treatments and dedicated support to underserved patient communities. The Company's lead product, EMCITATE(R)(tiratricol), is the first and only approved treatment for MCT8 deficiency, a rare and life-shortening genetic disorder, with marketing authorizations in the European Union and in the United States. Headquartered in Stockholm, Sweden, with operations in the U.S. and Europe, Egetis is building a sustainable global rare disease company. For more information, visit egetis.com and follow the Company on LinkedIn. For further information, please contact: Nicklas Westerholm, CEO +46 (0) 733 542 062 [email protected] Karl Hård, Head of Investor Relations, Communications & Business Development +46 (0) 733 011 944 [email protected] Attachments

Egetis Therapeutics AB wins FDA approval for Emcitate in MCT8 deficiency. First U.S. approval covers peripheral thyrotoxicosis in MCT8 deficiency; Egetis expects commercial availability eight to 10 weeks after Sept. 28. The first U.S. treatment for excess thyroid hormone in MCT8 deficiency moved toward launch as Egetis Therapeutics AB (publ) STOEGTX said Monday the FDA had approved Emcitate. The company expects the tablets for oral suspension to be commercially available eight to 10 weeks after the Sept. 28 decision. The approval covers peripheral thyrotoxicosis in adult and pediatric patients with MCT8 deficiency, also called Allan-Herndon-Dudley syndrome. The approved indication does not include the disorder's neurological impairment, and Egetis says Emcitate is not recommended for primary hypothyroidism. FDA also granted Egetis a rare pediatric disease priority review voucher. Egetis is a Stockholm-based drug developer focused on treatments for rare diseases. The issuer's Sept. 28 GlobeNewswire release was stamped 5:46 p.m. ET. Nasdaq's EGTX page dates its displayed quote to Sept. 28 at 18:00 CET. That quote predates the announcement and cannot show the market's response. Stockholm trading on Sept. 29 will provide the first regular-session test. FDA cites two studies of hormone levels. The FDA said efficacy was evaluated in an international, randomized, placebo-controlled study and a longer-term open-label study. Across the two studies, patients treated with Emcitate had reductions in excess circulating thyroid hormone and improvements in systolic blood pressure and heart rate. The agency's Sept. 28 announcement did not give an effect size, sample count or p value. MCT8 deficiency impairs a protein that transports thyroid hormone into the brain, leaving too much of the hormone in the bloodstream. According to the FDA, tiratricol can enter cells without that transporter and reduce the elevated blood levels. The drug is taken once daily as a liquid suspension, by mouth or through a feeding tube. The FDA identified diarrhea, vomiting, rash and excessive sweating as the most common side effects. It also advised patients taking another thyroid medication to speak with their clinician before starting Emcitate because the two should not be used together. Egetis's prescribing information carries a boxed warning against use for obesity or weight loss. "Our immediate focus is ensuring that eligible patients can access EMCITATE as quickly as possible," Egetis chief executive Nicklas Westerholm said in the Sept. 28 release. Egetis has opened its RareLink patient support program and enlisted PANTHERx Rare to support specialty distribution, education and care coordination. Commercial availability remains an eight-to-10-week forecast, while the Sept. 28 announcement gave neither a U.S. list price nor a sales projection. The voucher adds a separate asset. Egetis said on Sept. 28 it currently expects to explore monetizing the priority review voucher. A sale could potentially occur in the fourth quarter of 2026, subject to market conditions. The announcement named no buyer or sale price. Rare-disease peer Mirum Pharmaceuticals, Inc. NASDAQMIRM announced on Sept. 25 that the FDA approved Atebrioz for patients aged 12 and older with fibrodysplasia ossificans progressiva. Mirum expects U.S. availability in October. The same release says the associated priority review voucher went to its licensor, Incyte Corporation NASDAQINCY, rather than Mirum. The iShares Biotechnology ETF NASDAQIBB closed at US$209.77 at 4 p.m. EDT on Sept. 25. That preceded Egetis's approval and the first Stockholm session in which it could be traded. Egetis's next dated event is its investor call at 8 a.m. CEST on Sept. 29 to discuss the approval. Management's launch timetable will face its first test when Emcitate becomes commercially available, which the company estimates at eight to 10 weeks after the Sept. 28 approval.

Egetis Therapeutics has received US FDA approval for EMCITATE (tiratricol), the first approved treatment for peripheral thyrotoxicosis in patients with MCT8 deficiency, a rare genetic disorder. The approval covers both adults and paediatric patients. MCT8 deficiency is a life-limiting X-linked disorder causing severe neurodevelopmental impairment and thyrotoxicosis. Patients have a reported median life expectancy of approximately 35 years. The drug is expected to be commercially available in the US within eight to ten weeks. Egetis has launched Egetis RareLink, a patient support programme, partnering with PANTHERx Rare for distribution and care coordination. The FDA granted Egetis a Rare Pediatric Disease Priority Review Voucher with the approval. The company expects to explore monetising the voucher, potentially in the fourth quarter of 2026.