Gamma-Linolenic Acid Levels Correlate with Clinical Efficacy of Evening Primrose Oil in Patients with Atopic Dermatitis

The study was designed as a prospective, explorative, multi-center, open, non-controlled pilot trial at five centers in Switzerland. It was conducted according to ICH guidelines for Good Clinical Practice. All procedures followed were in accordance with the Helsinki Declaration of 1975, as revised in 2000 and 2008. Informed oral and written consent was obtained from all patients and/or their legal representatives for being included in the study. The study protocol was approved by the cantonal ethics committees and the regulatory agency. The study was registered at ClinicalTrials.gov (Identifier: NCT00878670).

Patients between 2 and 45 years old were included into the study if they had AD according to the criteria of Hanifin and Rajka [15] with predominant rough and fissured skin as well as pruritus for at least 2 months. Women of childbearing potential needed to use a highly effective method of contraception during the entire duration of the study. Pregnant or lactating women were excluded.

The main exclusion factors were the presence of chronic dermatosis such as seborrheic dermatitis, contact dermatitis, nummular eczema, psoriasis, ichthyosis, an immuno-deficiency or any immunological disorder, scabies, cutaneous fungal infection, HIV-associated skin disorders, malignant diseases, T cell-Lymphoma, Letterer-Siwe-disease, progressive systemic diseases, serious internal diseases (e.g., serious de-compensated diseases of the heart, liver, and/or kidneys, or diabetes mellitus) or hypersensitivity towards one of the ingredients in the investigational product. Study participants who had been taking part in another study or had taken an investigational product during the last 4 weeks before the start of treatment were not allowed to take part in the study.

The study participants were allowed to continue to use any medication which they had been taking prior to the study at the same dose, unless the medication could be discontinued or was listed as prohibited medication. Prohibited medication prior to study start and during the study were as follows. Thirty days prior to study start, physical or psychological therapy, anti-inflammatory medication to treat AD, and immuno-modulating medication were not allowed. Fourteen days prior to study start, non-steroidal anti-rheumatic drugs, systemic use of glucocorticosteroids, tranquillizers or antiemetic agents from the phenothiazine group were forbidden and 7 days prior to study start alpha- or beta-blockers, clonidine, alpha-sympathomimetic medication, azelastine, levocabastine, or antidepressants were not allowed to be taken by the patient.

The objective SCORing Atopic Dermatitis (SCORAD) index [16] and plasma GLA and DGLA levels were assessed before treatment (baseline) and 4 and 12 weeks after treatment initiation. As safety parameters, the occurrence of adverse events (AEs), hematological and clinical-chemical laboratory tests, and vital signs were assessed. A total of 36 patients were screened and 13 screening failures occurred; forbidden medication (pimecrolimus, antidepressants; n = 2), holidays (n = 2), refusal of blood sampling (n = 1), no interest to participate (n = 1), not possible to participate (n = 1), and no reason specified (n = 6).

The study medication (EPOGAM^® 1000, Zeller Medical AG, Romanshorn, Switzerland) contained 932–1,073 mg EPO (Oenothera seminis oleum), corresponding to 80 mg GLA per capsule. The dosages were two capsules twice daily for patients aged 2–12 years and three capsules twice daily for patients over 12 years. Treatment duration was 12 weeks. Treatment compliance was defined as intake of at least 75% of the trial medication. Rescue medication including prednicarbate cream 0.25% (Prednitop^®, Abbott AG, Baar, Switzerland) and hydroxyzine syrup 2 mg/ml (Atarax^®; UCB Pharma, Bulle, Switzerland) was disposed to coup eczema exacerbations and pruritus, respectively.

The DGLA and GLA measurements were performed at AZ Biopharm GmbH (Berlin, Germany). To stabilize fatty acids, butylated hydroxytoluene was added and blood was stored at −20 °C. As published elsewhere [17], absolute levels of GLA and DGLA in human plasma were determined applying a gas chromatographic method with mass selective detection. Additionally, safety laboratory parameters [routine parameters of blood count and blood chemistry as well as Immunoglobulin E (IgE) levels] were measured locally at each investigator’s site laboratory.

