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AuthorisedTherapeutic exploratory (Phase II)Interventional

A Multicenter, Open-Label, Long-Term Extension Study to Evaluate the Long Term Safety and Tolerability of KT-621 in Participants With Asthma Previously Enrolled in a KT-621 Asthma Study

Asthma can cause wheezing, coughing, and shortness of breath. In eosinophilic asthma, these symptoms are driven by high levels of certain white blood cells that cause swelling in the airways. This study is testing an experimental medicine called KT-621 to see if it is safe and well tolerated when taken over a longer period. This is an extension study, meaning it is only open to adults who have already completed an earlier trial with KT-621. Because this trial is 'open-label', there is no dummy drug (placebo); everyone who takes part will receive KT-621. Over the course of 52 weeks (one year), the study team will monitor participants closely. They will record any side effects, perform regular breathing tests to check lung function, take blood samples, and ask questions about everyday asthma symptoms and quality of life.

At a glance

Status
Authorised
Phase
Therapeutic exploratory (Phase II)
Sponsor
Kymera Therapeutics Inc.
Enrolment target
77
Start
09 Sep 2026

What is this study about?

Asthma is a common lung condition, but some forms are harder to treat than others. Eosinophilic asthma is a type of asthma where an overactive immune system produces too many white blood cells called eosinophils. These cells cause severe swelling and irritation in the airways. For many people, everyday steroid inhalers are not enough to keep symptoms under control, leading to frequent flare-ups and hospital visits.

Researchers are developing KT-621 to target the underlying causes of this airway swelling. Before any new medicine can become widely available on the NHS, doctors must be sure it is safe to use for months or years at a time. This trial is a 'long-term extension study', designed to follow patients who have already taken KT-621 in an earlier trial to see how they do over a full year.

Because this is an open-label study, every person enrolled will receive the actual study medicine. There is no placebo (dummy medicine) used in this extension phase. Doctors will monitor each participant's health, check how their lungs are working, and see how the body processes the medicine.

Studies like this are vital because they provide the long-term safety data needed to prove whether a new treatment is dependable. If successful, KT-621 could offer another treatment option for people whose lives are severely affected by uncontrolled asthma.

Key takeaways

  • Tests the long-term safety of the experimental medicine KT-621 over 52 weeks.
  • Only open to adults who have already completed an earlier KT-621 asthma trial.
  • All participants receive the active treatment; there is no dummy pill (placebo).
  • Involves regular clinic visits, breathing assessments, and blood tests to monitor safety.
  • Participation is entirely voluntary, and you can withdraw at any time.

Who may be eligible?

This trial is specifically for adults aged 18 and over who have moderate to severe eosinophilic asthma. Because it is an extension study, you must have already taken part in and completed an earlier clinical trial for KT-621.

You cannot join this study as your first clinical trial. It is only open to participants rolling over from the previous KT-621 asthma trial who are willing to continue regular check-ups for another year.

The study team will check your overall health and previous trial records to make sure it is still safe for you to continue receiving the study medicine.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

  1. I am aged 18 or older.
  2. I have moderate to severe eosinophilic asthma.
  3. I have already participated in an earlier clinical trial for KT-621.
  4. I am willing and able to attend clinic visits for around 52 weeks.
  5. I am happy to undergo routine breathing tests and blood checks.
Answer every question to see your result.

What does participation involve?

Taking part in this study lasts for approximately 52 weeks (one year). During this time, you will receive the study medicine, KT-621. You will have regular planned appointments at the trial clinic so the medical team can keep a close eye on your health.

At your clinic visits, the team will check your vital signs (such as blood pressure and heart rate) and ask about any side effects or changes in your health. You will do standard breathing tests (spirometry), where you blow into a tube before and after using a reliever inhaler to measure your lung capacity. You will also have blood tests to see how much medicine remains in your body and fill out short questionnaires about your daily asthma symptoms and overall quality of life.

Potential risks and benefits

A potential benefit of taking part is receiving the active study treatment under the close supervision of an asthma specialist team, which may help manage your asthma. However, because KT-621 is still being tested, there is no guarantee it will improve your symptoms, and you might experience unexpected side effects. You may also feel slight discomfort during blood tests or breathing tests. Taking part is completely voluntary. You can choose to leave the study at any point without giving a reason, and your regular NHS medical care will not be affected.

Locations (8)

Some site locations are approximate. We're improving this — please verify with the trial team before travelling.
  • —
    Unverified
    Austria
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    Unverified
    Germany
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    Unverified
    Belgium
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    Unverified
    Romania
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    Unverified
    Italy
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    Unverified
    Slovakia
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    Unverified
    Poland
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    Unverified
    Spain

Common questions

Will I receive a placebo (dummy medicine)?

No. This is an open-label study, which means all participants will receive the active study medicine, KT-621.

How long will I be in the study?

The study lasts for 52 weeks (around one year) from the time you begin this extension phase.

Can I join if I have never taken KT-621 before?

No. This study is only open to people who have already completed a previous clinical trial testing KT-621.

Do I have to pay for any study medicines or tests?

No. All study-related medicines, tests, and medical visits are provided free of charge, and travel expenses are often reimbursed.

Should I stop using my normal asthma inhalers?

No. You should never change or stop your regular prescribed asthma treatments unless the study doctors specifically instruct you to do so.

How to find out more

Always speak to your GP or specialist before deciding to take part in a study.

Discussion

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