In short
Parietaria judaica pollen extract is an allergen preparation derived from the pollen of the wall pellitory plant, a common cause of hay fever and asthma in the Mediterranean area. It is being investigated as a skin prick test solution to diagnose IgE-mediated allergies to this pollen. One authorised Phase 3 clinical trial is currently assessing the diagnostic performance of this extract in 1,140 participants with rhinitis or rhinoconjunctivitis.
Key points
- Parietaria judaica pollen extract is being studied as a diagnostic skin prick test for pollen allergy.
- The extract contains two major allergens, Par j 1 and Par j 2, which are lipid transfer proteins.
- One Phase 3 trial is assessing the extract's diagnostic sensitivity and specificity.
- The trial plans to enrol 1,140 participants with allergic rhinitis or rhinoconjunctivitis.
- The extract is given by intraepidermal use (skin prick test) in a 40 µl dose.
- The trial is currently authorised but not yet recruiting.
What is parietaria judaica pollen extract?
Parietaria judaica pollen extract is a preparation made from the pollen of Parietaria judaica, a weed commonly known as wall pellitory. This plant is one of the most important pollen allergen sources in the Mediterranean area, where it causes severe symptoms of hay fever and asthma in allergic patients. The extract contains two major allergens, Par j 1 and Par j 2, which belong to the family of lipid transfer proteins.
In the clinical trial registry, the extract appears under the name SPT-RX-PAR, a skin prick test solution from ROXALL. It is an investigational diagnostic product, not a treatment. The extract is being evaluated for its ability to identify people who are allergic to Parietaria judaica pollen.
How does parietaria judaica pollen extract work?
Pollen allergens are multivalent proteins that cross-link IgE antibodies on mast cells or basophils, inducing the secretion of biological mediators and resulting in allergic symptoms. When a small amount of the extract is placed into the top layer of the skin during a skin prick test, it comes into contact with immune cells. If the person has IgE antibodies against the pollen allergens, the cross-linking triggers a local allergic reaction visible as a small raised bump, or wheal.
Research on the recombinant forms of Par j 1 and Par j 2 shows that folded Par j 2 exhibits more than 100-fold higher allergenic activity than unfolded Par j 2 in basophil activation testing. IgE inhibition experiments demonstrated that Par j 1 and Par j 2 together resembled the majority of allergenic epitopes of the Parietaria allergome, suggesting that both allergens should be used for molecular diagnosis of Parietaria allergy.
Which conditions is parietaria judaica pollen extract used or studied for?
The extract is being studied for the diagnosis of IgE-mediated allergy in people who have symptoms after exposure to Parietaria judaica pollen. The clinical trial includes participants with the following conditions:
- Allergic rhinitis — inflammation of the nasal passages caused by pollen exposure, leading to sneezing, runny nose and nasal congestion.
- Rhinoconjunctivitis — allergic symptoms affecting both the nose and the eyes, including itchy and watery eyes.
- Mild-to-moderate asthma — well-controlled asthma may be present alongside the nasal symptoms, but is not required for participation.
In the trial, participants must have had symptoms for at least 2 years in the case of seasonal allergenic sources, or at least 1 year in the case of perennial allergenic sources.
How is parietaria judaica pollen extract given?
The extract is given as a skin prick test. In the clinical trial, a dose of 40 µl is applied by intraepidermal use, meaning the solution is introduced into the top layer of the skin. A skin prick test is a standard diagnostic procedure in which a small drop of allergen solution is placed on the skin, usually on the forearm, and the skin is lightly pricked through the drop. The reaction is then observed after a short period.
What do the clinical trials show?
One clinical trial is currently listed for this extract. It is an international, multicenter, blinded Phase 3 trial sponsored by ROXALL, with the identifier 2025-524676-32-00. The trial is authorised but not yet recruiting participants. It plans to enrol 1,140 participants with rhinitis or rhinoconjunctivitis, with or without well-controlled mild-to-moderate asthma, due to exposure to any of the allergen sources under investigation.
The trial includes several allergen extracts from ROXALL: SPT-RX-OLE (olive), SPT-RX-PAR (Parietaria), SPT-RX-BET (birch), SPT-RX-DPT (Dermatophagoides pteronyssinus, house dust mite) and SPT-RX-PHL (Phleum pratense, timothy grass). Each participant receives the extract relevant to their allergy.
The primary efficacy endpoint is the diagnostic performance of each allergenic extract, measured by two parameters: sensitivity, which is the ability of the test to correctly identify people who are allergic, and specificity, which is the ability to correctly identify people who are not allergic. For each extract, the lower limit of the 90% confidence interval for both sensitivity and specificity should be above 0.80.
The trial is blinded, meaning that neither the participants nor the investigators know which extract is being tested on a given occasion. This design helps to reduce bias in the assessment of the skin reactions.
What side effects are known?
The provided sources do not report specific side effects for this extract. Skin prick testing may cause local reactions at the site of application, such as redness, itching or a small swelling, but no data on the frequency or severity of such reactions for this specific extract were available in the supplementary sources.