SPK-843 is a water-soluble partricin derivative patented by SPA Societa Prodotti Antibiotici S.p.A. and developed by Aparts and Kaken for the potential treatment of systemic fungal infections. In preclinical models, SPK-843 shows in vitro inhibitory activity comparable to or better than that of Amphotericin B against Candida spp., Cryptococcus neoformans, and Aspergillus spp. SPK-843 exhibits dose-dependent efficacy on murine pulmonary aspergillosis models. SPK-843 doses of higher than 1.0 mg/kg of body weight exhibit no renal toxicities and a tendency toward better survival prolongation than the estimated maximum tolerated doses of amphotericin B (Fungizone) and liposomal amphotericin B.

Fialuridine, or 1-(2-deoxy-2-fluoro-1-D-arabinofuranosyl)-5-iodouracil (FIAU) is a thymidine nucleoside analog with activity against various herpesviruses and hepatitis B virus (HBV) in vitro and in vivo. Herpes virus thymidine kinase considered to be a target of FIAU. In a Phase II study, fialuridine induced a severe toxic reaction in chronic hepatitis B patients characterized by hepatic failure, lactic acidosis, pancreatitis, neuropathy, and myopathy. These clinical manifestations led to the hypothesis that the toxicity of FIAU was mediated through mitochondrial dysfunction, possibly as a result of the inhibition of mitochondrial DNA polymerase gamma and/or incorporation of FIAU into mitochondrial DNA.