CEP-11981 is an orally bioavailable inhibitor of vascular endothelial growth factor receptor (VEGFR) and Tie2 receptor tyrosine kinases with potential antiangiogenic and antineoplastic activities. Preclinical studies have shown that CEP-11981 exhibits promising permeability, metabolic stability, and pharmacokinetic properties across multiple species. Studies of pharmacologic activity across angiogenesis assays, animal tumor models, and human tumor models have shown sustained, dose-related antiangiogenic and antitumor inhibition. In clinical trals CEP-11981 administration leads to disease stabilization in patients with recurrent or refractory solid tumors. Despite acceptable tolerability of CEP-11981 at the MTD, further development by the sponsor has ceased.

Nitroarginine (LNNA), an analog of L-arginine, is a competitive inhibitor of nitric oxide synthase which has been shown to prevent glutamate toxicity. Nitroarginine has been experimentally tested for its ability to prevent ammonia toxicity and ammonia-induced alterations in brain energy and ammonia metabolites. The Kd value (k(off)/k(on)) of bovine brain cNOS for LNNA was 15 nM. In contrast to the potent and slow onset of LNNA inhibition of brain cNOS, LNNA inhibition of inducible mouse macrophage NOS (iNOS) was weaker (Ki = 4.4 uM) and rapidly reversible. Thus, LNNA was a 300-fold more potent inhibitor of bovine brain cNOS than mouse macrophage iNOS. By inhibiting nitric oxide synthase LNNA causes the selective reduction of blood flow to tumor cells. Despite the potential of LNNA to function as an adjuvant in cancer therapies, its poor solubility and stability have hindered the development of an injectable formulation of LNNA that is suitable for human administration.