D2.216 - Effectiveness and safety of subcutaneous immunotherapy with Depigmented-Polymerized Cat Extract: real-world clinical evidence

Cat allergy is a common cause of allergic rhinitis and asthma, particularly in patients with continuous domestic exposure. Subcutaneous immunotherapy (SCIT) with depigmented-polymerized (dpg-pol) cat extract aims to improve safety while maintaining clinical efficacy. This work combines real-world effectiveness data from observational studies conducted in Europe with post-marketing pharmacovigilance information to provide a comprehensive evaluation of its benefit–risk profile.

Data were obtained from three independent studies including patients with clinically relevant cat allergy under continuous exposure, treated with dpg-pol cat SCIT. Effectiveness was evaluated in two of these studies based on clinical and functional parameters at 12 months [symptom evolution, medication use, and lung function (FEV1)] and/or 24 months of treatment [asthma control (ACT), rhinitis-related quality of life (ESPRINT-15)], and immunologic response, depending on data availability in each centre. Safety information was compiled from adverse drug reactions (ADRs) recorded in the three studies and from spontaneous post-marketing reports across Europe (Jan 2018–Aug 2025), according to WAO 2010 criteria.

Effectiveness analyses included 94 patients. After 12 months of treatment, 79% reported improvement in rhinitis symptoms and 70% in asthma symptoms, with a reduction in symptomatic medication consumption. Mean FEV₁ increased from 97% to 116% of predicted values. In the 24-month cohort, 89% rated nasal symptoms as good–excellent, 88% achieved total or partial asthma control (ACT) and quality of life (ESPRINT-15) scores improved significantly. Immunologically, there was a marked increase in sIgG₄ to Fel d 1, 2, and 4, with a reduction in the sIgE/tIgE ratio.

Regarding safety evaluation, observational studies reported 145 ADRs in 191 patients treated with dpg-pol cat extract: 104 local reactions (LR) and 41 systemic reactions (SR), all of them of Grade 1–2. Across more than 128,900 administered doses in post-marketing surveillance, 80 cases reported 146 ADRs: 40 LR (0.0310%) and 106 SR (0.0822%), including 91 Grade 1–2 (0.0706%), 10 Grade 3 (0.0071%), 4 Grade 4 (0.0031%), and one of unknown intensity (0.008%). No Grade 5 reactions or fatalities occurred.

Dpg-pol cat SCIT shows consistent real-world effectiveness together with a favourable safety profile with SR rates remaining below the 0.1% per-dose threshold reported in the literature for modified allergen extracts.