Ra Pharmaceuticals, Inc. is a clinical-stage biopharmaceutical company. The Company is focused on developing therapeutics for the treatment of serious diseases that are caused by excessive or uncontrolled activation of the complement system. It is developing its lead product candidate, RA101495, a self-administered subcutaneous (SC) injection. RA101495 is injected into the tissue under the skin for the treatment of paroxysmal nocturnal hemoglobinuria (PNH). The Company is also developing RA101495 to treat other debilitating complement-mediated diseases such as generalized myasthenia gravis (gMG) and lupus nephritis (LN). It also focuses on discovery and preclinical programs targeting selective inhibition of other uncontrolled complement pathway factors to treat a variety of ophthalmic, renal and inflammatory diseases. The Company uses its Extreme Diversity platform, macrocyclic peptide chemistry technology which produces synthetic macrocyclic peptides.