PHASE I CLINICAL TRIAL USING OCTADECENEDIOIC ACID, AZELAIC ACID, AND BENZOYL PEROXIDE
When new chemical entities are tested on human skin, it is advisable to first conduct studies on healthy volunteers (so-called Phase I trials) prior to conducting
TABLE 2 Skin Delivery of Octadecenedioic Acid or Azelaic Acid to the Superficial Layers of the Stratum Corneum (Tapes), the Remainder of Skin (Skin), or the Receptor Fluid (Transdermal) Following Application of Three Different Formulations on Dermatomed Pig Skin in In Vitro Bronaugh Flow-Through Cells
FIGURE 4 (See color insert.) Autoradiography of octadecenedioic acid and azelaic acid following penetration through dermatomed pig skin for 20 hours. Images show transverse sections through the upper layers of skin treated with different formulations: untreated control (A and B); Skinorenw containing 20% azelaic acid (C and D); a gel containing 10% octadecenedioic acid (E and F); a gel containing 10% azelaic acid (G and H). Stratum corneum, epidermis, and upper dermis can be seen. Bright field (A, C, E, and G) and dark field (B, D, F, and H) images were obtained using a Leitz DMRB light microscope (Leica, Milton Keynes, U.K.). The bright reflectance in each dark field picture is the stratum corneum. The scale bar in all bright field images represents 100 mm.
FIGURE 5 (See color insert.) Examples of follicular delivery following skin penetration of octadecenedioic acid from an aqueous gel containing 10% w/w octadecenedioic acid (A and B), azelaic acid from an aqueous gel containing 10% azelaic acid (C and D), and Skinorenw containing
20% azelaic acid (E and F). Images show transverse sections through the upper layers of the skin. Bright field (A, C, and E) and dark field (B, D, and F) images were obtained using a Leitz DMRB light microscope (Leica, Milton Keynes, U.K.). The bright reflectance in each dark field picture is the stratum corneum and the infundibulum. Note that the stratum corneum in (A) and (B) has been predominantly lost from this section. The scale bar in all bright field images represents 100 mm.
studies on the intended product-user population. However, this has consequences for the type of measurements that one can undertake. The objective of this Phase I trial was to compare the in vivo antimicrobial activity of topically applied DCA with that of AZA and BPO. Because acne lesions cannot be measured on healthy
volunteers, the basis of this trial was to measure changes in the skin surface micro- flora count (Micrococcaceae and Propionibacteria) and skin-surface free fatty acid (FFA) levels on the faces of healthy volunteers as an indicator of potential anti- acne activity. The trial was performed as a double-blind study.
A group of 59 volunteers (37 male, 22 female) aged 16 to 35 were recruited into the study. All volunteers were medically screened to ensure their suitability to undertake the study. Their willingness to participate was documented through the completion of an informed consent form in the presence of medical staff.
Baseline levels of viable propionibacteria on the surface of the skin on the right cheek of each volunteer were determined seven days prior to commencement of the trial. The volunteers were assigned to one of five groups, as determined by previsit numbers of skin surface propionibacteria, so that each group had a similar statistical distribution of numbers of viable propionibacteria:
1. The first group (n ¼ 12) received the aqueous gel containing 10% w/w DCA, which was also investigated for skin delivery.
2. The second group (n ¼ 12) received the same aqueous gel formulation without the DCA (placebo).
3. The formulation of the third group (n ¼ 12) was the same aqueous gel again, but this time with 10% w/w AZA.
4. The fourth group (n ¼ 12) received “Panoxyl Aquagel 5,” a commercially available product containing 5% BPO (Stiefel Laboratories, High Wycombe, Bucks, U.K.).
5. The fifth group (n ¼ 11), finally, received Skinorenw, the commercially available product from Schering containing 20% AZA.
All volunteers were provided with a non-antimicrobial soap and instructed to wash the whole face twice daily prior to application of treatment products. Each volun- teer applied one of the products to the test site (right-hand side of the face including forehead, just beyond the midline, cheek, and chin, avoiding the eyes, nostrils, and mouth) for the 21 days of duration of the trial.
The surface microbial populations (Micrococcaceae and Propionibacteria) were enumerated on the right cheek at baseline and after 3, 7, 14, and 21 days of treatment. Sebum was collected from each volunteer at baseline and after 7, 14, and 21 days of treatment, and the FFA content was determined by gas – liquid chromatography. Volunteers were also asked to maintain a daily diary and note any positive or negative effects of the treatment. Data were analyzed using para- metric and nonparametric statistical tests.
The main findings of the study were as follows:
1. Of the 59 volunteers recruited into the study, only six individuals failed to com- plete the study (10.2% drop-out rate). The dropouts were evenly spread over the treatment groups, and there was no evidence that adverse reactions to any one treatment were responsible for noncompletion. Only those volunteers who completed the treatment were included in the subsequent statistical analysis of the results.
2. All preparations containing dicarboxylic acids (both AZA and DCA) were well tolerated. In the BPO-treated group, 92% of volunteers reported adverse events (irritancy and drying of the skin). However, the volunteers in this group were able to maintain the stipulated treatment regime throughout the study, although some were advised to use a moisturizing lotion.
3. None of the treatment regimes had any detectable effect on skin surface FFAs.
FIGURE 6 Scatter plot of changes in Micrococcaceae count from baseline following treatment with a 10% w/w octadecenedioic acid gel (A), placebo gel (B), 10% w/w azelaic acid gel (C), 5% w/w benzoyl peroxide (Panoxylw Aquagel 5) (D), or 20% w/w azelaic acid (Skinorenw) (E). Abbreviations: AZA, azelaic acid; BPO, benzoyl peroxide; DCA, octadecenedioic acid.
4. All the treatments, apart from the placebo, produced significant reductions in
Micrococcaceae after one week of treatment (Fig. 6).
5. Only BPO and DCA significantly reduced the propionibacteria population (Fig. 7). Both compounds achieved reductions in propionibacteria counts in the majority of volunteers in their respective user groups.
FIGURE 7 Scatter plot of the changes in propionibacteria count from baseline following treatment with a 10% w/w octadecenedioic acid gel (A), placebo gel (B), 10% w/w azelaic acid gel (C), 5% w/w benzoyl peroxide (Panoxylw Aquagel 5) (D), or 20% w/w azelaic acid (Skinorenw) (E). Abbreviations: AZA, azelaic acid; BPO, benzoyl peroxide; DCA, octadecenedioic acid.
The results of this phase I trial suggested that DCA combines activity against pro- pionibacteria with a good safety and tolerance profile. It outperformed Skinorenw in this trial. However, DCA did not produce the in vivo antimicrobial efficacy that would have been predicted from the in vitro data listed in Table 1. This suggested that the delivery of DCA from the gel formulation was not yet optimal, which was indeed confirmed in Table 2 and Figure 3.