Highlights of Gene and Cell Therapy for Epidermolysis Bullosa and Ichthyosis.

Advancements in the molecular genetics of epidermolysis bullosa (EB) and ichthyosis, two rare inherited skin conditions, have enabled the identification of genetic variants that cause these diseases. Alongside technological advancements in genetic medicine, the identification of variants causal of these rare skin conditions has led to preclinical research and the clinical development of various in vivo and ex vivo gene and cell therapies for their treatment. Gene and cell therapies are considered to be the most advanced forms of personalized medicine, demonstrating safety and efficacy in numerous rare diseases. Although the orphan drug development boom has resulted in regulatory approval of multiple gene and cell therapies for various rare conditions, the application of these modalities to rare inherited skin conditions remains limited. Nonetheless, there are successful examples of both in vivo gene therapy- and ex vivo cell therapy-based approaches developed to treat EB and ichthyosis. This review highlights preclinical research and the clinical development of gene and cell therapies for multiple subtypes of these two devastating congenital skin conditions, including a gene therapy recently approved by the U.S. Food and Drug Administration for the treatment of recessive dystrophic EB.

Advances in genetics research for skin diseases such as epidermolysis bullosa and ichthyosis have led to the discovery of many new subtypes of these severe skin conditions. Identifying new subtypes has in turn led to new treatments for these conditions, including gene and cell therapies. Gene and cell therapies aim to address the underlying genetic causes of disease and have already shown success in the clinic. While the development of such treatments for rare skin diseases has been limited, there are notable examples of gene and cell therapies developed for epidermolysis bullosa and ichthyosis. This review highlights recent developments in gene and cell therapy for epidermolysis bullosa and ichthyosis, including a newly approved gene therapy for recessive dystrophic epidermolysis bullosa.

Lipodystrophy in methylmalonic acidemia associated with elevated FGF21 and abnormal methylmalonylation.

A distinct adipose tissue distribution pattern was observed in patients with methylmalonyl-CoA mutase deficiency, an inborn error of branched-chain amino acid (BCAA) metabolism, characterized by centripetal obesity with proximal upper and lower extremity fat deposition and paucity of visceral fat, that resembles familial multiple lipomatosis syndrome. To explore brown and white fat physiology in methylmalonic acidemia (MMA), body composition, adipokines, and inflammatory markers were assessed in 46 patients with MMA and 99 matched controls. Fibroblast growth factor 21 levels were associated with acyl-CoA accretion, aberrant methylmalonylation in adipose tissue, and an attenuated inflammatory cytokine profile. In parallel, brown and white fat were examined in a liver-specific transgenic MMA mouse model (Mmut-/- TgINS-Alb-Mmut). The MMA mice exhibited abnormal nonshivering thermogenesis with whitened brown fat and had an ineffective transcriptional response to cold stress. Treatment of the MMA mice with bezafibrates led to clinical improvement with beiging of subcutaneous fat depots, which resembled the distribution seen in the patients. These studies defined what we believe to be a novel lipodystrophy phenotype in patients with defects in the terminal steps of BCAA oxidation and demonstrated that beiging of subcutaneous adipose tissue in MMA could readily be induced with small molecules.