Real-World Study Confirms Effectiveness of Cat Allergen Immunotherapy for Respiratory Allergies

A real-world study conducted at Hospital Central de La Cruz Roja (search)Search term in Madrid has demonstrated the clinical effectiveness and safety of subcutaneous immunotherapy using depigmented, polymerized cat epithelium extract (Dpg-pol-cat (search)Search drug) in adults with moderate to severe allergic rhinitis (search)Search disease and rhinoconjunctivitis (search)Search disease caused by cat sensitization.

The retrospective study, published in Frontiers in Allergy, followed 28 patients for a median treatment duration of 21.8 months, providing evidence for the therapeutic benefits of this specialized allergen immunotherapy approach in routine clinical practice.

Growing Clinical Need for Cat Allergy Treatment

Cat allergy (search)Search disease represents a significant public health concern, with approximately 10-20% of adults globally affected by cat sensitization. In Europe, about 26% of adults evaluated for suspected inhalant allergies are sensitized to cats, making it one of the most common respiratory allergens. The glycoprotein Fel d 1 (search)Search target serves as the major cat allergen, interacting with immunoglobulin E in over 90% of cat-sensitized individuals.

Traditional avoidance strategies prove largely ineffective due to the small particle size of cat allergens and their high surface adherence. Studies have shown cat hair particles can persist in household dust for up to 5 months after animal removal in concentrations sufficient to induce allergic sensitization.

Study Design and Patient Population

The observational study enrolled adult patients with moderate to severe allergic rhinitis (search)Search disease/rhinoconjunctivitis (search)Search disease with or without controlled asthma (search)Search disease due to clinically relevant cat epithelium sensitization. Participants had a median age of 35 years, with 67.9% being women. All patients demonstrated positive skin prick tests (≥3 mm) to cat epithelium and cat epithelium-specific IgE (search)Search target levels ≥0.35 kU/L.

At baseline, 92.9% of patients had rhinoconjunctivitis (search)Search disease, 85.7% had rhinitis, and all asthmatic patients (n=27) had controlled or partially controlled disease. Median cat epithelium-specific IgE (search)Search target levels were 42.5 kU/L, with total IgE levels at 294.0 kU/L.

Treatment Protocol and Clinical Outcomes

Patients received Dpg-pol-cat (search)Search drug through a rapid 1-day rush build-up schedule consisting of two doses (0.2 and 0.3 ml) administered 30 minutes apart, followed by monthly maintenance injections of 0.5 ml for at least 24 months.

Health-Related Quality of Life Improvements

The primary endpoint demonstrated significant and sustained improvements in health-related quality of life as measured by the validated ESPRINT-15 questionnaire. Median questionnaire scores decreased significantly from 36.0 points at baseline to 35.0 at 6 months (p=0.0052), 13.0 at 12 months (p=0.0002), and 16.0 at the final visit (p=0.0009).

When patients rated their overall quality of life considering only their rhinitis, the proportion reporting feeling good, very good, or excellent increased progressively from 76.8% at baseline to 90.9% at the final visit. Overall, the proportion of patients feeling better after treatment increased by approximately 13% from baseline to the last observation (78.6% to 88.9%, p=0.0082).

Symptom Reduction and Medication Use

Treatment resulted in substantial improvements in symptom severity across multiple domains. Most patients who had moderate to severe symptoms at baseline experienced improvement and had only mild symptoms or were asymptomatic at the final assessment, particularly for tearing (63% improvement, p=0.031), eye redness (48.1% improvement, p=0.001), and wheezing (70.4% improvement, p=0.006).

The percentage of asymptomatic patients increased significantly: from none to 11.1% for nasal symptoms, from 3.6% to 40.7% for ocular symptoms, and from 3.6% to 29.6% for bronchial symptoms.

Rescue medication use decreased substantially, with the mean daily medication score dropping from 1.79 at baseline to 0.96 at the final visit (p<0.0001). Specific medication reductions included antihistamines (search)Search drug by 31.0%, antileukotrienes (search)Search drug by 14.3%, nasal steroids (search)Search drug by 36%, and inhaled steroids plus long-acting β2 agonists by 28.6%.

Asthma Control Enhancement

In the asthmatic patient subgroup, treatment significantly improved asthma (search)Search disease control as measured by the Asthma Control Test (ACT). Mean ACT scores increased from 19.07 at baseline to 22.00 at the final visit (p=0.0121). The percentage of patients with good asthma control (ACT score ≥20) increased from 40.7% at baseline to 80.0% at the final assessment.

Immunological Response

The study documented significant immunological changes consistent with successful desensitization. Cat epithelium-specific IgG4 (search)Search target antibodies increased significantly from baseline to the final visit, from 3.84 to 4.43 kU/L (p=0.0092), reflecting the induction of blocking antibodies associated with immune tolerance.

Safety Profile

Dpg-pol-cat (search)Search drug demonstrated a favorable safety profile throughout the study period. Among 28 patients, 13 (46.4%) experienced a total of 20 adverse reactions, with 16 being local reactions (80.0%) and 5 systemic reactions. Most local reactions were mild (43.8%) or moderate (50.0%), with only one classified as severe.

All systemic reactions were classified as grade 1 or 2 according to the 2010 World Allergy Organization criteria, with no grade 3-4 reactions reported. Only one patient discontinued treatment due to adverse reactions, while most patients required no treatment adjustments during follow-up.

Clinical Significance and Real-World Application

"The clinical effectiveness of Dpg-pol-cat (search)Search drug was evident after 6 months of treatment and was maintained throughout the study until the final visit at 18/24 months," noted lead investigator María Aránzazu Jiménez-Blanco and colleagues.

The study's real-world design enhances its clinical relevance, demonstrating that the benefits observed in controlled trials translate effectively to routine clinical practice. The treatment's ability to reduce both symptom severity and medication dependence while maintaining a good safety profile supports its role as a disease-modifying therapy for cat allergy (search)Search disease.

These findings align with previous research showing that allergen immunotherapy represents a prototype of precision medicine, targeting the underlying disease process rather than merely masking symptoms. The observed improvements in quality of life measures are particularly significant, as they reflect patients' perception of their health burden and guide treatment decisions in clinical practice.