The isolation and identification of a toxic impurity in XP315 drug substance

In early safety assessment studies with the experimental anti-neoplastic dr ug XP315, a toxic reaction was observed in dogs immediately after intraveno us (iv) infusion. The reaction was characterized by severe erythema around the ears, eyes, face and body; ocular hyperemia; head shaking; swelling aro und the eyes, face, paws, head, neck and legs; scratching; and reddened gum s, which lasted several hours after dosing. By fractionating the drug subst ance using preparative HPLC and then infusing the residues into dogs by iv, this reaction was traced to an impurity in the drug substance. Following t he preparative isolation of the toxic impurity, characterization was perfor med using a combination of NMR and mass spectral methods. The proposed impu rity was found to be structurally related and nearly twice the molecular we ight of XP315, resulting from a dimerization by ring fusion of two 3-aminon aphthalene fragments during the synthetic process. This paper details the s teps taken to isolate the toxic impurity and characterize its structure usi ng off-line methods. (C) 2002 Published by Elsevier Science B.V.