Somatotropin Penetration Testing from Formulations Applied Topically to the Skin

Abstract

Growth hormone (somatotropin—STH) deficiency therapy requires daily injections of recombinant human growth hormone. The FDA approved treatment with STH with one dose per week for the first time in 2021. However, injectable drug application is accompanied by numerous inconveniences. Therefore, an attempt was made to formulate a less invasive STH formulation for topical application to the skin. A substrate was prepared based on a polymer, methylcellulose (MC), into which STH was introduced at a concentration of 1 mg/g. Simultaneously, formulations were made with STH, to which albumin (ALB) was added at different concentrations: 0.1%, 0.2% and 0.5%. A test of the degree of STH permeation was carried out, as well as the effect of ALB on STH permeation parameters. Selected rheological properties of the formulations obtained were investigated. A test of STH permeation in simulated in vivo conditions through porcine skin indicated a relatively good bioavailability of over 80% and confirmed the effectiveness of MC as a carrier for growth hormone. ALB prolonged the STH penetration rate and increased the penetration degree of STH to 93%. The hydrogels obtained were found to be typical shear-thinning, thixotropic fluids.