Diagonal Therapeutics to Present Insights from HHT IMPACT, a Natural History Study Initiated in Partnership with Cure HHT, at ASH 2025
Preliminary results indicate HHT patients are significantly impacted by bleeding events, with consistency in severity reporting at months one and three of the study
Final study analysis will inform design of interventional clinical trial, initiating in 2026, assessing DIAG723, a first-in-class, disease modifying treatment designed specifically to address the underlying cause of HHT
WATERTOWN, Mass., Dec. 04, 2025 (GLOBE NEWSWIRE) -- Diagonal Therapeutics, a biotechnology company developing disease-modifying clustering antibodies that correct dysregulated signaling in severe genetic diseases, will present interim data from its natural history study, HHT IMPACT, for hereditary hemorrhagic telangiectasia (HHT) at the 67th American Society of Hematology (ASH) Annual Meeting and Exposition, held December 6-9, 2025 in Orlando, Florida.
HHT is a rare disease in which abnormal blood vessel formation causes bleeding events that can be serious or life-threatening, and for which there are currently no approved therapies. Initiated in partnership with the leading patient advocacy organization, Cure HHT, HHT IMPACT is designed to characterize patient-reported outcomes in HHT, including epistaxis (nosebleed) frequency, severity, and duration, hematologic support, and quality of life (QoL), using a novel patient-reporting instrument, the “During My Day Diary,” as well as established assessment tools, such as Epistaxis Severity Score (ESS).
“The interim results from HHT IMPACT describe a patient population whose quality of life is deeply affected by HHT, with nearly two-thirds of participants reporting daily nosebleeds and nearly forty percent reporting multiple nosebleeds per day,” said John Lee, M.D., Ph.D., Chief Medical Officer of Diagonal Therapeutics. “Insights from this natural history study will inform the design of our first-in-human clinical trial of DIAG723, which will start enrolling mid-2026. With its unique receptor clustering mechanism, DIAG723 has the potential to prevent and reverse all manifestations and complications associated with HHT by directly addressing the root cause of the disease. We are grateful to all the individuals participating in this study and look forward to applying the valuable learnings toward advancing a much needed, disease-modifying treatment for this serious disease.”
HHT IMPACT enrolled 109 adult HHT patients with moderate-to-severe bleeding. The study implemented and validated the "During My Day Diary," which captured the frequency, duration, and intensity of each epistaxis event. Results from the interim analysis confirm the significant burden of HHT:
- Majority of patients reported daily epistaxis, including a large proportion reporting several epistaxis events per day.
- Nearly half of the participants reported being anemic in the three months prior to enrollment.
- Participants averaged more than 20 nosebleeds per month and a mean duration of nearly 20 minutes per bleeding event.
The final analysis will be presented at a future scientific congress and will report on additional characterization of bleeding events and QoL assessments, with further evaluation of the impact HHT has on activities of daily living.
Details for the poster presentation are as follows:
Title: An interim assessment of bleeding events in a prospective natural history study of hereditary hemorrhagic telangiectasia patients using a validated bleeding scale and a novel daily reporting instrument
Presenter: John Lee, M.D., Ph.D., Chief Medical Officer, Diagonal Therapeutics
Poster ID: 2702
Poster Session: Outcomes Research: Non-Malignant Conditions Excluding Hemoglobinopathies: Poster I
Location: OCCC – West Halls B3-B4
Poster Date & Time: Saturday, December 6, 5:30-7:30 pm EST
The poster will be available on the Diagonal website following the meeting.
About Hereditary Hemorrhagic Telangiectasia (HHT)
HHT is a rare disease that affects more than 330,000 people in the U.S. and EU, and for which there are currently no approved therapies. In HHT, loss of function point mutations in members of the TGF-ß receptor superfamily complex create abnormal blood vessels that are fragile and susceptible to rupture and bleeding. These bleeding events drastically reduce quality of life, result in emergency visits and hospitalizations, and lead to chronic anemia, necessitating frequent iron infusions or red blood cell transfusions in many patients. Solid organ arteriovenous malformations, if left untreated, are at risk of rupturing, resulting in lung and brain hemorrhage, stroke, heart failure, and death.
About HHT IMPACT Natural History Study
HHT IMPACT is a first-of-its-kind non-interventional, observational, longitudinal evaluation characterizing the variability of HHT patient-reported outcomes, including nosebleeds, hematologic support, and quality of life. The study is fully enrolled, and complete data are anticipated in 2026. To learn more about the HHT Impact study in partnership with Cure HHT, please visit: https://curehht.org/hhtimpact/.
About DIAG723
DIAG723 is a bispecific antibody designed to address HHT and PAH, in which dysregulated ALK1 signaling in endothelial cells drives the formation of fragile arteriovenous malformations or vascular hyperproliferation, respectively. DIAG723 restores signaling lost due to mutations that impair receptor function. In multiple HHT preclinical studies, DIAG723 prevented and reversed arteriovenous malformations and anemia – a hallmark of HHT that can cause a host of bleeding-related complications in various organs. DIAG723 was also found to restore signaling in multiple HHT patient donor samples. In preclinical models of PAH, DIAG723 prevented disease development and cardiac remodeling, and improved hemodynamics. DIAG723 also restored normal signaling in pulmonary microvascular endothelial cells derived from multiple PAH donors. DIAG723 has received orphan drug designation from the US FDA and the EMA for the treatment of HHT.
About Diagonal Therapeutics
Diagonal Therapeutics is a biotech company advancing novel disease-modifying clustering antibodies that repair dysregulated signaling implicated in a range of illnesses. The Company's DIAGONAL Product Engine combines proprietary computational and experimental techniques to overcome historical challenges associated with antibody drug discovery and efficiently deliver optimized therapeutic assets. Diagonal's pipeline comprises clustering antibodies designed to selectively address the underlying cause of disease across hematology, hepatology, and nephrology, offering the potential to deliver life-changing therapies for patients. For more information, please visit www.diagonaltx.com.
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