Efficacy and safety of adapalene gel as a reactive treatment for cetuximab-induced skin toxicity in recurrent or metastatic squamous cell carcinoma of the head and neck: A historical cohort comparison study

INTRODUCTION

Despite the common occurrence of cetuximab (Cmab)-induced skin toxicity, management strategies are not well established. The traditional mainstay method consists of topical steroids, which, if used excessively, may give rise to other concerns. Alternatively, adapalene can activate epidermal growth factor receptor pathways to potentially alleviate these toxicities.

METHODS

We prospectively studied 31 patients with recurrent or metastatic squamous cell carcinoma of the head and neck (R/M SCCHN) who were eligible to use adapalene gel as a reactive treatment for topical steroid-refractory skin toxicity. For comparison, we retrospectively reviewed 99 patients with R/M SCCHN (historical control cohort) whose skin toxicity was mainly treated with topical steroids. We compared the frequency and severity of Cmab-induced skin toxicity, Cmab therapy status (e.g., dose modification), side effects caused by topical steroids and adapalene gel itself, and other medical interventions.

RESULTS

Adapalene gel was used by eight patients (25.8%) in the prospective cohort. Patients in the historical control cohort more frequently required escalation of topical steroid potency (34.3% vs. 12.9%, p = 0.022). Although there was no statistically significant difference in the frequency of grade ≥3 facial skin rash and paronychia between the two cohorts, the prospective cohort showed a significantly shorter time to complete recovery from grade 2/3 paronychia (16 vs. 47 days, p = 0.017). Further, while no skin infections were observed in the prospective cohort, 13 patients in the historical control cohort developed skin infections, especially periungual infection (0% vs. 13.1%, p = 0.024). In addition, no patients in the prospective cohort received a dose reduction of Cmab due to skin toxicities, compared to 20 patients in the historical control cohort (0% vs. 20.2%, p = 0.003). No apparent adapalene gel-related side effects were observed.

CONCLUSIONS

Adapalene gel may be an effective management option for topical steroid-refractory Cmab-induced skin toxicities and could improve compliance with Cmab therapy.

Evaluation of the in vitro performance of generic and original adapalene gel

OBJECTIVE

The aim was to evaluate the difference of the in vitro behavior between the commercially available generic adapalene gel and original product with Topical Classification System (TCS), and to analyze the effect of changes of excipients on the release behavior.

SIGNIFICANCE

Establishing in vitro performance assays to understand the impact of formulation variables on the critical quality attributes (CQA) is critical for the quality assessment of semi-solid generic drug.

METHODS

In vitro release (IVR), in vitro permeation (IVP), viscosity, and pH measurement methods for adapalene gels were established and validated. The differences between generic adapalene gel from 7 companies and original products were evaluated by correlation analysis (CA) and principal component analysis (PCA), and the relationship among 4 parameters was elucidated. The effect of excipients on the above variables was examined by univariate tests.

RESULTS

There were some differences between the gels of 5 of the 7 imitation enterprises and reference listed drug (RLD). There were varying degrees of correlation between viscosity, pH, the adapalene amount retained in skin and release rate. The result validated the key role of IVR, and identified that pH value, type of suspending agent, the amount of carbomer, etc. had certain effects on the release rate.

CONCLUSIONS

The factors mentioned above should be considered when developing and manufacturing generic adapalene gels, and the application of TCS in the evaluation of generic topical drugs was advanced. Additionally, our research revealed some discrepancies from USP<1724>, which could be valuable information for the revision.