Spark Therapeutics, Inc. (Spark) is engaged in developing products in the field of gene therapy. The Company focuses on treating orphan diseases. It has a pipeline of product candidates targeting multiple rare blinding conditions, hematologic disorders and neurodegenerative diseases. Its SPK-RPE65 (voretigene neparvovec) targets genetic blinding conditions known as inherited retinal dystrophies (IRDs). Its product candidates include SPK-CHM and SPK-FIX. Its product development portfolio includes product candidates targeting expression of genes in the liver, with an initial focus on hematologic disorders. It is engaged in the development and commercialization of SPK-FIX product candidates for the treatment of hemophilia B. The Company is developing a lead product candidate for the treatment of a form of Batten disease in SPK-TPP1 program. The Company is also conducting preclinical studies on a product candidate for the treatment of Huntington's disease, a hereditary genetic disorder.