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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 trial about?

A plain-language summary of the goals, design and what participants do

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.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 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. Step 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. Step 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. Step 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. Step 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 trial?

12 criteria

  • 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 trial?

14 criteria

  • 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
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Investigated drugs

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.

What is already known about the treatment

SLI-RX-PHL – A sublingual immunotherapy medication designed for treating moderate to severe allergic rhinitis and rhinoconjunctivitis caused by grass pollen allergies. This medication is administered under the tongue and works by gradually desensitizing the immune system to grass pollen allergens, helping to reduce allergic reactions over time. Currently undergoing Phase II-III clinical trials to establish its optimal dosing and safety profile, this immunotherapeutic agent represents a potential treatment option for patients who have suffered from grass pollen allergies for at least two years, as defined by the Allergic Rhinitis and its Impact on Asthma (ARIA) guidelines.

Investigated diseases

  • 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 detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IVTrial ID2024-517524-18-00Protocol codeSL-3Q2AEstimated enrolment472 patientsSponsorROXALL Medizin GmbH

sourced from the EU Clinical Trials Register and site verification

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