Extension Study of XLHED-Affected Male Subjects Treated With EDI200 in Protocol ECP-002

X-linked hypohidrotic ectodermal dysplasia (XLHED) is a disorder of ectoderm development in which sweat and other secretory gland hypoplasias predispose affected infants to serious and potentially life-threatening hyperthermia and pneumonia. Those XLHED patients who survive infancy face a host of ectoderm-related clinical conditions including failure to thrive, oligodontia and misshapen teeth, mid-face hypoplasia, eczema, chronic dry eyes, asthma, respiratory infections, sinusitis and chronic nosebleeds. XLHED is caused by inherited defects in the ectodysplasin gene (EDA, www.ncbi.nlm.nih.gov/omim) resulting in a deficiency of the ectoderm signaling protein EDA-A1. As is the general case with X-linked disorders, hemizygous XLHED males are more consistently and severely affected, while heterozygous XLHED females have a more variable phenotype.

In normal development, EDA-A1 acts as an ectoderm signaling molecule that binds specifically to the EDA-A1 receptor (EDAR) triggering initiation and maturation of ectodermal appendages into sweat and other secretory glands, tooth buds and hair follicles. In the case of XLHED, EDA-A1 deficiency results in the absence or functional hypoplasia of the ectoderm appendages. There are no therapies currently available for XLHED that prevent or correct the underlying ectodermal abnormalities.

EDI200 is a fully humanized EDA-A1 replacement molecule under development as a novel therapeutic for XLHED. EDI200 comprises the human IgG1 Fc domain linked to the human EDA-A1 receptor-binding domain. On-target EDI200 activation of the EDA-A1/EDAR signaling pathway in vivo is evidenced by the remarkable phenotypic response in preclinical models. In XLHED-affected animals, EDA-A1 deficiency is corrected by a single course of EDI200 therapy, administered either prenatally (mice) or postnatally (newborn mice and dogs), resulting in a significant and sustained improvement in the health of the treated animals. Postnatal studies in both mice and dogs demonstrated a consistent and restricted window of efficacy. These results support the clinical development of EDI200 as a therapeutic to be administered to XLHED-affected patients in the neonatal period or earlier.

ECP-002, a Phase 2, international, first-in-neonate EDI200 study is enrolling treatment-naïve, XLHED-affected male newborns in the first two weeks of life. All subjects will meet entry criteria including documentation of an EDA mutation associated with XLHED. Following Baseline evaluations, EDI200 dosing is initiated between day-of-life 2 and 14, with each study subject receiving a single course of study drug administered at 2 doses/week for a total of 5 doses. The treatment study protocol incorporates comprehensive safety, pharmacokinetic (PK), immunogenetic, and pharmacodynamic (PD)/efficacy evaluations continuing through age 6 months.

The goal of the ECP-002e extension study is to continue the evaluation of all EDI200-treated ECP-002 subjects up to age 10 yrs. No additional study drug administration is planned. The efficacy evaluations will incorporate growth and development parameters, frequency of infections and hospitalizations, and age-appropriate assessments of ectoderm-derived organ function. The safety evaluations will include physical examinations, adverse events and concomitant medication documentation, and laboratory testing.