Study of sublingual immunotherapy with Phleum pratense pollen extract spray in patients with moderate to severe grass pollen allergic rhinitis

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What is this study about?

This clinical trial focuses on testing a treatment for allergic rhinitis and rhinoconjunctivitis caused by grass pollen allergy. These conditions cause symptoms like nasal congestion, runny nose, and eye irritation during grass pollen season. The study will test a medication called SLI-RX-PHL, which contains Phleum pratense pollen extract and is given as a spray under the tongue.

The purpose of the study is to determine how well different doses of SLI-RX-PHL work and how safe they are for treating grass pollen allergies. The treatment will be tested in three different strengths (low, medium, and high dose), and some participants will receive a placebo. The medication or placebo will be given as a spray that is applied under the tongue.

The study will take place during grass pollen season, when allergy symptoms are typically most severe. Participants will need to keep a daily record of their allergy symptoms and any additional medications they need to take for symptom relief. The treatment period will last up to 50 weeks, during which the effectiveness of the medication will be measured by tracking how well it reduces allergy symptoms and the need for additional relief medications.

1 Initial treatment phase

After joining the study, you will be assigned to one of four treatment groups: high dose, medium dose, low dose, or placebo

The medication is administered as a spray under the tongue

You will receive a special electronic diary to record your symptoms and any additional medications used

2 Grass pollen season monitoring

During the grass pollen season, you will need to record daily in your electronic diary:

Your nose symptoms (sneezing, runny nose, blocked nose, itchy nose)

Your eye symptoms (itchy eyes, watery eyes)

Any additional allergy medications used

Your overall discomfort level using a 0-10 scale

3 Quality of life assessment

You will complete a quality of life questionnaire before and after the treatment period

The questionnaire will assess how your allergies affect your daily activities

4 Nasal testing

A nasal provocation test will be performed before and after treatment

This test measures how your nose reacts to grass pollen

5 Safety monitoring

Any unusual reactions or side effects should be recorded

Regular laboratory tests will be conducted to ensure your safety

The study will continue until November 2027

Who Can Join the Study?

Must sign and date the consent form before any study procedures begin
Must be between 18 and 65 years old when signing the consent form
Must have moderate-to-severe allergic rhinitis (hay fever affecting nose) or rhinoconjunctivitis (hay fever affecting nose and eyes) caused by grass pollen for at least 2 years
Can participate if they have well-controlled mild-to-moderate asthma or no asthma
For patients with asthma: Must have FEV1 (amount of air that can be forcefully exhaled in one second) greater than 70% of normal value
Must show allergic reaction to Phleum pratense (timothy grass) through:
- Positive skin prick test
- Blood test showing specific antibodies to timothy grass
- History of significant allergy symptoms during grass pollen season
- Positive response to nasal allergen challenge test
Must be able to understand and use an electronic diary for recording symptoms and medication use
Must be willing to follow study staff instructions
Must have laboratory test results within normal range or considered not medically concerning

Who Cannot Join the Study?

Age under 18 or over 65 years old
History of severe allergic reactions requiring emergency medical treatment
Currently participating in another clinical trial
Pregnant women or women planning pregnancy during the study period
Breastfeeding women
Presence of asthma that is not well controlled (asthma is a condition that affects breathing)
Current treatment with medications that could interfere with the study results
History of serious medical conditions affecting the heart, liver, or kidneys
Known allergies to any components of the study medication
History of immunotherapy (allergy shots or tablets) in the past 5 years
Inability to follow study procedures or attend scheduled visits
Current smoking or substance abuse
Major surgery planned during the study period
Any condition that, in the opinion of the study doctor, would make participation unsafe

Where you can join this trial?

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Other Sites

Site Name	City	Country
Ptpnjl fmh Hpu usq Afxvzofjfknf Dkm Ytjn Ybpaf	Dresden	Germany
Phofjapiyuae Agllzpundyqb Potcoc Dbr Tzestt Goqye	Bonn	Germany
Hif Pbgmas Ddhsawf Dgr mjeq Uqr Sunihtv	Dresden	Germany

Trial status

Country	Status	Recruitment Start
Germany	Not recruiting	01.10.2025

Trial locations

Investigated drugs:

Phleum Pratense Pollen Extract

SLI-RX-PHL is a sublingual immunotherapy treatment, which means it’s given as drops or tablets placed under the tongue. This medication is designed to help people who are allergic to grass pollen. It works by gradually exposing the patient to small amounts of grass pollen allergens, which helps the immune system become less sensitive to these allergens over time. This type of treatment aims to reduce allergy symptoms and the need for other allergy medications during grass pollen season.

Allergic rhinitis – A chronic allergic condition affecting the nasal passages and often the eyes, triggered by grass pollen exposure. The condition causes inflammation of the nasal mucosa and conjunctiva, leading to symptoms such as sneezing, runny nose, nasal congestion, and itchy eyes. In moderate to severe cases, patients experience persistent symptoms during the grass pollen season, significantly affecting their daily activities. The condition is characterized by an overreaction of the immune system to grass pollen allergens. The symptoms typically worsen during peak grass pollen periods and may vary in intensity throughout the pollen season.

Allergic rhinoconjunctivitis – A combination of allergic rhinitis and conjunctivitis, where both nasal passages and eyes are affected by an allergic response to grass pollen. The condition manifests through both nasal symptoms (congestion, runny nose, sneezing) and eye symptoms (itching, redness, tearing). The allergic response occurs when the immune system reacts to grass pollen, causing inflammation in both the nasal passages and conjunctival tissue. The symptoms typically persist during grass pollen exposure and may fluctuate in severity based on pollen levels.

Trial ID:

2024-517524-18-00

Protocol code:

SL-3Q2A

Trial Phase:

Therapeutic use (Phase IV)

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Study of sublingual immunotherapy with Phleum pratense pollen extract spray in patients with moderate to severe grass pollen allergic rhinitis

What is this study about?

Who Can Join the Study?

Who Cannot Join the Study?