To compare SCORAD and fatty acid levels at baseline, week 4 and week 12, data were tested by non-parametric Wilcoxon Signed Rank Test for paired samples for the intention-to-treat (ITT) population. The relationship between the clinical response (percentage reduction of objective SCORAD from baseline to last visit) and the increase in GLA and DGLA in plasma from baseline to last visit was assessed by linear regression models in the per-protocol (PP) population including only patients with acceptable treatment compliance. The possible effect of the co-medication on the clinical improvement (relative change of objective SCORAD) was assessed using a non-parametric group comparison (users versus non-users) by means of Kruskal–Wallis test. The statistical analysis was performed with the software SPSS version 19.0 (SPSS Inc., Chicago, IL, USA).

A total of 36 patients were screened, of whom 23 were included in the study (safety population; 14 females). The mean age was 26.3 years (range 3–58 years). The age groups were as follows: under 12 years (n = 6), between 12 and 18 years (n = 2), and above 18 years (n = 15). Eighty-seven percent of the patients were Caucasian. Two patients were lost to follow-up, resulting in 21 patients in the ITT population. From the ITT population, seven patients had to be excluded because of poor treatment compliance (<75% of study medication intake). Thus, the PP population included 14 patients.

In total, 14 patients of the safety population (n = 23) had allergic concomitant diseases such as asthma bronchiale, allergic rhinitis, or rhinoconjunctivitis. No significant difference in the SCORAD index between patients of the PP population (n = 14) with allergic concomitant diseases (n = 8) and patients without (n = 6) could be found in a sub-analysis (data not shown).

The clinical efficacy of EPO was assessed in the ITT population by recording the objective SCORAD at baseline, 4 weeks and 12 weeks after initiation of EPO therapy. At baseline, 42.9% of the patients had mild symptoms (objective SCORAD <25) and 57.1% had moderate symptoms (objective SCORAD 25–50), according to Oranje et al. [16]. After the 12-week treatment period, 93.2% of the patients had mild symptoms, whereas only 6.8% had moderate symptoms. Accordingly, the mean objective SCORAD showed a time-dependent reduction with a statistically significant decrease after 4 and 12 weeks, respectively, compared to baseline (Fig. 1; Supplemental Table 1 in the Electronic Supplementary Material). With specific focus on SCORAD parameters, a significant decrease in both the extent and total intensity of AD after EPO treatment was noticed (Table 1). In addition, the intensity of individual AD symptoms except for weeping/crusting was significantly reduced. Supplementation of EPO had no effect on total IgE levels (data not shown).

In line with the results obtained for the objective SCORAD, the clinical efficacy of EPO could also be confirmed for the total SCORAD. The mean total SCORAD showed a time-dependent reduction with a statistically significant decrease after 4 (P = 0.019) and 12 weeks (P = 0.001), respectively. Results of all individual SCORAD parameters are illustrated in Table 1.

In the ITT population, the plasma levels of both GLA and DGLA showed a significant increase over the study period (Fig. 2; Supplemental Table 1 in the Electronic Supplementary Material). This increase was most evident from baseline to week 4, with no relevant further increase to week 12. For the PP population, it could be shown that the reduction of the objective SCORAD was inversely correlated with the increase in plasma GLA (Fig. 3). In the ITT population, the correlation of the objective SCORAD and plasma GLA was not significant (data not shown) For DGLA, no significant correlation could be demonstrated (P = 0.36; data not shown).

While EPO represents a long-term basic therapy for AD, the usage of concomitant treatment options reflects the usual practice. Patients were allowed to use the provided rescue medication (prednicarbate cream and hydroxyzine syrup), for example, in cases of severe itching. The influence of the co-medication was evaluated in the ITT population (n = 21). During the study, rescue medication was used by the majority of patients (71.4%). A total of nine patients used hydroxyzine (syrup, 10–50 mg orally). Twelve patients used prednicarbate (cream, 0.25% topically) as rescue medication. Six of these patients used both rescue medications. The treatment duration and dosage regimens varied quite differently in both rescue medications (Table 2). However, the patient groups relying on rescue medication did not show any significant difference regarding the improvement of the objective SCORAD compared to the group without usage of concomitant anti-pruritic medication (P = 0.20 and P = 0.89, respectively).

During the study, 26 AEs were recorded in 13 patients. No serious AEs occurred. Only five AEs were assessed to be related to the study drug (tiredness, impaired concentration, diarrhea, abdominal cramps, and pruritus). No clinically relevant abnormalities of safety laboratory parameters or vital signs were noticed.