Treatments
designed
with you
in mind
Our Commitment
At Diagonal, we are developing treatments that target the root cause of genetic diseases, offering potential to improve outcomes rather than just manage symptoms.
We believe meaningful impact is defined by improvements in patients’ lived experiences and achievable with thoughtfully designed treatments.
Our Areas of Focus
Diagonal is focused on developing innovative therapies for serious and rare diseases with limited effective treatments
Our Approach
Purpose-built to address the underlying cause of rare genetic diseases
Healthy Cell Signaling
The cells of the blood vessels are constantly sending and receiving signals that guide essential functions like the growth, repair, and maintenance of healthy tissues. These signals travel through specialized pathways that determine how cells behave and respond. Healthy signaling is activated when receptors on the surface of a cell come together in a highly precise configuration.
Disrupted Pathways
Certain genetic diseases can disrupt cell signaling pathways. In many cases, mutations alter how key receptors function, preventing them from assembling correctly. This can cause the signal to weaken or be lost entirely, interrupting critical cell functions and resulting in disease manifestations.
Healthy Cell Signaling: Restored
At Diagonal, we are developing new treatments specifically designed to address the disrupted cell signaling at the heart of many rare genetic diseases. Our treatments bring together the receptors needed to restore the cell’s ability to send messages and reverse the course of disease.
Our Solution
DIAG723 is an investigational product being evaluated for the treatment of the underlying causes of HHT and PAH
Hereditary Hemorrhagic Telangiectasia (HHT)
1.4M
individuals are affected with HHT across the globe
20%-25%
people living with the condition have received an official diagnosis, according to studies
In HHT, genetic mutations disrupt cell signaling pathways that regulate blood vessel growth, resulting in the formation of abnormal blood vessels. These fragile blood vessels, known as telangiectasias and arteriovenous malformations (AVMs), can appear throughout the body and cause life-threatening bleeding events.
Recurring nosebleeds are the most common symptom of HHT, appearing in 95% of people with the condition. Due to persistent bleeding, people with HHT often progress to chronic anemia. Complications such as stroke or heart failure can also occur. Talk to your doctor if you believe you or a loved one may have HHT.
Today, HHT is managed rather than treated. Current approaches rely on:
- Supportive care (such as iron infusions or transfusions) to address the impact of bleeding events
- Medications developed for other conditions to control bleeding
These approaches help manage immediate disease impacts but fail to alter the course of the disease.
DIAG723: a specialized treatment for HHT
DIAG723 is an investigational treatment designed to directly target the root cause of HHT: deficient signaling via the ALK1 pathway—a critical regulator of vascular formation and integrity.
DIAG723 addresses HHT caused by mutations in:
- ACVRL1 (ALK1)
- ENG (endoglin)
- GDF2 (BMP9)
Toggle below to see how DIAG723 regulates healthy blood vessel formation.
ALK1 Signaling in HHT
In people with HHT, certain genetic mutations reduce the availability or function of key components of the ALK1 signaling pathway. Without proper signaling, the cell’s instructions get scrambled, and the body produces fragile blood vessels that are prone to rupture and cause bleeding.
ALK1 Signaling with DIAG723
DIAG723 brings together key receptors on the cell’s surface to activate ALK1 signaling and restore healthy blood vessel growth. This approach offers potential to prevent and reverse manifestations of HHT, enabling disease modifying effects.
Clinical Studies
DIAG723 is expected to enter clinical development in 2026. If you or a loved one is living with HHT and would like to learn more about DIAMOND, our upcoming Phase 1/2 trial evaluating DIAG723 in HHT, please contact us at clinicalinfo@diagonaltx.com.
We cannot provide medical advice, and any questions about whether your participation in any future clinical study is appropriate should be directed to your physician.
Partnering with the Community
Our goal is to meaningfully impact the lives of individuals with genetic diseases with novel treatments. We work closely with advocacy organizations and patient groups to ensure patient perspectives guide treatment development.
In partnership with Cure HHT, we launched the HHT IMPACT Study to characterize the lived experiences of people with HHT. The study is fully enrolled, and complete data are anticipated in 2026.
Preliminary findings from the study confirm the impact of HHT on daily living:
60%
Percentage of participants who reported daily nosebleeds, including a large proportion reporting several events per day
47%
Percentage of participants who reported being anemic in the 3 months prior to enrolling in the study
>20
The average number of nosebleeds per month, with a mean duration of 20 minutes per event
View our poster presented at the American Society of Hematology (ASH) 2025 annual meeting for more early results from the HHT IMPACT study.
Pulmonary Arterial Hypertension (PAH)
192K
individuals are affected with PAH across the globe
45 56
years old
the average age at diagnosis over the past 20 years
PAH is a rare, serious condition that affects the blood vessels in the lungs and impacts an estimated 192,000 patients globally. In PAH, imbalanced cellular signaling causes arteries in the lungs and right side of the heart to narrow, resulting in high blood pressure in the lungs and eventually leading to death due to heart failure. Talk to your doctor if you believe you or a loved one may have PAH.
There are several approved treatments for PAH that help manage symptoms by relaxing and widening blood vessels; however, these treatments fail to address the underlying cause of the disease. Newer PAH treatments have demonstrated potential to improve patient outcomes but have been shown to disrupt the delicate balance of cellular signaling and cause HHT-like effects.
DIAG723: a treatment designed for PAH
DIAG723 is an investigational treatment designed to restore balance in a key vascular signaling pathway implicated in PAH. PAH is characterized by abnormal changes in the pulmonary arteries. These changes can result from disruption of the delicate signaling balance that regulates healthy blood vessel formation.
When this system falls out of balance, the cells multiply excessively, causing the blood vessels in the lungs and part of the heart to thicken and become narrow, increasing resistance to blood flow and placing strain on the right side of the heart.
In some patients with PAH, genetic mutations cause interruptions in the ALK1 signaling pathway, further amplifying the impacts of the disease.
DIAG723 is developed to rebalance the signaling pathway driving PAH. Our treatment can address multiple forms of PAH, including:
- Idiopathic PAH
- BMPR2 (BMPRII) mutations
- GDF2 (BMP9) mutations
Clinical Studies
A clinical study of DIAG723 in adults with moderate to severe PAH is expected to begin in 2026. If you or a loved one is living with PAH and would like to learn more, please visit our website for updates or contact us at clinicalinfo@diagonaltx.com.
We cannot provide medical advice, and any questions about whether your participation in any future clinical study is appropriate should be directed to your physician.
PAH Resources & Support
We recognize the urgency that patients and families may feel when facing a serious illness, and we are committed to advancing our investigational therapies as quickly and responsibly as possible. The safety profile of our therapy in humans is not yet established. To help ensure patient safety and to generate the high-quality data needed for regulatory approval, our therapies are currently available only through participation in authorized clinical trials.
Clinical trials are carefully designed and closely monitored to protect participants while helping bring potential new treatments to the broader patient community. We encourage patients and their physicians to explore ongoing clinical studies listed on our website at www.diagonaltx.com or www.clinicaltrials.gov to determine whether participation may be an option.
