Cat Allergen Immunotherapy Shows Real-World Effectiveness

A real-world study demonstrated the effectiveness of subcutaneous immunotherapy with depigmented, polymerized cat epithelium extract (Dpg-pol-cat) in adults with moderate to severe allergic rhinitis or rhinoconjunctivitis caused by cat allergy.1

“The clinical effectiveness of Dpg-pol-cat was evident after 6 months of treatment and was maintained throughout the study until the final visit at 18/24 months,” wrote study investigator María Aránzazu Jiménez-Blanco, from the Hospital Central de la Cruz Roja San José y Santa Adela in Spain, and colleagues.

Allergies to animal epithelium are becoming increasingly common—about 26% of European adults evaluated for suspected inhalant allergies are sensitized to cats.2 However, avoidance strategies remain difficult and are often ineffective.

Investigators conducted a retrospective study to assess the effectiveness and safety of subcutaneous Dpg-pol-cat in 28 patients with moderate to severe cat allergy-related rhinitis or rhinoconjunctivitis, including those with controlled asthma.1 Dpg-pol-cat is a depigmented, purified allergen extract of cat epithelium polymerized with glutaraldehyde into allergoids and adsorbed onto aluminum hydroxide.

The primary endpoint assessed treatment effectiveness under real-life conditions, measured by HRQoL via the ESPRINT-15 questionnaire 24 months after initiation. Secondary endpoints included changes in rhinitis HRQoL, symptoms, rescue medication use (via daily medication score), asthma control, and lung function (forced expiratory volume after 6, 12, 18, and 24 months). The study also evaluated immunologic responses at 12 and 24 months, including levels of total IgE, cat-specific IgE, anti–Fel d 1/2/4 IgE, total IgG₄, cat-specific IgG₄, and anti–Fel d 1/2/4 IgG₄.

Participants had a mean age of 35 years and received treatment for an average of 21.8 months; 67.9% were women. Most (92.9%) had rhinoconjunctivitis, 85.7% had rhinitis, and all had controlled or partially controlled asthma. Median cat epithelium–specific IgE levels were 42.5 kU/L, and total IgE levels were 294.0 kU/L.

Patients underwent a 1-day rush build-up schedule, consisting of 2 doses of 0.2 and 0.3 mL every 30 minutes on a single day, followed by monthly maintenance injections of 0.5 mL for ≥ 24 months. Treatment occurred between May 2018 and December 2021.

The team observed significant and sustained improvements in all domains of the ESPRINT-15 questionnaire from 6 months through the final visit at 24 weeks. The median questionnaire score improved from 36.0 points at baseline (IQR, 18.0–52.0) to 35.0 at 6 months (IQR, 10.0–45.0; P =.0052), 13.0 at 12 months (IQR, 8.0–35.0; P =.0002), and 16.0 at the final visit (IQR, 7.0–31.0; P =.0009). Investigators observed significant improvement in the questionnaire from 12 months to 24 months (P = .0470).

When asked to rate their overall quality of life related to rhinitis, patients reported progressive improvement over time. The proportion rating their condition as good, very good, or excellent rose from 76.8% at baseline to 81.8% at 6 months (P =.0009), 89.5% at 12 months (P =.0006), and 90.9% at the final visit (P =.2211). Overall, the percentage of patients reporting improvement increased by roughly 13%, from 78.6% at baseline to 88.9% at the last observation (P =.0082).

The study did not find significant improvement in symptoms of rhinitis, rhinorrhea, nasal itchiness, nasal obstruction, dyspnea, asthma, and ocular itchiness. Only wheezing significantly improved (P = .041). However, for many patients, symptoms were asymptomatic or mild at 24 months.

Participants also had a significant reduction of rescue medication use (1.79 to 0.96; P < .0001) and better asthma control (from 19.07 ACT mean score at baseline to 21.63 at 6 months (P = .0051) to 21.95 at 12 months (P = .0201). Additionally, the study found that most IgG4 levels significantly increased after 24 months of subcutaneous immunotherapy (from 3.84 at baseline to 4.43 at final visit kU/L; P = .0092), excluding mean anti-Fel d 1 IgG4 levels.

Most local reactions were mild or moderate, with only 1 classified as severe. All systematic reactions were <2 grade, according to the Allergy Organization grading system, and occurred mostly during the build-up phase.

“Dpg-pol-cat significantly improved rhinitis HRQoL, reduced rhinoconjunctivitis and asthma symptom severity, and significantly decreased the use of concomitant medications for both rhinitis and asthma,” investigators concluded.

References

1. Jiménez-Blanco MA, González-Mendiola MR, Boteanu C, et al. Effectiveness and safety of subcutaneous immunotherapy using a depigmented, polymerized extract of cat epithelium in allergic patients: a retrospective, real-world study. Front Allergy. 2025;6:1642315. Published 2025 Sep 18. doi:10.3389/falgy.2025.1642315

2. Warm K, Lindberg A, Lundbäck B, Rönmark E. Increase in sensitization to common airborne allergens among adults - two population-based studies 15 years apart. Allergy Asthma Clin Immunol. 2013;9(1):20. Published 2013 Jun 11. doi:10.1186/1710-1492-9-20