3,4-Diaminopyridine

3,4-Diaminopyridine (or 3,4-DAP) is an organic compound with the formula C₅H₃N(NH₂)₂. It is formally derived from pyridine by substitution of the 3 and 4 positions with an amino group.

The compound 3,4-diaminopyridine has the International Nonproprietary Name amifampridine and is used as a drug, predominantly in the treatment of a number of rare muscle diseases. The phosphate salt of amifampridine is a more stable formulation that does not require refrigeration; it is marketed in the EU by BioMarin Pharmaceutical under the trade name Firdapse and designated as an orphan drug in the EU. In the United States, amifampridine is under investigation for the treatment of Lambert-Eaton myasthenic syndrome (LEMS) by Catalyst Pharmaceuticals, and was granted a breakthrough therapy designation by the FDA in 2013. In a Phase 3 clinical trial, it demonstrated superiority over placebo in both co-primary endpoints. LEMS patients can receive amifampridine at no cost under an ongoing expanded access program. A study to develop patient entry criteria for a clinical trial of the free base form of amifampridine has also been completed by Jacobus Pharmaceutical Company. This form remains available at no cost to patients with Lambert-Eaton myasthenic syndrome and congenital myasthenic syndromes under a long-standing compassionate use program, with FDA oversight, from Jacobus Pharmaceutical Company (see also Medical uses and Economics, below).